U.S. patent application number 17/617755 was filed with the patent office on 2022-07-28 for refrigeration cycle apparatus.
The applicant listed for this patent is Mitsubishi Electric Corporation. Invention is credited to Takahito HIKONE, Kimitaka KADOWAKI, Takenori MATSUMOTO, Shohei TAKENAKA.
Application Number | 20220235982 17/617755 |
Document ID | / |
Family ID | |
Filed Date | 2022-07-28 |
United States Patent
Application |
20220235982 |
Kind Code |
A1 |
MATSUMOTO; Takenori ; et
al. |
July 28, 2022 |
REFRIGERATION CYCLE APPARATUS
Abstract
A refrigeration cycle apparatus includes a refrigerant circuit
in which a compressor, a refrigerant flow switching device, an
air-side heat exchanger, an expansion valve, a water-side heat
exchanger, and an accumulator are connected by refrigerant pipes
and refrigerant is circulated. G/A is less than or equal to a
predetermined threshold .chi., where G [L] is a difference in
volume between the air-side heat exchanger and the water-side heat
exchanger, and A [L] is a volume of the refrigerant circuit.
Inventors: |
MATSUMOTO; Takenori; (Tokyo,
JP) ; TAKENAKA; Shohei; (Tokyo, JP) ; HIKONE;
Takahito; (Tokyo, JP) ; KADOWAKI; Kimitaka;
(Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Mitsubishi Electric Corporation |
Tokyo |
|
JP |
|
|
Appl. No.: |
17/617755 |
Filed: |
August 7, 2019 |
PCT Filed: |
August 7, 2019 |
PCT NO: |
PCT/JP2019/031084 |
371 Date: |
December 9, 2021 |
International
Class: |
F25B 41/31 20060101
F25B041/31; F25B 13/00 20060101 F25B013/00 |
Claims
1. (canceled)
2. A refrigeration cycle apparatus comprising a refrigerant circuit
in which a compressor, a refrigerant flow switching device, an
air-side heat exchanger, an expansion valve, a water-side heat
exchanger, and an accumulator are connected by refrigerant pipes
and refrigerant is circulated, wherein the refrigerant pipes
include a high-pressure pipe that connects a discharge side of the
compressor with the water-side heat exchanger in a heating
operation and a low-pressure pipe that connects the air-side heat
exchanger with a suction side of the compressor in the heating
operation, G/A is less than or equal to a predetermined threshold
.chi., where G [L] is a difference in volume between the air-side
heat exchanger and the water-side heat exchanger, and A [L] is a
volume of the refrigerant circuit, and where an outer diameter of
the high-pressure pipe is 25.4 mm, and an outer diameter of the
low-pressure pipe is D mm, the threshold .chi. is expressed by the
following equation:
x=0.0000001479D.sup.3-0.0000245654D.sup.2+0.0000786935D+0.2018219300.
3. A refrigeration cycle apparatus comprising a refrigerant circuit
in which a compressor, a refrigerant flow switching device, an
air-side heat exchanger, an expansion valve, a water-side heat
exchanger, and an accumulator are connected by refrigerant pipes
and refrigerant is circulated, wherein the refrigerant pipes
include a high-pressure pipe that connects a discharge side of the
compressor with the water-side heat exchanger in a heating
operation and a low-pressure pipe that connects the air-side heat
exchanger with a suction side of the compressor in the heating
operation, G/A is less than or equal to a predetermined threshold
.chi., where G [L] is a difference in volume between the air-side
heat exchanger and the water-side heat exchanger, and A [L] is a
volume of the refrigerant circuit, and where an outer diameter of
the high-pressure pipe is 28.6 mm, and an outer diameter of the
low-pressure pipe is D mm, the threshold .chi. is expressed by the
following equation:
x=0.0000001432D.sup.3-0.0000239347D.sup.2+0.0000774572D+0.1991706771.
4. A refrigeration cycle apparatus comprising a refrigerant circuit
in which a compressor, a refrigerant flow switching device, an
air-side heat exchanger, an expansion valve, a water-side heat
exchanger, and an accumulator are connected by refrigerant pipes
and refrigerant is circulated, wherein the refrigerant pipes
include a high-pressure pipe that connects a discharge side of the
compressor with the water-side heat exchanger in a heating
operation and a low-pressure pipe that connects the air-side heat
exchanger with a suction side of the compressor in the heating
operation, G/A is less than or equal to a predetermined threshold
.chi.y, where G [L] is a difference in volume between the air-side
heat exchanger and the water-side heat exchanger, and A [L] is a
volume of the refrigerant circuit, and where an outer diameter of
the high-pressure pipe is 31.75 mm, and an outer diameter of the
low-pressure pipe is D mm, the threshold .chi. is expressed by the
following equation:
x=0.0000001376D.sup.3-0.0000231712D.sup.2+0.0000758817D+0.1959228337.
Description
TECHNICAL FIELD
[0001] The present disclosure relates to a refrigeration cycle
apparatus in which refrigerant circulates in a refrigerant
circuit.
BACKGROUND ART
[0002] In general, in an air-cooled chiller, refrigerant is highly
efficiently condensed at a water-side heat exchanger than at an
air-side heat exchanger. Thus, the volume of the water-side heat
exchanger can be reduced. Furthermore, in a heating operation, the
amount of refrigerant that is required for a refrigeration cycle
apparatus is smaller than that in a cooling operation. Therefore,
in the heating operation in which the water-side heat exchanger
operates as a condenser, it is necessary to store surplus
refrigerant because a required amount of refrigerant is smaller
than that in the cooling operation. In view of the above, a
refrigeration cycle apparatus is proposed that can store surplus
refrigerant that generates for the above reason (for example, see
Patent Literature 1).
[0003] The refrigeration cycle apparatus disclosed in Patent
Literature 1 includes a compressor, a refrigerant flow switching
device such as a four-way valve, an air-side heat exchanger, a main
expansion valve, a water-side heat exchanger, an accumulator, a
refrigerant-amount adjustment tank, two sub-expansion valves
serving as refrigerant flow control valves, a gas purge circuit,
and a heat-source-apparatus control device serving as a controller.
Furthermore, the compressor, the refrigerant flow switching device,
the air-side heat exchanger, the main expansion valve, the
water-side heat exchanger, and the accumulator are sequentially
connected by refrigerant pipes to form a main circuit of a
refrigerant circuit. In addition, the refrigerant-amount adjustment
tank, the sub-expansion valves, and the gas purge circuit form a
sub-circuit of the refrigerant circuit.
[0004] The refrigerant-amount adjustment tank included in the
refrigeration cycle apparatus is provided in parallel with the main
expansion valve, and stores surplus refrigerant that generates
because of a difference between an operation state of the cooling
operation and that of the heating operation.
CITATION LIST
Patent Literature
[0005] Patent Literature 1: Japanese Patent No. 6479203
SUMMARY OF INVENTION
Technical Problem
[0006] In the refrigeration cycle apparatus disclosed in Patent
Literature 1, the refrigerant-amount adjustment tank is housed in a
machine chamber. That is, the machine chamber needs to secure a
space to house the refrigerant-amount adjustment tank. Inevitably,
the apparatus is made larger.
[0007] The present disclosure is applied to solve the above
problem, and relates to a refrigeration cycle apparatus that can be
made smaller.
Solution to Problem
[0008] A refrigeration cycle apparatus according to an embodiment
of the present disclosure includes a refrigerant circuit in which a
compressor, a refrigerant flow switching device, an air-side heat
exchanger, an expansion valve, a water-side heat exchanger, and an
accumulator are connected by refrigerant pipes and refrigerant is
circulated. G/A is less than or equal to a predetermined threshold
.chi., where G [L] is a difference in volume between the air-side
heat exchanger and the water-side heat exchanger, and A [L] is a
volume of the refrigerant circuit.
Advantageous Effects of Invention
[0009] In the refrigeration cycle apparatus according to the
embodiment of the present disclosure, G/A is less than or equal to
the predetermined threshold .chi.. Therefore, the surplus
refrigerant that is refrigerant the amount of which corresponds to
the difference in volume between the air-side heat exchanger and
the water-side heat exchanger can be stored in the refrigerant
circuit, that is, the surplus refrigerant can be stored in the
compressor, the air-side heat exchanger, the expansion valve, the
water-side heat exchanger, the accumulator, and the refrigerant
pipes. As a result, a refrigerant tank configured to store the
surplus refrigerant does not need to be provided, and it is not
necessary to secure a space to house the refrigerant tank in the
machine chamber.
[0010] Accordingly, the refrigeration cycle apparatus can be made
smaller.
BRIEF DESCRIPTION OF DRAWINGS
[0011] FIG. 1 is a perspective view illustrating an air-cooled heat
pump chiller to which a refrigeration cycle apparatus according to
an embodiment of the present disclosure is applied.
[0012] FIG. 2 is a schematic diagram illustrating an example of the
circuit configuration of the refrigeration cycle apparatus
according to the embodiment in a cooling operation.
[0013] FIG. 3 is a schematic diagram illustrating an example of the
circuit configuration of the refrigeration cycle apparatus
according to the embodiment in a heating operation.
[0014] FIG. 4 is a diagram indicating volumes of common
high-pressure pipes for use in a refrigerant circuit, which
correspond to respective sizes of the common high-pressure
pipes.
[0015] FIG. 5 is a diagram indicating volumes of common
low-pressure pipes for use in the refrigerant circuit, which
corresponds to respective sizes of the common low-pressure
pipes.
[0016] FIG. 6 is a diagram indicating a relationship between the
volume of a refrigerant tank in each of existing apparatuses and a
difference in volume between an air-side heat exchanger and a
water-side heat exchanger in each existing apparatus.
[0017] FIG. 7 is a diagram indicating a relationship between the
volume of the refrigerant tank and the difference in volume
difference between the air-side heat exchanger and the water-side
heat exchanger.
[0018] FIG. 8 is a diagram indicating thresholds for respective
sizes of the high-pressure pipes and the low-pressure pipes
indicated in FIGS. 4 and 5.
[0019] FIG. 9 is a diagram indicating a relationship between the
thresholds and the respective sizes of the low-pressure pipes.
DESCRIPTION OF EMBODIMENTS
[0020] An embodiment of the present disclosure will be described
with reference to the drawings. It should be noted that the
following description is not limiting.
[0021] Furthermore, in figures to be referred to below,
relationships in size between components may be different from
actual ones.
Embodiment
[0022] A refrigeration cycle apparatus 100 according to the
embodiment will be described.
[0023] FIG. 1 is a perspective view illustrating an air-cooled heat
pump chiller 101 to which the refrigeration cycle apparatus 100
according to the embodiment is applied. FIG. 2 is a schematic
diagram illustrating an example of the circuit configuration of the
refrigeration cycle apparatus 100 according to the embodiment in a
cooling operation. FIG. 3 is a schematic diagram illustrating an
example of the circuit configuration of the refrigeration cycle
apparatus 100 according to the embodiment in a heating
operation.
[0024] The refrigeration cycle apparatus 100 according to the
embodiment is applied to, for example, an air-cooled heat pump
chiller 101 that is provided as illustrated in FIG. 1 and that
cools and heats water to generate cold water and hot water. The
refrigeration cycle apparatus 100 may be applied to an
air-conditioning apparatus that is provided to cool and heat an
indoor space. As illustrated in FIG. 1, a machine chamber 30 that
houses a compressor 11, an expansion valve 14, and other components
is provided at a lower portion of the air-cooled heat pump chiller
101. Furthermore, an air-side heat exchanger 13 is provided on the
machine chamber 30, and an air-side air-sending device is provided
on the air-side heat exchanger 13.
[Circuit Configuration of Refrigeration Cycle Apparatus]
[0025] As illustrated in FIGS. 2 and 3, the refrigeration cycle
apparatus 100 includes the compressor 11, a refrigerant flow
switching device 12, the air-side heat exchanger 13, the expansion
valve 14, a water-side heat exchanger 15, an accumulator 16, the
air-side air-sending device, and a heat-source-apparatus control
device 50 serving as a controller.
[0026] Furthermore, the refrigeration cycle apparatus 100 includes
a refrigerant circuit in which the compressor 11, the refrigerant
flow switching device 12, the air-side heat exchanger 13, the
expansion valve 14, the water-side heat exchanger 15, and the
accumulator 16 are sequentially connected by refrigerant pipes 20.
The refrigerant circuit is filled with refrigerant that circulates
in the circuit. The refrigerant pipes include gas pipes and a
liquid pipe. The gas pipes are a high-pressure pipe 20a that
connects a discharge side of the compressor 11 with the water-side
heat exchanger 15 in the heating operation and a low-pressure pipe
20b that connects the air-side heat exchanger 13 with a suction
side of the compressor 11 in the heating operation. The liquid pipe
connects the water-side heat exchanger 15 with the air-side heat
exchanger 13.
[0027] As the refrigerant to be filled in the refrigerant circuit,
for example, single-component refrigerant such as R-22 or R-134a,
pseudo-azeotropic refrigerant mixture such as R-410A and R-404A, or
non-azeotropic refrigerant mixture such as R-407C can be used.
Furthermore, refrigerant having a relatively small global warming
potential and including a double bond in a chemical formula, such
as CF.sub.3CF.dbd.CH.sub.2, a mixture thereof, natural refrigerant
such as CO.sub.2 or propane can be used.
[0028] The compressor 11 sucks low-temperature and low-pressure
refrigerant, compresses the low-temperature and low-pressure
refrigerant to change into high-temperature and high-pressure gas
refrigerant, and discharges the high-temperature and high-pressure
gas refrigerant. The compressor 11 is, for example, an inverter
compressor that can be controlled in volume that is a refrigerant
sending amount per unit time, by arbitrarily changing a driving
frequency.
[0029] The refrigerant flow switching device 12 switches a flow
direction of the refrigerant between a flow direction of the
refrigerant in the cooling operation and that in the heating
operation. To be more specific, in the cooling operation, the
refrigerant flow switching device 12 switches the flow direction of
the refrigerant such that the gas refrigerant discharged from the
compressor 11 flows into the air-side heat exchanger 13, as
illustrated in FIG. 2. In contrast, in the heating operation, the
refrigerant flow switching device 12 switches the flow direction of
the refrigerant such that the gas refrigerant discharged from the
compressor 11 flows tin the water-side heat exchanger 15, as
illustrated in FIG. 3. The refrigerant flow switching device 12 is,
for example, a four-way valve; however, other valves may be used in
combination as the refrigerant flow switching device 12.
[0030] The air-side heat exchanger 13 causes heat exchange to be
performed between the refrigerant and air that is supplied by, for
example, the air-side air-sending device, such as fan, which is
provided close to the air-side heat exchanger 13. More
specifically, in the cooling operation, the air-side heat exchanger
13 operates as a condenser that radiates heat of the refrigerant to
the air to condense the refrigerant. In addition, in the heating
operation, the air-side heat exchanger 13 operates as an evaporator
that evaporates the refrigerant to cool outdoor air with heat of
evaporation at that time. The air-side heat exchanger 13 is formed
by combining a plurality of plate fins and a plurality of
refrigerant pipes.
[0031] The expansion valve 14 has a function of reducing the
pressure of refrigerant that flows in the refrigerant circuit and
expanding of the refrigerant. The expansion valve 14 is, for
example, an electronic expansion valve, that is, a valve whose
opening degree can be controlled.
[0032] The water-side heat exchanger 15 operates as a condenser or
an evaporator, and causes heat exchange to be performed between the
refrigerant that flows in the refrigerant circuit and a heat medium
such as water.
[0033] The accumulator 16 is provided on the suction side of the
compressor 11, which is a low-pressure side of the compressor 11.
The accumulator 16 accumulates surplus refrigerant that generates
because of a difference between an operation state of the cooling
operation and an operation state of the heating operation, and
surplus refrigerant that generates because of a transient change of
the operation.
[0034] The heat-source-apparatus control device 50 controls the
entire refrigeration cycle apparatus 100. The heat-source-apparatus
control device 50 is, for example, dedicated hardware or a central
processing unit (CPU, also referred to as a central processing
device, a processing device, an arithmetic device, a
microprocessor, a microcomputer, or a processor) that executes
programs stored in a memory.
[0035] In the case where the heat-source-apparatus control device
50 is the dedicated hardware, the heat-source-apparatus control
device 50 corresponds to, for example, a single circuit, a
composite circuit, an application specific integrated circuit
(ASIC), a field programmable gate array (FPGA), or a combination
thereof. Functional units that are implemented by the
heat-source-apparatus control device 50 may be individual hardware,
or the functional units may be single hardware.
[0036] In the case where the heat-source-apparatus control device
50 is the CPU, the functions that are fulfilled by the
heat-source-apparatus control device 50 are fulfilled by software,
firmware, or a combination of software and firmware. The software
and the firmware are described as programs and are stored in the
memory. The CPU reads a program from the memory and executes the
read program to fulfill a function of the heat-source-apparatus
control device 50 that corresponds to the program. The memory is,
for example, a nonvolatile or volatile semiconductor memory such as
a RAM, a ROM, a flash memory, an EPROM, or an EEPROM. It should be
noted that of the functions of the heat-source-apparatus control
device 50, a function or functions may be fulfilled by the
dedicated hardware, and another function or other functions may be
fulfilled by the software or the firmware.
[0037] The heat-source-apparatus control device 50 receives
information indicating the results of detection from various kinds
of detection units such as a low-pressure sensor (not illustrated)
and an outside air temperature sensor (not illustrated).
Furthermore, the heat-source-apparatus control device 50 controls a
driving frequency of the compressor 11, a rotation speed (including
on/off) of the air-side air-sending device, a switching operation
of the refrigerant flow switching device 12, the opening degree of
the expansion valve 14, and other operations, on the basis of
operation information on the refrigeration cycle apparatus 100 that
is indicated by the results of the detection and an instruction
concerning the operation that is given by a user.
[0038] In the case where the amount of refrigerant that is required
for the refrigerant circuit in the cooling operation is compared
with that in the heating operation, the volume of the water-side
heat exchanger 15 can be reduced, since the refrigerant is further
efficiently condensed in the water-side heat exchanger 15 than in
the air-side heat exchanger 13. Therefore, the amount of the
refrigerant that is required for the refrigerant circuit in the
heating operation is smaller than that in the cooling
operation.
[0039] That is, in the heating operation, the amount of the
refrigerant that is required for the refrigerant circuit is
redundant. Therefore, in an existing apparatus, in order to
compensate for the difference in the amount of refrigerant between
the cooling operation and the heating operation, a refrigerant tank
is provided in parallel with the expansion valve 14, and surplus
refrigerant that generates in the heating operation is stored in
the refrigerant tank.
[0040] However, since the refrigerant tank is housed in the machine
chamber, it is necessary to secure a space for the refrigerant tank
in the machine chamber. Inevitably, the existing apparatus is made
larger. In view of this point, the refrigeration cycle apparatus
100 according to the embodiment is formed with no refrigerant
tank.
[0041] The amount of refrigerant that can be stored between the
air-side heat exchanger 13 and the water-side heat exchanger 15
varies between the cooling operation and the heating operation. In
the case where all the surplus refrigerant the amount of which
corresponds to the above variance in the amount of the refrigerant
can be stored in the refrigerant circuit, that is, in the air-side
heat exchanger 13, the water-side heat exchanger 15, the
accumulator 16, and the refrigerant pipes 20, it is not necessary
to provide a refrigerant tank.
[0042] In order that the surplus refrigerant be stored in the
refrigerant pipes 20, it is necessary that the refrigerant in the
gas pipe is present as gas refrigerant, not liquid refrigerant, to
prevent a failure from occurring at the compressor 11 due to a
liquid back. Furthermore, in order for the refrigerant in the gas
pipes included in the refrigerant pipes 20 to be present as the gas
refrigerant, it is necessary to reduce the pressure in the
refrigerant circuit to a predetermined value or less. The volume of
the entire refrigerant circuit is related to the pressure in the
refrigerant circuit. The pressure in the refrigerant circuit is
harder to raise, as the volume of the entire refrigerant circuit is
increased.
[0043] Therefore, where G [L] is the difference in volume between
the air-side heat exchanger 13 and the water-side heat exchanger
15, A [L] is the volume of the entire refrigerant circuit, when G/A
is less than or equal to a predetermined threshold .chi., that is,
when G/A.ltoreq..chi. is satisfied, it is possible to store all the
surplus refrigerant as gas refrigerant in the refrigerant circuit,
and it is therefore unnecessary to provide a refrigerant tank in
the refrigerant circuit. It should be noted that the threshold
.chi. is a threshold at which a refrigerant tank configured to
store surplus refrigerant becomes unnecessary, and is a threshold
determined for storing all the surplus refrigerant as gas
refrigerant in the refrigerant circuit. The volume of the entire
refrigerant circuit is the total volume of the compressor 11, the
air-side heat exchanger 13, the expansion valve 14, the water-side
heat exchanger 15, the accumulator 16, and the refrigerant pipes
20.
[0044] Next, a method of calculating the threshold .chi. will be
described.
[0045] FIG. 4 is a diagram indicating volumes of common
high-pressure pipes for use in the refrigerant circuit, which
correspond to respective sizes of the common high-pressure pipes.
FIG. 5 is a diagram indicating volumes of common low-pressure pipes
for use in the refrigerant circuit, which correspond to respective
sizes of the common low-pressure pipes. It should be noted that
each of the high-pressure pipes is a pipe that connects the
discharge side of the compressor with the water-side heat exchanger
in the heating operation, and each of the low-pressure pipes is a
pipe that connects the air-side heat exchanger with the suction
side of the compressor in the heating operation, in a refrigerant
circuit configuration similar to the refrigerant circuit
configuration of the refrigeration cycle apparatus 100.
[0046] As a calculation condition, the difference in volume between
the air-side heat exchanger and the water-side heat exchanger is
set to 5 L. The length of each of the refrigerant pipes is set to
1.2 m that corresponds to that of a refrigerant pipe for use in a
standard air-cooled heat pump chiller. The volume of the air-side
heat exchanger, that of the water-side heat exchanger, and that of
the accumulator are set to respective values that are determined
depending on the performances of the air-side heat exchanger, the
water-side heat exchanger and the accumulator. Furthermore, as
indicated in FIGS. 4 and 5, the size (outer diameter) of the
high-pressure pipe is set to 25.4 mm, 28.6 mm, or 31.75 mm, and the
size (outer diameter) of the low-pressure pipe is set to 25.4 mm,
28.6 mm, 31.75 mm, 34.93 mm, 38.1 mm, 41.28 mm, 44.45 mm, or 50.8
mm, based on JIS. The size (outer diameter) of the liquid pipe is
set to 12.7 mm that is the size of a liquid pipe that can reduce a
refrigerant pressure loss of the liquid refrigerant to a specified
value or less.
[0047] It will be descried why the difference in volume between the
air-side heat exchanger and the water-side heat exchanger is set to
5 L, as the calculation condition.
[0048] FIG. 6 is a diagram indicating a relationship between the
volume of a refrigerant tank in each of existing apparatuses and
the difference in volume between an air-side heat exchanger and a
water-side heat exchanger in each existing apparatus. It should be
noted that "air heat exchanger" described in FIG. 6 is an
abbreviation of the air-side heat exchanger, "water heat exchanger"
described in FIG. 6 is an abbreviation of the water-side heat
exchanger, and the same is true of the following description.
[0049] In an existing apparatus A, the volume of an air-side heat
exchanger is 19.6 L. the volume of a water-side heat exchanger is
5.4 L, and the difference in volume between the air-side heat
exchanger and the water-side heat exchanger is 14.2 L. In this
structure, in the existing apparatus A, a refrigerant tank having a
volume of 8.5 L is mounted. In an existing apparatus B, the volume
of an air-side heat exchanger is 13.9 L, the volume of a water-side
heat exchanger is 5.4 L, and the difference in volume between the
air-side heat exchanger and the water-side heat exchanger is 8.5 L.
In this structure, in the existing apparatus B, a refrigerant tank
having a volume of 4 L is mounted.
[0050] FIG. 7 is a diagram indicating a relationship between the
volume of the refrigerant tank and the difference in volume between
the air-side heat exchanger and the water-side heat exchanger. An
equation y of a straight line indicated in FIG. 7 is obtained from
the above structures of the existing apparatus A and the existing
apparatus B.
[0051] As indicated in FIG. 7, it can be seen from the equation y
of the straight line obtained from the existing apparatuses A and B
that in the case where the difference in volume between the
air-side heat exchanger and the water-side heat exchanger is less
than or equal to 3.43 L, the necessary volume of the refrigerant
tank is zero, that is, the refrigerant tank is unnecessary.
Therefore, in consideration of individual variability, it is
determined that in the case where the difference in volume between
the air-side heat exchanger and the water-side heat exchanger is
less than or equal to 4 L, the refrigerant tank is unnecessary.
Furthermore, the liquid refrigerant can be stored in the
refrigerant pipe that extends from the water-side heat exchanger to
the expansion valve. In this case, when the expansion valve is
provided close to the air-side heat exchanger, the length of the
refrigerant pipe from the water-side heat exchanger to the
expansion valve is increased, and the volume of refrigerant that
can be accumulated is increased. When the expansion valve is
provided close to the air-side heat exchanger, and for example, the
size (outer diameter) of the liquid pipe is set to 12.7 mm, the
volume of the refrigerant pipe from the water-side heat exchanger
to the expansion valve is approximately 1 L. Therefore, this value
is added to the difference in volume between the air-side heat
exchanger and the water-side heat exchanger, thereby obtaining 5 L.
Accordingly, as the calculation condition, the difference in volume
between the air-side heat exchanger and the water is 5 L.
[0052] FIG. 8 is a diagram indicating thresholds for sizes of the
high-pressure pipes and the low-pressure pipes that are indicated
regarding their volumes in FIGS. 4 and 5. FIG. 9 is a diagram
indicating a relationship between the thresholds and the sizes of
the low-pressure pipes. It should be noted that in FIG. 9, the
vertical axis indicates the threshold, and the horizontal axis
indicates the size of the low-pressure pipe.
[0053] When the threshold .chi. is calculated based on the above
calculation condition, the threshold .chi. varies as indicated in
FIG. 8.
[0054] Furthermore, where the size (outer diameter) of the
low-pressure pipe is a variable D mm, the threshold .chi. for each
of the sizes (outer diameters) of the high-pressure pipes is
expressed by the following equation as indicated in FIG. 9.
[High-Pressure Pipe: 25.4 mm (1 Inch)]
[0055]
x=0.0000001479D.sup.3-0.0000245654D.sup.2+0.0000786935D+0.20182193-
00
[High-Pressure Pipe: 28.6 mm (11/8 Inches)]
[0056]
x=0.0000001432D.sup.3-0.0000239347D.sup.2+0.0000774572D+0.19917067-
71
[High-Pressure Pipe: 31.75 mm (11/4 Inches)]
[0057]
x=0.0000001376D.sup.3-0.0000231712D.sup.2+0.0000758817D+0.19592283-
37
[0058] Therefore, when G/A is less than or equal to the
above-described threshold .chi., it is possible to store all the
surplus refrigerant as gas refrigerant in the refrigerant circuit,
and it is therefore unnecessary to provide a refrigerant tank in
the refrigerant circuit.
[0059] As described above, the refrigeration cycle apparatus 100
according to the embodiment includes the refrigerant circuit in
which the compressor 11, the refrigerant flow switching device 12,
the air-side heat exchanger 13, the expansion valve 14, the
water-side heat exchanger 15, and the accumulator 16 are connected
by the refrigerant pipes 20 and the refrigerant is circulated.
Where G [L] is the difference in volume between the air-side heat
exchanger 13 and the water-side heat exchanger 15, and A [L] is the
volume of the entire refrigerant circuit, G/A is less than or equal
to the predetermined threshold .chi..
[0060] In the refrigeration cycle apparatus 100 according to the
embodiment, G/A is less than or equal to the predetermined
threshold .chi.. Therefore, the surplus refrigerant that is
refrigerant the amount of which corresponds to the difference in
volume between the air-side heat exchanger 13 and the water-side
heat exchanger 15 can be stored in the refrigerant circuit, that
is, the surplus refrigerant can be stored in the compressor 11, the
air-side heat exchanger 13, the expansion valve 14, the water-side
heat exchanger 15, the accumulator 16, and the refrigerant pipes
20. As a result, a refrigerant storage tank does not need to be
provided. Accordingly, it is not necessary to secure, in the
machine chamber a space for a refrigerant-amount adjustment tank,
and the refrigerant cycle apparatus can thus be made smaller.
[0061] Further, since a refrigerant storage tank is unnecessary, it
is not necessary to provide a refrigerant-amount adjustment tank in
the machine chamber, and it is therefore possible to improve the
maintainability of the refrigerant cycle apparatus.
REFERENCE SIGNS LIST
[0062] 11: compressor, 12: refrigerant flow switching device, 13:
air-side heat exchanger, 14: expansion valve, 15: water-side heat
exchanger, 16: accumulator, 17: air-side air-sending device, 20:
refrigerant pipe, 20a: high-pressure pipe, 20b: low-pressure pipe,
30: machine chamber, 50: heat-source-apparatus control device, 100:
refrigeration cycle apparatus, 101: air-cooled heat pump
chiller
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