U.S. patent application number 09/725802 was filed with the patent office on 2001-03-22 for method for determining a charging amount of refrigerant for an air conditioner, a method for controlling refrigerant for an air conditioner and an air conditioner.
Invention is credited to Matsushita, Akihiro, Okazaki, Takashi, Sumida, Yoshihiro.
Application Number | 20010000050 09/725802 |
Document ID | / |
Family ID | 16518911 |
Filed Date | 2001-03-22 |
United States Patent
Application |
20010000050 |
Kind Code |
A1 |
Okazaki, Takashi ; et
al. |
March 22, 2001 |
Method for determining a charging amount of refrigerant for an air
conditioner, a method for controlling refrigerant for an air
conditioner and an air conditioner
Abstract
An air conditioner capable of conducting a natural circulation
operation by circulating refrigerant through an evaporator and a
condenser located at a higher position than the evaporator, which
are connected with pipes, wherein the air conditioner has means for
obtaining an air conditioning load quantity to an outdoor air
temperature in a temperature range, means for obtaining an air
conditioning ability quantity to an outdoor air temperature in a
temperature range in a case of using a predetermined mount of
refrigerant, means for obtaining the maximum outdoor air
temperature capable of conducting air conditioning at the time when
an air conditioning load quantity produced from the means for
obtaining an air conditioning load quantity substantially coincides
with an air conditioning ability quantity from the means for
determining an amount of refrigerant, as an amount to be charged,
in which a maximum outdoor air temperature capable of conducting
air conditioning among the obtained maximum outdoor air
temperatures becomes the maximum.
Inventors: |
Okazaki, Takashi; (Tokyo,
JP) ; Matsushita, Akihiro; (Tokyo, JP) ;
Sumida, Yoshihiro; (Tokyo, JP) |
Correspondence
Address: |
Platon N. Mandros
BURNS, DOANE, SWECKER & MATHIS, L.L.P.
P.O. Box 1404
Alexandria
VA
22313-1404
US
|
Family ID: |
16518911 |
Appl. No.: |
09/725802 |
Filed: |
November 30, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09725802 |
Nov 30, 2000 |
|
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|
09291952 |
Apr 15, 1999 |
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Current U.S.
Class: |
62/149 ;
62/77 |
Current CPC
Class: |
F25B 2500/01 20130101;
F25B 45/00 20130101; F25B 2700/04 20130101; F25B 25/00 20130101;
F25B 2345/001 20130101; F25B 9/002 20130101; F25B 2400/0401
20130101; F25B 41/00 20130101; F25B 2400/16 20130101; F25B 2600/19
20130101; F25B 2600/21 20130101 |
Class at
Publication: |
62/149 ;
62/77 |
International
Class: |
F25B 045/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 22, 1998 |
JP |
10-206166 |
Claims
What is claimed is:
1. In a method for determining a charging amount of refrigerant for
an air conditioner which conducts a natural circulation operation
by circulating refrigerant through an evaporator and a condenser
located at a higher position than the evaporator, which are
connected with pipes, said method being characterized by comprising
means for obtaining an air conditioning load quantity to an outdoor
air temperature among outdoor air temperatures, means for obtaining
an air conditioning ability quantity to an outdoor air temperature
in a temperature range in a case of using a predetermined amount of
refrigerant, means for obtaining the maximum outdoor air
temperature capable of conducting air-conditioning at the time when
an air conditioning load quantity produced from the means for
obtaining an air conditioning load quantity substantially coincides
with an air conditioning ability quantity from the means for
obtaining an air conditioning ability quantity in using a
predetermined amount of refrigerant, and means for obtaining
respective maximum outdoor air temperatures capable of conducting
air conditioning when said predetermined amount of refrigerant is
changed and for determining an amount of refrigerant, as an amount
to be charged, in which a maximum outdoor air temperature capable
of conducting air conditioning among the obtained maximum outdoor
air temperatures becomes the maximum.
2. In a method for controlling refrigerant for an air conditioner
capable of switching between a forced circulation operation for
circulating refrigerant through a compressor, a condenser, a
refrigerant flow controlling means, an evaporator and a refrigerant
storing means which are connected successively with pipes and a
natural circulation operation for circulating the refrigerant
through a bypass pipe for bypassing the compressor and the
refrigerant storing means, the condenser, the refrigerant flow
controlling means and the evaporator which are connected, said
method being characterized by comprising, at the time of switching
from the forced circulation operation to the natural circulation
operation, means for making the refrigerant in an outlet portion of
the evaporator to be a superheat state, and means for introducing a
refrigerant gas in a superheat state into the refrigerant storing
means to vaporize the refrigerant stored in the refrigerant storing
means whereby the refrigerant stored in the refrigerant storing
means during the forced circulation operation is recovered into a
refrigerant circuit for the natural circulation operation.
3. The method for controlling refrigerant for an air conditioner
according to claim 2, wherein the refrigerant flow controlling
means is controlled by said means for making the refrigerant in the
outlet portion of the evaporator to be an overheated state so that
the refrigerant flow rate is smaller than a refrigerant flow rate
in the forced circulation operation.
4. The method for controlling refrigerant for an air conditioner
according to claim 2, wherein a part of a superheated gas
discharged from the compressor is introduced into the refrigerant
storing means along with the superheated gas from the evaporator by
means of a refrigerant vaporizing means on the refrigerant stored
in the refrigerant storing means whereby the refrigerant stored in
the refrigerant storing means is vaporized.
5. The method for controlling refrigerant for an air conditioner
according to claim 4, wherein the refrigerant vaporizing means is
operated for a predetermined time to vaporize the refrigerant
stored in the refrigerant storing means.
6. The method for controlling refrigerant for an air conditioner
according to claim 2, wherein the refrigerant vaporizing means is
operated on the refrigerant stored in the refrigerant storing means
so that a degree of superheating in the outlet portion of the
evaporator reaches a predetermined degree of superheating.
7. The method for controlling refrigerant for an air conditioner
according to claim 2, wherein in the natural circulation operation,
at least one of a refrigerant flow rate, an air flow rate to the
evaporator and a refrigerant quantity in the evaporator is changed
so that a degree of superheating or a degree of dryness of the
refrigerant in the outlet portion of the evaporator becomes a
predetermined value.
8. The method for controlling refrigerant for an air conditioner
according to claim 7, wherein values to be set for the refrigerant
in the outlet portion of the evaporator in the natural circulation
operation are a value of not less than 0.9 in terms of a degree of
dryness and a value of not more than 10.degree. C. in terms of a
degree of superheating.
9. The method for controlling refrigerant for an air conditioner
according to claim 7, wherein at least one of the refrigerant flow
rate, the air flow rate to the condenser and the refrigerant
quantity in the condenser is changed so that a degree of
supercooling or a degree of dryness of the refrigerant in the
outlet portion of the condenser in the natural circulation
operation becomes a predetermined value.
10. The method for controlling refrigerant for an air conditioner
according to claim 9, wherein values of the refrigerant in the
outlet portion of the condenser in the natural circulation
operation are not more than 0.1 in terms of a degree of dryness and
not more than 20.degree. C. in terms of a degree of
supercooling.
11. The method for controlling refrigerant for an air conditioner
according to claim 7, wherein at least one of the refrigerant flow
rate, the air flow rate and the refrigerant quantity in the natural
circulation operation is changed with predetermined time
intervals.
12. In a method for controlling refrigerant for an air conditioner
capable of switching between a forced circulation operation for
circulating refrigerant through a compressor, a condenser, a
refrigerant flow controlling means, an evaporator and a refrigerant
storing means which are connected successively with pipes and a
natural circulation operation for circulating the refrigerant
through a bypass pipe for bypassing the compressor and the
refrigerant storing means, the condenser, the refrigerant flow
controlling means and the evaporator which are connected, said
method being characterized by comprising, at the time of switching
from the forced circulation operation to the natural circulation
operation, a refrigerant vaporizing means for vaporizing the
refrigerant stored in the refrigerant storing means, means for
detecting a temperature difference between an outdoor temperature
and a set temperature set for air conditioning, and means for
changing an evaporation quantity on the refrigerant depending on
the magnitude of a temperature difference detected by the
temperature difference detecting means when the refrigerant stored
is vaporized by the refrigerant vaporizing means, whereby an amount
of recovery of the refrigerant stored in the refrigerant storing
means in the forced circulation operation is increased or decreased
as a result that a refrigerant quantity in the refrigerant circuit
in the natural circulation operation is increased or decreased.
13. The method for controlling refrigerant for an air conditioner
according to claim 12, wherein a part of a superheated gas
discharged from the compressor is introduced into the refrigerant
storing means along with the superheated gas from the evaporator by
means of the refrigerant vaporizing means on the refrigerant stored
in the refrigerant storing means so that the refrigerant stored in
the refrigerant storing means is vaporized.
14. The method for controlling refrigerant for an air conditioner
according to claim 12, wherein the refrigerant vaporizing means is
operated for a predetermined time.
15. The method for controlling refrigerant for an air conditioner
according to claim 12, wherein the refrigerant vaporizing means is
operated on the refrigerant stored in the refrigerant storing means
until the degree of superheating of the refrigerant in the outlet
portion of the evaporator becomes a predetermined value of
superheating.
16. In an air conditioner comprising an evaporator and a condenser
located at a higher position than the evaporator, which is
connected to the evaporator with a pipe to conduct a natural
circulation operation by circulating refrigerant, said air
conditioner being characterized by comprising a refrigerant state
detecting means for detecting a state of the refrigerant in an
outlet portion of the evaporator in the natural circulation
operation, a refrigerant flow controlling means for controlling a
refrigerant flow rate in circulation and a controlling means for
controlling the refrigerant flow controlling means depending on a
state of the refrigerant detected by the refrigerant state
detecting means to change the refrigerant flow rate.
17. The air conditioner according to claim 16, which further
comprises a refrigerant storing means for storing an excessive
amount of the refrigerant resulted from the controlling of the
refrigerant flow rate.
18. The air conditioner according to claim 16, wherein the
refrigerant state detecting means is to detect a degree of
superheating or a degree of dryness of the refrigerant in the
outlet portion of the evaporator.
19. The air conditioner according to claim 16, wherein the
refrigerant state detecting means is to detect a degree of
supercooling or a degree of dryness of the refrigerant in the
outlet portion of the condenser, and the controlling means is to
operate the refrigerant flow controlling means to change the
refrigerant flow rate depending on a temperature difference between
an outdoor air temperature and a set temperature set for air
conditioning and a state of the refrigerant.
20. In an air conditioner capable of switching between a forced
circulation operation for circulating refrigerant through a
compressor, a condenser, a refrigerant flow controlling means, an
evaporator and a refrigerant storing means which are connected
successively with pipes and a natural circulation operation for
circulating the refrigerant through a bypass pipe for bypassing the
compressor, the condenser located at a higher position than the
evaporator, the refrigerant flow controlling means and the
evaporator which are connected, said air conditioner being
characterized in that the refrigerant flow controlling means is
located in a space where the evaporator is located.
Description
BACKGROUND OF THE INVENTION
1. 1. Field of the Invention
2. The present invention relates to an air conditioner operated
through the years. In particular, it relates to an improvement of
air conditioning ability on an air conditioner capable of
conducting a natural circulation operation without using the power
of a compressor. Further, the present invention relates to a method
for controlling refrigerant for an air conditioner capable of
conducting such natural circulation operation as well as a forced
circulation operation with the power of a compressor.
3. 2. Discussion of Background
4. In recent years, a technical field of removing heat from
electric machines in a location represented by a computer center or
a base station (hereinbelow, referred to as a shelter)
accommodating relay electric devices has rapidly spread with
spreading of mobile communication such as a portable telephone.
Such location is required to conduct an air cooling operation
throughout years. In the field of removing from the electric
devices requiring an air cooling operation throughout the years,
when an outdoor air temperature is low as in a winter season or a
night time, it is possible to cool electronic devices by air
ventilation. However, a special device for preventing fog, rain,
snow, dust and so on from entering therein is necessary. Further,
stable air cooling can not be performed because there is variations
in an indoor air temperature depending on variations in the outdoor
air temperature. Under such conditions, it is possible to use an
air conditioner in which natural circulation for carrying heat by
refrigerant from an indoor to an outdoor, by utilizing a
temperature difference between an indoor air temperature and an
outdoor air temperature and a difference of position in height
between an indoor unit and an outdoor unit. In the air conditioner
utilizing such natural circulation, the power of a compressor is
unnecessary when operations utilizing natural circulation
(hereinbelow, referred to as natural circulation operation) is to
be conducted. Accordingly, it can substantially reduce an annual
power consumption in comparison with an air cooling operation by
using an air conditioner which conducts operations by using the
compressor (hereinbelow, referred to as forced circulation
operation).
5. Now, the operational principle of air cooling operation by the
natural circulation will be described with reference to FIG. 17.
FIG. 17 is a diagram showing the basic circuit for an air cooling
apparatus as an air conditioner utilizing the natural circulation
wherein reference numeral 2 designates a condenser, numeral 3 an
outdoor fan, numeral 5 an outdoor unit, numeral 6 a liquid pipe,
numeral 7 an evaporator, numeral 8 an indoor fan, numeral 9 an
indoor unit located in a space to be air-conditioned and numeral 10
a gas pipe. In this case, for conducting air cooling, the
evaporator 7 is provided at an indoor side and the condenser 2 is
provided at an outdoor side.
6. The operation will be explained. When the condenser 2 is
arranged at a higher position than the evaporator 7, a liquid
refrigerant condensed in the condenser 2 descends by the gravity in
the liquid pipe 6 to be introduced into the evaporator 7. The
liquid refrigerant introduced into the evaporator 7 is vaporized by
receiving a thermal load in a space to be air-conditioned, e.g., a
room, and then, the vaporized refrigerant ascends in the gas pipe
10 to be returned to the condenser 2; thus, a cycle is formed.
7. Thus, the air cooling operation by the natural circulation
utilizes a density difference between a liquid refrigerant and a
gas refrigerant due to a relative position in height between the
evaporator 7 and the condenser 2, as a driving force for
circulating the refrigerant. The natural circulation can be
realized in a case that sum of pressure losses in a refrigerant
circuit comprising the condenser 2, the evaporator 7, the liquid
pipe 6, the gas pipe 10 and on-off valves in the refrigerant
circuit is equal to a pressure increase in the liquid pipe 6 caused
by a height of liquid column.
8. In an air conditioner utilizing such natural circulation, an
amount of refrigerant (a refrigerant quantity) to be charged has
been determined from experience. Further, a state of the
refrigerant has not been properly controlled in consideration of
the air conditioning ability during the natural circulation
operation.
9. Further, in an air conditioner utilizing the natural
circulation, the existence of a temperature difference between an
indoor air temperature and an outdoor air temperature is required.
Accordingly, there is a possibility that the natural circulation
operation does not function depending on environmental conditions.
In this case, an air conditioner capable of effecting the forced
circulation operation with use of the compressor in response to the
case that the natural circulation operation does not function, is
provided. In the air conditioner in combination of the natural
circulation operation and the forced circulation operation, it is
necessary to provide a refrigerant flow controlling means in the
refrigerant circuit from the reasons that there are a variation in
a refrigerant flow rate between the natural circulation operation
and the forced circulation operation as well as a variation of the
refrigerant flow rate due to a variation in the length of a liquid
portion, a variation of the refrigerant flow rate derived from a
variation of a load, and a difference of a refrigerant quantity
derived from the length of the pipes extended in the circuit. In
the conventional air conditioners, a reservoir provided at an
outlet of the condenser or an accumulator provided at a sucking
side of the compressor bore such refrigerant flow controlling
function. However, the method for properly controlling a
refrigerant quantity has not substantially been conducted.
CONVENTIONAL EXAMPLE 1
10. FIG. 18 is a diagrammatical view of a conventional air cooling
apparatus utilizing natural circuit disclosed in JP-A-9-68355. The
operation will be described.
11. In FIG. 18, reference numeral 1 designates a compressor,
numeral 2 a condenser, numeral 3 an outdoor fan, numeral 4 an
electronic expansion valve, numeral 5 an outdoor unit, numeral 6 a
liquid pipe, numeral 7 an evaporator, numeral 9 an indoor unit,
numeral 10 a gas pipe, numeral 11 a check valve, numeral 12 a
bypass pipe including the check valve 11 and numeral 14 an
accumulator. These structural elements are connected with the
liquid pipe 6, the gas pipe 10, the bypass pipe 12 and so on to
form a refrigerant circuit.
12. The outdoor unit comprises the compressor 1 to compress a
refrigerant gas, the condenser 2 to liquefy the refrigerant gas,
the accumulator 14 for preventing the liquid from returning to the
compressor 1 in case such as a transient phenomenon, supercharging
of refrigerant and so on, and the bypass pipe 12 including the
check valve 11 which bypasses the accumulator. The indoor unit 9
comprises the evaporator 7 and the electronic expansion valve 4
which is provided at a position closest to an inlet of the
evaporator.
CONVENTIONAL EXAMPLE 2
13. FIG. 19 is a diagrammatical view showing the circuit of an air
conditioner for controlling a refrigerant quantity in a
cooling/warming apparatus capable of conducting the forced
circulation operation and the natural circulation operation,
disclosed in JP-A-57-92666. In FIG. 19, reference numeral 1
designates a compressor, numeral 2 a condenser, numeral 5 an
outdoor unit, numerals 6, 10 designate refrigerant pipes, i.e. a
liquid pipe 6 and a gas pipe 10 used for the natural circulation
operation, numeral 7 designates an indoor heat exchanger, numeral 9
an indoor unit, numeral 14 an accumulator, numeral 20 a reservoir,
numeral 23 a refrigerant flow controlling device, numeral 24 a
dryer filter, numeral 25 a heating device, numeral 26 a refrigerant
heating coil, numeral 27 an electromagnetic valve, numeral 28 a
check valve, numeral 29 a reverse-flow preventing on-off valve for
conducting the starting of warming operation smoothly, numeral 30 a
high pressure controlling valve for preventing an abnormal increase
of pressure or temperature of the refrigerant at an outlet 26b of
the refrigerant heating coil, numeral 31 a capillary pipe, numeral
32 a partition, numeral 33 a refrigerant pipe, numeral 34 a branch,
numeral 35 a pipe, numeral 36 an electric heater, and numerals 37,
38 designate on-off valves.
14. In the air conditioner, when the forced circulation operation
is conducted by using the compressor 1, the electromagnetic valve
27 is closed to form a closed circuit comprising the compressor 1,
the condenser 2, the dryer filter 24, the check valve 28, the
capillary pipe 31, the refrigerant pipe 6, the indoor heat
exchanger 7, the refrigerant pipe 10 and the accumulator 14 of the
refrigerant flow controlling device 23 wherein the indoor heat
exchanger 7 is operated as an evaporator whereby cooling is
effected by utilizing the evaporation of the refrigerant.
15. On the other hand, in a case of warming by the natural
circulation operation, the electromagnetic valve is opened and the
heating device 25 is operated to thereby form a closed circuit
comprising the refrigerant heating coil 26, and end portion 26a at
a higher position side of the coil, the electromagnetic valve 27,
the accumulator 14, the refrigerant pipe 10, an end portion 7a at a
higher positional side of the indoor heat exchanger, the indoor
heat exchanger 7, an end portion 7b at a lower position side of the
indoor heat exchanger, the refrigerant pipe 6 and an end portion
26b at a low position side of the refrigerant heating coil 6. Then,
the indoor heat exchanger 7 is operated as a condenser whereby
warming is conducted by utilizing the condensation of the
refrigerant.
16. The inside of the refrigerant flow controlling device 23 is
divided to an outside room 20 and an inside room 14 with the
partition 32. The outside room 20 influenced by an outdoor air
temperature is used as a reservoir and the inside room 14 is as an
accumulator. The branch pipe 34 communicates a bottom portion of
the reservoir 20 with the refrigerant pipe 33.
17. The refrigerant pipe 33 connected to the reservoir 20 by means
of the branch pipe 34 is a pipe in which a liquid refrigerant of
low pressure is passed to the indoor heat exchanger 7 in the forced
circulation operation, and it is also a pipe in which the liquid
refrigerant after having subjected to heat exchanging in the indoor
heat exchanger 7 in the natural circulation operation is passed
therethrough.
18. The accumulator 14 constitutes a refrigerant pipe through which
a gas refrigerant after having subjected to heat exchanging in the
indoor heat exchanger 7 in the forced circulation operation is
passed and a refrigerant pipe through which the gas refrigerant to
be supplied to the indoor heat exchanger 7 in the natural
circulation operation is passed. A difference in refrigerant
quantity between the forced circulation operation and the natural
circulation operation is adjusted by the refrigerant flow
controlling device 23.
19. In the above mentioned conventional air conditioners, when an
outdoor air temperature is lower than a predetermined value, for
example, 5.degree. C. in the natural circulation operation, it is
necessary to increase a refrigerant flow rate because an air
conditioning load is increased. However, the refrigerant tends to
accumulate in the refrigerant controlling device 23 because the
refrigerant controlling device 23 is cooled by outdoor air. In such
case, the electric heater 36 is actuated to generate heat by an
instruction from an outdoor air temperature detecting thermostat
that the refrigerant flow controlling device 23 so that the
accumulated refrigerant is vaporized. Accordingly, a refrigerant
quantity in the refrigerant flow controlling device 23 can properly
be maintained even though an outdoor air temperature is low, and a
sufficient natural circulation ability can be obtained.
20. As described above, in the conventional air conditioners
utilizing the natural circulation, a refrigerant quantity to be
charged was roughly determined without considering the air
conditioning ability. Further, there was no attempt to improve the
air conditioning ability by controlling a state of the refrigerant
in the natural circulation operation.
21. Further, in the conventional air conditioners capable of
effecting the forced circulation operation and the natural
circulation operation, when an outdoor air temperature became lower
than a set value in a case that the refrigerant quantity in the
natural circulation operation was controlled in response to a
change of an air conditioning load, the electric heater 36 was made
to be conductive by an instruction from the outdoor air temperature
detecting thermostat to thereby generate heat whereby a
predetermined quantity of heat was given to the refrigerant flow
controlling device 23. In the conventional air conditioners, since
the control of the refrigerant quantity was not conducted in
consideration of how an outdoor air temperature or a refrigerant
flow rate influences the ability in the natural circulation
operation, there was a problem that an effect of reducing
consumption power by utilizing the natural circulation operation
became small.
22. Further, since the adjustment of the refrigerant quantity was
conducted by the electric heater, there is substantial power
consumed by the electric heater. Further, there was a problem that
an effect of reducing consumption power by utilizing the natural
circulation operation became small.
SUMMARY OF THE INVENTION
23. It is an object of the present invention to provide a method
for determining a charging amount of refrigerant for an air
conditioner utilizing a natural circulation wherein the optimum
amount of refrigerant can be charged in consideration of the air
conditioning ability while providing the maximum ability of the air
conditioner.
24. Further, it is an object of the present invention to provide a
method for controlling refrigerant for an air conditioner capable
of conducting a natural circulation operation wherein the optimum
state of refrigerant can be provided in consideration of the air
conditioning ability while performing the maximum air conditioning
ability.
25. Further, it is an object of the present invention to provide a
method for controlling refrigerant for an air conditioner capable
of conducting a forced circulation operation and a natural
circulation operation wherein the forced circulation operation can
smoothly be switched to the natural circulation operation without
requiring an external input such as electric heater, and
consumption power can substantially be reduced.
26. Further, it is an object of the present invention to provide a
method for controlling refrigerant for an air conditioner capable
of conducting a forced circulation operation and a natural
circulation operation wherein the forced circulation operation can
smoothly be switched to the natural circulation operation without
requiring an external input such as an electric heater, the natural
circulation operation can be conducted by utilizing the air
conditional ability to the maximum, and consumption power can
substantially be reduced.
27. Further, it is an object of the present invention to provide an
air conditioner which provides a high air conditioning ability in a
natural circulation operation.
28. In accordance with a first aspect of the present invention,
there is provided a method for determining a charging amount of
refrigerant for an air conditioner which conducts a natural
circulation operation by circulating refrigerant through an
evaporator and a condenser located at a higher position than the
evaporator, which are connected with pipes, said method being
characterized by comprising means for obtaining an air conditioning
load quantity to an outdoor air temperature among outdoor air
temperatures, means for obtaining an air conditioning ability
quantity to an outdoor air temperature in a temperature range in a
case of using a predetermined quantity of refrigerant, means for
obtaining the maximum outdoor air temperature capable of conducting
air conditioning at the time when an air conditioning load quantity
produced from the means for obtaining an air conditioning load
quantity substantially coincides with an air conditioning ability
quantity from the means for obtaining an air conditioning ability
quantity in using a predetermined quantity of refrigerant, and
means for obtaining respective maximum outdoor air temperatures
capable of conducting air conditioning when said predetermined
quantity of refrigerant is changed and for determining a
refrigerant quantity, as an amount to be charged, in which a
maximum outdoor air temperature capable of conducting air
conditioning among the obtained maximum outdoor air temperatures
becomes the maximum.
29. In accordance with a second aspect of the present invention,
there is provided a method for controlling refrigerant for an air
conditioner capable of switching between a forced circulation
operation for circulating refrigerant through a compressor, a
condenser, a refrigerant flow controlling means, an evaporator and
a refrigerant storing means which are connected successively with
pipes and a natural circulation operation for circulating the
refrigerant through a bypass pipe for bypassing the compressor and
the refrigerant storing means, the condenser, the refrigerant flow
controlling means and the evaporator which are connected, said
method being characterized by comprising at the time of switching
from the forced circulation operation to the natural circulation
operation, means for making the refrigerant in an outlet portion of
the evaporator to be a superheat state, and means for introducing a
refrigerant gas in a superheat state into the refrigerant storing
means to vaporize the refrigerant stored in the refrigerant storing
means whereby the refrigerant stored in the refrigerant storing
means during the forced circulation operation is recovered into a
refrigerant circuit for the natural circulation operation.
30. Further, there is provided the method for controlling
refrigerant for an air conditioner according to the second aspect,
wherein the refrigerant flow controlling means is controlled by
said means for making the refrigerant in the outlet portion of the
evaporator to be a superheat state so that the refrigerant flow
rate is smaller than a refrigerant flow rate in the forced
circulation operation.
31. In accordance with a third aspect of the present invention,
there is provided a method for controlling refrigerant for an air
conditioner capable of switching between a forced circulation
operation for circulating refrigerant through a compressor, a
condenser, a refrigerant flow controlling means, an evaporator and
a refrigerant storing means which are connected successively with
pipes and a natural circulation operation for circulating the
refrigerant through a bypass pipe for bypassing the compressor and
the refrigerant storing means, the condenser, the refrigerant flow
controlling means and the evaporator which are connected, said
method being characterized by comprising, at the time of switching
from the forced circulation operation to the natural circulation
operation, a refrigerant vaporizing means for vaporizing the
refrigerant stored in the refrigerant storing means, means for
detecting a temperature difference between an outdoor temperature
and a set temperature set for air conditioning, and means for
changing an evaporation quantity on the refrigerant depending on
the magnitude of a temperature difference detected by the
temperature difference detecting means in the evaporation of the
refrigerant by the refrigerant vaporizing means, whereby a quantity
of recovery of the refrigerant stored in the refrigerant storing
means in the forced circulation operation is increased or decreased
as a result that a refrigerant quantity in the refrigerant circuit
in the natural circulation operation is increased or decreased.
32. In accordance with the present invention, there is provided the
method for controlling refrigerant for an air conditioner according
to the third aspect wherein a part of a superheated gas discharged
from the compressor is introduced into the refrigerant storing
means along with the superheated gas from the evaporator by means
of a refrigerant vaporizing means on the refrigerant stored in the
refrigerant storing means whereby the refrigerant stored in the
refrigerant storing means is vaporized.
33. In accordance with the present invention, there is provided the
method for controlling refrigerant for an air conditioner according
to the third aspect, wherein the refrigerant vaporizing means is
operated for a predetermined time to vaporize the refrigerant
stored in the refrigerant storing means.
34. In accordance with the present invention, there is provided the
method for controlling refrigerant for an air conditioner according
to the third aspect, wherein the refrigerant vaporizing means is
operated on the refrigerant stored in the refrigerant storing means
so that a degree of superheating in the outlet portion of the
evaporator reaches a predetermined degree of superheating.
35. In accordance with a fourth aspect of the present invention,
there is provided a method for controlling refrigerant for an air
conditioner which conducts a natural circulation operation by
circulating refrigerant through an evaporator and a condenser
located at a higher position than the evaporator, which are
connected with a pipe, said method being characterizing in that in
the natural circulation operation, at least one of a refrigerant
flow rate, an air flow rate to the evaporator and a refrigerant
quantity in the evaporator is changed so that a degree of
superheating or a degree of dryness of the refrigerant in an outlet
portion of the evaporator becomes a predetermined value.
36. In accordance with the present invention, there is provided the
method for controlling refrigerant for an air conditioner according
to the fourth aspect, wherein values to be set for the refrigerant
in the outlet portion of the evaporator in the natural circulation
operation are a value of not less than 0.9 in terms of a degree of
dryness and a value of not more than 10.degree. C. in terms of a
degree of superheating.
37. In accordance with the present invention, there is provided the
method for controlling refrigerant for an air conditioner according
to the fourth aspect, wherein at least one of the refrigerant flow
rate, the air flow rate to the condenser and the refrigerant
quantity in the condenser is changed so that a degree of
supercooling or a degree of dryness of the refrigerant in the
outlet portion of the condenser in the natural circulation
operation becomes a predetermined value.
38. In accordance with the present invention, there is provided the
method for controlling refrigerant for an air conditioner according
to the fourth aspect, wherein values of the refrigerant in the
outlet portion of the condenser in the natural circulation
operation are not more than 0.1 in terms of a degree of dryness and
not more than 20.degree. C. in terms of a degree of
supercooling.
39. In accordance with the present invention, there is provided the
method for controlling refrigerant for an air conditioner according
to the fourth aspect, wherein at least one of the refrigerant flow
rate, the air flow rate and the refrigerant quantity in the natural
circulation operation is changed with predetermined time
intervals.
40. In accordance with the present invention, there is provided the
method for controlling refrigerant for an air conditioner according
to the fourth aspect, wherein at least one of the refrigerant flow
rate, the air flow rate and the refrigerant quantity in the natural
circulation operation is changed when a temperature difference
between an outdoor air temperature and a predetermined set
temperature for air conditioning is not more than 25.degree. C.
41. In accordance with a fifth aspect of the present invention,
there is provided an air conditioner comprising an evaporator and a
condenser located at a higher position than the evaporator, which
is connected to the evaporator with a pipe to conduct a natural
circulation operation by circulating refrigerant, said air
conditioner being characterized by comprising a refrigerant state
detecting means for detecting a state of the refrigerant in an
outlet portion of the evaporator in the natural circulation
operation, a refrigerant flow controlling means for controlling a
refrigerant flow rate in circulation and a controlling means for
controlling the refrigerant flow controlling means depending on a
state of the refrigerant detected by the refrigerant state
detecting means to change the refrigerant flow rate.
42. In accordance with the present invention, there is provided the
air conditioner according to the fifth aspect, which further
comprises a refrigerant storing means for storing an excessive
amount of the refrigerant resulted from the controlling of the
refrigerant flow rate.
43. In accordance with the present invention, there is provided the
air conditioner according to the fifth aspect, wherein the
refrigerant state detecting means is to detect a degree of
superheating or a degree of dryness of the refrigerant in the
outlet portion of the evaporator.
44. In accordance with the present invention, there is provided the
air conditioner according to the fifth aspect, wherein the
refrigerant state detecting means is to detect a degree of
supercooling or a degree of dryness of the refrigerant in the
outlet portion of the condenser, and the controlling means is to
operate the refrigerant flow controlling means to change the
refrigerant flow rate depending on a temperature difference between
an outdoor air temperature and the set temperature set for air
conditioning and a state of the refrigerant.
45. In accordance with a sixth aspect of the present invention,
there is provided an air conditioner capable of switching between a
forced circulation operation for circulating refrigerant through a
compressor, a condenser, a refrigerant flow controlling means, an
evaporator and a refrigerant storing means which are connected
successively with pipes and a natural circulation operation for
circulating the refrigerant through a bypass pipe for bypassing the
compressor, the condenser located at a higher position than the
evaporator, the refrigerant flow controlling means and the
evaporator which are connected, said air conditioner being
characterized in that the refrigerant flow controlling means is
located in a space where the evaporator is located.
BRIEF DESCRIPTION OF THE DRAWINGS
46. FIG. 1 is a circuit diagram showing the air conditioner
according to a first embodiment of the present invention;
47. FIG. 2 is a characteristic diagram showing an air cooling
ability, a degree of superheating at an outlet of an evaporator and
a degree of supercooling at an outlet of a condenser vs a charging
amount of refrigerant related to the first embodiment of the
present invention;
48. FIG. 3 is a characteristic diagram showing an air cooling
ability vs a charging amount of refrigerant related to the first
embodiment of the present invention;
49. FIG. 4 is a characteristic diagram showing a relation between
an outdoor air temperature and an air conditioning load and an air
cooling ability related to the first embodiment of the present
invention;
50. FIG. 5 is a diagram showing a simulation model related to the
first embodiment of the present invention;
51. FIGS. 6a and 6b are graphs showing changes of temperature to
time as a result of simulation related to the first embodiment of
the present invention;
52. FIG. 7 is a circuit diagram showing the air conditioner
according to a second embodiment of the present invention;
53. FIG. 8 is a circuit diagram showing the air conditioner
according to a third embodiment of the present invention;
54. FIG. 9 is a circuit diagram showing the air conditioner
according to a fourth embodiment of the present invention;
55. FIG. 10 is a pressure-enthalpy diagram related to a fifth
embodiment of the present invention;
56. FIG. 11 is a circuit diagram showing the air conditioner
according to a sixth embodiment of the present invention;
57. FIG. 12 is a circuit diagram showing the air conditioner
according to a seventh embodiment of the present invention;
58. FIG. 13 is a circuit diagram showing the air conditioner
according to the eighth embodiment of the present invention;
59. FIG. 14 is a flow chart showing a process for switching from a
forced circulation operation to a natural circulation operation
related to the eighth embodiment of the present invention;
60. FIG. 15 is a circuit diagram showing the air conditioner
according to a ninth embodiment of the present invention;
61. FIG. 16 is a flow chart showing a process for switching from a
forced circulation operation to a natural circulation operation
related to the ninth embodiment of the present invention;
62. FIG. 17 is a diagram showing the basic circuit of a
conventional air conditioner utilizing a natural circulation
operation;
63. FIG. 18 is a diagram showing the circuit of the air conditioner
according to the Conventional Example 1 with a natural circulation
operation and a forced circulation operation; and
64. FIG. 19 is a diagram showing the circuit of the air conditioner
according to the Conventional Example 2 with a natural circulation
operation and a forced circulation operation.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Embodiment 1
65. In the following, description will be made as to the first
embodiment of the present invention with reference to FIG. 1
showing a circuit diagram of an air conditioner such as an air
cooling apparatus. The air conditioner is adapted to conduct both a
forced circulation operation and a natural circulation
operation.
66. In FIG. 1, reference numeral 1 designates a compressor, numeral
2 a condenser, numeral 3 an outdoor fan, numeral 4 a refrigerant
flow controlling means such as an electronic expansion valve,
numeral 5 an outdoor unit, numeral 6 a liquid pipe, numeral 7 an
evaporator, numeral 8 an indoor fan, numeral 9 an indoor unit,
numeral 10 a gas pipe, numeral 11 an on-off means such as a check
valve, numeral 12 a bypass pipe, numeral 13 an on-off means such as
an on-off valve, numeral 14 an accumulator and numeral 15 an on-off
means such as a check valve.
67. As shown in FIG. 1, a refrigerant circuit is comprised of the
outdoor unit 5 and the indoor unit 9 which are connected by means
of the liquid pipe 6 and the gas pipe 10, wherein refrigerant is
circulated in the circuit.
68. The outdoor unit 5 comprises the compressor 1 for compressing a
refrigerant gas, the condenser 2 for liquefying the refrigerant
gas, the outdoor fan 3 as a blower to supply forcibly outer air to
an outer surface of the condenser 2, the electronic expansion valve
4 as a refrigerant flow controlling means which conducts pressure
reduction of a refrigerant liquid of high temperature and high
pressure discharged from the condenser to form a wet vapor in a
two-phase state, the accumulator 14 as a refrigerant storing means
which prevents the liquid from reversing to the compressor 1 in a
transient state or supercharging of the refrigerant, the bypass
pipe 12 including the check valve 11 to bypass the compressor 1 and
the accumulator 14 in the natural circulation operation, the on-off
valve 13 for preventing the refrigerant from entering into the
accumulator 14 in the natural circulation operation and the check
valve 15 for preventing the refrigerant from entering into the
compressor 1 in the natural circulation operation.
69. The indoor unit 9 comprises the evaporator 7 for vaporizing the
wet vapor introduced through the liquid pipe 6 into a refrigerant
gas depending on an air conditioning load in a space to be
air-conditioned and the indoor fan 8 as a blower to supply forcibly
to an outer surface of the evaporator 7.
70. The condenser 2 of the outdoor unit 5 is located at a higher
position than the evaporator 7 of the indoor unit 9, for example,
it is located with a positional difference in height of about 1.4
m.
71. The air conditioner is used in a place where air cooling is
required through the years, such as a shelter in which an electric
device which generates heat is housed. When an indoor air
temperature is lower than an outdoor air temperature, air cooling
in the room is conducted by the forced circulation operation in
which the compressor 1 is operated. Further, when an indoor air
temperature is higher than an outdoor air temperature, the
compressor 1 is stopped and air cooling in the room is conducted by
the natural circulation operation in which a cold outdoor air is
utilized. In the first embodiment, the cooling to a space to be
air-conditioned air is conducted by utilizing the refrigerant
vaporized in the evaporator 7.
72. In the following, description will be made as to the forced
circulation operation. A degree of opening of the electronic
expansion valve 4 is set to an appropriate degree of opening to
reduce the pressure of the refrigerant liquid discharged from the
condenser 2 to form a wet vapor of two-phase state; the
electromagnetic valve 13 at an inlet side of the accumulator 14 is
opened, and the compressor 1 is operated. In this case, the check
valve 11 is closed due to a pressure difference between a discharge
pressure and a suction pressure of the compressor 1. Thus,
refrigerant circuit for the forced circulation operation is
formed.
73. Then, description will be made as to the natural circulation
operation in a case that an outdoor air temperature is lower than
an indoor air temperature.
74. The compressor 1 is stopped; the electromagnetic valve 13 at an
inlet side of the accumulator 14 is closed, and the electronic
expansion valve 4 is fully opened to reduce a pressure loss in the
refrigerant circuit, for example. In this case, the check valve 11
is opened because of the flow of the refrigerant whereby the
refrigerant circuit for the natural circulation operation is
formed.
75. FIG. 2 shows an experimental result obtained under the
conditions as follows. An air conditioner as a test machine capable
of conducting the natural circulation operation by circulating
refrigerant in a refrigerant circuit comprising the evaporator 8
and the condenser 2 located at a higher position than the
evaporator 8, which were connected with a pipe, was prepared.
Different amounts of refrigerant (2.8 kg, 3.2 kg, 3.6 kg, 4.0 kg,
4.4 kg and 4.8 kg) were charged and natural circulation operations
were conducted to obtain a result of a cooling ability (kW), and a
degree of superheating at an outlet of the evaporator (.degree.C.)
and a degree of supercooling at an outlet of the condenser
(.degree.C.) to each charging amount of refrigerant in the natural
circulation operations. An upper graph in FIG. 2 shows a result of
the measurement of cooling abilities, and lower graph shows a
result of the measurement of degrees of superheating at an outlet
of the evaporator (black circles) and degrees of supercooling at an
outlet of condenser (white circles). The experiments were conducted
under the condition that a temperature difference .DELTA.T between
an indoor air temperature and an outdoor air temperature was
33.degree. C. and constant. The FIG. 2 shows the charging amount of
refrigerant in the refrigerant circuit for the natural circulation
operation.
76. As is understood from the upper graph of FIG. 2 showing the air
cooling ability, the cooling ability exhibits the maximum value
with a charging amount of refrigerant of 4 kg or its vicinity. The
reason why the air cooling ability increases with an increase of
the charging amount of refrigerant in a case that the charging
amount of refrigerant is less than 4 kg is that an effective height
of liquid column in the refrigerant circuit is increased with an
increase of the charging amount of refrigerant so that the
refrigerant flow rate is increased. Further, the reason why the air
cooling ability is decreased with an increase of the charging
amount of refrigerant in a case that the charging amount of
refrigerant exceeds 4 kg is that an enthalpy difference in the
evaporator is decreased because the refrigerant at the outlet of
the evaporator becomes a two-phase state, and a pressure loss in
the gas pipe extended from the outlet of the evaporator to the
inlet of the condenser is increased whereby the refrigerant flow
rate is decreased.
77. Further, as is understood from the lower graph of FIG. 2
showing the degree of superheating at the outlet of the evaporator,
the refrigerant at the outlet of the evaporator becomes a saturated
gas state (a degree of superheating at the outlet of the evaporator
of 0.degree. C.) in the charging amount of refrigerant in which the
air cooling ability becomes the maximum (a charging amount of
refrigerant of around 4 kg in the upper graph of FIG. 2).
Accordingly, when the charging amount of refrigerant is determined
to a value around 4 kg at the temperature difference of 33.degree.
C. between the outdoor and the indoor in this case, the cooling
ability in the natural circuit operation can be utilized to the
maximum and the maximum effect of reducing consumption power can be
obtained. Further, since the rate of reduction of the cooling
ability in using a refrigerant amount of 4 kg or more is larger
than that of a case of using an amount of 4 kg or lower, a nearly
maximum cooling ability can be obtained when the amount of the
refrigerant to be charged is not more than the charging amount
where the cooling ability becomes the maximum, for example, 3.5
kg-4.0 kg.
78. Further, as shown in FIG. 2, an appropriate charging amount of
refrigerant in the forced circulation operation under experimental
conditions is about 2 kg. In this case, it is understood that a
charging amount of refrigerant of about 2 times (4 kg/2 kg) in the
forced circulation operation should be charged in order to obtain
the maximum cooling ability in the natural circulation
operation.
79. FIG. 3 is a graph showing relations of a charging amount of
refrigerant (kg) in the natural circulation operation to a cooling
ability (kW) in cases of temperature difference .DELTA.T of
33.degree. C. and 10.degree. C. between an indoor air temperature
and an outdoor air temperature. As shown in FIG. 3, when the
temperature difference .DELTA.T between an indoor air temperature
and an outdoor air temperature becomes small, the charging amount
of refrigerant in which the maximum cooling ability can be obtained
is reduced. A dotted line in FIG. 3 is a linear line connecting
maximum values of the cooling ability in response to a change of
the temperature difference. This is derived from the fact that when
the temperature difference .DELTA.T becomes small, the degree of
supercooling at an outlet of condenser is decreased whereby an
effective height of liquid column in the refrigerant circuit is
decreased and the refrigerant flow rate is decreased. From this
fact, it is understood that when there is a small temperature
difference between the indoor and the outdoor because of, for
instance, outdoor temperature being higher, a smaller charging
amount of refrigerant provides a higher cooling ability in
comparison with a case that the temperature difference is
large.
80. FIG. 4 is a graph showing a relation between an outdoor air
temperature and a cooling ability (an air conditioning load) in the
natural circulation operation in a case of an indoor air
temperature of 38.degree. C. In FIG. 4, the abscissor represents an
outdoor air temperature (.degree.C.); the ordinate represents a
cooling ability and an air condition load; a curve A indicates an
air conditioning ability quantity to an outdoor air temperature in
a temperature range when a charging amount of refrigerant of 4 kg
is used; a curve B indicates an air conditioning ability quantity
to an outdoor air temperature in the temperature range when a
charging amount of refrigerant of 3.5 kg is used, and a curve C
indicates an air conditioning ability quantity to an outdoor air
temperature in the temperature range when a charging amount of
refrigerant of 3.0 kg is used. These air conditioning ability
quantities can be obtained by simulation or experiment using a
device constituting an air conditioner.
81. Further, in FIG. 4, dotted linear lines Z1 or Z2 indicates air
conditioning load quantity to an outdoor air temperature in a
temperature range when an indoor air temperature of 38.degree. C.
is determined.
82. The air conditioning load quantity to an outdoor air
temperature in several outdoor air temperatures can be obtained
based on a heat value of the device, a thermal capacity of the
shelter, and a heat value absorbed to or radiated from the wall in
a designing step.
83. In a case that an electric device is used in a space such as a
shelter where a man seldom comes in or goes out, and there is no
substantial change of heat value per unit time from the electric
device such as the air conditioner according to the first
embodiment, the air conditioning load quantity becomes large as the
outdoor air temperature becomes high, and the air conditioning load
quantity simply increases as indicated by linear lines Z1, Z2.
84. The air conditioning ability quantity, (i.e., the cooling
ability quantity in this case) in the natural circulation operation
is zero when the outdoor air temperature is 38.degree. C. which is
the same as the indoor temperature of 38.degree. C., and the air
conditioning ability quantity will increase as the outdoor air
temperature decreases from 38.degree. C. On the contrary, the air
conditioning load decreases as the outdoor air temperature
decreases because there is heat radiation from the indoor to the
outdoor. For example, assuming that an air conditioning load line
under a condition that the inside of the shelter is kept at
38.degree. C. or lower takes Z1. In this case, the outdoor air
temperature at which the cooling ability quantity is substantially
in agreement with the air conditioning load quantity, namely, the
outdoor air temperature at a crossing point of the cooling ability
curve and the air conditioning load line Z1 is the maximum outdoor
air temperature capable of conducting air conditioning at which the
natural circulation operation can cover the air conditioning load.
In more detail, when the charging amount of refrigerant indicated
by the cooling ability curve B is used, the curve B intersects the
air conditioning load line Z1 at an outdoor air temperature
21.degree. C., and therefore, the maximum outdoor air temperature
capable of conducting air conditioning is 21.degree. C. In this
case, the cooling ability in the natural circulation operation is
larger than or equal to the air conditioning load even at any
outdoor air temperature of the maximum outdoor air temperature
capable of air conditioning of 21.degree. C. or lower. Accordingly,
the cooling ability in the natural circulation operation is enough
to cover the air conditioning load.
85. Thus, the maximum outdoor air temperature capable of conducting
air conditioning at which the above-mentioned air conditioning
ability quantity and the above-mentioned air conditioning load
quantity substantially coincide is obtained in the respective
charging amounts of refrigerant.
86. In the first embodiment, in order to utilize at the maximum the
air conditioning ability of the air conditioner in the natural
circulation operation, the refrigerant is charged in the
refrigerant circuit so that the maximum outdoor air temperature
capable of conducting air conditioning has the highest value.
Namely, assuming that the air conditioning load quantity is
indicated by the linear line Z1 in FIG. 4, three curves A, B and C
intersects the linear line Z1. Among the intersecting points, the
charging amount of refrigerant of a cooling ability curve which
shows the highest outdoor air temperature is selected. Then, there
is obtainable a large temperature range wherein the air cooling
ability in the natural circulation operation can sufficiently cover
the air conditioning load quantity. In FIG. 4, the maximum outdoor
air temperature capable of conducting air conditioning at the point
of intersection of the curve B and linear line Z1 is the highest.
Accordingly, a refrigerant amount of 3.5 kg corresponding to the
curve B is the best. Thus, by determining the refrigerant amount to
be charged in the refrigerant circuit, a range of the outdoor air
temperature wherein the air conditioning load quantity is covered
by the natural circulation operation is the broadest, whereby the
maximum effect of reducing consumption power can be obtained.
87. The charging amount of refrigerant determined as described
above varies depending on a change of the air conditioning load
quantity. For example, in a case of the air conditioning load
quantity indicated by the linear line Z2, the maximum outdoor air
temperature capable of conducting air conditioning at the point of
intersection of the curve C and the linear line Z2 shows the
highest value. When the refrigerant amount of 3 kg corresponding to
the curve C is determined as a charging amount of refrigerant, the
outdoor air temperature range capable of covering the air
conditioning load quantity in the natural circulation operation
becomes the maximum.
88. In a range higher than the outdoor air temperature at the point
of the intersection of the air conditioning ability curve and the
air conditioning load linear line, it is impossible to cover the
air conditioning load quantity by the natural circulation
operation. Accordingly, the forced circulation operation is used
when the outdoor air temperature exceeds the value.
89. On the other hand, when the outdoor air temperature is lower
than the maximum outdoor temperature capable of conducting air
conditioning and if the outdoor air temperature eventually
increases to exceed the maximum outdoor air temperature whereby the
air conditioning load is increased, the degree of opening of the
electronic expansion valve 4 may be changed so that the degree of
superheating of the refrigerant in an outlet portion of the
evaporator 7 is controlled to nearly 0, for example. As shown in
FIG. 2, the cooling ability is the maximum when a state of the
refrigerant in the outlet portion of the evaporator is nearly
0.degree. C. in terms of a degree of superheating. In this case,
when the operation is conducted so that the degree of superheating
of the refrigerant in the outlet portion of the evaporator 7 takes
a value of nearly 0.degree. C., it is possible to increase the air
cooling ability in comparison with the case that the present
condition is continued.
90. Further, it is unnecessary to use the forced circulation
operation in a case that the outdoor air temperature does not
exceed a temperature at which the air conditioning load can be
covered by only the natural circulation operation. In this case,
the refrigerant circuit for the natural circulation operation is
used, and a refrigerant quantity wherein a temperature range in
which the air conditioning load quantity can be covered by the
natural circulation operation is the maximum is charged as
described above.
91. In the air conditioner utilizing the natural circulation
operation, only the outdoor fan 3 and the indoor fan 8 are required
as power for the operation, and accordingly, annual consumption
power can substantially be reduced. In particular, in the first
embodiment, since the charging amount is determined so that there
is obtainable a large range of outdoor air temperature capable of
air conditioning in the natural circulation operation, the annual
consumption power can further be reduced.
92. For example, a shelter model of 1.5 m wide, 3.7 m deep and 1.5
m high was prepared wherein Q1 represents a calorific power from
the device, Q2 represents heat absorbed to or emitted from the
wall, Q3 represents a cooling ability quantity of the indoor unit,
Q3c represents a cooling ability quantity of the indoor unit in the
forced circulation operation, and Q3n represents a cooling ability
quantity of the indoor unit in the natural circulation operation.
Simulation of temperature change in the shelter which was subject
to air conditioning was conducted. A set temperature range in air
conditioning in the shelter was determined to be 26.degree.
C.-38.degree. C. and an outdoor air temperature is to be 26.degree.
C.
93. FIGS. 6a and 6b show changes of temperature in the shelter with
time. FIG. 6a shows a change of temperature in a case that air
conditioning is conducted by only the forced circulation operation
with the compressor (usual type), and FIG. 6b shows a change of
temperature in a case that the natural circulation operation and
the forced circulation operation are used together (cooperation
type). When a temperature in the shelter becomes 38.degree. C. (as
an upper limit of the set temperature range) or higher, the
compressor is operated to conduct cooling operation by the forced
circulation operation. Further, when the temperature in the shelter
becomes 26.degree. C. (as a lower limit of the set temperature
range) or less, the compressor is stopped to stop the cooling
operation (FIG. 6a) and the compressor is stopped to conduct the
cooling by the natural circulation operation (FIG. 6b). In this
cooperation type, the maximum outdoor air temperature capable of
conducting air conditioning by the natural circulation operation is
to be 26.degree. C. or lower.
94. The inside of the shelter is cooled with a heat quantity of
Q1-Q2-Q3c by the forced circulation operation so that it is cooled
from 38.degree. C. to 26.degree. C. in .DELTA.tc (time). In the
usual type in FIG. 6a, when the operation of the compressor is
stopped, the temperature is gradually increased with a heat
quantity of Q1-Q2. Then, when the temperature reaches the upper
limit of the temperature range in .DELTA.tn1 (time), the compressor
is again operated. On the other hand, in the cooperation type in
FIG. 6b, when the operation of the compressor is stopped, the air
cooling operation is conducted by the natural circulation
operation. Accordingly, the temperature is gradually increased with
a heat quantity of Q1-Q2-Q3n. Then, it reaches the upper limit of
the set temperature range in .DELTA.tn2 (time) which is longer than
.DELTA.tn1 (time), and the compressor is again operated.
95. Thus, with the cooperation of the forced circulation operation
and the natural circulation operation, it is possible to elongate a
time in which the compressor is stopped, and operating efficiency
of the compressor is decreased from
.DELTA.tc/(.DELTA.tc+.DELTA.tn1) to
.DELTA.tc/(.DELTA.tc+.DELTA.tn2).
96. A result of the simulation reveals that the air conditioner of
cooperation type can reduce the annual operating efficiency of the
compressor to about 69-86% in comparison with the air conditioner
utilizing only the forced circulation operation. Further, the
number of stopping of the compressor can remarkably be decreased
and reliability is increased.
97. Further, the reduction of the operation time of the compressor
results the reduction the annual consumption power of about 51-66%.
In particular, in the air conditioner according to the first
embodiment wherein a charging amount of refrigerant which allows
the cooling ability by the natural circulation operation to be the
maximum, the above-mentioned effect can certainly be obtained.
Embodiment 2
98. An air cooling apparatus is exemplified as the air conditioner
according to the second embodiment of the present invention. FIG. 7
is a circuit diagram of the air conditioner according to the second
embodiment.
99. In FIG. 7, reference numerals 16 designate temperature
directing means such as temperature sensors, numerals 17 designate
pressure detecting means such as pressure sensors, numeral 18
designates a supercooling degree operating/controlling means to
operate a degree of supercooling of refrigerant in an outlet
portion of the condenser 2 to control it to be a predetermined
value, and numeral 19 designates a superheating degree
operating/controlling means to operate a degree of superheating of
the refrigerant in the outlet portion of the evaporator 7 to
control it to be a predetermined value. The supercooling degree
operating/controlling means 18 and the superheating degree
operating/controlling means 19 are respectively provided with a
refrigerant state detecting function and a controlling function to
properly controlling the refrigerant state detected. The same
reference numerals as in FIG. 1 designate the same or corresponding
parts.
100. The air conditioner of the second embodiment is constituted by
the outdoor unit 5, the indoor unit 9 and the liquid type 6 and the
gas pipe 10 which connect the outdoor unit 5 and the indoor unit 9
in the same manner as the first embodiment.
101. The outdoor unit 5 comprises the compressor 1 for compressing
a refrigerant gas, the condenser 2 for liquefying the refrigerant
gas, the outdoor fan 3, as a blower, to supply forcibly outer air
to an outer surface of the condenser 2, the electronic expansion
valve 4, as a refrigerant flow controlling means, which conducts
pressure reduction of the refrigerant of high temperature and high
pressure discharged from the condenser 2 to form a wet vapor in a
two-phase state, the accumulator 14 as a refrigerant storing means
which prevents the liquid from reversing to the compressor 1 in a
transient phenomenon or the supercharging of the refrigerant, the
bypass pipe 12 including a check valve 11 to bypass the compressor
1 and the accumulator 14 in the natural circulation operation, the
check value 11 as an on-off means for opening or closing the
accumulator 12 to the refrigerant circuit, the on-off valve 13 for
preventing the refrigerant from entering into the accumulator 14 in
the natural circulation operation and the check valve 15 as an
on-off means for preventing the refrigerant from entering into the
compressor 1 in the natural circulation operation.
102. The indoor unit 9 comprises the evaporator 7 for vaporizing
the wet vapor introduced through the liquid pipe 6 into a
refrigerant gas depending on an air conditioning load in a space to
be air-conditioned, and the indoor fan 8 as a blower to supply
outdoor air forcibly to a outer surface of the evaporator 7.
103. In this air conditioner, the forced circulation operation is
conducted when an outer air temperature is higher an indoor air
temperature. Namely, the degree of opening of the electronic
expansion valve 4 is set to an appropriate degree of opening so
that the pressure of the refrigerant liquid discharged from the
condenser 2 is reduced to form a wet vapor in a two-phase state;
the electromagnetic valve 13 at an inlet side of the accumulator 14
is opened, and the compressor 1 is operated. At this moment, the
check valve 11 is closed because of a pressure difference between a
discharge pressure and an intake pressure of the compressor 1,
whereby the refrigerant circuit for the forced c-circulation
operation is formed.
104. Further, when an outer air temperature is lower than an indoor
air temperature, the degree of opening of the electronic expansion
valve 4 is fully opened to reduce a pressure loss in the
refrigerant circuit and the electromagnetic valve 13 at an inlet
side of the accumulator 14 is closed. At this moment, the check
valve 11 is opened by the flow of the refrigerant, whereby the
refrigerant circuit for the natural circulation operation is
formed.
105. As mentioned in the first embodiment, in order to make the air
cooling ability in the natural circulation operation to be the
maximum, it is necessary for the forced circulation operation to
supply a charging amount of the refrigerant as about twice as that
in the natural circulation operation due to a difference in a
refrigerant flow rate or a length of the liquid portion.
Accordingly, the air conditioner should have such a structure that
an excessive amount of refrigerant liquid is stored in the
accumulator 14 as a refrigerant storing means in the forced
circulation operation. Then, at the time of switching to the
natural circulation operation, the excessive refrigerant stored in
the accumulator 14 is returned to the refrigerant circuit for the
natural circulation operation, i.e., a refrigerant recovering
operation is conducted.
106. As a method for recovering the refrigerant, the degree of
opening of the electronic expansion valve 4 is made smaller than
that in the forced circulation operation or the valve is fully
opened to throttle the refrigerant flow rate to be smaller or zero,
and the compressor 1 is operated for a predetermined time. At the
moment, the refrigerant in an outlet portion of the evaporator 7
becomes a state of superheating to produce a superheat gas. The
excessive refrigerant stored in the accumulator 14 is vaporized by
the superheat gas and the vaporized refrigerant is introduced into
the condenser 2 through the check valve 15. Such refrigerant
recovering operation is conducted for a predetermined time, e.g.,
about 2 minutes. After the refrigerant recovering operation is
finished, the compressor 1 is stopped. Then, the electromagnetic
valve 13 at an inlet side of the accumulator 14 is closed to
prevent the refrigerant from entering into the accumulator 14 which
is in a state of low temperature and low pressure at the time of
switching the operation to the natural circulation operation. In
this embodiment, a time necessary to evaporate the excessive
refrigerant stored in the accumulator 14 is previously obtained and
the refrigerant recovering operation is conducted in the previously
obtained time. However, means for detecting the temperature of the
refrigerant at a discharge side and an intake side of the
compressor 1 may be provided, and the refrigerant recovering
operation may be finished depending on set values.
107. In the following, description will be made as to a method for
controlling a refrigerant state in the natural circulation
operation.
108. As shown in FIG. 2, in the state where the cooling ability
becomes the maximum in the natural circulation operation, the
degree of superheating (indicated by a black circle) at an outlet
of the evaporator 7 is 0.degree. C. This phenomenon is utilized.
For example, a degree of superheating of 5.degree. C. which is near
0.degree. C. is taken as a set value. Then, when the degree of
superheating at the outlet of the evaporator 7 is controlled to
such set value of superheating, it is possible to operate the air
conditioner in a state around which the cooling ability becomes the
maximum. In this case, when the degree of superheating at the
outlet of the evaporator 7 takes a positive value, a detection
value on the degree of superheating changes in response to a change
of a state of the refrigerant. However, when the detection value on
the superheating is 0.degree. C., it shows a saturated gas
temperature whereby the detection value of the superheating is
0.degree. C. regardless of a state of the refrigerant, and the
detection value does not show a value lower than 0.degree. C.
Accordingly, it is preferred that the set value is a positive value
near 0.degree. C., for example, 5.degree. C. other than 0.degree.
C.
109. In fact, in the air conditioner according to the second
embodiment, when the natural circulation operation is conducted,
the degree of superheating at the outlet of the evaporator 7 is
controlled by changing the degree of opening of the electronic
expansion valve 4 as a refrigerant flow controlling means to
thereby change a refrigerant flow rate.
110. In the following, the controlling method is described. The
degree of superheating at the outlet of the evaporator 7 is
operated by the superheating degree operating/controlling means 19
based on values detected by the temperature sensor 16 and the
pressure sensor 17 located in the outlet portion of the evaporator
7. The degree of superheating can be operated according to a
superheating degree calculating formula (1) described below.
Degree of superheating (.degree.C.)=Detected value of
temperature-Saturated temperature based on detected value of
pressure (1)
111. Then, the calculated value of superheating degree and a set
value of superheating degree (for example, about 5.degree. C.) are
compared, and the degree of opening of the electronic expansion
valve 4 is operated based on a difference between the compared
values. Then, the degree of opening of the electronic expansion
valve 4 is set to the degree of opening obtained by the calculation
whereby the refrigerant flow rate is changed. For instance, when
the detected value of the superheating degree is larger than the
set value of superheating degree, the degree of opening of the
electronic expansion valve 4 is made large to increase the
refrigerant flow rate whereby the degree of superheating is
lowered. On the contrary, when the detected value of superheating
degree is smaller than the set value of superheating degree, the
degree of opening is made small to reduce the refrigerant flow rate
whereby the degree of superheating is increased. When such
processes are repeated with predetermined intervals, e.g. intervals
of about 5 minutes, the refrigerant flow rate can be changed
whereby the degree of superheating in the outlet portion of the
evaporator 7 is controlled to become the set value. Thus, the
natural circulation operation can be conducted so that the air
conditioning ability is usually at or around the maximum.
112. Particularly, since the flow rate of the refrigerant in the
natural circulation operation is smaller than that in the forced
circulation operation, the electronic expansion valve 4 should be
controlled with predetermined time intervals, e.g., time intervals
of about 5 minutes to change the refrigerant flow rate. This allows
the control at a rate suited for the movement of the refrigerant.
Accordingly, the natural circulation operation can stably be
conducted. The time intervals may be longer than 5 minutes, for
example, it is about 10 minutes.
113. Further, when an outdoor air temperature is high and a
temperature difference between the outdoor air temperature and a
set temperature for air conditioning for the room is small, a
refrigerant quantity which provides the maximum air cooling ability
is small as shown in FIG. 3. Accordingly, by changing the
refrigerant flow rate so that a degree of superheating in the
outlet portion of the evaporator 7 becomes a set value (for
example, about 5.degree. C. in superheating degree), a distribution
of the refrigerant quantity in the refrigerant circuit is changed,
an excessive refrigerant is accumulated in the outlet portion of
the condenser 2 whereby the degree of supercooling of the
refrigerant at the outlet of the condenser 2 is increased. Thus,
when the degree of supercooling of the refrigerant in the outlet
portion of the condenser 2 is increased, a surface area for the
condensation in the condenser 2 becomes small whereby efficiency in
the natural circulation operation becomes poor.
114. In the second embodiment, accordingly, the electromagnetic
valve is controlled so that a refrigerant state in the outlet
portion of the condenser 2 has a predetermined set value. For
example, the refrigerant flow rate is changed so that a degree of
superheating in the outlet portion of the evaporator 7 becomes a
set value in superheating degree, and at the same time, the
refrigerant quantity in the condenser 2 is changed so that the
degree of supercooling in the outlet portion of the condenser 2
becomes a set value in supercooling degree. Namely, the degree of
supercooling of the refrigerant in the outlet portion of the
condenser 2 is calculated by the supercooling degree
operating/controlling means 18 based on values detected by the
temperature sensor 16 and the pressure sensor 17 located at the
outlet portion of the condenser 2. The degree of supercooling can
be obtained by the supercooling degree calculating formula (2) as
follows.
Degree of supercooling (.degree.C.)=Saturated temperature based on
detected value of pressure-Detected value of temperature (2)
115. Then, the detected value in supercooling degree calculated and
the set value in supercooling degree (for example, about 8.degree.
C. in supercooling degree) are compared. When the detected value in
supercooling degree calculated exceeds a certain value with respect
to the set value in supercooling degree, the electromagnetic valve
13 located at the inlet side of the accumulator 14 is opened for a
predetermined time, e.g., about 10 seconds. Accordingly, excessive
refrigerant flowing in the gas pipe 10 flows into the accumulator
14 which is in a state of low temperature and low pressure. When
the electromagnetic valve 13 is again closed, the refrigerant
quantity in the refrigerant circuit in the natural circulation
operation is reduced and the refrigerant quantity in the condenser
is also reduced. Accordingly, the degree of supercooling of the
refrigerant in the outlet portion of the condenser 2 becomes small.
Thus, the degree of supercooling at the outlet of the condenser 2
can be controlled to a set value, and the state of the refrigerant
in the outlet portion of evaporator 7 and the condenser 2 can be
followed to a condition which renders the cooling ability to be the
maximum.
116. In this case, the excessive refrigerant in the accumulator 14
resulted from the control of the refrigerant quantity by the
supercooling degree operating/controlling means 18 is not
circulated in the refrigerant circuit during the natural
circulation operation. However, it can be returned to the
refrigerant circuit by the forced circulation operation with the
operation of the compressor 1 and the refrigerant recovering
operation.
117. As described above, the air conditioner according to the
second embodiment utilizes the phenomenon that in the natural
circulation operation, the air conditioning ability becomes the
maximum when the degree of superheating of the refrigerant in the
outlet portion of the evaporator 7. In the second embodiment,
control is conducted so that the degree of superheating at the
outlet of the evaporator 7 becomes a set value in superheating
degree (for example, about 5.degree. C. in superheating degree)
based on such phenomenon, whereby the air conditioner can provide
the maximum air conditioning ability in the natural circulation
operation without detecting an outdoor air temperature.
118. Further, in accordance with the second embodiment, the
reduction of efficiency caused by controlling the refrigerant state
in the outlet portion of the evaporator 7 can be prevented. For
this, control is so made that the refrigerant state in the outlet
portion of the condenser 2 becomes a set value (for example, about
8.degree. C. in supercooling degree). Thus, by controlling the
refrigerant state in the outlet portion of the evaporator 7 and the
condenser 2, a method for controlling the refrigerant so that the
air conditioning ability in the natural circulation operation
becomes the maximum, can be obtained. For example, there is a way
to store in the accumulator 14 as a refrigerant storing means an
excessive amount of refrigerant, which is resulted by changing the
refrigerant flow rate, in the condenser 2. In this case, even when
the temperature difference between an outdoor air temperature and
an indoor air temperature is small, the reduction of the surface
area for the condensation in the condenser 2 is prevented whereby
the deterioration of the efficiency in the natural circulation
operation can be prevented.
119. Further, in controlling the refrigerant state in the outlet
portion of the condenser 2 to be a predetermined degree of
supercooling, an excessive amount of refrigerant is stored in the
refrigerant storing means, i.e., the accumulator 14, which is
always required for the forced circulation operation, so that the
refrigerant quantity in the condenser 2 is changed. This permits
the control of the refrigerant quantity without requiring a special
device, and the air conditioning ability can be utilized to the
maximum in the natural circulation operation.
120. Further, since the adjustment of the refrigerant quantity is
conducted by the accumulator 14, the electromagnetic valve 13 and
the electronic expansion valve 4 without using any external device
such as an electric heater, a large effect of reducing consumption
power as an advantage of the natural circulation operation can be
obtained.
121. In the construction shown in FIG. 7, the refrigerant state in
the outlet portion of the condenser 2 is controlled along with the
control of the refrigerant state in the outlet portion of the
evaporator 7. This is, in particular, for the purpose that the
excessive refrigerant caused by changing the refrigerant flow rate
by the superheating degree operating/controlling means 19 does not
adversely affect the natural circulation operation. When the
temperature difference between an outdoor temperature and a set
temperature for air conditioning in the room is large, it is
unnecessary to reduce substantially the refrigerant flow rate, and
accordingly, a reduction on the efficiency due to an increase of
the degree of supercooling in the outlet portion of the condenser 2
is not so large. Accordingly, the control of the degree of
supercooling by the supercooling degree operating/controlling means
18 is not in particular required, and the supercooling degree
operating/controlling means 18 and the temperature sensor 18 and
the pressure sensor 17 used in association therewith can be
eliminated.
122. Further, since we have a higher outdoor air temperature in a
summer season and an effective refrigerant quantity in the
refrigerant circuit is preferred to be small, an excessive amount
of refrigerant is to be stored in the accumulator 14 by means of
the supercooling degree operating/controlling means 18. On the
other hand, since we have a lower outside air temperature in a
winter season and an excessive amount of refrigerant is not so
much, control for storing the refrigerant in the accumulator 14 is
not conducted.
123. Further, since the supercooling degree operating/controlling
means 18 and the superheating degree operating/controlling means 19
can be realized by microcomputer software respectively,
microcomputers may be housed in an electrical box for the outdoor
unit 5 or the indoor unit 9 to execute the software.
124. Target values for control on the refrigerant state in the
outlet portion of the evaporator 7 by means of the superheating
degree operating/controlling means 19 are such values: a degree of
dryness X of not less than 0.9 and a degree of superheating of not
more than 10.degree. C. The reason of determining a lower limit
value of 0.9 in terms of a degree of dryness in the outlet portion
of the evaporator 7 is that when the degree of dryness in the
outlet portion of the evaporator 7 is less than 0.9, a pressure
loss in the gas pipe 10 becomes large and therefore, the natural
circulation operation can not effectively performed. Further, when
the degree of superheating in the outlet portion of the evaporator
7 is larger than 10.degree. C., a superheating region in the
evaporator 7 is increased so that the heat transfer surface area
effective for the evaporation is decreased.
125. Further, it is desirable that the target values in terms of a
degree of supercooling in the outlet portion of the condenser 2 by
means of the supercooling degree controlling means 18 are a degree
of dryness of not more than 0.1 and a degree of supercooling of not
more than 20.degree. C. provided that the refrigerant state in the
outlet portion of the evaporator 7 is controlled by means of the
superheating degree operating/controlling means 19. If the degree
of dryness is larger than 0.1, the gas refrigerant will enter into
the liquid pipe 6 whereby the natural circulation operation becomes
unstable. Further, if the degree of supercooling is larger than
20.degree. C., the excessive refrigerant will accumulate around the
outlet portion of the condenser 2 so that a supercooling region in
the condenser 2 is increased to reduce the heat transfer surface
area effective for the condensation.
126. The degree of supercooling or the degree of dryness on the
refrigerant state in the outlet portion of the condenser 2 may be
controlled by changing the velocity of the outdoor fan 3 to change
an air flow rate to the condenser 2 other than by changing the
refrigerant quantity in the condenser 2 as described above. When
the velocity of the outdoor fan 3 is increased to increase the air
flow rate, the degree of supercooling is increased. On the other
hand, when the velocity of the outdoor fan 3 is reduced to reduce
the air flow rate, the degree of supercooling is reduced.
Embodiment 3
127. A method for controlling the air conditioner, as an air
cooling apparatus, according to the third embodiment of the present
invention will be described. FIG. 8 is a circuit diagram of the air
conditioner according to the third embodiment wherein the same
reference numerals as in FIG. 7 designate the same or corresponding
parts.
128. The superheating degree operating/controlling means 19 can
control to change the air flow rate to the evaporator 7 so that the
refrigerant state in the outlet portion of the evaporator 7 has a
predetermined degree of superheating. Further, the supercooling
degree operating/controlling means 18 opens or closes the on-off
valve 13 so that the refrigerant state in the outlet portion of the
condenser 2 has a predetermined degree of supercooling so that the
refrigerant quantity in the condenser 2 is changed by storing the
refrigerant in the accumulator 14, in the same manner as the second
embodiment.
129. Namely, the degree of superheating in the outlet portion of
the evaporator 7 is calculated by means of the superheating degree
operating/controlling means 19 based on detected values of the
temperature sensor 16 and the pressure sensor 17 located in the
outlet portion of the evaporator 7. The degree of superheating can
be calculated by the superheating degree calculating formula (1) as
follows.
Degree of superheating (.degree.C.)=Detected value of
temperature-Saturated temperature based on detected value of
pressure (1)
130. Then, the calculated value of superheating degree and a set
value on the superheating degree (for example, about 5.degree. C.
in superheating degree) are compared, and the velocity of the
indoor fan 8 is calculated based on a difference of the compared
values. Then, the velocity of the indoor fan 8 is determined to be
a velocity obtained by the calculation so as to change the air flow
rate. For example, when the detected value of superheating degree
is larger than the set value of superheating degree, the velocity
is reduced to reduce the air flow rate whereby the degree of
superheating is reduced. On the other hand, when the detected value
of superheating degree is smaller than the set value of
superheating degree, the velocity is increased to increase the air
flow rate whereby the degree of superheating becomes high. By
repeating such processes with predetermined intervals, e.g., time
intervals of about 5 minutes, the air flow rate to the evaporator 7
is changed so that the degree of superheating in the outlet portion
of the evaporator 7 can be controlled to reach the set value.
Accordingly, the natural circulation operation in which the air
conditioning ability is always at or around the maximum can be
conducted.
131. Target values on the refrigerant state in the outlet portion
of the evaporator 7 by means of the superheating degree
operating/controlling means 19 are set so that they are within a
value of a degree of dryness X of not less than 0.9 and a degree of
superheating of not more than 10.degree. C. The reason why a lower
limit value of 0.9 in terms of a degree of dryness in the outlet
portion of the evaporator 7 is that when the degree of dryness in
the outlet portion of the evaporator 7 is less than 0.9, a pressure
loss in the gas pipe 10 becomes large whereby the natural
circulation operation can not efficiently be conducted. On the
other hand, when the degree of superheating in the outlet portion
of the evaporator 7 is larger than 10.degree. C., a superheating
region in the evaporator 7 is increased so that the heat transfer
surface area effective for the evaporation is reduced.
132. Further, when the outdoor air temperature is high and the
temperature difference between the outdoor air temperature and a
set temperature for air conditioning in the room is small, the
refrigerant quantity for providing the maximum air cooling ability
is small as shown in FIG. 3. Accordingly, when the air flow rate is
changed so that the degree of superheating in the outlet portion of
the evaporator 7 becomes a set value (for example, about 5.degree.
C. in superheating degree), a distribution of refrigerant quantity
in the refrigerant circuit is changed, and the excessive
refrigerant is accumulated in the outlet portion of the condenser 2
whereby the degree of supercooling at the outlet of the condenser 2
is increased. Thus, an increase in the degree of supercooling in
the outlet portion of the condenser 2 causes the reduction of the
surface area of condensation in the condenser 2 become small
whereby efficiency in the natural circulation operation becomes
poor.
133. In the third embodiment of the present invention, the
refrigerant state in the outlet portion of the condenser 2 is also
controlled to have a predetermined set value in the same manner as
the second embodiment. For example, the refrigerant quantity in the
condenser is changed by using the accumulator 14 so that the degree
of supercooling in the outlet portion of the condenser 2 becomes a
set value in supercooling degree, e.g., 15.degree. C. Further, the
degree of supercooling can be controlled even by changing the
velocity of the indoor fan 3. Description with respect to the
control is omitted because it has been made in detail in the second
embodiment.
134. As descried above, the air conditioner according to the third
embodiment utilizes the phenomenon that the air conditioning
ability becomes maximum when the degree of superheating in the
outlet portion of the evaporator 7 is 0.degree. C. in the natural
circulation operation. By utilizing such phenomenon, control is so
made that the degree of superheating at the outlet of the
evaporator 7 becomes a set value in superheating degree (e.g.,
about 5.degree. C. in superheating degree). Accordingly, the air
conditioning ability in the natural circulation operation can be
utilized at maximum without detecting the outdoor air
temperature.
135. Further, the third embodiment of the present invention can
prevent the reduction of the efficiency of the air conditioner
caused by controlling the refrigerant state in the outlet portion
of the evaporator 7 for this, the refrigerant state in the outlet
portion of the condenser 2 is controlled so that it approaches a
suitable set value (e.g., about 15.degree. C. in supercooling
degree). Thus, by controlling the refrigerant state in the outlet
portion of the evaporator 7 and the condenser 2, a method for
controlling the refrigerant so that the maximum air conditioning
ability can be performed in the natural circulation operation, can
be provided.
Embodiment 4
136. A method for controlling the refrigerant in the air
conditioner such as an air cooling apparatus according to the
fourth embodiment of the present invention will be described. FIG.
9 is a circuit diagram of the air conditioner of the fourth
embodiment wherein the same reference numerals as in FIG. 7
designate the same or corresponding parts.
137. The superheating degree operating/controlling means 19
controls the refrigerant state in the outlet portion of the
evaporator 7 to be a predetermined degree of superheating by
changing the refrigerant quantity in the evaporator 7.
138. Namely, the degree of superheating in the outlet portion of
the evaporator 7 is calculated by means of the superheating degree
operating/controlling means 19 on the basis of values detected by
the temperature sensor 16 and the pressure sensor 17 located in the
outlet portion of the evaporator 7. The degree of superheating can
be calculated by the following superheating degree calculation
formula (1).
Degree of superheating (.degree.C.)=Detected value of
temperature-Saturated temperature based on detected value of
pressure (1)
139. Then, the detected value of superheating degree thus
calculated and a set value of superheating degree (e.g., about
5.degree. C. of superheating degree) are compared. When the
detected value of superheating degree is lower than the set value
of superheating degree, the on-off valve 13 is opened for a
predetermined time, e.g., about 10 seconds based on a difference in
the comparison. The fact that the detected value of superheating
degree is lower than the set value of superheating degree means
that the refrigerant quantity in the evaporator 7 is large and an
excessive refrigerant liquid flows in the gas pipe 10. Accordingly,
by opening and closing appropriately the on-off valve 13, a part of
the refrigerant liquid flowing in the gas pipe 10 flows into the
accumulator 14 to be stored. Accordingly, the degree of dryness in
the outlet portion of the evaporator 7 is increased, and the
refrigerant quantity is reduced, whereby the evaporator 7 keeps an
appropriate amount of the refrigerant, and the degree of
superheating in the outlet portion is changed to approach the set
value of superheating degree.
140. By repeating such processes with predetermined time intervals,
for example, intervals of about 5 minutes, the refrigerant quantity
in the evaporator 7 is changed, and the degree of superheating in
the outlet portion of the evaporator 7 is controlled to reach the
set value. Accordingly, the natural circulation operation can be
conducted so that the air conditional ability is always at or
around the maximum.
141. In this case, the change of the refrigerant quantity by
opening the on-off valve 13 means that the excessive refrigerant is
removed from the refrigerant circuit in the natural circulation
operation, and only the reduction of the refrigerant quantity in
the evaporator 7 is possible. However, there is no problem in
operation if a sufficient refrigerant quantity is put in the
circuit in consideration that an excessive amount of refrigerant is
produced in the natural circulation operation, and the excessive
refrigerant is gradually stored in the accumulator by checking a
change of the superheating degree, without varying a much amount
refrigerant in the accumulator 14 at once.
142. The excessive refrigerant in the accumulator 14 caused by
controlling the refrigerant quantity by means of the superheating
degree operating/controlling means 19 is not again circulated in
the refrigerant circuit during continued operation of natural
circulation. However, it can be returned to the refrigerant circuit
by the forced circulation operation with the operation of the
compressor 1 and the refrigerant recovering operation.
143. The control of the degree of superheating in the fourth
embodiment causes the reduction of the refrigerant quantity in the
evaporator 7. In fact, however, it reduces the refrigerant quantity
in the entire refrigerant circuit in the natural circulation
operation. Accordingly, such phenomenon that as in the second
embodiment and the third embodiment, a distribution of refrigerant
quantity is changed by changing the refrigerant flow rate or the
air flow rate and the excessive refrigerant stays in the condenser
2 does not appear. Accordingly, unlike the second embodiment and
the third embodiment wherein the refrigerant state in the outlet
portion of the condenser 2 is controlled, the natural circulation
operation in which the air conditioning ability is performed at the
maximum can be conducted. The second embodiment to the fourth
embodiment concern such method that the refrigerant flow rate, the
air flow rate to the evaporator 7 or the refrigerant quantity in
the evaporator 7 is changed so that the refrigerant state in the
outlet portion of the evaporator 7 has a predetermined degree of
superheating. Namely, it is sufficient to change at least one of
the refrigerant flow rate, the air flow rate to the evaporator 7
and the refrigerant quantity in the evaporator 7. Depending on
circumstances, however, all these three conditions: the refrigerant
flow rate, the air flow rate to the evaporator 7 and the
refrigerant quantity in the evaporator 7 may be changed so that the
refrigerant state in the outlet portion of the evaporator 7 becomes
to have a predetermined degree of superheating, or two conditions
among the above-mentioned three conditions may be changed so as to
render the refrigerant state to have a predetermined degree of
superheating.
Embodiment 5
144. Description will be made as to a method for controlling
refrigerant in an air conditioner according to the fifth embodiment
of the present invention. In the fifth embodiment, a controlled
target range for the degree of superheating is used for the
refrigerant state in the outlet portion of the evaporator, and a
controlled target range for the degree of supercooling is used for
the refrigerant state in the outlet portion of the condenser. The
circuit diagram of the air conditioner according to the fifth
embodiment is the same as that of FIG. 7.
145. FIG. 10 is a pressure-enthalpy diagram wherein F represents a
saturated liquid line (a saturated gas line) G1 represents a
saturated pressure corresponding to an indoor air temperature and
G2 represents a saturated pressure corresponding to an outdoor air
temperature. H represents a cycle showing a change of state on the
pressure-enthalpy line wherein a range D represents a controlled
target range on a degree of dryness (inside of the saturated gas
line F) and a degree of superheating (outside of the saturated gas
line F) in the outlet portion of the evaporator 7, and a range E is
a controlled target range on a degree of dryness (inside of the
saturated liquid line F) and a degree of supercooling (outside of
the saturated liquid line F) in the outlet portion of the condenser
2.
146. In the controlled target range D, when the refrigerant state
in the outlet portion of the evaporator 7 shows a degree of
superheating=0.degree. C., the air conditioning ability is the
maximum and it is on the saturated gas line. The degree of
superheating increases as the state is shifted to a right side on
the saturated gas line in FIG. 10. On the other hand, the degree of
superheating is remained 0.degree. C. in a left side portion on the
saturated gas line. For that portion, a degree of dryness X is used
instead of the degree of superheating, as an index representing the
refrigerant state. The degree of dryness decreases as the state is
shifted on a left side on the saturated gas line. The controlled
target range D of the refrigerant state in the outlet portion of
the evaporator 7 is preferably in ranges of not less than 0.9 in
terms of a degree of dryness X and not more than 10.degree. C. in
terms of a degree of superheating.
147. Here, the degree of dryness is the ratio of a refrigerant gas
flow rate to the entire refrigerant flow rate, and it can be
calculated by the following dryness calculation formula (3).
Degree of dryness=Gas flow rate in mass/Gas flow rate in
mass+Liquid flow rate) (3)
148. A set value for the refrigerant state in the outlet portion of
the evaporator 7 is determined within the range D, and then, the
refrigerant flow rate, the air flow rate to the evaporator 7 or the
refrigerant quantity in the evaporator 7 is controlled so that
refrigerant state reaches the set value. As described before, the
degree of superheating can be calculated from the above mentioned
formula (1) based on values detected by the temperature sensor 16
and the pressure sensor 17 by using the before-mentioned formula 1.
Further, the degree of dryness can be obtained by, for example,
providing a dryness degree detecting sensor in the outlet portion
of the evaporator 7.
149. The reason why a lower limit of 0.9 in terms of degree of
dryness in the outlet portion of the evaporator 7 is that when the
degree of dryness in the outlet portion of the evaporator 7 is less
than 0.9, a pressure loss in the gas pipe 10 becomes large, and the
natural circulation operation can not efficiently be performed. On
the other hand, when the degree of superheating in the outlet
portion of the evaporator 7 is larger than 10.degree. C., a
superheating region in the evaporator 7 is increased so that the
heat transfer surface area effective for the evaporation is
reduced. Accordingly, the set value for the refrigerant state in
the outlet portion of the evaporator 7 should be values in the
range of not less than 0.9 in terms of a degree of dryness and not
more than 10.degree. C. in terms of a degree of superheating so
that the heat transfer surface area in the evaporator can
effectively be utilized while an increase in the pressure loss in
the gas pipe is controlled.
150. For example, when the refrigerant state in the outlet portion
of the evaporator 7 is controlled by changing the refrigerant flow
rate by means of the electronic expansion valve 4 within the target
range D and if the refrigerant state is desired to change in a
right side direction i.e., the degree of superheating is made
larger or the degree of dryness is made larger, the degree of
opening of the electronic expansion valve 4 is throttled to reduce
the refrigerant flow rate. On the contrary, when the refrigerant
state is to be changed in a left side direction, namely, the degree
of superheating is made smaller or the degree of dryness is made
smaller, the degree of opening of the electronic expansion valve 4
is increased so as to increase the refrigerant flow rate.
151. Further, for example, when the refrigerant state in the outlet
portion of the evaporator 7 is controlled by changing the velocity
of the indoor fan 8, hence, the air flow rate to the evaporator 7
is changed and if the refrigerant state is to be changed in a right
side direction, i.e., the degree of superheating is made larger or
the degree of dryness is made larger, the velocity of the indoor
fan 8 is increased to increase the air flow rate. On the contrary,
when refrigerant state is to be changed in a left side direction,
i.e., the degree of superheating is made smaller or the degree of
dryness is made smaller, the velocity of the indoor fan 8 is
decreased to decrease the air flow rate.
152. Further, for example, when the refrigerant state in the outlet
portion of the evaporator 7 by opening the electromagnetic valve 13
to change the refrigerant quantity in the evaporator 7, i.e., the
refrigerant quantity in the evaporator 7 is reduced, the
refrigerant state is changed in a right side direction.
153. Further, the controlled target range E for the refrigerant
state at the outlet of the condenser 2 is preferably in the range
of not more than 0.1 in terms of a degree of dryness X and not more
than 20.degree. C. in terms of a degree of supercooling. As
described before, the degree of supercooling can be calculated from
the before-mentioned supercooling degree calculation formula (2)
based on values detected by the temperature sensor 16 and the
pressure sensor 17. Further, the degree of dryness can be obtained
by providing, for instance, a dryness sensor in the outlet portion
of the condenser 2.
154. The reason why an upper limit of 0.1 in terms of a degree of
dryness in the outlet portion of the condenser 2 is that if the
degree of dryness in the outlet portion of the condenser 2 is
larger than 0.1, the gas refrigerant flows into the liquid pipe 6
and the natural circulation operation becomes unstable. On the
other hand, when the degree of supercooling in the outlet portion
of the condenser 2 is larger than 20.degree. C., a supercooling
region in the condenser 2 is increased and the heat transfer
surface area effective for the condensation is reduced.
Accordingly, the set value for the refrigerant state in the outlet
portion of the condenser should be within the range of not more
than 0.1 in terms of a degree of dryness and not more than
20.degree. C. in terms of a degree of supercooling so that the heat
transfer surface area in the condenser can effectively utilized and
the natural circulation operation can stablly be conducted.
155. For example, when the refrigerant state in the outlet portion
of the condenser 2 is controlled by changing the refrigerant flow
rate by means of the electronic expansion valve 4 in the controlled
target range E, and if the refrigerant state is to be changed in a
right side direction, i.e., the degree of supercooling is made
smaller or the degree of dryness is made larger, the degree of
opening of the electronic expansion valve 4 is increased so as to
increase the refrigerant flow rate. On the contrary, when the
refrigerant state is to be changed in a left side direction, i.e.,
the degree of supercooling is made larger or the degree of dryness
is made smaller, the degree of opening of the electronic expansion
valve 4 is made small so as to reduce the refrigerant flow
rate.
156. Further, for example, when the refrigerant state in the outlet
portion of the condenser 7 is controlled by changing the velocity
of the outdoor fan 3 to change the air flow rate to the condenser
2, and if the refrigerant state is to be changed in a right side
direction, i.e., the degree of supercooling is made smaller or the
degree of dryness is made larger, the velocity of the outdoor fan 3
is reduced to reduce the air flow rate. On the contrary, when the
refrigerant state is to be changed in a left side direction, i.e.,
the degree of superheating is made larger or the degree of dryness
made smaller, the velocity of the outdoor fan 3 is increased to
increase the air flow rate.
157. Further, for example, when the refrigerant state in the outlet
portion of the condenser 2 is controlled by opening the
electromagnetic valve 13 to change the refrigerant quantity in the
condenser 2 and if the refrigerant quantity in the condenser 2 is
reduced by opening the electromagnetic valve 13, the refrigerant
state is changed in a right side direction.
158. Thus, by controlling the refrigerant state in the outlet
portion of the evaporator 7 and the refrigerant state in the outlet
portion of the condenser 2, the maximum air conditioning ability
can be performed in the natural circulation operation, and effect
for reducing consumption power as an advantage in the natural
circulation operation can further be improved.
159. The above-mentioned operation to obtain the maximum air
conditioning ability in the natural circulation operation by
controlling the refrigerant state in the outlet portion of the
evaporator 7 and/or the outlet portion of the condenser 2 is
preferably conducted in a case that the temperature difference
between the outdoor air temperature and a set temperature for air
conditioning is 25.degree. C. or lower. The reason is described
with reference to FIG. 4. Assuming that the temperature difference
between the outdoor air temperature and a set temperature for air
conditioning is 25.degree. C. or higher and a set temperature for
the room is 38.degree. C. When the outdoor air temperature becomes
lower than 13.degree. C., the air conditioning load is reduced so
that the inside of the shelter as a space to be air-conditioned is
excessively cooled due to an excessive air cooling ability.
Accordingly, use of the above-mentioned temperature difference
prevents reduction in reliability for communication devices
disposed in the shelter.
Embodiment 6
160. Description will be made as to the air conditioner, e.g., an
air cooling apparatus according to the sixth embodiment of the
present invention.
161. FIG. 11 is a circuit diagram of the air conditioner of the
sixth embodiment. In FIG. 11, reference numeral 20 designates a
refrigerant storing means as a reservoir located in an outlet
portion of the condenser 2 to store the refrigerant liquid from the
condenser 2. The outdoor unit 5 is provided with an outdoor air
temperature sensor 16 for detecting an outdoor air temperature. In
FIG. 11, the same reference numerals as FIG. 1 designate the same
or corresponding parts.
162. The air conditioner of the sixth embodiment comprises the
outdoor unit 5, the indoor unit 9 and the liquid pipe 6 and the gas
pipe 10 which connect these units.
163. The outdoor unit 5 comprises the compressor 1 for compressing
refrigerant gas, the condenser 2 for liquefying the refrigerant
gas, the outdoor fan 3, as a blower, to supply forcibly outer air
to an outer surface of the condenser 2, the electronic expansion
valve 4 as a refrigerant flow controlling means, which conducts
pressure reduction of the refrigerant of high temperature and high
pressure discharged from the condenser 2 to form a wet vapor in
two-phase state and the reservoir 20 for storing the refrigerant
liquid.
164. The indoor unit 9 comprises the evaporator 7 for vaporizing
the wet vapor introduced through the liquid pipe into refrigerant
gas depending on an air conditioning load in a space to be
air-conditioned, and the indoor fan 8 as a blower to supply room
air forcibly to the outer surface of the evaporator 7.
165. The reservoir 20 as a refrigerant storing means is located at
a level corresponding to a lower portion of the condenser 2. A pipe
connecting the reservoir 20 to the condenser 2 to pass the
refrigerant from the condenser 2 and a pipe connecting the
reservoir 20 to the electronic expansion valve 4 are respectively
connected to lower portions of the reservoir 20. The reservoir 20
has a capacity sufficient to receive the refrigerant liquid
corresponding to a proper quantity of refrigerant which is resulted
from the difference in function between the forced circulation
operation and the natural circulation operation. In this case, the
reservoir 20 is provided in place of the accumulator 14 used in the
second embodiment.
166. In the air conditioner of the sixth embodiment, when the
forced circulation operation is conducted, the degree of opening of
the electronic expansion valve 4 is adjusted to an appropriate
degree of opening to reduce the pressure of the refrigerant liquid
discharged from the condenser 2 to be a wet vapor in a two-phase
state. And also, the compressor 1 is operated. In this case, the
check valve 11 is closed due to the pressure difference between a
discharge pressure and an intake pressure of the compressor 1, thus
a cycle of the forced circulation operation is formed.
167. Further, in starting the natural circulation operation, when
the electronic expansion valve 4 is fully opened for example, the
check valve 11 is opened according to the refrigerant flow and a
cycle of natural circulation is formed. In this case, the
refrigerant tends to flow in a flow path to the compressor 1.
However, the flow resistance of the inside of the compressor 1 is
very high in comparison with the flow resistance of the bypass pipe
12. Accordingly, the refrigerant flow rate passing through the
compressor 1 is small as being neglected with respect to the
refrigerant flow rate passing through the bypass pipe 12.
168. In the above-mentioned second embodiment to fourth embodiment,
description has been made on the method for controlling the
refrigerant so that the air cooling ability in the natural
circulation operation can be utilized to the maximum wherein a
degree of superheating as a refrigerant state in the outlet portion
of the evaporator 7 is detected by means of the temperature sensor
16 and the pressure sensor 17 provided in the outlet portion of the
evaporator 7, and the detected degree of superheating is determined
to be a set value to conduct the control. In the sixth embodiment,
however, a degree of supercooling of the refrigerant at the outlet
of the condenser 2 is detected by means of the temperature sensor
16 and the pressure sensor 17 provided in the outlet portion of the
condenser 2, and the degree of supercooling in the outlet portion
of the condenser 2 is determined to be a set value for conducting
the control in response to the detected degree of supercooling and
an outdoor air temperature. The sixth embodiment uses a method for
controlling the degree of superheating in the outlet portion of the
evaporator 7 to be a set value by controlling the degree of
supercooling in the outlet portion of the condenser 2.
169. As shown in FIG. 2, the degree of superheating in the outlet
portion of the evaporator is simply reduced and the degree of
supercooling in the outlet portion of the condenser is simply
increased as the refrigerant amount is increased. Namely, a value
of superheating degree in the outlet portion of the evaporator and
a value of supercooling degree in the outlet portion of the
condenser is in a relation of 1:1. For example, the graph at a
lower side of FIG. 2 shows a change of the superheating degree
(black circles) in the outlet portion of the evaporator and a
change of the supercooling degree (white circles) in the outlet
portion of the condenser with respect to a refrigerant quantity
when the temperature difference between an outdoor air temperature
and a set temperature for air conditioning is 33.degree. C. From
this relation, control may be conducted such that the degree of
superheating in the outlet portion of the evaporator is determined
to be a desired set value, e.g., 0.degree. C., and instead, the
degree of supercooling in the outlet portion of the condenser is
determined to a set value such as 15.degree. C. so as to correspond
to the value of superheating. The relation of the degree of
superheating to the degree of supercooling will change depending on
a change of the temperature difference between an outdoor air
temperature and a set temperature for air conditioning.
Accordingly, in the sixth embodiment, control is so made that a
degree of supercooling at the outlet of the condenser which
corresponds to a set value (e.g., 0.degree. C.) in terms of a
degree of superheating of the refrigerant state at the outlet of
the evaporator; an outdoor air temperature is detected; the
temperature difference between the detected outdoor air temperature
and the set temperature for air conditioning is obtained, and the
degree of supercooling in the outlet portion of the condenser is
determined to be a set value under the condition of the temperature
difference. Specifically, the degree of supercooling in the outlet
portion of the condenser 2 is controlled by changing the
refrigerant flow rate by means of the electronic expansion valve 4,
by increasing or decreasing the velocity of the outdoor fan 3 to
change the air flow rate to the condenser 2, or by increasing or
decreasing the velocity of the indoor fan 8 to change the air flow
rate to the evaporator 7.
170. The method for controlling refrigerant in the sixth embodiment
will be described in more detail.
171. In the sixth embodiment, an accumulator is not disposed near
an sucking portion of the compressor 1. Accordingly, the reservoir
20 functions to adjust a difference of refrigerant quantity
resulted from the difference of function between the forced
circulation operation and the natural circulation operation.
Namely, since a refrigerant quantity required in the forced
circulation operation is smaller than that in the natural
circulation operation, an excessive refrigerant in a state of
supercooled liquid from the outlet portion of the condenser 2 is
stored in the reservoir 20.
172. In the natural circulation operation, the degree of
supercooling in the outlet portion of the condenser 2 is calculated
by the supercooling degree operating/controlling means 18 based on
values detected by the temperature sensor 16 and the pressure
sensor 17 provided in the outlet portion of the condenser 2. The
calculation can be conducted according to the following
supercooling degree circulation formula (2).
Degree of supercooling (.degree.C.)=Saturated temperature based on
detected value of pressure-Detected value of temperature (2)
173. Then, the degree of supercooling obtained by the calculation
and the set value of degree of supercooling based on the
temperature difference between the outdoor air temperature detected
by the outdoor temperature sensor 16 and the set temperature for
air conditioning are compared. Then, the degree of opening of the
electronic expansion valve 4 is calculated based on a value of
difference obtained by comparison. Finally, the degree of opening
of the electronic expansion valve 4 is set to a value obtained by
the calculation. By repeating such operations with predetermined
time intervals, e.g., 5 minutes, the degree of supercooling at the
outlet of the condenser 2 can be controlled to a set value in
response to the temperature difference between the outdoor air
temperature and the set temperature for air conditioning. Such
control is the same as the control wherein the degree of
superheating showing the refrigerant state in the outlet portion of
the evaporator 7 is so adjusted that the air conditioning ability
is at or around the maximum.
174. For example, when the refrigerant state in the outlet portion
of the condenser 2 is controlled by changing the refrigerant flow
rate by the electronic expansion valve 4 and if the degree of
supercooling is made smaller or the degree of dryness is made
larger, the degree of opening of the electronic expansion valve 4
is made large so as to increase the refrigerant flow rate. On the
other hand, when the degree of supercooling is to be made large or
the degree of dryness is to be made small, the degree of opening of
the electronic expansion valve 4 is made small so as to reduce the
refrigerant flow rate.
175. Further, the refrigerant state in the outlet portion of the
condenser 2 can be controlled by changing the velocity of the
outdoor fan 3 to change the air flow rate to the condenser 2. For
example, when the degree of supercooling is made small or the
degree of dryness is made large, the velocity of the outdoor fan 3
is reduced so as to reduce the air flow rate. On the other hand,
when the degree of supercooling is made large or the degree of
dryness is made small, the velocity of the outdoor fan 3 is
increased so as to increase the air flow rate.
176. In case that an outdoor air temperature is high and a
temperature difference between the outdoor air and the room is
small, a refrigerant quantity providing the maximum air cooling
ability becomes small as shown in FIG. 3. Accordingly, an excessive
refrigerant quantity is accumulated in the outlet portion of the
condenser 2 by properly changing the refrigerant flow rate or the
air flow rate. In the sixth embodiment, since the excessive
refrigerant is stored in the reservoir 20 provided in the outlet
portion of the condenser 2, it is possible to maintain the
refrigerant in the vicinity of the condenser 2 to be an appropriate
state regardless of a change of the outdoor air temperature.
177. Further, the air conditioner of the sixth embodiment may be
provided with the accumulator 14 as shown in FIG. 7 without
providing the reservoir 20, and the supercooling degree
operating/controlling means 18 is so controlled as to open or close
the on-off valve 13 so that the degree of supercooling in the
outlet portion of the condenser is calculated, and the calculated
value of supercooling is determined to be a set value. In this
case, the degree of supercooling or the degree of dryness in the
outlet portion of the condenser is controlled by changing an
effective quantity of refrigerant in the refrigerant circuit in the
natural circulation operation. In this case, the degree of opening
of the electronic expansion valve 4 should be fixed to be constant
such as being fully opened.
178. As described above, since the air conditioner of the sixth
embodiment wherein an outdoor air temperature is detected, and the
degree of supercooling or the degree of dryness in the outlet
portion of the condenser 2 is controlled to be an appropriate
value, the evaporator 7 and the condenser 2 are always maintained
in a suitable state, and the air cooling ability in the natural
circulation operation is performed to the maximum.
179. Further, in the circuit structure shown in FIG. 11, since the
adjustment of the refrigerant quantity is conducted by the
reservoir 20 provided near a lower portion of the outlet portion of
the condenser 2 without using an external input such as an electric
heater, a large effect of reducing consumption power can be
obtained.
180. Further, the reservoir 20 is provided between the outlet of
the condenser 2 and the electronic expansion valve 4. Accordingly,
when the operation is changed from the forced circulation operation
to the natural circulation operation, the above-mentioned
refrigerant recovering operation is unnecessary. Namely, the
refrigerant liquid stored in the reservoir 20 can instantaneously
be circulated by increasing, e.g., fully opening, the degree of
opening of the electronic expansion valve 4 for the natural
circulation operation.
181. An excessive refrigerant produced in the natural circulation
operation or the forced circulation operation is automatically
stored in the reservoir 20 as a refrigerant storing means.
Therefore, it is unnecessary to examine an excessive refrigerant or
to conduct a complicated control such as opening or closing the
on-off valve in response to the excessive refrigerant. Further, the
adjustment of the refrigerant quantity can be automatically
conducted in such a manner that the refrigerant quantity in the
condenser or the evaporator is reduced by storing the excessive
refrigerant or the refrigerant quantity in the condenser or the
evaporator is increased by discharging the stored refrigerant.
182. Further, since the refrigerant state in the outlet portion of
the evaporator 7 can be controlled by controlling the refrigerant
state only in the outlet portion of the condenser, the air
conditioner having a simple structure wherein the air conditioning
ability in the natural circulation operation can be performed to
the maximum is obtainable.
183. Concerning the controlled target value for the refrigerant
state in the outlet portion of the condenser 2, the same
explanation as in the fifth embodiment applies. Namely, the degree
of supercooling or the degree of dryness in the outlet portion of
the condenser 2 is determined to be in ranges of not less than 0.9
in terms of a degree of dryness X and not more than 10.degree. C.
in terms of a degree of superheating. The reason why an upper limit
value of 0.9 in terms of a degree of dryness in the outlet portion
of the evaporator 7 is determined is that if the degree of dryness
is smaller than 0.9, a pressure loss in the gas pipe 10 is
increased so that the natural circulation operation can not
effectively be conducted. On the other hand, when the degree of
superheating in the outlet portion of the evaporator 7 is larger
than 10.degree. C., a superheating region in the evaporator 7 is
increased whereby the heat transfer surface area effective for the
evaporation is reduced.
184. In determining the degree of supercooling in the outlet
portion of the condenser 2 based on a set value of superheating in
the outlet portion of the evaporator 7, the set value of
supercooling may be modified slightly so that the degree of dryness
in the outlet portion of the condenser 2 is not more than 0.1 and
the degree of supercooling is not more than 20.degree. C. The
reason is as follows. When the degree of dryness in the outlet
portion of the condenser 2 is larger than 0.1, the gas refrigerant
enters in the liquid pipe 6 to make the natural circulation
operation unstable, and when the degree of supercooling is larger
than 20.degree. C., the supercooling region in the condenser 2 is
increased whereby the heat transfer surface area effective for
condensation is reduced.
Embodiment 7
185. In the following, description will be made as to the air
conditioner as an air cooling apparatus according to the seventh
embodiment of the present invention.
186. FIG. 12 is a circuit diagram of the air conditioner of the
seventh embodiment. The air conditioner of the seventh embodiment
is operated so that air cooling is conducted only by the natural
circulation operation under the condition that the outdoor air
temperature is not higher than a set value in a space to be
air-conditioned. Namely, the air conditioner is usually used for
air cooling by a cold heat from the outside.
187. The air cooling apparatus according to the seventh embodiment
will be described with reference to FIG. 12 wherein the same
reference numerals designate the same or corresponding parts.
188. The condenser 2 is placed at, for example, a position of about
1.4 m higher than the evaporator 7 in the same manner as the first
embodiment. Further, the circuit structure is constituted by the
outdoor unit 5, the indoor unit 9 and liquid pipe 6 and the gas
pipe 10 which connect these units in the same manner as the first
embodiment.
189. The outdoor unit 5 comprises the condenser 2 for liquefying
the refrigerant gas, the outdoor fan 3, as a blower, to supply
outer air forcibly to an outer surface of the condenser 2, the
electronic expansion valve 4, as a refrigerant flow controlling
means, which is disposed in a pipe at a position between an outlet
portion of the condenser 2 and an inlet portion of the evaporator 7
to control the refrigerant flow rate, and the reservoir 20 as a
refrigerant storing means for storing the refrigerant liquid in the
outlet portion of the condenser.
190. The indoor unit 9 comprises the evaporator 7 for vaporizing
the refrigerant liquid introduced from the liquid pipe 6 into the
refrigerant gas depending on an air conditioning load in a space to
be air-conditioned and the indoor fan 8 as a blower to supply
indoor air forcibly to an outer surface of the evaporator 7.
191. The reservoir 20 is disposed at a level corresponding to a
lower portion of the condenser 2. A pipe through which the
refrigerant from the condenser 2 flows and a pipe for passing the
refrigerant into the electronic expansion valve 4 are connected to
lower portions of the reservoir 20. The reservoir 20 is to supply
an effective amount of refrigerant in the refrigerant circuit in
the natural circulation operation depending on a temperature
difference between an outdoor air temperature and a set temperature
for air conditioning. It is sufficient for the reservoir in the
seventh embodiment to have a smaller capacity than the reservoir
used in the air conditioner usable for both the forced circulation
operation and the natural circulation operation in the sixth
embodiment.
192. In the following, a method for controlling refrigerant in the
natural circulation operation will be described.
193. First, as shown in FIG. 4, an amount of refrigerant in which
the outdoor air temperature capable of air conditioning shows the
maximum with respect to an air conditioning load to the air
conditioner, is charged in the refrigerant circuit of the seventh
embodiment. Then, the natural circulation operation is started.
When the outdoor air temperature is lower than the maximum outdoor
air temperature capable of air conditioning, the air conditioning
ability sufficiently covers the air conditioning load. If the air
conditioning ability is too large to cover the air conditioning
load so that the room to be air-conditioned is excessively cooled,
the operation of, for example, the indoor fan 8 and/or the outdoor
fan 3 should be stopped so as to control the air flow rate to the
evaporator 7 and/or the condenser 2 whereby the heat exchanging
rate be reduced.
194. On the other hand, when the outdoor air temperature exceeds
the maximum outdoor air temperature capable of air conditioning,
the operation is controlled so as to provide the maximum air
conditioning ability obtainable in the structure of this
embodiment. As shown in FIG. 2, there is the phenomenon that the
degree of superheating in the outlet portion of the evaporator 7 is
0.degree. C. at which the air conditioning ability becomes the
maximum even though there is a change of the temperature difference
between the outdoor air temperature and a set temperature for air
conditioning. This phenomenon is utilized. For example, the set
temperature of superheating is determined to have a positive value
close to 0.degree. C. such as 5.degree. C., and the degree of
superheating at the outlet of the evaporator 7 is controlled to
reach the set value of superheating whereby the operation in a
state that the air cooling ability is at or around the maximum can
be obtained.
195. In the air conditioner according to the seventh embodiment,
the control for the degree of superheating in the outlet portion of
the evaporator 7 in the natural circulation operation is as
follows. Namely, the degree of superheating in the outlet portion
of the evaporator 7 is calculated by means of the superheating
degree operating/controlling means 19 based on values detected by
the temperature sensor 16 and the pressure sensor 17 located in the
outlet portion of the evaporator 7. The degree of superheating can
be calculated by the following superheating degree calculation
formula (1).
Degree of superheating (.degree.C.)=Detected value of
temperature-Saturated temperature based on detected value of
pressure (1)
196. Then, the detected value of superheating obtained by the
calculation and a set value of superheating (e.g., about 5.degree.
C.) are compared. The degree of opening of the electronic expansion
valve 4 is calculated based on a difference obtained by the
comparison. Then, the degree of opening of the electronic expansion
valve 4 is adjusted to have the degree of opening obtained by the
calculation. For example, when the detected value of superheating
is larger than the set value of superheating, the degree of opening
of the valve is made large to increase the refrigerant flow rate to
thereby reduce the degree of superheating. On the contrary, when
the detected value of superheating is smaller than the set value of
superheating, the degree of opening is made small to reduce the
refrigerant flow rate with the result of increasing the degree of
superheating. By repeating the above-mentioned processes with
predetermined time intervals, e.g., time intervals of about 5
minutes, the degree of superheating in the outlet portion of the
evaporator is controlled to be the set value. Thus, the natural
circulation operation in which the air conditioning ability is
usually maintained at or around the maximum can be conducted.
197. Since the air conditioner according to the seventh embodiment
does not use an electric heater or the like, the effect for
reducing consumption power as a characteristic feature of the
natural circulation operation can be obtained.
198. As shown in FIG. 3, when the outdoor air temperature is high
and the temperature difference between the outdoor and the indoor
is small, a refrigerant quantity in which the air cooling ability
is the maximum is small. Accordingly, an excessive amount
refrigerant is stored in the reservoir 20 by changing the degree of
opening of the electronic expansion valve 4 so that the degree of
superheating in the outlet portion of the evaporator 7 reaches a
set value of superheating (e.g., about 5.degree. C. in terms of a
degree of superheating). In a structure without providing the
reservoir 20, the excessive refrigerant liquid is accumulated in
the outlet portion of the condenser 2 whereby the degree of
supercooling in the outlet portion of the condenser 2 increases.
Thus, when the degree of supercooling in the outlet portion of the
condenser 2 is increased, the surface area for condensation in the
condenser 2 becomes small to thereby deteriorate efficiency in the
natural circulation operation. In the seventh embodiment, however,
the excessive refrigerant is naturally stored in the reservoir 20
and a reduction of efficiency can be prevented.
199. Further, when a higher air conditioning ability is obtainable
with an increased refrigerant quantity in the refrigerant circuit
as a result of increasing the temperature difference between the
outdoor temperature and a set temperature for air conditioning, an
excessive amount of refrigerant stored in the reservoir 20 is
gradually reduced in the course of controlling properly the
refrigerant state in the outlet portion of the evaporator 7. The
reduced amount of refrigerant is circulated in the refrigerant
circuit whereby the adjustment of the refrigerant quantity is made
naturally.
200. Further, the supercooling degree operating/controlling means
18 for calculating and controlling the degree of supercooling in
the outlet portion of the condenser 2 as in the second embodiment
may be provided in place of the superheating degree
operating/controlling means 19. In this case, the supercooling
degree operating/controlling means 18 is so adapted to change the
degree of opening of the electronic expansion valve 4 based on the
degree of supercooling calculated based on the temperature and the
pressure in the outlet portion of the condenser 2 and the
temperature difference between the outdoor air temperature and the
set temperature for air conditioning.
201. Further, the refrigerant state in the outlet portion of the
evaporator 7 may be controlled by changing the velocity of the
indoor fan 8 or the outdoor fan 3, or changing the air flow rate to
the evaporator 7 or the condenser 2 in the same manner as in the
third embodiment.
Embodiment 8
202. In the following, description will be made as to the air
conditioner according to the eighth embodiment of the present
invention, by taking an air conditioning apparatus as example.
203. FIG. 13 is a circuit diagram of the air conditioner according
to the eighth embodiment wherein the same reference numerals as in
FIG. 1 designate the same or corresponding parts.
204. In FIG. 13, reference numeral 21 designates a second bypass
pipe for connecting a high pressure pipe connected to an outlet
portion of the compressor 1 with a low pressure pipe connected to
an inlet portion of the accumulator 14. An on-off valve 22 as a
switching means is interposed in the second bypass pipe 21. Numeral
4 designates a refrigerant flow controlling means such as an
electronic expansion valve which conducts pressure reduction of the
refrigerant of high temperature and high pressure passing through
the liquid pipe 6 to form a wet vapor of two-phase state. In the
eighth embodiment, the electronic expansion valve 4 is located at
an indoor unit side having the evaporator 7 in order to absorb a
difference in refrigerant quantity which is caused due to a
difference in the length of liquid portion between the forced
circulation operation and the natural circulation operation.
205. The air conditioner of the eighth embodiment comprises the
outdoor unit 5, the indoor unit 9 and liquid pipe 6 and the gas
pipe 10 which connect these units in the same manner as the first
embodiment.
206. The outdoor unit 5 comprises the compressor 1 for compressing
a refrigerant gas, the condenser 2 for liquefying the refrigerant
gas, the outdoor fan 3 as a blower, to supply forcibly outer air to
an outer surface of the condenser 2, the accumulator 14 as a
refrigerant storing means which prevents the liquid from reversing
to the compressor 1 in a case of a transient phenomenon or the
supercharging of the refrigerant, the on-off valve 13 for bypassing
the compressor 1 and the accumulator 14 in the natural circulation
operation, the bypass pipe 12 including the check valve 11, the
check valve 15 preventing the refrigerant from entering into the
compressor in the natural circulation operation, and the second
bypass pipe for connecting by interposing the on-off valve 22 the
high pressure pipe connected to the outlet portion of the
compressor 1 with the low pressure pipe connected to the inlet
portion of the accumulator 14.
207. The indoor unit 9 comprises the electronic expansion valve 4
which reduces the pressure of the refrigerant liquid of high
temperature and high pressure introduced through the liquid pipe 6
to be a wet vapor of two-phase state, the evaporator 7 for
vaporizing the wet vapor throttled by the electronic expansion
valve 4 depending on an air conditioning load and the indoor fan 8
as a blower provided at an indoor side.
208. In the forced circulation operation, the air conditioner of
the eighth embodiment is so adapted that the degree of opening of
the electronic expansion valve 4 is set to an appropriate degree of
opening by which the refrigerant liquid discharged from the
condenser 2 is subjected to pressure reduction to be a wet vapor
having a two-phase state; the electromagnetic valve 13 at an inlet
side of the accumulator is opened, and the compressor is operated.
At this moment, the check valve 11 is closed by a pressure
difference between a discharge pressure and an intake pressure of
the compressor 1 to thereby form the refrigerant circuit for forced
circulation.
209. Further, in the natural circulation operation, the degree of
opening of the electronic expansion valve 14 is fully opened to
reduce a pressure loss in the refrigerant circuit, and the
electromagnetic valve 13 at an inlet side of the accumulator 14 is
closed whereby the check valve 11 is opened according to the
refrigerant flow and the refrigerant circuit for natural
circulation is formed.
210. As described with respect to the first embodiment, when a
refrigerant quantity wherein the air cooling ability in the natural
circulation operation is the maximum is charged in the refrigerant
circuit, there produces an excessive amount of refrigerant in the
forced circulation operation and the excessive refrigerant is
accumulated in the accumulator 14. Accordingly, when the operation
is switched, it is necessary to conduct the refrigerant recovery
operation for returning the excessive refrigerant to the
refrigerant circuit for the natural circulation operation. As the
refrigerant recovery operation, there is a way to entirely closing
the degree of opening of the electronic expansion valve 4 for the
forced circulation operation. In this method, however, an intake
pressure of the compressor 1 is suddenly reduced whereby bubbles
are formed in the refrigerant liquid sucked into the compressor 1
and a machine oil for refrigeration flows into the refrigerant
circuit along with the discharge gas with the result that an amount
of the machine oil inside the compressor 1 decreases to cause the
burning due to a failure of lubrication. In particular, in a scroll
type compressor, when an oil feeding rate to sliding portions is
decreased due to a reduction of sucking pressure or the production
of bubbles in the refrigerant liquid in the compressor 1, there
cause the destruction due to the sliding portions thermally
deformed by temperature rise.
211. FIG. 14 is a flow chart showing a process for switching the
forced circulation operation to the natural circulation operation
in the air conditioner according to the eighth embodiment. A
refrigerant quantity necessary for the forced circulation operation
is about half as much as a refrigerant quantity to be circulated in
the natural circulation operation, and an excessive refrigerant is
stored in the accumulator in the forced circulation operation.
Accordingly, when the operation is switched from the forced
circulation operation to the natural circulation operation, it is
necessary to recover the refrigerant stored in the accumulator 14
to the refrigerant circuit for the natural circulation
operation.
212. In Step ST1 for the forced circulation operation, the on-off
valve 13 is opened; the on-off valve 22 is closed, and the degree
of opening of the electronic expansion valve 4 is set to an
appropriate degree of opening by which the pressure of the
refrigerant liquid discharged from the condenser 2 is reduced so as
to form a wet vapor having a two-phase state. At Step ST2, an
instruction of switching of the operation is given and the
refrigerant recovery operation is started. Namely, the on-off valve
22 is opened at Step ST3, and the degree of opening of the
electronic expansion valve 4 is throttled to a degree of opening
whereby the refrigerant state in the outlet portion of the
evaporator 7 becomes a state of superheating at Step ST4. In such
state, the compressor 1 is actuated for a predetermined time such
as about 2 minutes to conduct the refrigerant recovering operation
at Step ST5.
213. When the degree of opening of the electronic expansion valve 4
is made smaller than the degree of opening in the forced
circulation operation, the refrigerant flow rate is reduced so that
the refrigerant state in the outlet portion of the evaporator 7
becomes a state of superheating. Then, the superheating gas from
the evaporator 7 flows into the accumulator 14. With this, a part
of the superheating gas of high temperature and high pressure
discharged from the compressor 1 flows into the accumulator 14. The
refrigerant liquid in the accumulator 14 is vaporized by the
superheating gas from the evaporator 7 and the superheating gas
discharged from the compressor 1 through the bypass pipe 21 via the
on-off valve 22, and the vaporized refrigerant gas is recovered
toward a side of the condenser 2.
214. Then, at Step ST6, the compressor 1 is stopped, and at Step
ST7, the on-off valve 13 is closed to prevent the refrigerant from
flowing into the accumulator 14. At Step ST8, the on-off valve 22
is closed. At Step ST9, the degree of opening of the electronic
expansion valve 4 is opened, for example, fully opened in order to
reduce a pressure loss in the refrigerant circuit. Then, at Step
ST10, the operation is moved to the natural circulation
operation.
215. As described above, in the refrigerant recovering operation at
Step ST5 in the eighth embodiment, the bypass pipe 21 for
connecting the inlet side and the outlet side of the compressor 1
and the on-off valve 22 are provided, and a part of the
superheating gas of high temperature and high pressure discharged
from the compressor 1 is bypassed to the intake side. Accordingly,
the refrigerant stored in the accumulator 14 can smoothly be
recovered to the refrigerant circuit for the natural circulation
operation without reducing the pressure of the compressor 1.
216. In the eighth embodiment, an outdoor air temperature sensor 16
detects an outdoor air temperature, and a temperature difference
between the detected outdoor air temperature and a set temperature
for air conditioning is compared as shown in FIG. 13. Then, the
degree of opening of the electronic expansion valve 4 is changed
(Step ST4), or a refrigerant recovering time is changed (Step ST5)
depending on the temperature difference obtained by the comparison
whereby an evaporation amount of the excessive refrigerant stored
in the accumulator 14 is changed as shown in FIG. 14. Namely, a
refrigerant quantity to be recovered is changed in response to the
temperature difference between the detected value of outdoor air
temperature and a set temperature for air conditioning so that the
refrigerant amount in the refrigerant circuit in the natural
circulation operation is increased or decreased. As shown in FIG.
3, there exists the optimum amount of refrigerant by which the air
conditioning ability can be utilized to the maximum, with respect
to the temperature difference between an outdoor air temperature
and an indoor air temperature in the natural circulation operation.
Accordingly, by changing the refrigerant quantity depending on the
temperature difference between the outdoor air temperature and the
set temperature for air conditioning, it is possible to change the
refrigerant quantity in the refrigerant circuit in the natural
circulation operation while it is possible to obtain the maximum
air conditioning ability at the outdoor air temperature.
217. In order to change the evaporation rate of the excessive
refrigerant stored in the accumulator 14 depending on a temperature
difference between a detected value of outdoor air temperature and
the set temperature for air conditioning, the degree of opening of
the electronic expansion valve 4 is changed to adjust the
evaporation rate at Step ST4 in FIG. 14. Since it is preferable
that the refrigerant quantity in the natural circulation operation
is more when the temperature difference is large, the degree of
opening of the electronic expansion valve 4 should be increased to
increase the refrigerant flow rate. On the other hand, since the
air conditioning ability can be increased with a smaller
refrigerant quantity in the natural circulation operation when the
temperature difference is small, the degree of opening of the
electronic expansion valve 4 is reduced to reduce the refrigerant
flow rate. In this case, the refrigerant recovery operation should
be fixed to about 2 minutes.
218. Further, the evaporation rate can be changed by changing a
time for the refrigerant recovery operation depending on a
temperature difference at Step ST5. When the temperature difference
is larger, the refrigerant recovery operation is made longer. On
the other hand, when the difference is smaller, the refrigerant
recovery operation should be shortened since a smaller refrigerant
quantity in the natural circulation operation increases the air
conditioning ability. In this case, the electronic expansion valve
4 is fixed to a certain degree of opening which is smaller than
that in the forced circulation operation.
219. Further, the air conditioner may be so constructed that the
refrigerant recovery operation is conducted until the discharge
temperature and the intake temperature of the compressor 1, which
are previously detected, reach set values, and the set values are
changed depending on a temperature difference between an outdoor
air temperature and the set temperature for air conditioning.
220. Further, the air conditioner may be so constructed that the
refrigerant recovery operation is conducted until the degree of
superheating in the outlet portion of the evaporator 7, which is
previously detected, reaches a predetermined set value of
superheating, e.g., 20.degree. C. wherein the set value may be
changed depending on a temperature difference between an outdoor
air temperature and the set temperature for air conditioning.
221. The operating time, the degree of opening of the electronic
expansion valve 4, the discharge temperature and the intake
temperature of the compressor 1 and the set value of the degree of
superheating in the outlet portion of the evaporator 7 used for the
refrigerant recovery operation may be previously memorize by
obtaining relations between parameters of them, the evaporation
rate from the accumulator 14 and the refrigerant quantity remained
therein in conducting experiments or simulation.
222. In this case, it is preferable that the operation for changing
an excessive refrigerant to be recovered which is stored in the
accumulator 14 depending on the temperature difference between the
outdoor air temperature and the set temperature for air
conditioning, is conducted under the temperature difference between
the outdoor air temperature and the set temperature for air
conditioning, for example, a temperature not less than 25.degree.
C. This is because of, as described with reference to FIG. 4,
preventing reduction in reliability on communication devices
disposed in the shelter due to an excessive air cooling ability
which will cause excessively cooling the inside of the shelter.
Namely, when the temperature difference between an outdoor air
temperature and a set temperature for air conditioning is not less
than 25.degree. C. wherein for example, the set temperature is set
to be 38.degree. C., and if the outdoor air temperature is lower
than about 13.degree. C., the air conditioning load decreases to
result the excessive air cooling ability.
223. As described above, the air conditioner according to the
eighth embodiment can recover the refrigerant stored in the
accumulator 14 to the refrigerant circuit during the natural
circulation operation without reducing the intake pressure of the
compressor 1 whereby reliability on the compressor can be
improved.
224. Further, since the outdoor air temperature is detected and the
time for the refrigerant recovering operation and the degree of
opening of the electronic expansion valve 4 in the recovering
operation are controlled, the refrigerant quantity can suitably be
controlled depending on the temperature difference between the
outdoor air temperature and the set temperature for air
conditioning whereby the maximum cooling ability in the natural
circulation operation can be provided. Accordingly, the refrigerant
can smoothly be recovered without requiring a special heating means
such as an electric heater, and effect for reducing consumption
power as a characteristic feature of the natural circulation
operation is sufficiently performed.
225. In the eighth embodiment, the electronic expansion valve 4 is
disposed near the evaporator in the indoor unit. Accordingly, a
difference of the refrigerant quantity due to a difference of the
length of the liquid portion between the natural circulation
operation and the forced circulation operation can be minimized.
Namely, in the natural circulation operation and the forced
circulation operation, when the distance between the electronic
expansion valve 4 and the evaporator 7 is large, the difference of
the liquid portion becomes large, whereas, when the distance is
small, the difference becomes large whereby the difference in the
length of the liquid portion can be made smaller. With such
construction, the size of the accumulator 14 as a refrigerant
storing means can be made smaller.
Embodiment 9
226. In the following, the ninth embodiment of the preset invention
will be described with reference to FIG. 15, which shows a circuit
diagram of the air conditioner, for example, an air conditioning
apparatus according to the ninth embodiment. In this embodiment,
the natural circulation operation and the forced circulation
operation can be utilized. The structure of the ninth embodiment is
the same as that of the first embodiment except that the electronic
expansion valve 4 is disposed near the evaporator 7 in the indoor
unit 9. The construction that the electronic expansion valve 4 is
in the indoor unit 9 minimizes as possible a difference of
refrigerant quantity due to a difference of the length of the
liquid portion in the natural circulation operation and the forced
circulation operation in the same manner as the eighth embodiment,
whereby the accumulator 14 as a refrigerant storing means can be
miniaturized.
227. In the following, description will be made mainly as to the
refrigerant recovering operation conducted when the forced
circulation operation is switched to the natural circulation
operation.
228. In the forced circulation operation, the degree of opening of
the electronic expansion valve 4 is set to have an appropriate
degree of opening to reduce the pressure of the refrigerant liquid
discharged from the condenser 2 so that the refrigerant liquid is
formed to be a wet vapor in a two-phase state. The electromagnetic
valve 13 at an inlet side of the accumulator 14 is opened, and the
compressor 1 is started. At this moment, the check valve 11 is
closed due to the pressure difference between the discharge
pressure and the intake pressure of the compressor 1, thus, the
refrigerant circuit for the forced circulation operation is
formed.
229. In the natural circulation operation, the compressor 1 is
stopped; the electromagnetic valve 13 at the inlet side of the
accumulator 14 is closed, and the degree of opening of the
electronic expansion valve 4 is fully opened so as to reduce a
pressure loss in the refrigerant circuit. At this moment, the check
valve 11 is opened by the flow of the refrigerant, thus, the
refrigerant circuit for the natural circulation operation is
formed.
230. FIG. 16 is a flow chart showing a process for switching from
the forced circulation operation to the natural circulation
operation in the air conditioner of the ninth embodiment. The
refrigerant quantity required for the forced circulation operation
is about 1/2 as much as the refrigerant quantity circulated in the
natural circulation operation, and an excessive refrigerant is
gradually stored in the accumulator 14 during the forced
circulation operation. In switching the operation from the forced
circulation operation to the natural circulation operation, it is
necessary to recover the refrigerant stored in the accumulator 14
to the refrigerant circuit for the natural circulation operation.
In the ninth embodiment, it is assumed that the refrigerant stored
in the accumulator 14 is all recovered to the refrigerant circuit
for the natural circulation operation.
231. First, at Step ST11, the forced circulation operation is
started. At Step ST12, an operation switching instruction is
received. At Step ST13, the on-off valve 13 is opened to start the
refrigerant recover operation under such condition that the degree
of opening of the electronic expansion valve 4 is in a proper
degree of opening so that the pressure of the refrigerant liquid
discharge from the condenser 2 is reduced to render it to be a wet
vapor of two-phase state. Namely, at Step ST14, the degree of
opening of the electronic expansion valve 4 is throttled to such a
degree that the refrigerant state in the outlet portion of the
evaporator 7 to be in a state of superheating. Specifically, the
degree of opening of the electronic expansion valve 4 is made
smaller or fully closed from the degree of opening for the forced
circulation operation so that the refrigerant flow rate is made
smaller or 0. Then, at Step ST15, the refrigerant recover operation
is conducted by actuating the compressor 1 for a predetermined
time, e.g., about 2 minutes. Since the refrigerant flow rate is
made smaller or 0 at this moment, the refrigerant state in the
outlet portion of the evaporator 7 becomes a superheat state, and
the superheat gas flows into the accumulator 14. The refrigerant
liquid in the accumulator 14 is vaporized by the superheat gas and
the vapor is recovered towards a condenser side.
232. Then, at Step ST16, the compressor 1 is stopped. At Step ST17,
the on-off valve 13 is closed to prevent the refrigerant from
entering into the accumulator 14. At Step ST18, the degree of
opening of the electronic expansion valve is, for example, fully
opened to reduce a pressure loss in the refrigerant circuit. Then,
at step ST 19, the operation is moved to the natural circulation
operation.
233. In the ninth embodiment, the refrigerant state in the outlet
portion of the evaporator 7 is in a superheat state, and the
refrigerant in the accumulator 14 is vaporized by the superheat gas
thus resulted. Accordingly, the effect of reducing consumption
power as a characteristic feature of the natural circulation
operation is obtainable without requiring a special heating means
such as electric heater to the accumulator 14. Further, the forced
circulation operation can be switched smoothly to the natural
circulation operation according to a simple procedure.
234. As described above, in order to render the refrigerant state
in the outlet portion of the evaporator 7 to be a state of
superheating and to vaporize the refrigerant in the accumulator 14
by the superheat gas obtained, the degree of opening of the
electronic expansion valve 4 is made smaller or fully closed from
the degree of opening in the forced circulation operation to
throttle the refrigerant flow rate to be smaller or 0, and the
compressor 1 is started for a predetermined time in this state. In
the refrigerant recovering operation according to the ninth
embodiment, a time necessary for evaporating entirely the excessive
refrigerant stored in the accumulator 14 is previously determined
so that the refrigerant recovering operation is finished when the
excessive refrigerant is entirely vaporized. The determination of
operating time permits easy judgement of the completion of the
refrigerant recovery operation.
235. Further, for the judgement of the completion of the
refrigerant recovering operation, the following technique may be
utilized. A temperature sensor and a pressure sensor are provided
to detect a degree of superheating at an outlet side and a degree
of superheating at an intake side of the compressor 1; the degree
of opening of the electronic expansion valve 4 is made smaller or
fully closed from the degree of opening in the forced circulation
operation to throttle the refrigerant flow rate to be smaller or 0;
and the compressor 1 is operated until values detected on degrees
of superheating at the outlet and inlet sides reach predetermined
set values.
236. Further, the completion of the refrigerant recovering
operation can be detected by providing a temperature sensor for
detecting temperatures at a discharge side and an intake side of
the compressor 1, and by detecting a rate of temperature rise based
on the temperatures detected by the temperature sensor. There is no
substantial increase of the temperatures at the discharge side and
the intake side of the compressor 1 when the refrigerant liquid
flows at the outlet side of the accumulator 4. However, when the
degree of opening of the electronic expansion valve 4 is made small
whereby the degree of superheating of the refrigerant in the
accumulator 14 is increased and a refrigerant gas follows through
an intake portion and a discharge portion of the compressor 1, the
rate of temperature rise at these portions is increased. For this,
the refrigerant recovering operation may be deemed to be completed
when the rate of temperature rise in the intake portion or the
discharge portion of the compressor 1 reaches a predetermined set
value, for example, exceeds 5.degree. C./min.
237. Further, the completion of the refrigerant recovering
operation may be determined in such a case that a relation between
the state of superheating in the outlet portion of the evaporator 7
and temperatures of discharge and intake sides of the compressor 1
is previously obtained, and the recovering operation is finished
when the temperature of discharge side and/or the temperature of
intake side reaches a predetermined set value.
238. Further, the completion of the refrigerant recovering
operation may be determined such that a detector for detecting the
degree of superheating in the outlet portion of the evaporator 7 is
disposed; the degree of opening of the electronic expansion valve 4
is made smaller or fully closed from the degree of opening in the
forced circulation operation to throttle the refrigerant flow rate
to be smaller or 0; and the compressor 1 is operated until the
detected degree of superheating reaches the set value. In this case
also, the completion of the refrigerant recovering operation can be
detected. The technique of detecting the degree of superheating is
omitted since it has been described in the second embodiment.
239. In order to detect the completion of the refrigerant
recovering operation, it is necessary to previously determine set
values for the operating time, the discharge temperature, the
intake temperature and the degree of superheating under the
condition that the degree of opening of the electronic expansion
valve 4 is made smaller or entirely closed from the degree of
opening in the forced circulation operation whereby the refrigerant
flow rate is made smaller or made entirely 0. As an example of the
method for the determination, experiments or simulation should be
conducted so as to obtain a relation between the degree of opening
of the electronic expansion valve 4 and the operating time
necessary for vaporizing refrigerant when a 1/2 amount of
refrigerant based on the total amount is stored in the accumulator
14, and values of the temperatures at the outlet and inlet sides of
the compressor 1 and values of degree of superheating at the outlet
of the evaporator 7 at the time when there remains no substantial
amount of refrigerant in the accumulator 14.
240. In the construction as shown in FIG. 15, when the second
bypass pipe 21 connecting the inlet side and the outlet side of the
compressor 1 and the on-off valve 22 are provided so that a part of
the superheated gas of high temperature and high pressure
discharged from the compressor 1 is introduced along with the
superheated gas from the evaporator 7 into the accumulator 14, as
described in the eighth embodiment, the refrigerant stored in the
accumulator 14 can smoothly be recovered to the refrigerant circuit
for the natural circulation without causing a reduction of pressure
in the compressor 1.
241. In the above-mentioned embodiments 1 to 9, the electronic
expansion valve is used as the refrigerant flow controlling means
4. However, the present invention is not limited thereto. In
particular, the refrigerant flow controlling means 4 in the second,
sixth, seventh and eighth embodiment may be such one capable of
changing the refrigerant flow rate by receiving a control signal
from the superheating degree operating/controlling means 19 or the
supercooling operating/controlling means 18 during the operation of
the air conditioner. For example, a combination of a plurality of
capillary pipes and a plurality of different kinds of on-off valves
may be used. In this case, the number of capillary pipes through
which the refrigerant is passed can be changed depending on the
kinds of the on-off valves operated in response to the control
signal.
242. In the above-mentioned third embodiment, the velocity of the
indoor fan 8 or the outdoor fan 3 as means for changing the air
flow rate to the evaporator 7 or the condenser 2, is changed.
However, this is not in particular limited. For example, the shape
of an air flow path can be changed to change an air flow resistance
instead of changing the velocity. Further, the velocity may be
changed along with the shape of an air flow path.
243. In the air conditioner according to the first to ninth
embodiments, the refrigerant used may be flon R22, flon R410A
having flon R32/R125 of a ratio of 50/50 wt % as a refrigerant
mixture, flon R407C having flon R32/R125/R134a of a ratio of
23/25/52 wt %, a refrigerant mixture contains hydrocarbon or
hydrocarbon refrigerant, ammonia or the like.
244. When flon R410A (R32/R125=50/50 wt %) is used as the
refrigerant, a pressure loss in the refrigerant circuit is smaller
than R22, and the air cooling ability in the natural circulation
operation can be increased.
245. Further, the hydrocarbon refrigerant may be propane (R290) or
isobutane (R600a) for example. These are known as refrigerant
wherein the ozone layer destruction performance (ODP) is 0; the
earth warming performance (GWP) is smaller by a unit of 1 order of
more than that of the refrigerant such as flon R22 or flon R410A,
and are more harmless to global environments. In particular,
propane (R290) as the hydrocarbon refrigerant is about 2.3 times in
terms of evaporation heat transmission coefficient and about 1.3
times in terms of condensation heat transmission coefficient than
flon R22 having the same mass velocity. Further, it is preferable
from the viewpoint of the pressure loss, and it is more harmless to
global environments and provides the performance similar to flon
R22.
246. As described above, description is made so that propane (R290)
as the hydrocarbon refrigerant is suitable for the natural
circulation operation. However, another hydrocarbon refrigerant or
refrigerant mixture including hydrocarbon having a large thermal
transmission coefficient and small power loss may be utilized as
the refrigerant for the natural circulation operation while it is
more harmless to global environments. Specifically, the refrigerant
mixture including hydrocarbon refrigerant may be carbon dioxide
(CO.sub.2)/propane (R290) or ammonia (NH.sub.3)/propane (R290) for
example.
247. Further, in the first to ninth embodiments, the air cooling
apparatus is explained as the air conditioner. However, the present
invention is applicable to a warming apparatus provided with a
condenser at an indoor side and an evaporator at an outdoor side
wherein an outdoor warm heat is utilized to perform the same
effect.
248. Obviously, numerous modifications and variations of the
present invention are possible in light of the above teachings. It
is therefore to be understood that within the scope of the appended
claims, the invention may be practiced otherwise than as
specifically described herein.
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