U.S. patent application number 14/368704 was filed with the patent office on 2014-12-25 for refrigeration apparatus.
The applicant listed for this patent is DAIKIN INDUSTRIES, LTD.. Invention is credited to Satoshi Ishida, Nobuki Matsui, Tadafumi Nishimura.
Application Number | 20140373564 14/368704 |
Document ID | / |
Family ID | 48697382 |
Filed Date | 2014-12-25 |
United States Patent
Application |
20140373564 |
Kind Code |
A1 |
Nishimura; Tadafumi ; et
al. |
December 25, 2014 |
REFRIGERATION APPARATUS
Abstract
A refrigeration apparatus has a compressor, a radiator, and an
evaporator connected in order to form a refrigerant circuit. The
refrigeration apparatus includes an expansion mechanism disposed at
an inflow side of the evaporator, a detector that detects a
supercooled state of the refrigerant at the inflow side of the
evaporator, and a control part. The expansion mechanism controls
expansion of refrigerant based on at least one of a high-pressure
target value of the refrigerant circuit, a low-pressure target
value of the refrigerant circuit, and a superheat target value at
an outflow side of the evaporator. The control part causes at least
one of a settings change to raise the high-pressure target value,
to lower the low-pressure target value and to raise the superheat
target value upon determining based on detection results from the
detector that refrigerant at the evaporator inflow side is in a
supercooled state.
Inventors: |
Nishimura; Tadafumi;
(Sakai-shi, JP) ; Ishida; Satoshi; (Sakai-shi,
JP) ; Matsui; Nobuki; (Sakai-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DAIKIN INDUSTRIES, LTD. |
Osaka-shi, Osaka |
|
JP |
|
|
Family ID: |
48697382 |
Appl. No.: |
14/368704 |
Filed: |
December 26, 2012 |
PCT Filed: |
December 26, 2012 |
PCT NO: |
PCT/JP2012/083565 |
371 Date: |
June 25, 2014 |
Current U.S.
Class: |
62/222 |
Current CPC
Class: |
F25B 39/028 20130101;
F25B 49/022 20130101; F25B 2700/2106 20130101; F25B 2700/21174
20130101; F25B 1/005 20130101; F25B 2600/027 20130101; F25B
2313/0233 20130101; F25B 2700/21163 20130101; F25B 13/00 20130101;
F25B 2600/2513 20130101; F25B 2600/2509 20130101; F25B 2700/1933
20130101; F25B 2700/2104 20130101; F25B 2700/21175 20130101; F25B
49/02 20130101 |
Class at
Publication: |
62/222 |
International
Class: |
F25B 39/02 20060101
F25B039/02; F25B 1/00 20060101 F25B001/00; F25B 49/02 20060101
F25B049/02 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 28, 2011 |
JP |
2011-290079 |
Claims
1. A refrigeration apparatus in which a compressor, a radiator, and
an evaporator are connected in order to form a refrigerant circuit
through which a refrigerant circulates, the refrigeration apparatus
comprising: an expansion mechanism disposed at an inflow side of
the evaporator, the expansion mechanism being arranged and
configured to control expansion of refrigerant flowing into the
evaporator based on at least one of a high-pressure target value of
the refrigerant circuit, a low-pressure target value of the
refrigerant circuit, and a superheat target value at an outflow
side of the evaporator; a detector arranged and configured to
detect supercooled state of the refrigerant at the inflow side of
the evaporator; and a control part configured and arranged to cause
at least one of a settings change to raise the high-pressure target
value, a settings change to lower the low-pressure target value and
a settings change to raise the superheat target value upon
determining based on detection results from the detector that the
refrigerant at the inflow side of the evaporator is in a
supercooled state.
2. The refrigeration apparatus according to claim 1, wherein the
control part is further configured to return the at least one
settings change to an original settings when a supercooled state no
longer exists after the at least one settings change has been
made.
3. The refrigeration apparatus according to claim 2, wherein the
control part is further configured to furnish a margin to
preventing hunting between a value when determining that a
supercooled state exists in a case where the at least one settings
change is to be effected, and a value when determining that a
departure has been made from a supercooled state in a case where
the at least one settings change is restored to the original
settings.
4. The refrigeration apparatus according to claim 1, wherein the
evaporator is a usage-side heat exchanger; and the control part is
configured and arranged to cause at least one of a settings change
to lower the low-pressure target value and a settings change to
raise the superheat target value upon determining based on
detection results from the detector that the refrigerant at an
inflow side of the usage-side heat exchanger is in a supercooled
state.
5. The refrigeration apparatus according to claim 4, wherein the
detector includes a first detector arranged and configured to
detect pressure saturation temperature at the inflow side of the
usage-side heat exchanger, and one of a second detector arranged
and configured to detect temperature of the refrigerant at the
inflow side of the usage-side heat exchanger, and a third detector
arranged and configured to detect temperature of the refrigerant at
an inflow side of the expansion mechanism; and the control part is
further configured and arranged to determine whether the
refrigerant at the inflow side of the usage-side heat exchanger is
in a supercooled state based on a comparison of detection results
from the first detector and the second detector, or a comparison of
detection results from the first detector and the third
detector.
6. The refrigeration apparatus according to claim 5, wherein the
third detector is a liquid line temperature sensor disposed at an
outflow side of the radiator; and the control part is further
configured to determine whether the refrigerant at the inflow side
of the usage-side heat exchanger is in a supercooled state using an
obtained temperature as the temperature of the refrigerant at the
inflow side of the expansion mechanism, the obtained temperature
being obtained by subtracting a correction value from the detected
temperature of the liquid line temperature sensor, and the
correction value being equivalent to a thermal loss experienced
from the liquid line temperature sensor installation location to
the expansion mechanism.
7. The refrigeration apparatus according to claim 5, wherein the
first detector is an intake pressure sensor arranged and configured
to detect pressure at an intake side of the compressor; and the
control part is further configured to calculate the pressure
saturation temperature from the pressure detected by the intake
pressure sensor.
8. The refrigeration apparatus according to claim 6, wherein the
first detector is an intake pressure sensor arranged and configured
to detect pressure at an intake side of the compressor; and the
control part is further configured to calculate the pressure
saturation temperature from the pressure detected by the intake
pressure sensor.
9. The refrigeration apparatus according to claim 2, wherein the
evaporator is a usage-side heat exchanger; and the control part is
configured and arranged to cause at least one of a settings change
to lower the low-pressure target value and a settings change to
raise the superheat target value upon determining based on
detection results from the detector that the refrigerant at an
inflow side of the usage-side heat exchanger is in a supercooled
state.
10. The refrigeration apparatus according to claim 9, wherein the
detector includes a first detector arranged and configured to
detect pressure saturation temperature at the inflow side of the
usage-side heat exchanger, and one of a second detector arranged
and configured to detect temperature of the refrigerant at the
inflow side of the usage-side heat exchanger, and a third detector
arranged and configured to detect temperature of the refrigerant at
an inflow side of the expansion mechanism; and the control part is
further configured and arranged to determine whether the
refrigerant at the inflow side of the usage-side heat exchanger is
in a supercooled stake based on a comparison of detection results
from the first detector and the second detector, or a comparison of
detection results from the first detector and the third
detector.
11. The refrigeration apparatus according to claim 10, wherein the
third detector is a liquid line temperature sensor disposed at an
outflow side of the radiator; and the control part is further
configured to determine whether the refrigerant at the inflow side
of the usage-side heat exchanger is in a supercooled state using an
obtained temperature as the temperature of the refrigerant at the
inflow side of the expansion mechanism, the obtained temperature
being obtained by subtracting a correction value from the detected
temperature of the liquid line temperature sensor, and the
correction value being equivalent to a thermal loss experienced
from the liquid line temperature sensor installation location to
the expansion mechanism.
12. The refrigeration apparatus according to claim 10, wherein the
first detector is an intake pressure sensor arranged and configured
to detect pressure at an intake side of the compressor; and the
control part is further configured to calculate the pressure
saturation temperature from the pressure detected by the intake
pressure sensor.
13. The refrigeration apparatus according to claim 3, wherein the
evaporator is a usage-side heat exchanger; and the control part is
configured and arranged to cause at least one of a settings change
to lower the low-pressure target value and a settings change to
raise the superheat target value upon determining based on
detection results from the detector that the refrigerant at an
inflow side of the usage-side heat exchanger is in a supercooled
state.
14. The refrigeration apparatus according to claim 13, wherein the
detector includes a first detector arranged and configured to
detect pressure saturation temperature at the inflow side of the
usage-side heat exchanger, and one of a second detector arranged
and configured to detect temperature of the refrigerant at the
inflow side of the usage-side heat exchanger, and a third detector
arranged and configured to detect temperature of the refrigerant at
an inflow side of the expansion mechanism; and the control part is
further configured and arranged to determine whether the
refrigerant at the inflow side of the usage-side heat exchanger is
in a supercooled state based on a comparison of detection results
from the first detector and the second detector, or a comparison of
detection results from the first detector and the third
detector.
15. The refrigeration apparatus according to claim 14, wherein the
third detector is a liquid line temperature sensor disposed at an
outflow side of the radiator; and the control part is further
configured to determine whether the refrigerant at the inflow side
of the usage-side heat exchanger is in a supercooled state using an
obtained temperature as the temperature of the refrigerant at the
inflow side of the expansion mechanism, the obtained temperature
being obtained by subtracting a correction value from the detected
temperature of the liquid line temperature sensor, and the
correction value being equivalent to a thermal loss experienced
from the liquid line temperature sensor installation location to
the expansion mechanism.
16. The refrigeration apparatus according to claim 14, wherein the
first detector is an intake pressure sensor arranged and configured
to detect pressure at an intake side of the compressor; and the
control part is further configured to calculate the pressure
saturation temperature from the pressure detected by the intake
pressure sensor.
Description
TECHNICAL HELD
[0001] The present invention relates to a refrigeration apparatus,
and in particular to a refrigeration apparatus having a
refrigerating circuit that includes an evaporator.
BACKGROUND ART
[0002] Air conditioning apparatus provided with a refrigerating
circuit for circulating a refrigerant, and incorporating a
refrigeration device for transferring heat between an indoor heat
exchanger and an outdoor heat exchanger in the refrigerating
circuit, are known in the prior art. In such an air conditioning
apparatus, superheat control is carried out in order to control the
degree of superheat of the refrigerant at the outlet of the
evaporator, in the manner disclosed, for example, in Patent
Literature 1 (Japanese Laid-Open Patent Application 2004-271066),
in order to carry out heat exchange in appropriate fashion in the
indoor heat exchanger and/or the outdoor heat exchanger.
SUMMARY OF THE INVENTION
Technical Problem
[0003] Demands to conserve energy in order to reduce power
consumption by air conditioning apparatus have increased in recent
years. For example, one measure for doing so is to adopt a low
differential pressure, i.e. a small differential between high
pressure and low pressure in the refrigerating cycle. In this sort
of air conditioning apparatus, if the system is operated at
increased evaporation temperature under conditions of being filled
with a large quantity of refrigerant and low outside temperature,
the refrigerant may reach a supercooled state short of reaching the
indoor heat exchanger, which functions as an evaporator. When a
supercooled state occurs in the indoor heat exchanger in this
manner, the problem of loss of superheat control of the indoor heat
exchanger arises.
[0004] An object of the present invention is to carry out superheat
control in appropriate fashion, in a refrigeration apparatus that
is susceptible to the refrigerant reaching a supercooled state
short of the evaporator.
Solution to Problem
[0005] A refrigeration apparatus according to a first aspect of the
present invention is a refrigeration apparatus in which a
compressor, a radiator, and an evaporator are connected in the
stated order to form a refrigerating circuit through which a
refrigerant circulates, the apparatus being provided with: an
expansion mechanism, furnished to an inflow side of the evaporator,
and adapted for controlling expansion of refrigerant inflowing to
the evaporator, doing so on the basis of at least one value from
among a high-pressure target value of the refrigerant circuit, a
low-pressure target value of the refrigerant circuit, and a
superheat target value at an outflow side of the evaporator; a
detector for detecting a supercooled state of the refrigerant at
the inflow side of the evaporator; and a control part configured
and arranged to make at least one settings change from among a
settings change to raise the high-pressure target value, a settings
change to lower the low-pressure target value and a settings change
to raise the superheat target value when it is decided on the basis
of the detection results from the detector that the refrigerant at
the inflow side of the evaporator is in a supercooled state.
[0006] In the refrigeration apparatus according to the first
aspect, in the case that a determination is made that the
refrigerant at the inflow side of the evaporator is in a
supercooled state, at least one settings change from among a
settings change to raise the high-pressure target value, to lower
the low-pressure target value, and to raise the superheat target
value, is made, thus avoiding a situation in which superheat
control of the evaporator is lost, whereby the degree of superheat
of the evaporator can be controlled in an appropriate manner.
[0007] A refrigeration apparatus according to a second aspect of
the present invention is the refrigeration apparatus according to
the first aspect, wherein the evaporator is a usage-side heat
exchanger; and the control part (47) is configured and arranged to
make a settings change to lower the low-pressure target value
and/or a settings change to raise the superheat target value when
it is decided on the basis of the detection results from the
detector that the refrigerant at an inflow side of the usage-side
heat exchanger is in a supercooled state.
[0008] In the refrigeration apparatus according to the second
aspect, in the case of a determination that the refrigerant at the
inflow side of the usage-side heat exchanger is in a supercooled
state, at least one of a settings change to lower the low-pressure
target value and a settings change to raise the superheat target
value is made, thus avoiding a supercooled state, whereby it is
possible to satisfactorily deal with cases in which, due to the
large quantity of refrigerant, the refrigerant tends to reach a
supercooled state short of the usage-side heat exchanger which
functions as an evaporator.
[0009] A refrigeration apparatus according to a third aspect of the
present invention is the refrigeration apparatus according to the
second aspect, wherein the detectors include a first detector for
detecting the pressure saturation temperature at the inflow side of
the usage-side heat exchanger, a second detector for detecting the
temperature of the refrigerant at the inflow side of the usage-side
heat exchanger, or a third detector for detecting the temperature
of the refrigerant at an inflow side of the expansion mechanism and
the first detector; and the control part is configured and arranged
to determine whether the refrigerant at the inflow side of the
usage-side heat exchanger is in a supercooled state, on the basis
of a comparison of the detection results from the first detector
and the second detector, or a comparison of detection results from
the first detector and the third detector.
[0010] In the refrigeration apparatus according to the third
aspect, a determination as to whether or not the refrigerant at the
inflow side of the usage-side heat exchanger is in a supercooled
state is made on the basis of a comparison of the detection results
from the first detector and the second detector, or a comparison of
the detection results from the first detector and the third
detector, whereby the determination as to whether a supercooled
state exists can be made correctly, even when the refrigerant at
the inflow side of the usage-side heat exchanger is
supercooled.
[0011] A refrigeration apparatus according to a fourth aspect of
the present invention is the refrigeration apparatus according to
the second or third aspect, wherein the third detector is a liquid
line temperature sensor disposed to an outflow side of the
radiator; and the control part determines whether the refrigerant
at the inflow side of the usage-side heat exchanger is in a
supercooled state, using a obtained temperature as the temperature
of the refrigerant at the inflow side of the expansion mechanism.
The obtained temperature is obtained by subtracting a correction
value from the detected temperature of the liquid line temperature
sensor. And the correction value is equivalent to the thermal loss
experienced from the liquid line temperature sensor installation
location to the expansion mechanism.
[0012] In the refrigeration apparatus according to the fourth
aspect, a conventional heat source-side liquid line temperature
sensor can be employed in making the determination as to whether
the refrigerant at the inflow side of the usage-side heat exchanger
is in a supercooled state.
[0013] A refrigeration apparatus according to a fifth aspect of the
present invention is the refrigeration apparatus according to the
second or third aspect, wherein the first detector is an intake
pressure sensor for detecting pressure at an intake side of the
compressor, and the control part is able to calculate the pressure
saturation temperature from the pressure detected by the intake
pressure sensor.
[0014] In the refrigeration apparatus according to the fifth
aspect, because the control part is able to calculate the pressure
saturation temperature from the pressure detected by the intake
pressure sensor, a conventional intake pressure sensor can be
employed.
Advantageous Effects of Invention
[0015] With the refrigeration apparatus according to the first
aspect, situations in which superheat control of the evaporator is
lost are avoided, and control of the degree of superheat of the
evaporator can be carried out in an appropriate manner, whereby
superheat control may be carried out appropriately in a
refrigeration apparatus susceptible to the refrigerant reaching a
supercooled state short of the evaporator.
[0016] With the refrigeration apparatus according to the second
aspect, situations in which superheat control of the usage-side
heat exchanger is lost are avoided, and control of the degree of
superheat of the usage-side heat exchanger can be carried out in an
appropriate manner, whereby superheat control may be carried out
appropriately in a refrigeration apparatus susceptible to the
refrigerant reaching a supercooled state short of the usage-side
heat exchanger.
[0017] With the refrigeration apparatus according to the third
aspect, the determination as to whether a supercooled state exists
can be made correctly, whereby superheat control carried out
appropriately in a refrigeration apparatus in which the refrigerant
reaches a supercooled state short of the evaporator.
[0018] With the refrigeration apparatus according to the fourth
aspect, a conventional heat source-side liquid line temperature
sensor can be employed, thereby suppressing the increase in
cost.
[0019] With the refrigeration apparatus according to the fifth
aspect, a conventional intake pressure sensor can be employed,
thereby minimizing the increase in cost.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a view showing a refrigerant pipeline system of an
air conditioning apparatus that includes a refrigeration apparatus
according to an embodiment of the present invention;
[0021] FIG. 2 is a block diagram showing a control system in the
air conditioning apparatus of FIG. 1; and
[0022] FIG. 3 is a graph describing operation of a refrigerating
circuit.
DESCRIPTION OF EMBODIMENTS
(1) Overall Constitution of Air Conditioning Apparatus
[0023] FIG. 1 shows a refrigerant pipeline system of an air
conditioning apparatus that includes a refrigeration apparatus
according to an embodiment of the present invention. An air
conditioning apparatus 1 is a distributed air conditioning
apparatus of refrigerant line design, the apparatus being used for
cooling and heating rooms of building through vapor compression
refrigerating cycle operation. The air conditioning apparatus 1 is
provided with an outdoor air conditioning unit 2 as the heat source
unit, a plurality of indoor air conditioning units 4 (in FIG. 1,
the two units of an indoor air conditioning unit 4a and an indoor
air conditioning unit 4b are shown) as usage units, and a first
refrigerant communication line 6 and a second refrigerant
communication line 7 as refrigerant communication lines connecting
the outdoor air conditioning unit 2 and the indoor air conditioning
units 4.
[0024] A refrigeration apparatus 10 of the air conditioning
apparatus 1 is constituted by connecting the outdoor air
conditioning unit 2, the indoor air conditioning units 4, and the
refrigerant communication lines 6, 7. The refrigeration apparatus
10 has a refrigerant sealed therein, and carries out a
refrigerating cycle operation in which the refrigerant is
compressed, cooled, decompressed, evaporated by heating, and again
is compressed as referred to hereinafter. As the refrigerant, it is
possible to employ one selected, for example, from R410A, R407C,
R22, R134a, carbon dioxide, or the like.
(2) Detailed Constitution of Air Conditioning Apparatus
(2-1) Indoor Air Conditioning Unit
[0025] The indoor air conditioning units are installed by being
flush-mounted in or suspended from an interior ceiling of a
building or the like, or by being hung from an interior wall
surface or the like. The indoor air conditioning units 4 are
connected to the outdoor air conditioning unit 2 through the
refrigerant communication lines 6, 7, and constitute apart of the
refrigeration apparatus 10.
[0026] The indoor air conditioning units 4 are described next. In
FIG. 1, the two units of the indoor air conditioning unit 4a and
the indoor air conditioning unit 4b are shown as the indoor air
conditioning units 4, but since each of the indoor air conditioning
units 4 is substantially identical in constitution, only the
constitution of the indoor air conditioning unit 4a will be
described here.
[0027] The indoor air conditioning unit 4a has an indoor-side main
refrigerant circuit 10a constituting a part of the refrigeration
apparatus 10. The indoor-side main refrigerant circuit 10a mainly
has an indoor expansion valve 41 serving as a decompressor, and an
indoor heat exchanger 42 serving as a usage-side heat
exchanger.
[0028] The indoor expansion valve 41 is a mechanism for
decompression of the refrigerant, and is an electrically driven
valve with an adjustable valve opening. The indoor expansion valve
41 is connected at one end thereof to the first refrigerant
communication line 6, and at the other end to the indoor heat
exchanger 42.
[0029] The indoor heat exchanger 42 is, for example, a fin-and-tube
heat exchanger of cross-fin type constituted by heat transfer tubes
and a multitude of fins. During cooling operations, the heat
exchanger functions as an evaporator for the refrigerant, to cool
the indoor air, and during heating operations functions as a
condenser for the refrigerant, to heat the indoor air. The indoor
heat exchanger 42 is connected at one end thereof to the indoor
expansion valve 41, and at the other end to the second refrigerant
communication line 7.
[0030] The indoor air conditioning unit 4a is provided with an
indoor fan 43 for drawing indoor air into the unit and supplying it
back to the indoors, and is designed to bring about heat exchange
between indoor air and the refrigerant flowing through the indoor
heat exchanger 42. The indoor fan 43 permits adjustment of the air
flow of air supplied to the indoor heat exchanger 42, and the
rotation of the fan is driven by an indoor fan motor 43a comprising
a DC fan motor or the like. In the indoor fan 43, the indoor fan
motor 43a drives, for example, a centrifugal fan and/or a
multiblade fan or the like, in order to force air into the indoor
heat exchanger 42.
[0031] The indoor air conditioning unit 4a is additionally
furnished with sensors of various kinds. In specific terms, the
unit is furnished with an indoor liquid line temperature sensor 44
comprising a thermistor, and/or with an indoor gas line temperature
sensor 45, for measuring the temperature of the refrigerant, from
the temperature of the refrigerant line in the vicinity of the
indoor heat exchanger 42. The unit is further furnished with an
indoor temperature sensor 46; this indoor temperature sensor 46
detects the temperature of indoor air drawn into the indoor air
conditioning unit 4 prior to heat exchange taking place. The indoor
air conditioning unit 4a further has an indoor control apparatus 47
for controlling the operation of the parts that constitute the
indoor air conditioning unit 4a. The indoor control apparatus 47
has a memory and/or a microcomputer or the like, furnished for the
purpose of controlling the indoor air conditioning unit 4a, and is
designed to exchange control signals or the like with respect to a
remote control part (not shown) for individual control of the
indoor air conditioning unit 4a, and to exchange control signals or
the like with respect to an outdoor control apparatus 30 of the
outdoor air conditioning unit 2 via a transmission cable 8a,
discussed below.
(2-2) Outdoor Air Conditioning Unit
[0032] The outdoor air conditioning unit 2 is installed outside a
building or the like, and is connected to the indoor air
conditioning units 4a, 4b through the first refrigerant
communication line 6 and the second refrigerant communication line
7. The outdoor air conditioning unit 2 has a supercooling
refrigerant channel 61 that shunts off from the refrigeration
apparatus 10 and an outdoor-side main refrigerant circuit 10c
constituting apart of the refrigeration apparatus 10.
(2-2-1) Outdoor-Side Main Refrigerant Circuit
[0033] The outdoor-side main refrigerant circuit 10c primarily has
a compressor 21, a switchover mechanism 22, an outdoor heat
exchanger 23, a first outdoor expansion valve 25, a liquid vapor
heat exchanger 27, a liquid-side close off valve 28a, a gas-side
close off valve 28b, and an accumulator 29. This outdoor-side main
refrigerant circuit 10c primarily has the compressor 21, the
switchover mechanism 22, the outdoor heat exchanger 23 as the heat
exchanger on the heat source side, the first outdoor expansion
valve 25 as a second shutoff mechanism or expansion mechanism on
the heat source side, the liquid vapor heat exchanger 27 as a
temperature regulating mechanism, the liquid-side close off valve
28a as a first shutoff mechanism, and the gas-side shutoff valve
28b. (*1)
[0034] The compressor 21 is a hermetic compressor driven by a
compressor motor 21a. The rotation speed of the compressor motor
21a is controlled, for example, by an inverter, and the compressor
21 is constituted such that the operating capacity is variable.
[0035] The switchover mechanism 22 is a mechanism for switching the
direction of flow of the refrigerant. During cooling operations, it
prompts the outdoor heat exchanger 23 to function as a radiator for
refrigerant compressed by the compressor 21, and the indoor heat
exchanger 42 to function as an evaporator for refrigerant that has
cooled in the outdoor heat exchanger 23. For this purpose, the
switchover mechanism 22 connects the refrigerant line on the
discharge side of the compressor 21 to one end of the outdoor heat
exchanger 23, as well as connecting a compressor inlet-side line
29a (including the accumulator 29) to the gas-side close off valve
28b (see the solid lines of the switchover mechanism 22 in FIG. 1).
During heating operations, the switchover mechanism 22 prompts the
indoor heat exchanger 42 to function as a radiator for refrigerant
compressed by the compressor 21, and the outdoor heat exchanger 23
to function as an evaporator for refrigerant that has cooled in the
indoor heat exchanger 42. For this purpose, the switchover
mechanism 22 connects the refrigerant line on the discharge side of
the compressor 21 to the gas-side close off valve 28b, as well as
connecting the compressor inlet-side line 29a to one end of the
outdoor heat exchanger 23 (see the broken lines of the switchover
mechanism 22 in FIG. 1). The switchover mechanism 22 is a four-way
valve, for example.
[0036] The outdoor heat exchanger 23 is a fin-and-tube heat
exchanger of cross-fin type constituted by heat transfer tubes and
a multitude of fins, and is connected at one end to the switchover
mechanism 22, and at the other end to the first outdoor expansion
valve 25.
[0037] The outdoor air conditioning unit 2 has an outdoor fan 26
for drawing outside air into the unit, and again discharging it
outdoors. The outdoor fan 26 brings about heat exchange between
outside air and refrigerant flowing through the outdoor heat
exchanger 23.
[0038] The first outdoor expansion valve 25 is a mechanism for
decompressing the refrigerant in the refrigeration apparatus 10,
and is an electrically driven valve having an adjustable valve
opening. In order to be able to regulate the pressure and/or flow
rate and the like of the refrigerant flowing inside the
outdoor-side main refrigerant circuit 10c, the first outdoor
expansion valve 25 is situated to the downstream side from the
outdoor heat exchanger 23 and to the upstream side from the liquid
vapor heat exchanger 27, in the direction of flow of the
refrigerant in the refrigeration apparatus 10 during cooling
operations, making it possible to shut off passage of the
refrigerant as well. One end of the first outdoor expansion valve
25 is connected to the outdoor heat exchanger 23, while the other
end is connected to the liquid-side close off valve 28a through the
liquid vapor heat exchanger 27, and connected to the liquid side of
the indoor heat exchanger 42.
[0039] The outdoor air conditioning unit 2 has the outdoor fan 26
as a blower fan for drawing outside air into the unit, and for
discharging it to the outdoors after undergoing heat exchange with
the refrigerant in the outdoor heat exchanger 23. This outdoor fan
26 is capable of varying the flow rate of air supplied to the
outdoor heat exchanger 23, and is, for example, a propeller fan or
the like, driven by a motor 26a composed of a DC fan motor or the
like.
[0040] The liquid vapor heat exchanger 27 is connected between the
first outdoor expansion valve 25 and the liquid-side close off
valve 28a. The liquid vapor heat exchanger 27 is a pipe heat
exchanger of dual pipe structure in which contact is brought about
between a shunt line 64, discussed below, and the refrigerant tube
through which the refrigerant condensed in the heat source-side
heat exchanger flows. In the liquid vapor heat exchanger 27, heat
exchange takes place between refrigerant flowing through the
refrigeration apparatus 10 from the outdoor heat exchanger 23
towards the indoor air conditioning unit 4, and refrigerant flowing
through the supercooling refrigerant channel 61 from the second
outdoor expansion valve 62 to the compressor inlet-side line 29a.
In so doing, the liquid vapor heat exchanger 27, through this
exchange of heat, further cools the refrigerant that has condensed
in the outdoor heat exchanger 23 during cooling operations,
imparting a high degree of supercooling to the refrigerant destined
for the indoor air conditioning unit 4.
[0041] The accumulator 29 is situated on the compressor inlet-side
line 29a, between the switchover mechanism 22 and the compressor
21.
(2-2-2) Supercooling Refrigerant Channel
[0042] The supercooling refrigerant channel 61 is constituted by a
refrigerant line running through the liquid vapor heat exchanger 27
from the second outdoor expansion valve 62 and towards the
compressor inlet-side line 29a between the switchover mechanism 22
and the accumulator 29. The second outdoor expansion valve 62 is a
mechanism for decompressing the refrigerant in the supercooling
refrigerant channel 61, and is an electrically driven valve with an
adjustable valve opening. The second outdoor expansion valve 62 is
furnished to the supercooling refrigerant channel 61, and is
situated at a location after the supercooling refrigerant channel
61 shunts off from the line leading from the first outdoor
expansion valve 25 to the liquid-side close off valve 28a, but
before entering the liquid vapor heat exchanger 27.
[0043] The liquid vapor heat exchanger 27 is furnished with the
shunt line 64 as a cooling source. The main refrigerant circuit is
the section of the refrigeration apparatus 10 excluding the
supercooling refrigerant channel 61. The supercooling refrigerant
channel 61 is connected to the main refrigerant circuit in such a
way that the refrigerant branched between the liquid vapor heat
exchanger 27 and the first outdoor expansion valve 25 is returned
to the inlet side of the compressor 21. The refrigerant shunted
into the supercooling refrigerant channel 61 is decompressed, and
thereafter introduced into the liquid vapor heat exchanger 27. The
refrigerant shunted into the supercooling refrigerant channel 61
then passes from the outdoor heat exchanger 23 to the first
refrigerant communication line 6 where it undergoes heat exchange
with the refrigerant fed to the indoor expansion valve 41, and is
then returned to the inlet side of the compressor 21.
[0044] Seen in greater detail, the supercooling refrigerant channel
61 has the shunt line 64, a junction line 65, and the second
outdoor expansion valve 62. The shunt line 64 is connected in such
a way that a portion of the refrigerant fed from the first outdoor
expansion valve 25 to the indoor expansion valve 41 is shunted at a
location between the outdoor heat exchanger 23 and the liquid vapor
heat exchanger 27. The junction line 65 is connected to the inlet
side of the compressor 21, in such way as to return to the inlet
side of the compressor 21 from the outlet on the supercooling
refrigerant channel side of the liquid vapor heat exchanger 27. The
second outdoor expansion valve 62 is composed of an electrically
driven expansion valve, and functions as a communication line
expansion mechanism for regulating the flow rate of the refrigerant
flowing through the supercooling refrigerant channel 61. In so
doing, the refrigerant fed from the outdoor heat exchanger 23 to
the indoor expansion valve 41 is cooled in the liquid vapor heat
exchanger 27, by the refrigerant flowing through the supercooling
refrigerant channel 61 subsequent to decompression by the second
outdoor expansion valve 62. That is, the liquid vapor heat
exchanger 27 carries out capability control by regulating the valve
opening of the second outdoor expansion valve 62.
[0045] As discussed below, the supercooling refrigerant channel 61
functions as a communication line connecting a section of the inlet
side of the compressor 21, and a section between the liquid-side
close off valve 28a and the first outdoor expansion valve 25 in the
refrigeration apparatus 10.
[0046] The liquid-side close off valve 28a and the gas-side close
of valve 28b are valves furnished to the connection ports to the
outdoor units/pipelines (specifically, the first refrigerant
communication line 6 and the second refrigerant communication line
7). The liquid-side close of valve 28a is connected to the liquid
vapor heat exchanger 27, while the gas-side close off valve 28b is
connected to the switchover mechanism 22, and can shut off the
passage of refrigerant thereby.
(2-2-3) Outdoor Control Device and Various Sensors
[0047] The outdoor air conditioning unit 2 has the outdoor control
apparatus 30 for controlling operations of the parts that
constitute the outdoor air conditioning unit 2. The outdoor control
apparatus 30 has a memory and a microcomputer furnished for the
purpose of controlling the outdoor air conditioning unit 2, and/or
an inverter circuit or the like for controlling the motor 26a, and
is designed to be capable of exchanging control signals and the
like with respect to the indoor control apparatus 47 of the indoor
air conditioning units 4a, 4b via the transmission cable 8a. That
is, an air conditioning control apparatus 8 for controlling
operation of the entire air conditioning apparatus 1 is constituted
by the indoor control apparatus 47 and the transmission cable 8a
connecting the outdoor control apparatus 30 and the indoor control
apparatus 47.
[0048] The outdoor air conditioning unit 2 is furnished with
sensors of various kinds. The refrigerant line on the discharge
side of the compressor 21 is furnished with a discharge pressure
sensor 31 for detecting the compressor discharge pressure, and with
a discharge temperature sensor 32 for detecting the compressor
discharge temperature. The compressor inlet-side line 29a is
furnished with an intake temperature sensor 34 for detecting the
temperature of the gas refrigerant drawn into the compressor 21,
and with an intake pressure sensor 33 for detecting the compressor
intake pressure. The outdoor control apparatus 30 is constituted in
such a way as to control the operating capacity of the compressor
21, and has a target low-pressure value representing a target value
for the intake pressure of the compressor 21 during cooling
operations, and a target high-pressure value representing a target
value for the discharge pressure of the compressor 21 during
heating operations. During cooling operations, the operating
capacity of the compressor 21 is controlled in such a way that the
intake pressure sensor 33 reaches the target low-pressure value,
and during heating operations, the operating capacity of the
compressor 21 is controlled in such a way that the discharge
pressure sensor 31 reaches the target high-pressure value.
[0049] The outlet at the main refrigerant circuit side of the
liquid vapor heat exchanger 27 is furnished with a liquid line
temperature sensor 35 for detecting the refrigerant temperature
(specifically, the liquid line temperature). The outside air inlet
side of the outdoor air conditioning unit 2 is furnished with an
outside air temperature sensor 36 for detecting the temperature of
the outside air (specifically, the outside air temperature)
inflowing to the interior. The junction line 6 of the supercooling
refrigerant channel 61 leading from the liquid vapor heat exchanger
27 to the low-pressure refrigerant line between the switchover
mechanism 22 and the accumulator 29 is furnished with a bypass
temperature sensor 63 for detecting the temperature of the
refrigerant flowing through the outlet at the supercooling
refrigerant channel side of the liquid vapor heat exchanger 27. The
discharge temperature sensor 32, the intake temperature sensor 34,
the liquid line temperature sensor 35, the outside air temperature
sensor 36, and the bypass temperature sensor 63 are composed of
thermistors.
(2-3) Refrigerant Communication Lines
[0050] The refrigerant communication lines 6, 7 are refrigerant
lines constructed on-site during installation of the outdoor air
conditioning unit 2 and the indoor air conditioning units 4 at the
installation site. The first refrigerant communication line 6 is
connected to the outdoor air conditioning unit 2 and the indoor air
conditioning units 4a, 4b; this refrigerant line, during cooling
operation, feeds liquid refrigerant having reached a high degree of
supercooling in the liquid vapor heat exchanger 27, to the indoor
expansion valve 41 and the indoor heat exchanger 42, and during
heating operation feeds liquid refrigerant having been condensed in
the indoor heat exchanger 42 to the outdoor heat exchanger 23 of
the outdoor air conditioning unit 2. The second refrigerant
communication line 7 is connected to the outdoor air conditioning
unit 2 and the indoor air conditioning units 4a, 4b; this
refrigerant line, during cooling operation, feeds gas refrigerant
having evaporated in the indoor heat exchanger 42 to the compressor
21 of the outdoor air conditioning unit 2, and during heating
operation feeds gas refrigerant having been compressed in the
compressor 21 to the indoor heat exchanger 42 of the indoor air
conditioning units 4a, 4b.
(2-4) Air Conditioning Control Apparatus
[0051] FIG. 2 shows a control block diagram of the air conditioning
apparatus 1. As shown in FIG. 2, the air conditioning control
apparatus 8, which serves as control means for controlling the
various operations of the air conditioning apparatus 1, is
constituted by the indoor control apparatus 47 and the outdoor
control apparatus 30 which are hooked up through the transmission
cable 8a. The air conditioning control apparatus 8 receives
detection signals from the various sensors 31-36, 44-46, 63, and on
the basis of these detection signals controls the various pieces of
equipments 21, 22, 25, 26, 41, 43, 62.
(3) Operation of Air Conditioning Apparatus
[0052] Next, the basic operations of the air conditioning apparatus
1 according to the present embodiment will be described. The air
conditioning control apparatus 8 performs control in the various
operations described below.
(3-1) Cooling Operation
[0053] In an air conditioning apparatus that operates at a low
differential pressure whereby there is only small differential
between high pressure and low pressure in the refrigerating cycle,
when the system is operated, for example, at increased evaporation
temperature under conditions of being filled with a large quantity
of refrigerant and low outside air temperature, the refrigerant may
reach a supercooled state short of reaching the indoor heat
exchanger 42, which functions as the evaporator. In the following
description, operation at times when the refrigerant has not
reached supercooled state short of reaching the indoor heat
exchanger 42 is termed a normal cooling operation, and operation at
times when refrigerant has reached supercooled state short of
reaching the indoor heat exchanger 42 is termed an abnormal cooling
operation, to distinguish the two in the description.
(3-1-1) Normal Cooling Operation
[0054] During a cooling operation, the switchover mechanism 22
enters the state shown by the solid lines in FIG. 1, specifically,
a state in which the discharge side of the compressor 21 is
connected to the gas side of the outdoor heat exchanger 23, and the
inlet side of the compressor 21 is connected to the gas side of the
indoor heat exchanger 42 through the gas-side close off valve 28b
and the second refrigerant communication line 7. During the cooling
operation, the first outdoor expansion valve 25 enters the
completely open state, and the liquid-side close off valve 28a and
the gas-side close off valve 28b enter the open state.
[0055] The indoor expansion valves 41 are designed to regulate the
valve opening in such a way that a degree of superheat of the
refrigerant at the outlet of the indoor heat exchanger 42
(specifically, the gas side of the indoor heat exchanger 42)
becomes steadily a first superheat target value Tsh1.
[0056] For example, in FIG. 3, a point C at pressure P1 is at the
inflow side of the indoor expansion valve 41, and a point B at
pressure P2 is at the outflow side of the indoor expansion valve
41. The degree of superheat of the refrigerant at the outlet of
each of the indoor heat exchangers 42 is detected in the indoor
control apparatus 47, by subtracting the refrigerant temperature
Th2 detected by the indoor liquid line temperature sensor 44 from
the refrigerant temperature Th1 detected by the indoor gas line
temperature sensor 45.
[0057] At this time, from the fact that indoor unit liquid line
pressure saturation temperature Tein does not exceed the
refrigerant temperature Th2 detected by the indoor liquid line
temperature sensor 44 (Tein.ltoreq.Th2), it is determined in the
indoor control apparatus 47 that a supercooled state does not exist
short of reaching the indoor heat exchanger 42. This indoor unit
liquid line pressure saturation temperature Tein may be obtained,
for example, through conversion of intake pressure LP of the
compressor 21 detected by the intake pressure sensor 33, to
saturation temperature corresponding to evaporation temperature
Te.
[0058] The second outdoor expansion valve 62 regulates the valve
opening in such a way as to bring the degree of superheat of the
refrigerant in the outlet at the supercooling refrigerant channel
side of the liquid vapor heat exchanger 27 to a superheat target
value (hereinafter termed superheating control). The degree of
superheat of the refrigerant in the outlet at the supercooling
refrigerant channel side of the liquid vapor heat exchanger 27 is
detected by converting the intake pressure of the compressor 21
detected by the intake pressure sensor 33 to a saturation
temperature corresponding to evaporation temperature, and
subtracting this saturation temperature of the refrigerant from the
refrigerant temperature detected by the bypass temperature sensor
63.
[0059] With the refrigeration apparatus 10 in this state, operating
the compressor 21, the outdoor fan 26, and the indoor fan 43
prompts low-pressure gas refrigerant to be drawn into the
compressor 21 and compressed, becoming high-pressure gas
refrigerant. Thereafter, the high-pressure gas refrigerant is fed
through the switchover mechanism 22 and into the outdoor heat
exchanger 23, where it undergoes heat exchange with outside air
supplied by the outdoor fan 26, and condenses to become
high-pressure liquid refrigerant. Then, after this high-pressure
liquid refrigerant has passed through the first outdoor expansion
valve 25, it flows into the liquid vapor heat exchanger 27, where
it undergoes heat exchange with the refrigerant flowing through the
supercooling refrigerant channel 61, becoming further cooled to a
supercooled state. At this time, a portion of the high-pressure
liquid refrigerant condensed in the outdoor heat exchanger 23 is
shunted into the supercooling refrigerant channel 61, and after
being decompressed by the second outdoor expansion valve 62, is
returned to the inlet side of the compressor 21. Here, the
refrigerant passing through the second outdoor expansion valve 62
is decompressed to close to the intake pressure of the compressor
21, causing a portion to evaporate. Then, the refrigerant flowing
from the outlet of the second outdoor expansion valve 62 of the
supercooling refrigerant channel 61 towards the inlet side of the
compressor 21 passes through the liquid vapor heat exchanger 27,
and undergoes heat exchange with the high-pressure liquid
refrigerant fed to the indoor air conditioning unit 4 from the
outdoor heat exchanger 23 in the main refrigerant circuit side.
[0060] The high-pressure liquid refrigerant in the supercooled
state is fed to the indoor air conditioning unit 4 through the
liquid-side close off valve 28a and the first refrigerant
communication line 6.
[0061] The high-pressure liquid refrigerant fed to the indoor air
conditioning unit 4 is decompressed by the indoor expansion valve
41 to close to the intake pressure of the compressor 21, becoming a
low-pressure refrigerant having a gas-liquid two-phase state, which
is fed to the indoor heat exchanger 42, undergoes heat exchange
with indoor air in the indoor heat exchanger 42, and evaporates to
become low-pressure gas refrigerant.
[0062] This low-pressure gas refrigerant is fed to the outdoor air
conditioning unit 2 through the second refrigerant communication
line 7, and is again drawn into the compressor 21 through the
liquid-side close off valve 28b and the switchover mechanism 22. In
this way, the air conditioning apparatus 1 carries out a cooling
operation in which the outdoor heat exchanger 23 functions as a
condenser for the refrigerant compressed in the compressor 21, and
the indoor heat exchanger 42 functions as an evaporator for
refrigerant fed through the first refrigerant communication line 6
and the indoor expansion valve 41 after being condensed in the
outdoor heat exchanger 23.
(3-1-2) Abnormal Cooling Operation
[0063] The switch from normal cooling operation to abnormal cooling
operation is made when it has been determined in the indoor control
apparatus 47 that a supercooled state exists short of reaching the
indoor heat exchanger 42. The indoor control apparatus 47
determines a supercooled state to exist short of reaching the
indoor heat exchanger 42, when the indoor unit liquid line pressure
saturation temperature Tein exceeds the refrigerant temperature Th2
detected by the indoor liquid line temperature sensor 44
(Tein>Th2).
[0064] A state in which the indoor unit liquid line pressure
saturation temperature Tein exceeds the refrigerant temperature Th2
detected by the indoor liquid line temperature sensor 44 refers to
a state of operation in a refrigerating cycle like that shown in
FIG. 3. That is, the state is one in which an enthalpy hB of the
refrigerant at the point B subsequent to expansion by the indoor
expansion valve 41 is lower than an enthalpy hA at point A at which
a saturated liquid line L1 intersects an evaporating pressure P2 in
FIG. 3. In such a state, the refrigerant inflowing to the indoor
heat exchanger 42 is supercooled; therefore, if superheat control
is performed on the basis of the temperature differential before
and after the indoor heat exchanger 42, the actual degree of
superheat will be misdetected. As a result, the two-phase state of
the refrigerant at the outlet of the indoor heat exchanger 42 will
be erroneously recognized as being a superheated state, and the
temperature of the refrigerant in the two-phase state will remain
unchanged despite regulating the valve opening of the indoor
expansion valve 41 to a greater or lesser degree, leading to a loss
of control.
[0065] Accordingly, when the indoor control apparatus 47 has
determined that Tein>Th2, it performs valve opening regulation
of the indoor expansion valve 41 while switching the target value
for the degree of superheat of the refrigerant from the first
superheat target value Tsh1 to the second superheat target value
Tsh2. Here, the second superheat target value Tsh2 is greater than
the first superheat target value Tsh1 (Tsh2>Tsh1).
[0066] By evaluating the degree of supercooling which may occur at
the inlet of the indoor heat exchanger 42, and changing to the
second superheat target value Tsh2 which has been set to higher
temperature than the first superheat target value Tsh1, the
refrigerant at the outlet of the indoor heat exchanger 42 can be
transformed to superheated refrigerant in a reliable manner during
superheating control, so that diminished controllability can be
prevented.
[0067] However, operation of the system when the target value for
the degree of superheat has been changed to the second superheat
target value Tsh2 leads to a drop in efficiency. Therefore, upon
entering a state permitting return to the first superheat target
value Tsh1, the indoor control apparatus 47 returns the target
value for the degree of superheat to the first superheat target
value Tsh1. In specific terms, for example, the indoor control
apparatus 47, at the point in time of detecting that the indoor
unit liquid line pressure saturation temperature Tein is lower than
the refrigerant temperature Th2 detected by the indoor liquid line
temperature sensor 44 by a preset temperature .beta. (a few degrees
e.g., 3.degree. C.)), changes the target value for the degree of
superheat from the second superheat target value Tsh2 to the first
superheat target value Tsh1. That is, the target value for the
degree of superheat is switched at the point in time that the
condition Tein<Th2-.beta. is satisfied. This temperature .beta.
is a margin for preventing hunting.
(3-2) Heating Operation
[0068] During heating operation, the switchover mechanism 22 enters
the state shown by the broken lines in FIG. 1, specifically, a
state in which the discharge side of the compressor 21 is connected
to the gas side of the indoor heat exchanger 42 through the
gas-side close-off valve 28b and the second refrigerant
communication line 7, and the inlet side of the compressor 21 is
connected to the gas side of the outdoor heat exchanger 23. The
valve opening of the first outdoor expansion valve 25 is regulated
in order to decompress the refrigerant inflowing to the outdoor
heat exchanger 23, down to a pressure such that evaporation is
possible in the outdoor heat exchanger 23 (i.e., to evaporation
pressure). The liquid-side close off valve 28a and the gas-side
close off valve 28b are in the open state. The valve opening of the
indoor expansion valve 41 is regulated such that the degree of
supercooling of the refrigerant at the outlet of the indoor heat
exchanger 42 becomes the supercooling target value steadily. The
degree of supercooling of the refrigerant at the outlet of the
indoor heat exchanger 42 is detected by converting the discharge
pressure of the compressor 21 detected by the discharge pressure
sensor 31 to saturation temperature corresponding to the
condensation temperature, and subtracting the refrigerant
temperature detected by the indoor liquid line temperature sensor
44 from the this refrigerant saturation temperature.
[0069] With the refrigeration apparatus 10 in this state, operating
the compressor 21, the outdoor fan 26, and the indoor fan 43
prompts low-pressure gas refrigerant to be drawn into the
compressor 21 and compressed, becoming high-pressure gas
refrigerant which is fed to the indoor air conditioning unit 4
through the switchover mechanism 22, the gas-side close off valve
28b, and the second refrigerant communication line 7.
[0070] In the indoor heat exchanger 42, the high-pressure gas
refrigerant fed to the indoor air conditioning unit 4 undergoes
heat exchange with the indoor air and is condensed to become
high-pressure liquid refrigerant, which is then decompressed
according to the valve opening of the indoor expansion valve 41
during passage through the indoor expansion valve 41.
[0071] The refrigerant having passed through the indoor expansion
valve 41 is fed to the outdoor air conditioning unit 2 through the
first refrigerant communication line 6, and after further
decompression through the liquid-side close off valve 28a, the
liquid vapor heat exchanger 27, and the first outdoor expansion
valve 25, flows into the outdoor heat exchanger 23. The
low-pressure refrigerant in a gas-liquid two-phase state inflowing
to the outdoor heat exchanger 23 undergoes heat exchange with
outdoor air supplied by the outdoor fan 26, and evaporates to
become low-pressure gas refrigerant, which is again drawn into the
compressor 21 through the switchover mechanism 22.
[0072] Control of operations such as the above is carried out by
the air conditioning control apparatus 8 (the indoor control
apparatus 47, the outdoor control apparatus 30, and the
transmission cable 8a connecting these), which carries out normal
operations including cooling operations and heating operations.
(4) Features of Refrigeration Apparatus
[0073] (4-1) In the refrigeration apparatus 10 according to the
present embodiment, during cooling operations, the compressor 21,
the outdoor heat exchanger 23 (example of a radiator), and the
indoor heat exchanger 42 (example of an evaporator) are connected
in the stated order to form the indoor-side main refrigerant
circuit 10a and the outdoor-side main refrigerant circuit 10c
(example of a refrigerating circuit) for circulating the
refrigerant. The indoor expansion valve 41 (example of an expansion
mechanism) furnished to the inflow side of the indoor heat
exchanger 42 controls expansion of refrigerant inflowing to the
indoor heat exchanger 42, doing so on the basis of the superheat
target value at the outflow side of the indoor heat exchanger 42.
The indoor liquid line temperature sensor 44 and the intake
pressure sensor 33 (example of detectors) detect the supercooled
state of the refrigerant at the inflow side of the indoor heat
exchanger 42. The indoor control apparatus 47 (example of a control
part), in the case of a determination, made on the basis of the
detection results from the indoor liquid line temperature sensor 44
and the intake pressure sensor 33, that the refrigerant at the
inflow side of the indoor heat exchanger 42 is in a supercooled
state, makes a settings change to raise the superheat target value
from the first superheat target value Tsh1 to the second superheat
target value Tsh2.
[0074] Because a settings change to raise the superheat target
value is made in cases of a determination that the refrigerant at
the inflow side of the indoor heat exchanger 42 is in a supercooled
state, situations in which superheat control of the indoor heat
exchanger 42 is lost are avoided, and control of the degree of
superheat of the indoor heat exchanger 42 can be carried out in an
appropriate manner. Therefore, superheat control may be carried out
appropriately in the refrigeration apparatus 10 which is
susceptible to the refrigerant reaching a supercooled state short
of the indoor heat exchanger 42. In particular, it is possible to
satisfactorily deal with cases in which, due to the large quantity
of refrigerant, the refrigerant tends to reach a supercooled state
short of the indoor heat exchanger 42 (example of a usage-side heat
exchanger) which functions as an evaporator.
[0075] (4-2) The intake pressure sensor 33 is a first detector for
detecting the pressure saturation temperature at the inflow side of
the indoor heat exchanger 42 (the usage-side heat exchanger), and
the indoor liquid line temperature sensor 44 is a second detector
for detecting the temperature of the refrigerant at the inflow side
of the indoor heat exchanger 42. The indoor control apparatus 47
(the control part), on the basis of whether or not the indoor unit
liquid line pressure saturation temperature Tein exceeds the
refrigerant temperature Th2 detected by the indoor liquid line
temperature sensor 44 (example of a comparison of detection results
from the first detector and the second detector), determines
whether the refrigerant at the inflow side of the indoor heat
exchanger 42 is in a supercooled state. Therefore, the
determination as to whether a supercooled state exists can be made
correctly, even when the refrigerant at the inflow side of the
indoor heat exchanger 42 is supercooled.
[0076] Because the indoor liquid line temperature sensor 44 of
conventional design can be employed as the second detector for
making the determination as to whether the refrigerant at the
inflow side of the indoor heat exchanger 42 (the usage-side heat
exchanger) is in a supercooled state, increase in cost can be
minimized. Likewise, because the intake pressure sensor 33 of
conventional design can be employed as the first detector for
making the determination as to whether the refrigerant at the
inflow side of the indoor heat exchanger 42 is in a supercooled
state, increase in cost can be suppressed.
(5) Modification Examples
(5-1) Modification Example A
[0077] For the refrigeration apparatus 10 of the aforedescribed
embodiment, there was described a case in which, during cooling
operations, when determined that the indoor heat exchanger 42 (the
evaporator) is in a supercooled state, the indoor control apparatus
47 raises the superheat target value; however, the settings may
instead be changed in such a way that the outdoor control apparatus
30 lowers the low-pressure target value when the indoor control
apparatus 47 has determined that a supercooled state exists. In the
case of the refrigeration apparatus 10, the low-pressure target
value is the indoor unit liquid line pressure saturation
temperature Tein. In such a case, the air conditioning control
apparatus 8 would be the control part. In the above manner, from
the detection results of the indoor liquid line temperature sensor
44 and the intake pressure sensor 33, the air conditioning control
apparatus 8 changes the low-pressure target value from a first
low-pressure target value PL2 to a second low-pressure target value
PL2 which is lower. That is PL1>PL2.
[0078] Once the low-pressure target value is changed to the lower
second low-pressure target value PL2 which is lower than the first
low-pressure target value PL1, the superheat target value is
unchanged, thereby producing a large pressure drop in the indoor
expansion valve 41 and a drop in evaporation pressure. Therefore,
the state of the refrigerant at time B1 having passed through the
indoor expansion valve 41 changes to a gas-liquid two-phase state
to the downstream side of the indoor expansion valve 41 (the inflow
side of the indoor heat exchanger 42) in association with the drop
in evaporation pressure, for example, to P3 as shown in FIG. 3,
whereupon control of the degree of superheat may proceed.
[0079] In the case of being set to the second low-pressure target
value L2, the indoor control apparatus 47 operates, for example, at
a low-pressure target upper limit value [such that] the indoor unit
liquid line pressure saturation temperature Tein target value
equals the indoor unit liquid line pressure Th2. During operation
under these conditions, in the case of a drop in low pressure
(Tein) related to the load factor or the like, the system will
automatically depart from the aforedescribed judgment condition,
and transition to normal control. That is, the indoor control
apparatus 47 detects that the indoor unit liquid line pressure
saturation temperature Tein is equal to or less than the
temperature Th2 detected by the indoor liquid line temperature
sensor 44 (Tein.ltoreq.Th2), and on the basis of the detected
result changes the low-pressure target value from the second
low-pressure target value PL2 to the first low-pressure target
value
(5-2) Modification Example B
[0080] In the refrigeration apparatus 10 of the aforedescribed
embodiment, during cooling operations, when the indoor unit liquid
line pressure saturation temperature Tein exceeds the refrigerant
temperature Th2 detected by the indoor liquid line temperature
sensor 44 (Tein>Th2), the inflow side of the indoor heat
exchanger 42 is determined to be in a supercooled state; however,
the outdoor unit liquid line inlet temperature T1 can also be
employed to make this determination. The outdoor unit liquid line
inlet temperature T1 is the temperature detected, for example, by
the liquid line temperature sensor 35 (example of a third
detector). Taking the heat loss component into consideration, the
indoor control apparatus 47 determines that the inflow side of the
indoor heat exchanger 42 is in a supercooled state, when the
condition Tein>T1-.alpha. is met. Then, when this condition is
met, the indoor control apparatus 47 changes the superheat target
value from the first superheat target value Tsh1 to the second
superheat target value Tsh2, or changes the low-pressure target
value from the first low-pressure target value PL1 to the second
low-pressure target value PL2. .alpha. is a value relating to heat
loss, derived empirically or the like, and is a value of about
3.degree. C., for example.
[0081] Switching of the superheat target value and/or switching of
the low-pressure target value performed by the indoor control
apparatus 47 when it has been determined that the inflow side of
the indoor heat exchanger 42 is in a supercooled state is
accomplished in the same manner as in the aforedescribed embodiment
and modification example B.
[0082] Likewise, the determination as to whether the inflow side of
the indoor heat exchanger 42 has transitioned from a supercooled
state to a non-supercooled state, making it acceptable to return to
the original superheat target value and/or low-pressure target
value, is made employing the outdoor unit liquid line inlet
temperature T1. That is, at the point in time it is detected that
the condition Tein.ltoreq.T1-.alpha.-.beta. is met, the superheat
target value is changed from the second superheat target value Tsh2
to the first superheat target value Tsh1 or the low-pressure target
value is changed from the second low-pressure target value PL2 to
the first low-pressure target value PL1.
[0083] In this way, because the liquid line temperature sensor 35
(example of a heat source-side liquid line temperature sensor) of
conventional design can be employed as the third detector for
making the determination as to whether the refrigerant at the
inflow side of the indoor heat exchanger 42 (the usage-side heat
exchanger) is in a supercooled state, increase in cost can be
minimized. Likewise, because the intake pressure sensor 33 of
conventional design can be employed as the first detector for
making the determination as to whether the refrigerant at the
inflow side of the indoor heat exchanger 42 is in a supercooled
state, increase in cost can be minimized.
(5-3) Modification Example C
[0084] While the aforedescribed embodiment and the aforedescribed
modification example A described a case in which the indoor heat
exchanger 42 functions as the evaporator during cooling operations,
the present invention can be applied also to cases in which the
refrigerant at the inflow side of the outdoor heat exchanger 23
tends to reach a supercooled state during heating operations.
[0085] In the outdoor control apparatus 30, it can be determined
whether or not a supercooled state has arisen at the inflow side of
the outdoor heat exchanger 23, from the low pressure Tein and the
outdoor unit liquid line inlet temperature T1, by detecting whether
or not the condition Tein>T1-.alpha. is being met.
[0086] As heating operations involve setting a high-pressure target
value, when it is determined that a supercooled state has arisen at
the inflow side of the outdoor heat exchanger 23, the high-pressure
target value is changed from a first high-pressure target value HP1
to a second high-pressure target value HP2. In this case, the
second high-pressure target value HP2 is set higher than the first
high-pressure target value HP1 (HP2>HP1).
[0087] In the same manner as in the aforedescribed embodiment and
modification examples A and B, when it is detected that the
condition Tein.ltoreq.T1-.alpha.-.beta. is met, the high-pressure
target value returns to the normal state. That is, when it is
determined that a supercooled state no longer exists at the inflow
side of the outdoor heat exchanger 23, the high-pressure target
value is changed from the second high-pressure target value HP2 to
the first high-pressure target value HP1.
(5-4) Modification Example D
[0088] While the aforedescribed embodiment described a case in
which the indoor air conditioning unit 4 is constituted by
connecting the two indoor air conditioning units 4a, 4b, it would
be acceptable to instead connect a single indoor air conditioning
unit, or three or more. In the case of connecting multiple indoor
air conditioning units, indoor air conditioning units constituted
differently may be connected.
(5-5) Modification Example E
[0089] The aforedescribed embodiment described a case in which the
superheat target value is changed to the second superheat target
value Tsh2 which is set to a higher temperature than the first
superheat target value Tsh1. However, a plurality of different
superheat target values can be set as the second superheat target
values. For example, a constitution whereby a third superheat
target value Tsh3 higher than the second superheat target value
Tsh2 is provided, employing the second superheat target value Tsh2
when a degree of supercooling Tsc meets the condition
0<Tsc.ltoreq.Tsc1 is met, and employing the third superheat
target value Tsh3 when the degree of supercooling Tsc meets the
condition Tsc1<Tsc is met, can be adopted. Moreover, a
relational expression of the second superheat target value Tsh2 and
the degree of supercooling Tsc may be prepared in advance, and the
degree of supercooling evaluated at the inlet of the indoor heat
exchanger 42, changing the second superheat target value Tsh2 to a
higher temperature than the first superheat target value Tsh1,
according to the extent of the degree of supercooling. The
relational expression of the second superheat target value Tsh2 and
the degree of supercooling Tsc may be selected, for example,
through prior experimentation and/or test operation or the like, as
appropriate.
REFERENCE SIGNS LIST
[0090] 10 Refrigeration apparatus [0091] 21 Compressor [0092] 23
Outdoor heat exchanger [0093] 30 Outdoor control apparatus [0094]
32 Discharge temperature sensor [0095] 33 Intake pressure sensor
[0096] 41 Indoor expansion valve [0097] 42 Indoor heat exchanger
[0098] 44 Indoor liquid line temperature sensor [0099] 47 Indoor
control apparatus
CITATION LIST
Patent Literature
[0100] [Patent Literature 1] Japanese Laid-Open Patent Application
2004-271066
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