U.S. patent application number 10/571940 was filed with the patent office on 2008-09-25 for subcooling apparatus.
Invention is credited to Azuma Kondo, Satoru Sakae, Iwao Shinohara, Masaaki Takegami, Kenji Tanimoto.
Application Number | 20080229769 10/571940 |
Document ID | / |
Family ID | 35503162 |
Filed Date | 2008-09-25 |
United States Patent
Application |
20080229769 |
Kind Code |
A1 |
Takegami; Masaaki ; et
al. |
September 25, 2008 |
Subcooling Apparatus
Abstract
A subcooling unit (200) includes a refrigerant passage (205)
connected to liquid side communication pipes (21, 22) of a
refrigerating apparatus (10). When a subcooling compressor (221) is
operated, subcooling refrigerant circulates in a subcooling
refrigerant circuit (220) to perform a refrigeration cycle, thereby
cooling refrigerant of the refrigerating apparatus (10) which flows
in the refrigerant passage (205). A controller (240) of the
subcooling unit (200) receives the detection value of an outside
air temperature sensor (231) or a refrigerant temperature sensor
(236). The controller (240) controls the operation of the
subcooling compressor (221) with the use of only information
obtainable within the subcooling unit (200).
Inventors: |
Takegami; Masaaki; (Osaka,
JP) ; Tanimoto; Kenji; (Osaka, JP) ; Sakae;
Satoru; (Osaka, JP) ; Shinohara; Iwao; (Osaka,
JP) ; Kondo; Azuma; (Osaka, JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
35503162 |
Appl. No.: |
10/571940 |
Filed: |
June 9, 2005 |
PCT Filed: |
June 9, 2005 |
PCT NO: |
PCT/JP2005/010611 |
371 Date: |
March 15, 2006 |
Current U.S.
Class: |
62/175 |
Current CPC
Class: |
F25B 13/00 20130101;
F25B 2700/2106 20130101; F25B 2400/22 20130101; F25B 2700/2103
20130101; F25B 40/02 20130101; F25B 2313/02331 20130101 |
Class at
Publication: |
62/175 |
International
Class: |
F25B 1/00 20060101
F25B001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 11, 2004 |
JP |
2004-174579 |
Claims
1. A subcooling apparatus which is incorporated to a refrigerating
apparatus (10) that performs a vapor compression refrigeration
cycle by circulating refrigerant between a heat source unit (11)
and a utility unit (12, 13, 14) connected to each other by means of
communication pipes and which cools the refrigerant of the
refrigerating apparatus (10) sent from the heat source unit (11) to
the utility unit (12, 13, 14), the subcooling apparatus,
comprising: a refrigerant passage (205) connected to liquid side
communication pipes of the refrigerating apparatus (10); a cooling
fluid circuit (220) including a subcooling heat exchanger (210)
that cools the refrigerant of the refrigerant passage (205) by heat
exchange with cooling fluid; and control means (240) for adjusting
cooling temperature of the refrigerant of the refrigerant passage
(205) in the subcooling heat exchanger (210) on the basis of an
ambient condition of the subcooling heat exchanger (210).
2. The subcooling apparatus of claim 1, wherein the control means
(240) includes a control section (242) for adjusting a flow rate of
the cooling fluid flowing in the subcooling heat exchanger (210) on
the basis of a target cooling temperature of the refrigerant of the
refrigerant passage (205) in the subcooling heat exchanger (210)
which is set in advance according to the ambient condition of the
subcooling heat exchanger (210).
3. The subcooling apparatus of claim 2, wherein the cooling fluid
circuit serves as a subcooling refrigerant circuit (220) which
includes a capacity variable subcooling compressor (221) and a heat
source side heat exchanger (222) and which performs the vapor
compression refrigeration cycle by circulating subcooling
refrigerant as the cooling fluid, and the control section (242) of
the control means (240) adjusts a flow rate of the subcooling
refrigerant flowing in the subcooling heat exchanger (210) by
controlling operation frequency of the subcooling compressor (221)
on the basis of the target cooling temperature.
4. The subcooling apparatus of claim 2, wherein the cooling fluid
circuit serves as a subcooling refrigerant circuit (220) which
includes a capacity variable subcooling compressor (221) and a heat
source side heat exchanger (222) and which performs the vapor
compression refrigeration cycle by circulating subcooling
refrigerant as the cooling fluid, and the control section (242) of
the control means (240) adjusts a flow rate of the subcooling
refrigerant flowing in the subcooling heat exchanger (210) by
controlling operation frequency of a fan (230) of the heat source
side heat exchanger (222) on the basis of the target cooling
temperature.
5. The subcooling apparatus of claim 3, wherein the control section
(242) of the control means (240) controls the operation frequency
of the subcooling compressor (221) on the basis of difference
between the target cooling temperature and temperature of the
refrigerant of the refrigerant passage (205) which is cooled in the
subcooling heat exchanger (210).
6. The subcooling apparatus of claim 3, wherein the control section
(242) of the control means (240) controls the operation frequency
of the subcooling compressor (221) on the basis of difference
between the target cooling temperature and set temperature set from
saturation temperature corresponding to low pressure of the
subcooling refrigerant of the subcooling refrigerant circuit
(220).
7. The subcooling apparatus of claim 3, wherein the control section
(242) of the control means (240) controls the operation frequency
of the subcooling compressor (221) on the basis of difference
between the target cooling temperature and set temperature set from
suction temperature of the subcooling compressor (221).
8. The subcooling apparatus of claim 4, wherein the control section
(242) of the control means (240) controls the operation frequency
of the fan (230) on the basis of difference between the target
cooling temperature and temperature of the refrigerant of the
refrigerant passage (205) which is cooled in the subcooling heat
exchanger (210).
9. The subcooling apparatus of claim 4, wherein the control section
(242) of the control means (240) controls the operation frequency
of the fan (230) on the basis of difference between the target
cooling temperature and set temperature set from saturation
temperature corresponding to low pressure of the subcooling
refrigerant in the subcooling refrigerant circuit (220).
10. The subcooling apparatus of claim 4, wherein the control
section (242) of the control means (240) controls the operation
frequency of the fan (230) on the basis of difference between the
target cooling temperature and set temperature set from suction
temperature of the subcooling compressor (221).
11. The subcooling apparatus of claim 1, wherein the ambient
condition of the subcooling heat exchanger (210) is outside air
temperature.
12. The subcooling apparatus of claim 1, wherein the ambient
condition of the subcooling heat exchanger (210) is a flow rate of
the refrigerant of the refrigerant passage (205).
13. The subcooling apparatus of claim 1, wherein the ambient
condition of the subcooling heat exchanger (210) is temperature of
the refrigerant of the refrigerant passage (205) before cooled in
the subcooling heat exchanger (210) or temperature of the
refrigerant of the refrigerant passage (205) after cooled in the
subcooling heat exchanger (210).
14. The subcooling apparatus of claim 1, wherein the cooling fluid
circuit is a subcooling refrigerant circuit (220) that performs a
vapor compression refrigeration cycle by circulating subcooling
refrigerant as the cooling fluid, and the ambient condition of the
subcooling heat exchanger (210) is low pressure or high pressure of
the subcooling refrigerant in the subcooling refrigerant circuit
(220).
15. The subcooling apparatus of claim 1, wherein the cooling fluid
circuit is a subcooling refrigerant circuit (220) that performs a
vapor compression refrigeration cycle by circulating subcooling
refrigerant as the cooling fluid, and the ambient condition of the
subcooling heat exchanger (210) is temperature of the subcooling
refrigerant after cooled, in the subcooling heat exchange (210),
the refrigerant of the refrigerant passage (205).
Description
TECHNICAL FIELD
[0001] The present invention relates to a refrigerating apparatus
and particularly relates to measures for increasing power of a
refrigerating apparatus including a refrigerant circuit that
performs a two-stage compression refrigerating cycle and for
enhancing reliability.
BACKGROUND ART
[0002] Conventionally, as disclosed in Japanese Patent Application
Laid Open Publication No. 10-185333A, a subcooling apparatuses is
known which is incorporated to a refrigerating apparatus for the
purpose of increasing cooling power and which cools refrigerant
sent from a heat source unit to a utility unit in the refrigerating
apparatus.
[0003] This subcooling apparatus is incorporated to an air
conditioner including an outdoor unit and an indoor unit.
Specifically, the subcooling apparatus, which includes a subcooling
refrigerant circuit, is provided in the middle of a liquid side
communication pipe that connects the outdoor unit and the indoor
unit. The subcooling unit performs a refrigeration cycle by
circulating the refrigerant of the subcooling refrigerant circuit
to cool by an evaporator of the subcooling refrigerant circuit the
refrigerant of the air conditioner sent from the liquid side
communication pipe. The subcooling apparatus cools the liquid
refrigerant sent from the outdoor unit to the indoor unit of the
air conditioner, thereby lowering the enthalpy of the liquid
refrigerant sent to the indoor unit to increase the cooling
capacity.
[0004] In the above subcooling apparatus, a control section of the
subcooling apparatus is connected to a control section of the air
conditioner to form one control system. The control section of the
subcooling apparatus receives a signal indicating a load state of
the air conditioner from the control section of the air
conditioner. Then, the subcooling apparatus performs driving
operation on the basis of the signal input from the control section
of the air conditioner. For example, when it is judged from the
input signal that the cooling load is large, the subcooling
apparatus starts operating to increase the cooling power of the air
conditioner. In reverse, when it is judged small, the subcooling
apparatus stops its operation. Namely, the subcooling apparatus
adjusts the cooling power appropriately by sending and receiving a
signal to and from the air conditioner.
PROBLEMS THAT THE INVENTION IS TO SOLVE
[0005] In the aforementioned conventional subcooling apparatus,
however, in order to incorporate the subcooling apparatus to the
refrigerating apparatus, wiring for transmitting a signal
therebetween is necessary, thereby complicating installation of the
subcooling apparatus. Further, mis-wiring may be involved in its
wiring works, resulting in invitation of troubles caused due to
human errors.
[0006] The present invention has been made in view of the foregoing
and has its objectives of enabling operation control of a
subcooling apparatus without sending and receiving a signal to and
from a refrigerating apparatus to which the subcooling apparatus is
incorporated, of simplifying installation of the subcooling
apparatus, and of obviating troubles caused due to human errors at
installation.
MEANS FOR SOLVING THE PROBLEMS
[0007] The means for solving the problem provided in the present
invention is as follows.
[0008] Specifically, the first problem solving means directs to a
subcooling apparatus which is incorporated to a refrigerating
apparatus (10) that performs a vapor compression refrigeration
cycle by circulating refrigerant between a heat source unit (11)
and a utility unit (12, 13, 14) connected to each other by means of
communication pipes and which cools the refrigerant of the
refrigerating apparatus (10) sent from the heat source unit (11) to
the utility unit (12, 13, 14). The subcooling apparatus includes: a
refrigerant passage (205) connected to liquid side communication
pipes of the refrigerating apparatus (10); a cooling fluid circuit
(220) including a subcooling heat exchanger (210) that cools the
refrigerant of the refrigerant passage (205) by heat exchange with
cooling fluid; and control means (240) for adjusting cooling
temperature of the refrigerant of the refrigerant passage (205) in
the subcooling heat exchanger (210) on the basis of an ambient
condition of the subcooling heat exchanger (210).
[0009] In the above problem solving means, the refrigerant passes
to and fro between the heat source unit (11) and the utility unit
(12, 13, 14) through communication pipes in the refrigerating
apparatus (10) to which the subcooling apparatus is incorporated.
The refrigerant passage (205) of the subcooling apparatus is
connected to the liquid side communication pipes (21, 22) of the
refrigerating apparatus (10) so that the refrigerant of the
refrigerating apparatus (10) flows therethrough. The cooling fluid
such as refrigerant, water, air, or the like flows in the cooling
fluid circuit (220) of the subcooling apparatus. In the subcooling
heat exchanger (210), the refrigerant of the refrigerating
apparatus (10) flowing in the refrigerant passage (205) is
heat-exchanged with the cooling fluid. In the subcooling heat
exchanger (210), the cooling fluid absorbs heat from the
refrigerant of the refrigerating apparatus (10) to be evaporated,
thereby cooling the refrigerant of the refrigerating apparatus
(10).
[0010] In the subcooling apparatus of this problem solving means,
the control means (240) adjusts the cooling temperature of the
refrigerant of the refrigerating apparatus (10) flowing in the
refrigerant passage (205) on the basis of the ambient condition of
the subcooling heat exchanger (210), such as outside air
temperature, the refrigerant flow rate, or the like. For example,
in the case where the outside air temperature is used as the
ambient condition of the subcooling heat exchanger (210), the
cooling temperature of the refrigerant is adjusted to be low when
outside air temperature is high or to be high when outside air
temperature is low. In detail, the load state of the refrigerating
apparatus (10) can be known from the ambient condition of the
subcooling heat exchanger (210), and therefore, adjustment
according to the ambient condition attains driving operation
appropriate to the load state. Thus, the cooling power of the
subcooling apparatus can be adjusted without receiving a signal
relating to the load state or the like from the refrigerating
apparatus (10).
[0011] Referring to the second problem solving means, in the first
problem solving means, the control means (240) includes a control
section (242) for adjusting a flow rate of the cooling fluid
flowing in the subcooling heat exchanger (210) on the basis of a
target cooling temperature of the refrigerant of the refrigerant
passage (205) in the subcooling heat exchanger (210) which is set
in advance according to the ambient condition of the subcooling
heat exchanger (210).
[0012] The above problem solving means sets in advance the target
cooling temperature of the refrigerant of the refrigerating
apparatus (10) according to the ambient condition of the subcooling
heat exchanger (210), such as outside air temperature, that is, a
load state. For example, the target cooling temperature is set
comparatively low when outside air temperature is high or is set
comparatively high when outside air temperature is low. When the
target cooling temperature is set low, the control section (242)
increases the flow rate of the cooling fluid such as refrigerant,
water, or the like in the subcooling heat exchanger (210). This
increases an amount of heat exchange between the refrigerant of the
refrigerating apparatus (10) and the cooling fluid in the
subcooling heat exchanger (210), thereby attaining further cooling
of the refrigerant of the refrigerating apparatus (10). In reverse,
when the target cooling temperature is set high, the control
section (242) reduces the flow rate of the cooling fluid such as
refrigerant, water, or the like in the subcooling heat exchanger
(210). This reduces the heat exchange amount in the subcooling heat
exchanger (210), so that the refrigerant of the refrigerating
apparatus (10) is not so cooled.
[0013] Referring to the third problem solving means, in the second
problem solving means, the cooling fluid circuit serves as a
subcooling refrigerant circuit (220) which includes a capacity
variable subcooling compressor (221) and a heat source side heat
exchanger (222) and which performs the vapor compression
refrigeration cycle by circulating subcooling refrigerant as the
cooling fluid, and the control section (242) of the control means
(240) adjusts a flow rate of the subcooling refrigerant flowing in
the subcooling heat exchanger (210) by controlling operation
frequency of the subcooling compressor (221) on the basis of the
target cooling temperature.
[0014] In the above problem solving means, the cooling fluid
circuit serves as the subcooling refrigerant circuit (220).
Further, in the subcooling refrigerant circuit (220), the
refrigerant discharged from the subcooling compressor (221) is
heat-exchanged with, for example, air in the heat source side heat
exchanger (222), is heat-exchanged with the refrigerant of the
refrigerant passage (205) in the subcooling heat exchanger (210),
and then, returns to the subcooling compressor (221), which is
circulation repeated. In addition, the control section (242)
increases, when the target cooling temperature is set low, the flow
rate of the subcooling refrigerant flowing in the subcooling heat
exchanger (210) by increasing the operation frequency of the
subcooling compressor (221). In reverse, the control section (242)
reduces, when the target cooling temperature is set high, the flow
rate of the subcooling refrigerant flowing in the subcooling heat
exchanger (210) by reducing the operation frequency of the
subcooling compressor (221).
[0015] Referring to the fourth problem solving means, in the second
problem solving means, the cooling fluid circuit serves as a
subcooling refrigerant circuit (220) which includes a capacity
variable subcooling compressor (221) and a heat source side heat
exchanger (222) and which performs the vapor compression
refrigeration cycle by circulating subcooling refrigerant as the
cooling fluid, and the control section (242) of the control means
(240) adjusts a flow rate of the subcooling refrigerant flowing in
the subcooling heat exchanger (210) by controlling operation
frequency of a fan (230) of the heat source side heat exchanger
(222) on the basis of the target cooling temperature.
[0016] In the above problem solving means, in the subcooling
refrigerant circuit (220), the refrigerant discharged from the
subcooling compressor (221) is heat-exchanged with air taken in by
the fan (230) in the heat source side heat exchanger (222), is
heat-exchanged with the refrigerant of the refrigerant passage
(205) in the subcooling heat exchanger (210), and then, returns to
the subcooling compressor (221), which is circulation repeated.
Further, the control section (242) increases, when the target
cooling temperature is set low, the flow rate of the subcooling
refrigerant flowing in the subcooling heat exchanger (210) by
reducing the operation frequency of the fan (230) of the heat
source side heat exchanger (222). In reverse, the control section
(242) reduces, when the target cooling temperature is set high, the
flow rate of the subcooling refrigerant flowing in the subcooling
heat exchanger (210) by increasing the operation frequency of the
fan (230) of the heat source side heat exchanger (222).
[0017] Referring to the fifth problem solving means, in the third
problem solving means, the control section (242) of the control
means (240) controls the operation frequency of the subcooling
compressor (221) on the basis of difference between the target
cooling temperature and temperature of the refrigerant of the
refrigerant passage (205) which is cooled in the subcooling heat
exchanger (210).
[0018] In the above problem solving means, when the temperature of
the refrigerant of the refrigerant passage (205) after cooled is
higher than the target cooling temperature, the cooling temperature
of the refrigerant in the subcooling heat exchanger (210) is
lowered by increasing the operation frequency of the subcooling
compressor (221). In reverse, when the temperature of the
refrigerant of the refrigerant passage (205) after cooled is lower
than the target cooling temperature, the cooling temperature of the
refrigerant in the subcooling heat exchanger (210) is raised by
reducing the operation frequency of the subcooling compressor
(221). Thus, acquisition of the actual temperature of the cooled
refrigerant as information attains reliable adjustment of the
cooling power. The temperature of the refrigerant after cooled is
information obtainable from the temperature sensor or the like
within the subcooling apparatus. Accordingly, also in this
invention, the cooling power of the subcooling apparatus can be
adjusted reliably without receiving any signal relating to the load
state from the refrigerating apparatus (10).
[0019] Referring to the sixth problem solving means, in the third
problem solving means, the control section (242) of the control
means (240) controls the operation frequency of the subcooling
compressor (221) on the basis of difference between the target
cooling temperature and set temperature set from saturation
temperature corresponding to low pressure of the subcooling
refrigerant of the subcooling refrigerant circuit (220).
[0020] In the above problem solving means, the set temperature
regarded as the temperature of the refrigerant after cooled in the
subcooling heat exchanger (210) is set from the saturation
temperature corresponding to low pressure of the subcooling
refrigerant. Hence, substantially the same information as the
actual temperature of the cooled refrigerant can be obtained
without receiving any signal relating to the load state or the like
from the refrigerating apparatus (10), thereby attaining reliable
adjustment of the cooling power.
[0021] Referring to the seventh problem solving means, in the third
problem solving means, the control section (242) of the control
means (240) controls the operation frequency of the subcooling
compressor (221) on the basis of difference between the target
cooling temperature and set temperature set from suction
temperature of the subcooling compressor (221).
[0022] In the above problem solving means, the set temperature
regarded as the temperature of the refrigerant after cooled in the
subcooling heat exchanger (210) is set from the suction temperature
of the subcooling compressor (221). Hence, substantially the same
information as the actual temperature of the cooled refrigerant can
be obtained without receiving any signal relating to the load state
or the like from the refrigerating apparatus (10), thereby
attaining reliable adjustment of the cooling power.
[0023] Referring to the eighth problem solving means, in the fourth
problem solving means, the control section (242) of the control
means (240) controls the operation frequency of the fan (230) on
the basis of difference between the target cooling temperature and
temperature of the refrigerant of the refrigerant passage (205)
which is cooled in the subcooling heat exchanger (210).
[0024] In the above problem solving means, when the temperature of
the refrigerant of the refrigerant passage (205) after cooled is
higher than the target cooling temperature, the operation frequency
of the fan (230) is reduced to lower the cooling temperature of the
refrigerant in the subcooling heat exchanger (210). In reverse,
when the temperature of the refrigerant of the refrigerant passage
(205) after cooled is lower than the target cooling temperature,
the driving frequency of the fan (230) is increased to raise the
cooling temperature of the refrigerant in the subcooling heat
exchanger (210). Thus, acquisition of the actual temperature of the
cooled refrigerant as information attains reliable adjustment of
the cooling power. The temperature of the refrigerant after cooled
is information obtainable from the temperature sensor or the like
within the subcooling apparatus. Accordingly, also in this
invention, the cooling power of the subcooling apparatus can be
adjusted reliably without receiving any signal relating to the load
state or the like from the refrigerating apparatus (10).
[0025] Referring to the ninth problem solving means, in the fourth
problem solving means, the control section (242) of the control
means (240) controls the operation frequency of the fan (230) on
the basis of difference between the target cooling temperature and
set temperature set from saturation temperature corresponding to
low pressure of the subcooling refrigerant in the subcooling
refrigerant circuit (220).
[0026] In the above problem solving means, the set temperature
regarded as the temperature of the refrigerant after cooled in the
subcooling heat exchanger (210) is set from the saturation
temperature corresponding to low pressure of the subcooling
refrigerant. Hence, substantially the same information as the
actual temperature of the cooled refrigerant can be obtained
without receiving any signal relating to the load state or the like
from the refrigerating apparatus (10), thereby attaining reliable
adjustment of the cooling power.
[0027] Referring to the tenth problem solving means, in the fourth
problem solving means, the control section (242) of the control
means (240) controls the operation frequency of the fan (230) on
the basis of difference between the target cooling temperature and
set temperature set from suction temperature of the subcooling
compressor (221).
[0028] In the above problem solving means, the set temperature
regarded as the temperature of the refrigerant after cooled in the
subcooling heat exchanger (210) is set from the suction temperature
of the subcooling compressor (221). Hence, substantially the same
information as the actual temperature of the cooled refrigerant can
be obtained without receiving any signal relating to the load state
or the like from the refrigerating apparatus (10), thereby
attaining reliable adjustment of the cooling power.
[0029] Referring to the eleventh problem solving means, in the
first problem solving means, the ambient condition of the
subcooling heat exchanger (210) is outside air temperature.
[0030] In the above problem solving means, the cooling temperature
of the refrigerant of the refrigerant passage (205) in the
subcooling heat exchanger (210) is adjusted on the basis of outside
air temperature. For example, the cooling temperature of the
refrigerant is adjusted to be low when outside air temperature is
high or is adjusted to be high when outside air temperature is low.
In short, the control means (240) judges the load state of the
refrigerating apparatus (10) on the basis of outside air
temperature.
[0031] Referring to the twelfth problem solving means, in the first
problem solving means, the ambient condition of the subcooling heat
exchanger (210) is a flow rate of the refrigerant of the
refrigerant passage (205).
[0032] In the above problem solving means, the cooling temperature
of the refrigerant of the refrigerant passage (205) in the
subcooling heat exchanger (210) is adjusted on the basis of the
actual flow rate of the refrigerant of the refrigerant passage
(205). For example, the cooling temperature of the refrigerant is
adjusted to be low when the refrigerant flow rate is large or is
adjusted to be high when the refrigerant flow rate is small. In
short, the control means (240) judges the load state of the
refrigerating apparatus (10) on the basis of the refrigerant flow
rate.
[0033] Referring to the thirteenth problem solving means, in the
first problem solving means, the ambient condition of the
subcooling heat exchanger (210) is temperature of the refrigerant
of the refrigerant passage (205) before cooled in the subcooling
heat exchanger (210) or temperature of the refrigerant of the
refrigerant passage (205) after cooled in the subcooling heat
exchanger (210).
[0034] In the above problem solving means, the cooling temperature
of the refrigerant of the refrigerant passage (205) in the
subcooling heat exchanger (210) is adjusted on the basis of the
actual temperature of the refrigerant before or after cooled. For
example, the cooling temperature of the refrigerant is adjusted to
be low when the refrigerant temperature is high or is adjusted to
be high when the refrigerant temperature is low. In short, the
control means (240) judges the load state of the refrigerating
apparatus (10) on the basis of the refrigerant temperature.
[0035] Referring to the fourteenth problem solving means, in the
first problem solving means, the cooling fluid circuit is a
subcooling refrigerant circuit (220) that performs a vapor
compression refrigeration cycle by circulating subcooling
refrigerant as the cooling fluid, and the ambient condition of the
subcooling heat exchanger (210) is low pressure or high pressure of
the subcooling refrigerant in the subcooling refrigerant circuit
(220).
[0036] In the above problem solving means, the cooling temperature
of the refrigerant of the refrigerant passage (205) in the
subcooling heat exchanger (210) is adjusted on the basis of the
actual low pressure or high pressure of the subcooling refrigerant
in the subcooling refrigerant circuit (220). Wherein, the low
pressure of the subcooling refrigerant is regarded as suction
pressure of the compressor of the subcooling refrigerant circuit
(220) while the high pressure of the subcooling refrigerant is
regarded as discharge pressure of the compressor of the subcooling
refrigerant circuit (220). For example, the cooling temperature of
the refrigerant is adjusted to be low when the low pressure or high
pressure is high or is adjusted to be high when the low pressure or
high pressure is low. In short, the control means (240) judges the
load state of the refrigerating apparatus (10) on the basis of the
low pressure or the high pressure in the vapor compression
refrigeration cycle of the subcooling refrigerant circuit
(220).
[0037] Referring to the fifteenth problem solving means, in the
first problem solving means, the cooling fluid circuit is a
subcooling refrigerant circuit (220) that performs a vapor
compression refrigeration cycle by circulating subcooling
refrigerant as the cooling fluid, and the ambient condition of the
subcooling heat exchanger (210) is temperature of the subcooling
refrigerant after cooled, in the subcooling heat exchange (210),
the refrigerant of the refrigerant passage (205).
[0038] In the above problem solving means, the cooling temperature
of the refrigerant of the refrigerant passage (205) in the
subcooling heat exchanger (210) is adjusted on the basis of the
actual temperature of the subcooling refrigerant after cooled.
Wherein, the temperature of the subcooling refrigerant may be
regarded as the suction temperature of the compressor of the
subcooling refrigerant circuit (220). For example, the cooling
temperature of the refrigerant is adjusted to be low when the
temperature of the subcooling refrigerant is high or is adjusted to
be high when the temperature of the subcooling refrigerant is low.
In short, the control means (240) judges the load state of the
refrigerating apparatus (10) on the basis of the temperature of the
subcooling refrigerant after cooled in the subcooling refrigerant
circuit (220).
[0039] --Effects--
[0040] As described above, in the first problem solving means, the
cooling temperature of the refrigerant of the refrigerant passage
(205) is adjusted on the basis of the ambient condition of the
subcooling heat exchanger (210) which can be detected within the
apparatus. Hence, appropriate operation can be performed according
to the load state of the utility unit (12, 13, 14) without sending
and receiving any signal between the heat source unit (11) and the
utility unit (12, 13, 14). As a result, for incorporating the
subcooling apparatus to the refrigerating apparatus (10), only
connection of the refrigerant passage (205) of the subcooling
apparatus to the communication pipes of the refrigerating apparatus
(10) is required. This eliminates the need to wire any
communication wirings for sending and receiving a signal between
the refrigerating apparatus (10) and the subcooling apparatus.
Accordingly, the number of operation steps for incorporating the
subcooling apparatus to the refrigerating apparatus (10) can be
reduced, and in turn, troubles caused due to human errors in
installation, such as mis-wiring and the like, can be obviated.
[0041] Further, in the second problem solving means, the flow rate
of the cooling fluid flowing in the subcooling heat exchanger (210)
is adjusted on the basis of the target cooling temperature of the
refrigerant of the refrigerating apparatus (10) in the subcooling
heat exchanger (210), which is set according to the ambient
condition of the subcooling heat exchanger (210). Hence,
appropriate adjustment of the cooling power can be attained with
information obtainable within the subcooling apparatus, as
well.
[0042] Furthermore, in the third or fourth problem solving means,
the subcooling refrigerant circuit (220) serves as the cooling
fluid circuit and the flow rate of the subcooling refrigerant in
the subcooling heat exchanger (210) is adjusted by controlling the
operation of the subcooling compressor (221) or the fan (230) of
the heat source side heat exchanger (222). Hence, the cooling
temperature of the refrigerant of the refrigerating apparatus (10)
can be adjusted reliably.
[0043] Moreover, the operation of the subcooling compressor (221)
or the fan (230) is controlled on the basis of the difference
between the actual temperature of the refrigerant cooled in the
subcooling heat exchanger (210) and the target cooling temperature
in the fifth or eighth problem solving means, on the basis of the
difference between the set temperature set from the saturation
temperature corresponding to the low pressure of the subcooling
refrigerant and the target cooling temperature in the sixth or
ninth problem solving means, or on the basis of the difference
between the set temperature set from the suction temperature of the
subcooling compressor (221) and the target cooling temperature in
the seventh or tenth problem solving means. In each case, the
cooling power can be adjusted to be further appropriate to the load
state only with information obtainable within the subcooling
apparatus.
[0044] In the eleventh to fifteenth problem solving means, the
outside air temperature, the flow rate or the temperature of the
refrigerant as a state quantity of the refrigerant of the
refrigerating apparatus (10), or pressure or temperature of the
refrigerant as a state quantity of the refrigerant of the
subcooling refrigerant circuit (220) is used as the ambient
condition of the subcooling heat exchanger (210). Thus, such values
can be obtained as the information obtainable within the subcooling
apparatus reliably and readily. As a result, highly reliable
apparatus can be provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0045] FIG. 1 is a piped system diagram showing a construction of a
refrigeration system including a subcooling unit.
[0046] FIG. 2 is a piped system diagram showing operation in
cooling operation of the refrigeration system.
[0047] FIG. 3 is a piped system diagram showing operation in first
heating operation of the refrigeration system.
[0048] FIG. 4 is a piped system diagram showing another operation
in the first heating operation of the refrigeration system.
[0049] FIG. 5 is a piped system diagram showing operation of second
heating operation of the refrigeration system.
[0050] FIG. 6 is a flowchart showing control operation by a
controller in the subcooling unit.
[0051] FIG. 7 is graph presenting the relationship between outside
air temperature and target cooling temperature.
BEST MODE FOR CARRYING OUT THE INVENTION
[0052] Embodiments of the present invention will be described in
detail with reference to the drawings.
[0053] A refrigeration system in the present embodiment is
installed in a convenience store or the like for conditioning air
in the store and cooling showcases. The refrigeration system
includes a subcooling unit (200) as a subcooling apparatus
according to the present invention and a refrigerating apparatus
(10) to which the subcooling unit (200) is incorporated.
[0054] As shown in FIG. 1, the refrigeration system includes an
outdoor unit (11), an air conditioning unit (12), a cooling
showcase (13), a refrigeration showcase (14), a booster unit (15),
and the subcooling unit (200). The refrigerating apparatus (10) is
composed of the outdoor unit (11), the air conditioning unit (12),
the cooling showcase (13), the refrigeration showcase (14), and the
booster unit (15). In the refrigeration system, the outdoor unit
(11) and the subcooling unit (200) are installed outdoors while the
other units such as the air conditioning unit (12) and the like are
installed in a store such as a convenience store.
[0055] The outdoor unit (11) includes an outdoor circuit (40), the
air conditioning unit (12) includes an air conditioning circuit
(100), the cooling showcase (13) includes a cooling circuit (110),
the refrigeration showcase (14) includes a refrigeration circuit
(130), and the booster unit (15) includes a booster circuit (140).
Further, the subcooling unit (20) includes a refrigerant passage
(205). In the refrigeration system, the aforementioned circuits
(40, 100, . . . ) and the refrigerant passage (205) of the
subcooling unit (200) are connected by means of pipes to form a
refrigerant circuit (20).
[0056] A first liquid side communication pipe (21), a second liquid
side communication pipe (22), a first gas side communication pipe
(23), and a second gas side communication pipe (24) are provided in
the refrigerant circuit (20).
[0057] The first liquid side communication pipe (21) connects one
end of the refrigerant passage (205) of the subcooling unit (200)
and the outdoor circuit (40). One end of the second liquid side
communication pipe (22) is connected to the other end of the
refrigerant passage (205). The other end of the second liquid side
communication pipe (22) branches into three ends to be connected to
the air conditioning circuit (100), the cooling circuit (100), and
the refrigeration circuit (130). A liquid side closing valve (25)
is provided in one of branch pipes of the second liquid side
communication pipe (22) which is connected to the refrigeration
circuit (130).
[0058] One end of the first gas side communication pipe (23)
branches into two ends connected to the cooling circuit (110) and
the booster circuit (140). A gas side closing valve (26) is
provided in one of the branch pipes of the first gas side
communication pipe (23) which is connected to the booster circuit
(140). The other end of the first gas side communication pipe (23)
is connected to the outdoor circuit (40). The second gas side
communication pipe (24) connects the air conditioning circuit (100)
and the outdoor circuit (40).
[0059] <Outdoor Unit>
[0060] The outdoor unit (11) serves as a heat source unit of the
refrigerating apparatus (10). The outdoor circuit (40) of the
outdoor unit (11) includes a variable capacity compressor (41), a
first fixed capacity compressor (42), a second fixed capacity
compressor (43), an outdoor heat exchanger (44), a receiver (45),
and an outdoor expansion valve (46). The outdoor circuit (40) also
includes three intake pipes (61, 62, 63), two discharge pipes (64,
65), four liquid pipes (81, 82, 83, 84), and one high-pressure gas
pipe (66). The outdoor circuit (40) further includes three four-way
switching valves (51, 52, 53), one liquid side closing valve (54),
and two gas side closing valves (55, 56).
[0061] In the outdoor circuit (40), the first liquid side
communication pipe (21), the first gas side communication pipe
(23), and the second gas side communication pipe (24) are connected
to the liquid side closing valve (54), the first gas side closing
valve (55), and the second gas side closing valve (56),
respectively.
[0062] Each of the variable capacity compressor (41), the first
fixed capacity compressor (42), and the second fixed capacity
compressor (43) is a hermetic scroll compressor of high-pressure
dome type. Electric power is supplied to the variable capacity
compressor (41) through an inverter. The variable capacity
compressor (41) is variable in capacity by changing the rotation
speed of its compressor motor by changing the output frequency of
the inverter. In contrast, the first and second fixed capacity
compressors (42, 43) are operated by driving their compressor
motors always at a given rotation speed, so that the capacities
thereof are invariable.
[0063] The first suction pipe (61) is connected at one end thereof
to the first gas closing valve (55). The first suction pipe (61)
branches at the other end thereof into a first branch pipe (61a)
and a second branch pipe (61b), wherein the first branch pipe (61a)
is connected to the intake side of the variable capacity compressor
(41) while the second branch pipe (61b) is connected to the third
four-way switching valve (53). A check valve (CV-1) for allowing
the refrigerant to flow from the first gas side closing valve (55)
towards the third four-way switching valve (53) is provided in the
second branch pipe (64b) of the first suction pipe (61).
[0064] The second suction pipe (62) is connected at one end thereof
to the third four-way switching valve (53) and at the other end
thereof to the suction side of the first fixed capacity compressor
(42).
[0065] The third suction pipe (63) is connected at one end thereof
to the second four-way switching valve (52). The third suction pipe
(63) branches at the other end thereof into a first branch pipe
(63a) and a second branch pipe (63b), wherein the first branch pipe
(63a) is connected to the suction side of the second fixed capacity
compressor (43) while the second brand pipe (63b) is connected to
the third four-way switching valve (53). A check valve (CV-2) for
allowing the refrigerant to flow from the second four-way switching
valve (52) towards the third four-way switching valve (53) is
provided in the second branch pipe (63b) of the third suction pipe
(63).
[0066] The first discharge pipe (64) branches at one end thereof
into a first branch pipe (64a) and a second branch pipe (64b),
wherein the first branch pipe (64a) is connected to the discharge
side of the variable capacity compressor (41) while the second
branch pipe (64b) is connected to the discharge side of the first
fixed capacity compressor (42). The other end of the first
discharge pipe (64) is connected to the first four-way switching
valve (51). A check valve (CV-3) for allowing the refrigerant to
flow from the first fixed capacity compressor (42) towards the
first four-way switching valve (51) is provided in the second
branch pipe (64b) of the first discharge pipe (64).
[0067] The second discharge pipe (65) is connected at one end
thereof to the suction side of the second fixed capacity compressor
(43) and at the other end thereof to a part of the discharge pipe
(64) immediately before the first four-way switching valve (51). A
check valve (CV-4) for allowing the refrigerant to flow from the
second fixed capacity compressor (43) towards the first four-way
switching valve (51) is provided in the second discharge pipe
(65).
[0068] The outdoor heat exchanger (44) is a fin and tube heat
exchanger of cross fin type. The outdoor heat exchanger (44)
performs heat exchange between the refrigerant and outdoor air. One
end of the outdoor heat exchanger (44) is connected to the first
four-way switching valve (51) via a closing valve (57). The other
end of the outdoor heat exchanger (44) is connected to the head of
the receiver (45) through the first liquid pipe (81). A check valve
(CV-5) for allowing the refrigerant to flow from the outdoor heat
exchanger (44) towards the receiver (45) is provided in the first
liquid pipe (81).
[0069] To the bottom of the receiver (45), one end of the second
liquid pipe (82) is connected via a closing valve (58). The other
end of the second liquid pipe (82) is connected to the liquid side
closing valve (54). A check valve (CV-6) for allowing the
refrigerant to flow from the receiver (45) towards the liquid side
closing valve (54) is provided in the second liquid pipe (82).
[0070] One end of the third liquid pipe (83) is connected between
the check valve (CV-6) and the liquid side closing valve (54) in
the second liquid pipe (82). The other end of the third liquid pipe
(83) is connected to the head of the receiver through the first
liquid pipe (81). A check valve (CV-7) for allowing the refrigerant
to flow from the one end towards the other end is provided in the
third liquid pipe (83).
[0071] One end of the fourth liquid pipe (84) is connected between
the closing valve (58) and the check valve (CV-6) in the second
liquid pipe (82). The other end of the fourth liquid pipe (84) is
connected between the outdoor heat exchanger (44) and the check
valve (CV-5) in the first liquid pipe (81). A check valve (CV-8)
and the outdoor expansion valve (46) are provided in this order
from the one end towards the other end of the fourth liquid pipe
(84). The check valve (CV-8) is provided for allowing the
refrigerant to flow from the one end towards the other end of the
fourth liquid pipe (84). The outdoor expansion valve (46) is an
electronic expansion valve.
[0072] The high-pressure gas pipe (66) is connected at one end
thereof to a part of the first discharge pipe (64) immediately
before the first four-way switching valve (51). The other end of
the high-pressure gas pipe (66) branches into a first branch pipe
(66a) and a second branch pipe (66b), wherein the first branch pipe
(66a) is connected to the downstream side of the check valve (CV-5)
in the first liquid pipe (81) while the second branch pipe (66b) is
connected to the third four-way switching valve (53). A solenoid
valve (SV-7) and a check valve (CV-9) are provided in the first
branch pipe (66a) of the high-pressure gas pipe (66). The check
valve (CV-9) is arranged downstream of the solenoid valve (SV-7)
for allowing the refrigerant to flow from the solenoid valve (SV-7)
towards the first liquid pipe (81).
[0073] In the first four-way switching valve (51), the first port,
the second port, the third port, and the fourth port are connected
to the terminal end of the first discharge pipe (64), the second
four-way switching valve (52), the outdoor heat exchanger (44), and
the second gas side closing valve (56), respectively. The first
four-way switching valve (51) is exchangeable between the first
state that the first port and the third port communicate with each
other while the second port and the fourth port communicate with
each other and the second state that the first port and the fourth
port communicate with each other while the second port and the
third port communicate with each other.
[0074] In the second four-way switching valve (52), the first port,
the second port, and the fourth port are connected to the
downstream side of the check valve (CV-4) in the second discharge
pipe (65), the start end of the second suction pipe (62), and the
second port of the first four-way switching valve (51),
respectively. The third port of the second four-way switching valve
(52) is closed. The second four-way switching valve (52) is
exchangeable between the first state that the first port and the
third port communicate with each other while the second port and
the fourth port communicate with each other and the second state
that the first port and the fourth port communicate with each other
while the second port and the third port communicate with each
other.
[0075] In the third four-way switching valve (53), the first port,
the second port, the third port, and the fourth port are connected
to the terminal end of the second branch pipe (66b) of the
high-pressure gas pipe (66), the start end of the second suction
pipe (62), the terminal end of the second branch pipe (61b) of the
first suction pipe (61), and the terminal end of the second branch
pipe (63b) of the third intake pipe (63), respectively. The third
four-way switching valve (53) is exchangeable between the first
state that the first port and the third port communicate with each
other while the second port and the fourth port communicate with
each other and the second state that the first port and the fourth
port communicate with each other while the second port and the
third port communicate with each other.
[0076] The outdoor circuit (40) further includes an injection pipe
(85), a communication pipe (87), an oil separator (75), and an oil
return pipe (76). The outdoor circuit (40) also includes four oil
level equalizing pipes (71, 72, 73, 74).
[0077] The injection pipe (85) is provided for liquid injection.
The injection pipe (85) is connected at one end thereof between the
check valve (CV-8) and the outdoor expansion valve (46) in the
fourth liquid pipe (84) and at the other end thereof to the first
suction pipe (61). A closing valve (59) and a flow rate adjusting
valve (86) are provided in this order from the one end towards the
other end of the injection pipe (85). The flow rate adjusting valve
(86) is an electronic expansion valve.
[0078] The communication pipe (87) is connected at one end thereof
between the closing valve (59) and the flow rate adjusting valve
(86) in the injection pipe (85) and at the other end thereof to the
upstream side of the solenoid valve (SV-7) in the first branch pipe
(66a) of the high-pressure gas pipe (66). In the communication pipe
(87), a check valve (CV-10) is provided for allowing the
refrigerant to flow from the one end towards the other end
thereof.
[0079] The oil separator (75) is provided upstream of the
connection point of the first discharge pipe (64) where the second
discharge pipe (65) and the high-pressure gas pipe (66) are
connected to each other. The oil separator (75) is provided for
separating the refrigerator oil from the discharged gas in the
compressors (41, 42).
[0080] The oil return pipe (76) is connected at one end thereof to
the oil separator (75). The oil return pipe (76) branches at the
other end thereof into a first branch pipe (76a) and a second
branch pipe (76b), wherein the first branch pipe (76a) is connected
to the downstream side of the flow rate adjusting valve (86) in the
injection pipe (85) while the second branch pipe (76b) is connected
to the second suction pipe (62). Further, solenoid valves (SV-5,
SV-6) are provided at the first branch pipe (76a) and the second
branch pipe (76b) of the oil return pipe (76), respectively. When
the solenoid valve (SV-5) of the first branch pipe (76a) opens, the
refrigerator oil separated in the oil separator (75) returns to the
first suction pipe (61) through the injection pipe (85). On the
other hand, when the solenoid valve (SV-6) of the second branch
pipe (76b) opens, the refrigerator oil separated in the oil
separator (75) returns to the second suction pipe (62).
[0081] The first oil level equalizing pipe (71) is connected at one
end thereof to the variable capacity compressor (41) and at the
other end thereof to the second suction pipe (62). A solenoid valve
(SV-1) is provided in the first oil level equalizing pipe (71). The
second oil level equalizing pipe (72) is connected at one end
thereof to the first fixed capacity compressor (42) and at the
other end thereof to the first branch pipe (63a) of the third
suction pipe (63). A solenoid valve (SV-2) is provided in the
second oil level equalizing pipe (72). The third oil level
equalizing pipe (73) is connected at one end thereof to the second
fixed capacity compressor (43) and at the other end thereof to the
first branch pipe (61a) of the first suction pipe (61). A solenoid
valve (SV-3) is provided in the third oil level equalizing pipe
(73). The fourth oil level equalizing pipe (74) is connected at one
end thereof to the upstream side of the solenoid valve (SV-2) in
the second oil level equalizing pipe (72) and at the other end
thereof to the first branch pipe (61a) of the first suction pipe
(61). A solenoid valve (SV-4) is provided in the fourth oil level
equalizing pipe (74). Appropriate opening/closing of the solenoid
valves (SV-1 to SV-4) of the oil level equalizing pipes (71 to 74)
equalizes each amount of the refrigerator oil reserved in the
compressors (42, 42, 43).
[0082] A variety of sensors and pressure switches are provided in
the outdoor circuit (40). Specifically, a first suction temperature
sensor (91) and a first suction pressure sensor (92) are provided
in the first suction pipe (61). A second suction pressure sensor
(93) is provided in the second suction pipe (62). A third suction
temperature sensor (94) and a third suction pressure sensor (95)
are provided in the third suction pipe (63). A first discharge
temperature sensor (97) and a first discharge pressure sensor (98)
are provided in the first discharge pipe (64). A high-pressure
switch (69) is provided at each of the branch pipes (64a, 64b) of
the first discharge pipe (64). A second discharge temperate sensor
(99) and a high pressure switch (96) are provided in the second
discharge pipe (65).
[0083] The outdoor unit (11) further includes an outdoor air
temperature sensor (90) and an outdoor fan (48). The outdoor fan
(48) sends outdoor air to the outdoor heat exchanger (44).
[0084] <Air Conditioning Unit>
[0085] The air conditioning unit (12) composes a utility unit. The
air conditioning circuit (100) of the air conditioning unit (12) is
connected at the liquid side end thereof to the second liquid side
communication pipe (22) and at the gas side end thereof to the
second gas side communication pipe (24).
[0086] The air conditioning circuit (100) includes an air
conditioning expansion valve (102) and an air conditioning heat
exchanger (101) in this order form the liquid side end towards the
gas side end. The air conditioning heat exchanger (101) is a fin
and tube heat exchanger of cross fin type. The air conditioning
heat exchanger (101) performs heat exchange between the refrigerant
and room air. The air conditioning expansion valve (102) is an
electronic expansion valve.
[0087] The air conditioning unit (12) includes a heat exchanger
temperature sensor (103) and a refrigerant temperature sensor
(104). The heat exchanger temperature sensor (103) is incorporated
at the heat transfer tube of the air conditioning heat exchanger
(101). The refrigerant temperature sensor (104) is incorporated in
the vicinity of the gas side end of the air conditioning circuit
(100). The air conditioning unit (12) also includes an indoor air
temperature sensor (106) and an air conditioning fan (105). The air
conditioning fan (105) sends room air in the store to the air
conditioning heat exchanger (101).
[0088] <Cooling Showcase>
[0089] The Cooling showcase (13) composes the utility unit. The
cooling circuit (110) of the cooling showcase (13) is connected at
the liquid side end thereof to the second liquid side communication
pipe (22) and at the gas side end thereof to the first gas side
communication pipe (23).
[0090] The cooling circuit (110) includes a cooling solenoid valve
(114), a cooling expansion valve (112), and a cooling heat
exchanger (111) in this order from the liquid side end towards the
gas side end. The cooling heat exchanger (111) is a fin and tube
heat exchanger of cross fin type. The cooling heat exchanger (111)
performs heat exchange between the refrigerant and the inside air
of the cooling showcase (13). The cooling expansion valve (112) is
a thermostatic expansion valve. The cooling expansion valve (112)
has a temperature sensing bulb (113) incorporated at the pipe on
the outlet side of the cooling heat exchanger (111).
[0091] The cooling showcase (13) includes a cooler temperature
sensor (116) and a cooler fan (115). The cooler fan (115) sends the
inside air of the cooling showcase (13) to the cooling heat
exchanger (111).
[0092] <Refrigeration Showcase>
[0093] The refrigeration showcase (14) composes the utility unit.
The refrigeration circuit (130) of the refrigeration showcase (14)
is connected at the liquid side end thereof to the second liquid
side communication pipe (22) and at the gas side end thereof to the
booster unit (15) through a pipe.
[0094] The refrigeration circuit (130) includes a refrigeration
solenoid valve (134), a refrigeration expansion valve (132), and a
refrigeration heat exchanger (131) in this order from the liquid
side end towards the gas side end. The refrigeration heat exchanger
(131) is a fin and tube heat exchanger of cross fin type. The
refrigeration heat exchanger (131) performs heat exchange between
the refrigerant and the inside air of the refrigeration showcase
(14). The refrigeration expansion valve (132) is a thermostatic
expansion valve. The refrigeration expansion valve (132) has a
temperature sensing bulb (133) incorporated at the pipe on the
outlet side of the refrigeration heat exchanger (131).
[0095] The refrigeration showcase (14) includes a refrigerator
temperature sensor (136) and a refrigerator fan (135). The
refrigerator fan (135) sends the inside air of the refrigeration
showcase (14) to the refrigeration heat exchanger (131).
[0096] <Booster Unit>
[0097] The booster circuit (140) of the booster unit (15) includes
a booster compressor (141), a suction pipe (143), a discharge pipe
(144), and a bypass pipe (150).
[0098] The booster compressor (141) is a hermetic scroll compressor
of high pressure dome type. Electric power is supplied to the
booster compressor (141) through an inverter. The booster
compressor (141) is variable in capacity by changing the rotation
speed of its compressor motor by changing the output frequency of
the inverter.
[0099] The suction pipe (143) is connected at the terminal end
thereof to the suction side of the booster compressor (141) and at
the start end thereof to the gas side end of the refrigeration
circuit (130) through a pipe.
[0100] The discharge pipe (144) is connected at the start end
thereof to the discharge side of the booster compressor (141) and
at the terminal end thereof to the first gas side communication
pipe (23). The discharge pipe (144) includes a high-pressure switch
(148), an oil separator (145), and a discharge side check valve
(149) in this order from the start end towards the terminal end
thereof. The discharge side check valve (149) allows the
refrigerant to flow from the start end towards the terminal end of
the discharge pipe (144).
[0101] The oil separator (145) is provided for separating the
refrigerator oil from the discharge gas of the booster compressor
(141). One end of an oil return pipe (146) is connected to the oil
separator (145). The other end of the oil return pipe (146) is
connected to the suction pipe (143). The oil return pipe (146)
includes a capillary tube (147). The refrigerator oil separated in
the oil separator (145) is sent back to the suction side of the
booster compressor (141) through the oil return pipe (146).
[0102] The bypass pipe (150) is connected at the start end thereof
to the suction pipe (143) and at the terminal end thereof to a part
of the discharge pipe (64) between the oil separator (145) and the
discharge side check valve (149). The bypass pipe (150) includes a
bypass check valve (151) for allowing the refrigerant to flow from
the start end towards the terminal end thereof.
[0103] <Subcooling Unit>
[0104] The subcooling unit (200) includes the refrigerant passage
(205), a subcooling refrigerant circuit (220), and a controller
(240).
[0105] The refrigerant passage (205) is connected at one end
thereof to the first liquid side communication pipe (21) and at the
other end thereof to the second liquid side communication pipe
(22).
[0106] The subcooling refrigerant circuit (220) is a closed circuit
formed in such a fashion that the subcooling compressor (221), a
subcooling outdoor heat exchanger (222), a subcooling expansion
valve (223), and a subcooling heat exchanger (210) are connected in
this order by means of pipes. The subcooling refrigerant circuit
(220) serves as a cooling fluid circuit for performing a vapor
compression refrigeration cycle by circulating the subcooling
refrigerant as the cooling fluid filled therein.
[0107] The subcooling compressor (221) is a hermetic scroll
compressor of high pressure dome type. Electric power is supplied
to the subcooling compressor (221) through an inverter. The
subcooling compressor (221) is variable in capacity by changing the
rotation speed of its compressor motor by changing the output
frequency of the inverter.
[0108] The subcooling outdoor heat exchanger (222) is a fin and
tube heat exchanger of cross fin type and serves as a heat source
side heat exchanger. The subcooling outdoor heat exchanger (222)
performs heat exchange between the subcooling refrigerant and
outdoor air. The subcooling expansion valve (223) is an electronic
expansion valve.
[0109] The subcooling heat exchanger (210) is a generally-called a
plate type heat exchanger and serves as a utility side heat
exchanger. A plurality of first flow paths (211) and a plurality of
second flow paths (212) are formed in the subcooling heat exchanger
(210). The first flow paths (211) and the second flow paths (211)
are connected to the subcooling refrigerant circuit (220) and the
refrigerant passage (205), respectively. The subcooling heat
exchanger (210) performs heat exchange between the subcooling
refrigerant flowing in the first flow paths (211) and the
refrigerant of the refrigerating apparatus (10) flowing in the
second flow paths (212).
[0110] The subcooling unit (200) also includes a variety of sensors
and pressure switches. Specifically, in the subcooling refrigerant
circuit (220), a suction temperature sensor (235) and a suction
pressure sensor (234) are provided on the suction side of the
subcooling compressor (221) and a discharge temperature sensor
(233) and a high pressure switch (232) are provided on the
discharge side of the subcooling compressor (221). A refrigerant
temperature sensor (236) is provided at a part of the refrigerant
passage (205) nearer the other end than the subcooling heat
exchanger (210), that is, a part thereof near the end connected to
the second liquid side communication pipe (22). The refrigerant
temperature sensor (236) serves as refrigerant temperature
detection means.
[0111] The subcooling unit (200) also includes an outside air
temperature sensor (231) and an outdoor fan (230). The outdoor fan
(230) sends outdoor air to the subcooling outdoor heat exchanger
(222).
[0112] The controller (240) serves as control means. The controller
(240) includes a setting section (241) and a control section
(242).
[0113] The setting section (241) receives outside air temperature
as detection temperature of the outside air temperature sensor
(231). The setting section (241) sets a target cooling temperature
(Eom) of the refrigerant of the refrigerant passage (205) in the
subcooling heat exchanger (210) which is set in advance on the
basis of the input outside air temperature. For example, when
outside air temperature is high, the cooling load in the store
becomes large, and therefore, the target cooling temperature (Eom)
of the refrigerant is set low. In reverse, when outside air
temperature is low, the cooling load in the store becomes small,
and therefore, the target cooling temperature (Eom) of the
refrigerant is set high. In short, the setting section (241) in the
present embodiment uses the outside air temperature as an ambient
condition of the subcooling heat exchanger (210).
[0114] The control section (242) receives the detection temperature
(Tout) of the refrigerant temperature sensor (236) and the
detection pressure (LP) of the suction pressure sensor (234). As
far as the refrigerant temperature sensor (236) can perform the
detection normally, the control section (242) controls the
operation frequency of the subcooling compressor (221) on the basis
of the difference between the detection temperature (Tout) of the
refrigerant temperature sensor (246) and the target cooling
temperature (Eom) of the setting section (241).
[0115] In the case where the refrigerant temperature sensor (236)
becomes abnormal and cannot perform the detection, the control
section (242) controls the operation frequency of the subcooling
compressor (221) on the basis of the difference between set
temperature (Tout) set from the saturation temperature (TG) of the
subcooling refrigerant which corresponds to the detection pressure
(LP) of the suction pressure sensor (234) and the target cooling
temperature (Eom). In other words, in the control section (242),
the set temperature (Tout) set from the saturation temperature (TG)
corresponding to the low pressure of the subcooling refrigerant of
the subcooling refrigerant circuit (220) is regarded as the
detection temperature of the refrigerant temperature sensor (236).
In the present embodiment, for example, the set temperature (Tout)
is set at a temperature obtained by adding .alpha..degree. C. to
the saturation temperature (TG) (TG+.alpha..degree. C.). Wherein,
.alpha. can be set arbitrarily.
[0116] It is noted that in the present embodiment, the control
section (242) regards the set temperature set from the detection
pressure (LP) of the suction pressure sensor (234) as the detection
temperature (Tout) of the refrigerant but may regard set
temperature (Tout) set from the suction temperature, which is the
detection temperature (Ti) of the suction temperature sensor (235),
as the detection temperature (Tout) of the refrigerant. In this
case, the control section (242) receives the detection temperature
(Tout) of the refrigerant temperature sensor (236) and the
detection temperature (Ti) of the suction temperature sensor (235).
In the case where the refrigerant temperature sensor (236) becomes
abnormal and cannot perform the detection, the control section
(242) controls the operation frequency of the subcooling compressor
(221) on the basis of the difference between the set temperature
(Tout) set from the detection temperature (Ti) of the suction
temperature sensor (235) and the target cooling temperature (Eom).
In this case, the set temperature (Tout) is set at, for example, a
temperature obtained by adding .beta..degree. C. to the detection
temperature (Ti) (Ti+.beta..degree. C.). Wherein, .beta. can be set
arbitrarily.
[0117] When the operation frequency of the subcooling compressor
(21) is increased, the circulation amount of the subcooling
refrigerant of the subcooling refrigerant circuit (220) increases
to increase the amount of heat exchange between the subcooling
refrigerant and the refrigerant of the refrigerating apparatus (10)
in the subcooling heat exchanger (210). This lowers the cooling
temperature of the refrigerant of the refrigerating apparatus (10),
increasing the cooling power and the like of the air conditioning
unit (12). In reverse, when the operation frequency of the
subcooling compressor (221) is reduced, the circulation amount of
the subcooling refrigerant of the subcooling refrigerant circuit
(220) reduces to reduce the amount of heat exchange between the
subcooling refrigerant and the refrigerant of the refrigerating
apparatus (10) in the subcooling heat exchanger (210), raising the
cooling temperature of the refrigerant of the refrigerating
apparatus (10) and lowering the cooling power and the like of the
air conditioning unit (12). In sum, the controller (240) adjusts
the cooling temperature of the refrigerant of the refrigerating
apparatus (10) in such a manner that the capacity of the subcooling
compressor (221) is controlled on the basis of the outside air
temperature to adjust the flow rate of the subcooling refrigerant
in the subcooling heat exchanger (210).
[0118] As described above, the controller (240) receives none of
signals from the refrigerating apparatus (10) composed of the
outdoor unit (11), the air conditioning unit (12), and the like. In
other words, the controller (240) controls the operation of the
subcooling compressor (221) on the basis of only information
obtained within the subcooling unit (200), such as the detection
values of the sensors provided in the subcooling unit (200). This
eliminates the need of works of wiring for transmitting signals
between the subcooling unit (200) and the refrigerating apparatus
(10).
[0119] It is noted that the setting section (241) in the present
embodiment sets the target cooling temperature (Eom) of the
refrigerant on the basis of the outside air temperature as the
ambient condition of the subcooling heat exchanger (210) but may
use the followings (parameters) rather than the outside air
temperature.
[0120] For example, the setting section (241) may use as the
ambient condition of the subcooling heat exchanger (210) the
refrigerant flow rate of the refrigerant passage (205), that is,
the flow rate of the refrigerant of the refrigerating apparatus
(10) in the subcooling heat exchanger (210). In this case,
refrigerant flow rate detection means is provided upstream of the
subcooling heat exchanger (210) in the refrigerant passage (205) so
that the detection flow rate of the flow rate detection mean is
input into the setting section (241) of the controller (240). The
setting section (241) judges that the cooling load in the store is
large when the input detection flow rate is large to set the target
cooling temperature (Eom) of the refrigerant to be low or sets the
target cooling temperature (Eom) of the refrigerant to be high when
the detection flow rate is small, with the cooling load in the
store judged small.
[0121] Alternatively, the setting section (241) may use as the
ambient condition of the subcooling heat exchanger (210) the
temperature of the refrigerant of the refrigerant passage (205)
before cooled in the subcooling heat exchanger (210) or the
temperature of the refrigerant of the refrigerant passage (205)
after cooled in the subcooling heat exchanger (210). In this case,
refrigerant temperature detection means is provided upstream of the
subcooling heat exchanger (210) in the refrigerant passage (205) so
that the detection temperature of the flow rate detection means is
input as the temperature of the refrigerant before cooled into the
setting section (241) of the controller (240). Or, the detection
temperature of the refrigerant temperature sensor (236) provided
downstream of the subcooling heat exchanger (210) is input into the
setting section (241) of the controller (240). Then, the setting
section (241) judges that the cooling load in the store is large
when the input detection temperature is high to set the target
cooling temperature (Eom) of the refrigerant to be low or sets the
target cooling temperature (Eom) of the refrigerant to be high when
the detection temperature is low, with the cooling load in the
store judged small.
[0122] Further, the setting section (241) may use as the ambient
condition of the subcooling heat exchanger (210) low pressure or
high pressure of the subcooling refrigerant in the subcooling
refrigerant circuit (220). In this case, the detection pressure of
the intake pressure sensor (234) provided on the suction side of
the subcooling compressor (221) is input as the low pressure into
the setting section (241). Or, refrigerant pressure detection means
is provided on the discharge side of the subcooling compressor
(221) so that the detection pressure of the pressure detection
means is input as the high pressure into the setting section (241).
Then, the setting section (241) judges that the cooling load in the
store is large when the input detection pressure is high to set the
target cooling temperature (Eom) of the refrigerant to be low or
sets the target cooling temperature (Eom) of the refrigerant to be
high when the detection pressure is low, with the cooling load in
the store judged small.
[0123] Moreover, the setting section (241) may use as the ambient
condition of the subcooling heat exchanger (210) the temperature of
the subcooling refrigerant after cooled in the subcooling heat
exchanger (210). In this case, the detection temperature of the
suction temperature sensor (235) of the subcooling compressor (221)
is input into the setting section (241). Or, refrigerant
temperature detection means is provided immediately downstream of
the subcooling heat exchanger (210) in the subcooling refrigerant
circuit (220) so that the detection temperature of the temperature
detection means is input into the setting section (241) in lieu to
the detection temperature of the aforementioned suction temperature
sensor (235). Then, setting section (241) judges that the cooling
load in the store is large when the input detection temperature is
high to set the target cooling temperature (Eom) of the refrigerant
to be low or sets the target cooling temperature (Eom) of the
refrigerant to be high when the detection temperature is low, with
the cooling load in the store judged small.
[0124] As described above, any of the above parameters are
information obtainable within the subcooling unit (200), and
therefore, eliminates the need for signal transmission to and from
the refrigerating apparatus (10).
[0125] --Driving Operation of Refrigeration System--
[0126] Main operations of driving operation that the refrigeration
system performs will be described.
[0127] <Cooling Operation>
[0128] Cooling operation is operation for cooling the inside air of
the cooling showcase (13) and of the refrigeration showcase (14)
and for cooling room air by the air conditioning unit (12) to cool
the store.
[0129] As shown in FIG. 2, during the cooling operation, the first
four-way switching valve (51), the second four-way switching valve
(52), and the third four-way switching valve (53) are set to the
first state. The outdoor expansion valve (46) is closed fully while
each opening of the air conditioning expansion valve (102), the
cooling expansion valve (112), and the refrigeration expansion
valve (132) is adjusted appropriately. In this condition, the
variable capacity compressor (41), the first fixed capacity
compressor (42), the second fixed capacity compressor (43), and the
booster compressor (141) are operated. During the cooling
operation, the subcooling unit (200) is operated. Driving operation
of the subcooling unit (200) will be described later.
[0130] The refrigerant discharged from the variable capacity
compressor (41), the first fixed capacity compressor (42), and the
second fixed capacity compressor (43) is sent to the outdoor heat
exchanger (44) via the first four-way switching valve (51). In the
outdoor heat exchanger (44), the refrigerant radiates heat to
outdoor air to be condensed. The refrigerant condensed in the
outdoor heat exchanger (44) passes through the first liquid pipe
(81), the receiver (45), and the second liquid pipe (82) in this
order, and then, flows into the first liquid side communication
pipe (21).
[0131] The refrigerant flowing in the first liquid side
communication pipe (21) flows into the refrigerant passage (205) of
the subcooling unit (200). The refrigerant flowing in the
refrigerant passage (205) is cooled when passing through the second
flow paths (212) of the subcooling heat exchanger (210). The
subcooled liquid refrigerant cooled in the subcooling heat
exchanger (210) passes through the second liquid side communication
pipe (22), and then, is divided to flow into the air conditioning
circuit (100), the cooling circuit (110), and the refrigeration
circuit (130).
[0132] The refrigerant flowing in the air conditioning circuit
(100) is pressure-reduced when passing through the air conditioning
expansion valve (102), and then, is introduced into the air
conditioning heat exchanger (101). In the air conditioning heat
exchanger (101), the refrigerant absorbs heat from room air to be
evaporated. For the evaporation, the air conditioning heat
exchanger (101) is so set that the evaporation temperature of the
refrigerant is 5.degree. C., for example. The air conditioning unit
(12) supplies the room air cooled in the air conditioning heat
exchanger (101) to the store.
[0133] The refrigerant evaporated in the air conditioning heat
exchanger (101) passes through the second gas side communication
pipe (24), flows into the outdoor circuit (40), passes through the
first four-way switching valve (51) and the second four-way
switching valve (52) in this order, and then, flows into the third
suction pipe (63). Part of the refrigerant flowing in the third
suction pipe (63) passes through the first branch pipe (63a), and
then, is sucked into the second fixed capacity compressor (43)
while the other part thereof passes through the third four-way
switching valve (53) and the second suction pipe (62) in this
order, and then, is sucked into the first fixed capacity compressor
(42).
[0134] The refrigerant flowing in the cooling circuit (100) is
pressure-reduced when passing through the cooling expansion valve
(112), and then, is introduced into the cooling heat exchanger
(111). In the cooling heat exchanger (111), the refrigerant absorbs
heat from the inside air to be evaporated. For the evaporation, the
cooling heat exchanger (111) is so set that the evaporation
temperature of the refrigerant is -5.degree. C., for example. The
refrigerant evaporated in the cooling heat exchanger (111) flows
into the first gas side communication pipe (23). In the cooing
showcase (13), the inside air cooled in the cooling heat exchanger
(111) is supplied thereto so that the inside temperature is kept at
5.degree. C., for example.
[0135] The refrigerant flowing in the refrigeration circuit (130)
is pressure-reduced when passing through the refrigeration
expansion valve (132), and then, is introduced into the
refrigeration heat exchanger (131). In the refrigeration heat
exchanger (131), the refrigerant absorbs heat from the inside air
to be evaporated. For the evaporation, the refrigeration heat
exchanger (131) is so set that the evaporation temperature of the
refrigerant is -30.degree. C., for example. In the refrigeration
showcase (14), the inside air cooled in the refrigeration heat
exchanger (131) is supplied to the inside thereof so that the
inside temperature is kept at -20.degree. C., for example.
[0136] The refrigerant evaporated in the refrigeration heat
exchanger (131) flows into the booster circuit (140) to be sucked
into the booster compressor (141). The refrigerant compressed in
the booster compressor (141) passes through the discharge pipe
(144) and flows into the first gas side communication pipe
(23).
[0137] In the first gas side communication pipe (23), the
refrigerant sent from the cooling circuit (110) and the refrigerant
sent from the booster circuit (140) are combined together. Then,
the combined refrigerant passes through the first gas side
communication pipe (23) and flows into the first suction pipe (61)
of the outdoor circuit (40). The refrigerant flowing in the first
suction pipe (61) passes through the first branch pipe (61a)
thereof to be sucked into the variable capacity compressor
(41).
[0138] <First Heating Operation>
[0139] First heating operation is operation for cooling the inside
air of the cooling showcase (13) and of the refrigeration showcase
(14) and for heating room air by the air conditioning unit (12) to
heat the store.
[0140] As shown in FIG. 3, in the outdoor circuit (40), the first
four-way switching valve (51), the second four-way switching valve
(52), and the third four-way switching valve (53) are set to the
second state, the first state, and the first state, respectively.
The outdoor expansion valve (46) is closed fully while each opening
of the air conditioning expansion valve (102), the cooling
expansion valve (112), and the refrigeration expansion valve (132)
is adjusted appropriately. In this condition, the variable capacity
compressor (41) and the booster compressor (14) are operated while
the first fixed capacity compressor (42) and the second fixed
capacity compressor (43) are stopped. The outdoor heat exchanger
(44) is stopped with no refrigerant sent thereto. During this first
heating operation, the subcooling unit (200) is stopped.
[0141] The refrigerant discharged from the variable capacity
compressor (41) passes through the first four-way switching valve
(51) and the second gas side communication pipe (24) in this order,
is introduced into the air conditioning heat exchanger (101) of the
air conditioning circuit (100), and then, radiates heat to room air
to be condensed. The air conditioning unit (12) supplies the room
air heated in the air conditioning heat exchanger (101) to the
store. The refrigerant condensed in the air conditioning heat
exchanger (101) passes through the second liquid side communication
pipe (22) to be divided to flow into the cooling circuit (110) and
the refrigeration circuit (130).
[0142] In the cooling showcase (13) and the refrigeration showcase
(14), the inside air is cooled, like in the cooling operation. The
refrigerant flowing in the cooling circuit (110) is evaporated in
the cooling heat exchanger (111), and then, flows into the first
gas side communication pipe (23). On the other hand, the
refrigerant flowing in the refrigeration circuit (130) is
evaporated in the refrigeration heat exchanger (131), is compressed
in the booster compressor (141), and then, flows into the first gas
side communication pipe (23). The refrigerant flowing in the first
gas side communication pipe (23) passes through the first suction
pipe (61), and then, is sucked into the variable capacitor
compressor (41) to be compressed.
[0143] As described above, in the first heating operation, the
refrigerant absorbs heat in the cooling heat exchanger (111) and in
the refrigeration heat exchanger (131) while radiating heat in the
air conditioning heat exchanger (101). Then, the store is heated by
utilizing the heat that the refrigerant absorbs from the inside air
of the cooling heat exchanger (111) and of the refrigeration heat
exchanger (131).
[0144] It is noted that the first fixed capacity compressor (42)
may be operated as shown in FIG. 4 during the first heating
operation. The operation of the first fixed capacity compressor
(42) depends on cooling loads in the cooling showcase (13) and the
refrigeration showcase (14). In this case, the third four-way
switching valve (53) is set to the second state. Further, part of
the refrigerant flowing in the first suction pipe (61) passes
through the first branch pipe (61a) thereof to be sucked into the
variable capacity compressor (42) while the other part thereof
passes through the second branch pipe (61b) thereof, the third
four-way switching valve (53), and the second suction pipe (62) in
this order to be sucked into the first fixed capacity compressor
(42).
[0145] <Second Heating Operation>
[0146] Second heating operation is operation for heating the store,
similarly to the first heating operation. The second heating
operation is performed in the case where the heating power in the
first heating operation only is insufficient.
[0147] As shown in FIG. 5, in the outdoor circuit (40), the first
four-way switching valve (51), the second four-way switching valve
(52), and the third four-way switching valve (53) are set to the
second state, the first state, and the first state, respectively.
Each opening of the outdoor expansion valve (46), the air
conditioning expansion valve (102), the cooling expansion valve
(112), and the refrigeration expansion valve (132) is adjusted
appropriately. In this condition, the variable capacity compressor
(41), the second fixed capacity compressor (43), and the booster
compressor (14) are operated while the first fixed capacity
compressor (42) is stopped. During this first heating operation,
the subcooling unit (200) is stopped.
[0148] The refrigerant discharged from the variable capacity
compressor (41) and the second fixed capacity compressor (43)
passes through the first four-way switching valve and the second
gas side communication pipe (24) in this order, is introduced into
the air conditioning heat exchanger (101) of the air conditioning
circuit (100), and then, radiates heat to room air to be condensed.
The air conditioning unit (12) supplies the room air heated in the
air conditioning heat exchanger (101) to the store. The refrigerant
condensed in the air conditioning heat exchanger (101) flows into
the second liquid side communication pipe (22). Part of the
refrigerant flowing in the second liquid side communication pipe
(22) is divided to flow into the cooling circuit (110) and the
refrigeration circuit (130) while the other part thereof is
introduced into the refrigerant passage (205) of the subcooling
unit (200).
[0149] In the cooling showcase (13) and the refrigeration showcase
(14), the inside air is cooled, like in the cooling operation. The
refrigerant flowing in the cooling circuit (110) is evaporated in
the cooling heat exchanger (111), and then, flows into the first
gas side communication pipe (23). On the other hand, the
refrigerant flowing in the refrigeration circuit (130) is
evaporated in the refrigeration heat exchanger (131), is compressed
in the booster compressor (141), and then, flows into the first gas
side communication pipe (23). The refrigerant flowing in the first
gas side communication pipe (23) passes through the first suction
pipe (61), and then, is sucked into the variable capacitor
compressor (41) to be compressed.
[0150] The refrigerant flowing in the refrigerant passage (205) of
the subcooling unit (200) passes through the first liquid side
communication pipe (21) and the third liquid pipe (83) in this
order, flows into the receiver (45), passes through the second
liquid pipe (82), and then, flows into the fourth liquid pipe (84).
The refrigerant flowing in the fourth liquid pipe (84) passes
through the outdoor expansion valve (46) to be pressure-reduced, is
introduced into the outdoor heat exchanger (44), and then, absorbs
heat from outdoor air to be evaporated. The refrigerant evaporated
in the outdoor heat exchanger (44) passes through the first
four-way switching valve (51), the second four-way switching valve
(52) in this order, flows into the second suction pipe (62), and
then, is sucked into the second fixed capacity compressor (43) to
be compressed.
[0151] As described above, in the second heating operation, the
refrigerant absorbs heat in the cooling heat exchanger (111), the
refrigeration heat exchanger (131), and the outdoor heat exchanger
(44) while radiating heat in the air conditioning heat exchanger
(101). Then, the store is heated by utilizing the heat that the
refrigerant absorbs from the inside air in the cooling heat
exchanger (111) and the refrigerant heat exchanger (131) and the
heat that the refrigerant absorbs from outdoor air in the outdoor
heat exchanger (44).
[0152] --Driving Operation of Subcooling Unit--
[0153] Driving operation of the subcooling unit (200) will be
described. In the condition that the subcooling unit (200) is
operated, the subcooling compressor (211) is operated and the
opening of the subcooling expansion valve (223) is adjusted
appropriately.
[0154] As shown in FIG. 1, the subcooling refrigerant discharged
from the subcooling compressor (221) radiates heat to outdoor air
in the subcooling outdoor heat exchanger (222) to be condensed. The
subcooling refrigerant condensed in the subcooling outdoor heat
exchanger (222) passes through the subcooling expansion valve (223)
to be pressure-reduced, and then, flows into the first flow paths
(211) of the subcooling heat exchanger (210). In the first flow
paths (211) of the subcooling heat exchanger (210), the subcooling
refrigerant absorbs heat from the refrigerant in the second flow
paths (212) to be evaporated. The subcooling refrigerant evaporated
in the subcooling heat exchanger (210) is sucked into the
subcooling compressor (221) to be compressed.
[0155] As described above, the controller (240) controls the
capacity of the subcooling compressor (221) on the basis of the
input outside air temperature. Herein, the control operation by the
controller (240) will be described with reference to FIG. 6. The
control operation of the controller (240) is repeated every given
time period (30 seconds, for example).
[0156] First, when the control starts, a value is calculated in a
step ST1 by subtracting the target cooling temperature (Eom) set in
the setting section (241) of the controller (240) from the
detection temperature (Tout) of the refrigerant temperature sensor
(236). In the present embodiment, the target cooling temperature
(Eom) is set as shown in FIG. 7. Specifically, when the outside air
temperature is not exceeding 25.degree. C., comparatively low, the
target cooling temperature (Eom) is set to be 25.degree. C. Or,
when the outside air temperature is exceeding 40.degree. C., the
target cooling temperature (Eom) is set to be 0.degree. C. When the
outside air temperature is within the range between 25.degree. C.
and 40.degree. C., the target cooling temperature (Eom) is set so
as to be lowered from 25.degree. C. to 0.degree. C. in proportion.
It is noted that the target refrigerant temperature (Eom) is not
limited to the above set values.
[0157] In the step ST1, when the difference between the detection
value (Tout) and the target cooling temperature (Eom) is less than
"-1.0," the routine proceeds to a step ST2. When the difference is
larger than "+1.0," the routine proceeds to a step ST3. When the
difference is within the range between "-1.0 and +1.0," the routine
returns so that the control terminates. Specifically, the routine
proceeds to the step ST2 when the cooling power and the like are
excessive because of excessive cooling of the refrigerant of the
refrigerating apparatus (10). The routine proceeds to the step ST3
when the cooling power and the like is insufficient because of
insufficient cooling of the refrigerant of the refrigerating
apparatus (10). The difference within the range between "-1.0 and
+1.0" falls in a no change necessitating range that necessitates no
change in operation frequency of the subcooling compressor (221),
wherein the set width thereof is exchangeable to, for example,
between "-1.5 and +1.5" and between "-2.0 and +2.0." In this case,
the above set values, "less than -1.0" and larger than "+1.0" are
exchanged accordingly.
[0158] In the step ST2, whether or not the operation frequency of
the subcooling compressor (221) is the lowest frequency is judged.
When it is judged as the lowest frequency, the routine returns so
that the control terminates. When it is judged as not the lowest
frequency, the routine proceeds to a step ST4. In the step ST4, the
control section (242) of the controller (240) reduces one level the
operation frequency of the subcooling compressor (221). This raises
the cooling temperature of the refrigerant of the refrigerating
apparatus (10), lowering the cooling power and the like, which have
been excessive, to appropriate power according to the load.
[0159] In the step ST3, whether or not the operation frequency of
the subcooling compressor (221) is the highest frequency is judged.
When it is judged as the highest frequency, the routine returns so
that the control terminates. When it is judged as not the highest
frequency, the routine proceeds to a step ST5. In the step ST5, the
control section (242) of the controller (240) increases one level
the operation frequency of the subcooling compressor (221). This
lowers the cooling temperature of the refrigerant of the
refrigerating apparatus (10), increasing the cooling power and the
like, which have been insufficient, to appropriate power according
to the load. It is noted that in the present embodiment, the
operation frequency of the subcooling compressor (221) is
changeable among 20 levels.
[0160] In the case where the temperature of the subcooling
refrigerant cannot be detected correctly due to disorder or the
like of the refrigerant temperature sensor (236), in the step ST1,
a value is calculated by subtracting the target cooling temperature
(Eom) of the setting section (241) from the set temperature (Tout)
set with the use of the detection pressure of the suction pressure
sensor (234). The following control subsequent thereto is the same
as the control as described above.
EFFECTS OF EMBODIMENT
[0161] As described above, according to the present embodiment, in
the subcooling unit (200), the operation of the subcooling
compressor (221) is controlled on the basis of the outside air
temperature as the detection value of the sensor provided in the
subcooling unit (200), that is, information obtainable within the
subcooling unit (200) to adjust the cooling temperature of the
refrigerant of the refrigerating apparatus (10). Hence, appropriate
operation can be performed according to the load state of the air
conditioning unit (12) or the like without sending and receiving
any signal to and from the outdoor unit (11) or the air
conditioning unit (12) of the refrigerating apparatus (10). As a
result, for incorporating the subcooling unit (200) to the
refrigerating apparatus (10), only connection of the refrigerant
passage (205) of the subcooling unit (200) to the first and second
liquid side communication pipes (21, 22) of the refrigerating
apparatus (10) is required. This eliminates the need to wire any
communication wirings for sending and receiving a signal between
the refrigerating apparatus (10) and the subcooling unit (200).
[0162] Hence, according to the present embodiment, the number of
operation steps for incorporating the subcooling unit (200) to the
refrigerating apparatus (10) can be reduced and troubles caused due
to human errors in installation, such as mis-wiring, can be
obviated.
[0163] Moreover, the controller (240) controls the driving
operation of the subcooling compressor (221) on the basis of the
difference between the detection temperature (Tout) of the
refrigerant and the target cooling temperature (Eom) set according
to the outside air temperature, thereby enabling reliable
adjustment of the cooling power with only information obtainable
within the subcooling unit (200), as well.
[0164] Furthermore, even in the case where the refrigerant
temperature sensor (236) becomes abnormal and cannot perform the
detection, the set temperature set from the saturation temperature
(TG) of the subcooling refrigerant in the detection pressure (LP)
of the suction pressure sensor (234) provided within the subcooling
unit (200) is regarded as the detection temperature of the
refrigerant, thereby attaining further reliable adjustment of the
cooling power.
[0165] In order to send and receive a signal between the subcooling
unit (200) and the refrigerating apparatus (10), a communication
interface is needed at the refrigerating apparatus (10) as well as
at the subcooling unit (200). For this reason, in the case where
operation control of a subcooling unit (200) requires signal input
from a refrigerating apparatus (10), an applicable type of the
refrigerating apparatus (10) is limited, resulting in poor
usability of the subcooling unit (200).
[0166] In contrast, the subcooling unit (200) in the present
embodiment eliminates the need to send and receive any signal to
and from the refrigerating apparatus (10) and no limitation is
imposed on the type of the refrigerating apparatus (10) as an
object to which the subcooling unit (200) is to be incorporated.
Hence, the usability of the subcooling unit (200) is enhanced
remarkably.
Modified Example 1 of Embodiment
[0167] In Modified Example 1, the flow rate of the subcooling
refrigerant in the subcooling heat exchanger (210) is adjusted by
controlling the operation frequency of the outdoor fan (230) of the
subcooling outdoor heat exchanger (222), rather than the control of
the subcooling compressor (221). The outdoor fan (230) of the
present modified example is changeable in capacity by changing the
operation frequency of its fan motor.
[0168] Specifically, when the operation frequency of the outdoor
fan (230) is reduced, the high pressure in the subcooling
refrigerant circuit (220) increases to increase the circulation
amount of the subcooling refrigerant. Accordingly, the flow rate of
the subcooling refrigerant in the subcooling heat exchanger (210)
increases. This increases the amount of heat exchange between the
subcooling refrigerant and the refrigerant of the refrigerating
apparatus (10) in the subcooling heat exchanger (210) to lower the
cooling temperature of the refrigerant of the refrigerating
apparatus (10), increasing the cooling power and the like of the
air conditioning unit (12). In reverse, when the operation
frequency of the outdoor fan (230) is increased, the high pressure
in the subcooling refrigerant circuit (220) reduces to reduce the
circulation amount of the subcooling refrigerant. Accordingly, the
flow rate of the subcooling refrigerant in the subcooling heat
exchanger (210) reduces. This reduces the amount of heat exchange
between the subcooling refrigerant and the refrigerant of the
refrigerating apparatus (10) in the subcooling heat exchanger (210)
to raise the cooling temperature of the refrigerant of the
refrigerating apparatus (10), lowering the cooling power and the
like of the air conditioning unit (12).
[0169] In the present modified example, the control operation by
the controller (240) is as follows. In the step ST2 in FIG. 6,
whether or not the operation frequency of the outdoor fan (230) is
the highest frequency is judged. When it is judged as the highest
frequency, the routine returns so that the control terminates. When
it is judged as not the highest frequency, the routine proceeds to
the step ST4. In the step ST4, the control section (242) of the
controller (240) increases one level the operation frequency of the
outdoor fan (230). This raises the cooling temperature of the
refrigerant of the refrigerating apparatus (10), enabling lowering
of the cooling power and the like, which have been excessive, to
appropriate power according to the load.
[0170] In the step ST3, whether or not the operation frequency of
the outdoor fan (230) is the lowest frequency is judged. When it is
judged as the lowest frequency, the routine returns so that the
control terminates. When it is judged as not the lowest frequency,
the routine proceeds to the step ST5. In the step ST5, the control
section (242) of the controller (240) reduces one level the
operation frequency of the outdoor fan (230). This lowers the
cooling temperature of the refrigerant of the refrigerating
apparatus (10), enabling increase in cooling power and the like,
which have been insufficient, to appropriate power according to the
load.
[0171] It is noted that in the present invention, the flow rate of
the subcooling refrigerant in the subcooling heat exchanger (210)
may be adjusted by controlling both the subcooling compressor (221)
and the outdoor fan (230). In this case, the controllability of the
cooling temperature of the refrigerant is enhanced.
Modified Example 2 of Embodiment
[0172] In Modified Example 2, the cooling fluid circuit in the
above embodiment is modified, though not shown. While the
refrigerant circuit serves as the cooling fluid circuit in the
above embodiment, a cold water circuit in which cold water flows
serves as the cooling fluid circuit in this modified example.
Specifically, the cold water circuit includes the subcooling heat
exchanger (210) and a pump so that the pump circulates the cold
water between a cooling tower and the subcooling heat exchanger
(210). In the subcooling heat exchanger (210), the cold water is
heat-exchanged with the refrigerant of the refrigerant passage
(205) to cool the refrigerant thereof. In short, the cold water
flows as the cooling fluid in the cooling fluid circuit in the
present modified example.
[0173] In this modified example, for example, when the outside air
temperature is high, the operation frequency of the pump is
increased for increasing the flow rate of the cold water in the
subcooling heat exchanger (210) to lower the cooling temperature of
the refrigerant, thereby increasing the cooling power and the like
of the air conditioning unit (12). In reverse, when the outside air
temperature is low, the operation frequency of the pump is reduced
for reducing the flow rate of the cold water in the subcooling heat
exchanger (210) to raise the cooling temperature of the
refrigerant, thereby lowering the cooling power and the like of the
air conditioning unit (12). The other composition, operation and
effects thereof are the same as those in the embodiment.
[0174] It is noted that in the present modified example, the
setting section (241) of the controller (240) may use as the
ambient condition of the subcooling heat exchanger (210) the
temperature of the cold water after cooled in the subcooling heat
exchanger (210), rather than the outside air temperature.
Other Embodiments
[0175] In the above embodiment, either the detection pressure (LP)
of the suction pressure sensor (234) or the detection temperature
(Ti) of the suction temperature sensor (235) is input into the
control section (242) of the controller (240) when the refrigerant
temperature sensor (236) is abnormal, but both of them may be
input. In this case, the detection pressure (LP) of the suction
pressure sensor (234) is used first when the refrigerant
temperature sensor (236) is abnormal. Then, the detection
temperature (Ti) of the suction temperature sensor (235) is used in
the case where both the refrigerant temperature sensor (236) and
the suction pressure sensor (234) are abnormal.
[0176] Further, in the above embodiment and the modified examples
thereof, only the detection pressure (LP) of the suction pressure
sensor (234) or the detection temperature (Ti) of the suction
temperature sensor (235) may be input into the control section
(242) without inputting the detection temperature (Tout) of the
refrigerant temperature sensor (236). In this case, the difference
between the set temperature (Tout) set from the detection pressure
(LP) or the detection temperature (Ti) and the target cooling
temperature (Eom) is used as a reference value for controlling the
subcooling compressor (221) or the outdoor fan (230), irrespective
of normal or abnormal operation of the refrigerant temperature
sensor (236).
[0177] Moreover, if a four-way switching valve or the like is
provided in the subcooling refrigerant circuit (220) of the above
embodiment so that the refrigerant circulating direction is
exchangeable and the refrigerant passage (205) is connected to the
gas side communication pipes such as the first gas side
communication pipe (23) and the second gas side communication pipe
(24), the refrigerant of the refrigerating apparatus (10) can be
heated. This prevents generally-called wet vapor suction to the
respective compressors (41, . . . ) of the outdoor unit (11).
Hence, with the subcooling refrigerant circuit (220) exchangeable
in direction of the refrigerant circulation, the subcooling unit
(200) in the present invention can be exchangeable between the
subcooling apparatus and a heating apparatus for the refrigerant as
needed.
[0178] It should be noted that the above embodiments are
substantially preferred examples and do not intend to limit the
scopes of the present invention, applicable objects, and use
thereof.
INDUSTRIAL APPLICABILITY
[0179] As described above, the present invention is useful in
subcooling apparatuses for cooling refrigerant sent from a heat
source unit to a utility unit in a refrigerating apparatus.
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