US20220316767A1

US20220316767A1 - Refrigerant cycle system

Info

Publication number: US20220316767A1
Application number: US17/618,075
Authority: US
Inventors: Takuro Yamada; Eiji Kumakura; Atsushi Yoshimi; Ikuhiro Iwata; Tomoatsu Minamida
Original assignee: Daikin Industries Ltd
Current assignee: Daikin Industries Ltd
Priority date: 2019-06-12
Filing date: 2020-06-10
Publication date: 2022-10-06
Also published as: EP3978831A4; WO2020250952A1; ES2961904T3; JP2020201011A; EP3978831B1; PL3978831T3; CN113950602B; CN113950602A; EP3978831A1

Abstract

A refrigerant cycle system includes a primary-side cycle that circulates a first refrigerant, a secondary-side cycle that circulates a second refrigerant, and a cascade heat exchanger that exchanges heat between the first refrigerant and the second refrigerant. The primary-side cycle includes a primary-side connection pipe. The secondary-side cycle includes a secondary-side connection pipe. The primary-side connection pipe includes a primary-side gas connection pipe and a primary-side liquid connection pipe. The secondary-side connection pipe includes a secondary-side gas connection pipe and a secondary-side liquid connection pipe. The pipe diameter of the secondary-side gas connection pipe is smaller than the pipe diameter of the primary-side gas connection pipe, or the pipe diameter of the secondary-side liquid connection pipe is smaller than the pipe diameter of the primary-side liquid connection pipe.

Description

TECHNICAL FIELD

The present disclosure relates to a refrigerant cycle system including a cascade heat exchanger.

BACKGROUND

PTL 1 (Japanese Patent Application Laid-Open Publication No. 2014-74508) discloses a refrigerant cycle system including a cascade heat exchanger. By introducing a cascade heat exchanger, a refrigerant cycle system constitutes a dual refrigerant cycle that includes a primary-side cycle including a heat-source heat exchanger and a secondary-side cycle including a usage heat exchanger.
Compared with a single refrigerant cycle that includes no cascade heat exchanger, the flow speed of refrigerant tends to be slow in a secondary-side cycle of a dual refrigerant cycle. In this case, a refrigerating-machine oil that has flowed out from a compressor does not easily return again to the compressor.

SUMMARY

A refrigerant cycle system according to one or more embodiments includes a vapor compression primary-side cycle that circulates a first refrigerant, a vapor compression secondary-side cycle that circulates a second refrigerant, and a cascade heat exchanger that exchanges heat between the first refrigerant and the second refrigerant. The primary-side cycle includes a heat-source heat exchanger for giving cold or heat to the first refrigerant, and a primary-side connection pipe that connects the cascade heat exchanger and the heat-source heat exchanger. The secondary-side cycle includes a usage heat exchanger for using the cold or the heat obtained by the second refrigerant from the cascade heat exchanger, and a secondary-side connection pipe that connects the cascade heat exchanger and the usage heat exchanger. The primary-side connection pipe includes a primary-side gas connection pipe and a primary-side liquid connection pipe. The secondary-side connection pipe includes a secondary-side gas connection pipe and a secondary-side liquid connection pipe. The pipe diameter of the secondary-side gas connection pipe is smaller than the pipe diameter of the primary-side gas connection pipe, or the pipe diameter of the secondary-side liquid connection pipe is smaller than the pipe diameter of the primary-side liquid connection pipe.
According to this configuration, the pipe diameter of the connection pipe in the secondary-side cycle is smaller than the pipe diameter of the connection pipe in the primary-side cycle. Consequently, it is possible to increase the flow speed of refrigerant in the secondary-side cycle. Therefore, a refrigerating-machine oil that has flowed out from the compressor easily returns to the compressor.
In a refrigerant cycle system according to one or more embodiments, the second refrigerant is carbon dioxide. The refrigerating capacity of the secondary-side cycle is 4.5 kW or more and 5.6 kW or less. The pipe diameter of the secondary-side gas connection pipe is 7.9 mm ( 5/16 inches).
In a refrigerant cycle system according to one or more embodiments, the second refrigerant is carbon dioxide. The refrigerating capacity of the secondary-side cycle is 7.1 kW or more and 9.0 kW or less. The pipe diameter of the secondary-side gas connection pipe is 9.5 mm (⅜ inches).
In a refrigerant cycle system according to one or more embodiments, the second refrigerant is carbon dioxide. The refrigerating capacity of the secondary-side cycle is 16 kW or more and 22.4 kW or less. The pipe diameter of the secondary-side gas connection pipe is 12.7 mm (½ inches). In a refrigerant cycle system according to one or more embodiments, the second refrigerant is carbon dioxide. The refrigerating capacity of the secondary-side cycle is 5.6 kW or more and 8.0 kW or less. The pipe diameter of the secondary-side liquid connection pipe is 4.8 mm ( 3/16 inches).
In a refrigerant cycle system according to one or more embodiments, the second refrigerant is carbon dioxide. The refrigerating capacity of the secondary-side cycle is 11.2 kW or more and 16 kW or less. The pipe diameter of the secondary-side liquid connection pipe is 6.4 mm (¼ inches).
In a refrigerant cycle system according to one or more embodiments, the second refrigerant is carbon dioxide. The refrigerating capacity of the secondary-side cycle is 16 kW or more and 28 kW or less. The pipe diameter of the secondary-side liquid connection pipe is 7.9 mm ( 5/16 inches).
In a refrigerant cycle system according to one or more embodiments, the second refrigerant is carbon dioxide. The refrigerating capacity of the secondary-side cycle is 33.5 kW or more and 45 kW or less. The pipe diameter of the secondary-side liquid connection pipe is 9.5 mm (⅜ inches).
In a refrigerant cycle system according to one or more embodiments, the second refrigerant is R32. The refrigerating capacity of the secondary-side cycle is 16 kW or more and 22.4 kW or less. The pipe diameter of the secondary-side gas connection pipe is 15.9 mm (⅝ inches).
In a refrigerant cycle system according to one or more embodiments, the second refrigerant is R32. The refrigerating capacity of the secondary-side cycle is 2.8 kW or more and 3.6 kW or less. The pipe diameter of the secondary-side liquid connection pipe is 4.8 mm ( 3/16 inches).
In a refrigerant cycle system according to one or more embodiments, the second refrigerant is R32. The refrigerating capacity of the secondary-side cycle is 14 kW or more and 16 kW or less. The pipe diameter of the secondary-side liquid connection pipe is 7.9 mm ( 5/16 inches).
In a refrigerant cycle system according to one or more embodiments, the second refrigerant is R32. The refrigerating capacity of the secondary-side cycle is 28 kW or more and 33.5 kW or less. The pipe diameter of the secondary-side liquid connection pipe is 9.5 mm (⅜ inches).
In a refrigerant cycle system according to one or more embodiments, the second refrigerant is R454B. The refrigerating capacity of the secondary-side cycle is 9.0 kW or more and 11.2 kW or less. The pipe diameter of the secondary-side gas connection pipe is 15.9 mm (⅝ inches).
In a refrigerant cycle system according to one or more embodiments, the second refrigerant is R454B. The refrigerating capacity of the secondary-side cycle is 16.0 kW or more and 22.4 kW or less. The pipe diameter of the secondary-side gas connection pipe is 19.1 mm (¾ inches).
In a refrigerant cycle system according to one or more embodiments, the second refrigerant is R454B. The refrigerating capacity of the secondary-side cycle is 16 kW or more and 22.4 kW or less. The pipe diameter of the secondary-side liquid connection pipe is 9.5 mm (⅜ inches).
In a refrigerant cycle system according to one or more embodiments, the second refrigerant is R454B. The refrigerating capacity of the secondary-side cycle is 45 kW or more and 56 kW or less. The pipe diameter of the secondary-side liquid connection pipe is 12.7 mm (½ inches).
In a refrigerant cycle system according to one or more embodiments, the second refrigerant is R454B. The refrigerating capacity of the secondary-side cycle is 85 kW or more and 109 kW or less. The pipe diameter of the secondary-side liquid connection pipe is 15.9 mm (⅝ inches).
In a refrigerant cycle system according to one or more embodiments, the pipe diameter of the secondary-side gas connection pipe is less than or equal to 90% of the pipe diameter of the primary-side gas connection pipe, or the pipe diameter of the secondary-side liquid connection pipe is less than or equal to 90% of the pipe diameter of the primary-side liquid connection pipe.
In a refrigerant cycle system according to one or more embodiments, a compression ratio of the secondary-side cycle is smaller than a compression ratio of the primary-side cycle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view illustrating a refrigerant cycle system 100 according to a first embodiment.

DETAILED DESCRIPTION

(1) Overall Configuration
FIG. 1 illustrates a refrigerant cycle system 100. The refrigerant cycle system 100 is configured to acquire cold or heat from a heat source and supply the cold or the heat to a user. Here, the “acquire cold from a heat source” means releasing heat to the heat source. The “acquire heat from a heat source” means absorbing heat from the heat source. The “supply the cold to a user” means absorbing heat from an environment in which the user is present. The “supply heat to a user” means releasing heat into an environment in which the user is present.
The refrigerant cycle system 100 includes one heat source unit 10, one cascade unit 30, and one usage unit 50.
The heat source unit 10 and the cascade unit 30 are connected to each other to configure a primary-side cycle 20. The primary-side cycle 20 is a vapor compression circuit that circulates a first refrigerant.
The cascade unit 30 and the usage unit 50 are connected to each other to configure a secondary-side cycle 40. The secondary-side cycle 40 is a vapor compression circuit that circulates a second refrigerant. The first refrigerant and the second refrigerant may be the same refrigerant and may be different refrigerants.
(2) Detailed Configuration
(2-1) Heat Source Unit 10
The heat source unit 10 acquires cold or heat from outside air that is a heat source. The heat source unit 10 includes a compressor 11, a four-way switching valve 12, a heat-source heat exchanger 13, a heat-source expansion valve 14, a subcooling expansion valve 15, a subcooling heat exchanger 16, a liquid shutoff valve 18, and a gas shutoff valve 19.
The compressor 11 sucks and compresses low-pressure gas refrigerant that is the first refrigerant and discharges high-pressure gas refrigerant. The four-way switching valve 12 makes connection indicated by the solid lines in FIG. 1 during cooling operation and makes connection indicated by the broken lines in FIG. 1 during heating operation. The heat-source heat exchanger 13 exchanges heat between the first refrigerant and outside air. The heat-source heat exchanger 13 functions as a condenser during cooling operation and functions as an evaporator during heating operation. The heat-source expansion valve 14 adjusts the flow rate of the first refrigerant. The heat-source expansion valve 14 also functions as a decompression device that decompresses the first refrigerant.
The subcooling expansion valve 15 produces cooling gas by decompressing the first refrigerant that circulates. The subcooling heat exchanger 16 exchanges heat between the first refrigerant that circulates and the cooling gas, thereby giving a degree of subcooling to the first refrigerant.
The liquid shutoff valve 18 and the gas shutoff valve 19 shut off a flow path in which the first refrigerant circulates, for example, during work of installation of the heat source unit 10.
(2-2) Cascade Unit 30
The cascade unit 30 is configured to exchange heat between the first refrigerant and the second refrigerant.
The cascade unit 30 includes a primary-side expansion valve 31, a secondary-side expansion valve 32, a compressor 33, a four-way switching valve 34, a cascade heat exchanger 35, a liquid shutoff valve 38, and a gas shutoff valve 39.
The primary-side expansion valve 31 adjusts the amount of the first refrigerant that circulates in the primary-side cycle 20. The primary-side expansion valve 31 also decompresses the first refrigerant.
The secondary-side expansion valve 32 adjusts the amount of the second refrigerant that circulates in the secondary-side cycle 40. The secondary-side expansion valve 32 also decompresses the second refrigerant.
The compressor 33 sucks and compresses low-pressure gas refrigerant that is the second refrigerant and discharges high-pressure gas refrigerant. The four-way switching valve 34 functions as a switching device and makes connection indicated by the solid lines in FIG. 1 during cooling operation and connection indicated by the broken lines in FIG. 1 during heating operation.
The cascade heat exchanger 35 exchanges heat between the first refrigerant and the second refrigerant. The cascade heat exchanger 35 is, for example, a plate heat exchanger. The cascade heat exchanger 35 includes a first refrigerant passage 351 and a second refrigerant passage 352. The first refrigerant passage 351 allows the first refrigerant to pass therethrough. The second refrigerant passage 352 allows the second refrigerant to pass therethrough. The cascade heat exchanger 35 functions as an evaporator for the first refrigerant and a condenser for the second refrigerant during cooling operation and functions as an evaporator for the first refrigerant and a condenser for the second refrigerant during heating operation.
The liquid shutoff valve 38 and the gas shutoff valve 39 shut off a flow path in which the second refrigerant circulates, for example, during work of installation of the cascade unit 30.
(2-3) Usage Unit 50
The usage unit 50 is configured to supply cold or heat to a user. The usage unit 50 includes a usage heat exchanger 51 and a usage expansion valve 52. The usage heat exchanger 51 is configured to cause cold or heat to be used by a user. The usage heat exchanger 51 is a microchannel heat exchanger and includes a flat multi-hole pipe. The usage expansion valve 52 adjusts the amount of the second refrigerant that circulates in the secondary-side cycle 40. The usage expansion valve 52 also functions as a decompression device that decompresses the second refrigerant.
(2-4) Primary-Side Connection Pipe
A primary-side connection pipe includes a primary-side liquid connection pipe 21 and a primary-side gas connection pipe 22. The primary-side liquid connection pipe 21 connects the liquid shutoff valve 18 of the heat source unit 10 and the cascade unit 30. The primary-side gas connection pipe 22 connects the gas shutoff valve 19 of the heat source unit 10 and the cascade unit 30.
(2-5) Secondary-Side Connection Pipe
A secondary-side connection pipe includes a secondary-side liquid connection pipe 41 and a secondary-side gas connection pipe 42. The secondary-side liquid connection pipe 41 connects the liquid shutoff valve 38 of the cascade unit 30 and the usage unit 50. The secondary-side gas connection pipe 42 connects the gas shutoff valve 39 of the cascade unit 30 and the usage unit 50.
(3) Operation
(3-1) Cooling Operation
(3-1-1) Operation of Primary-Side Cycle 20
The compressor 11 sucks low-pressure gas refrigerant that is the first refrigerant and discharges high-pressure gas refrigerant. The high-pressure gas refrigerant reaches the heat-source heat exchanger 13 via the four-way switching valve 12. The heat-source heat exchanger 13 condenses the high-pressure gas refrigerant and thereby produces high-pressure liquid refrigerant. At this time, the refrigerant that is the first refrigerant releases heat into outside air. The high-pressure liquid refrigerant passes through the heat-source expansion valve 14 that is full opened, passes through the subcooling heat exchanger 16, and reaches the primary-side expansion valve 31 via the liquid shutoff valve 18 and the primary-side liquid connection pipe 21. The primary-side expansion valve 31 whose opening degree is appropriately set decompresses the high-pressure liquid refrigerant and thereby produces low-pressure gas-liquid two-phase refrigerant. The low-pressure gas-liquid two-phase refrigerant enters the first refrigerant passage 351 of the cascade heat exchanger 35. The cascade heat exchanger 35 evaporates the low-pressure gas-liquid two-phase refrigerant and thereby produces low-pressure gas refrigerant. At this time, the first refrigerant absorbs heat from the second refrigerant. The low-pressure gas refrigerant exits the first refrigerant passage 351, passes through the primary-side gas connection pipe 22 and the gas shutoff valve 19, and is sucked by the compressor 11 via the four-way switching valve 12.
A portion of the high-pressure liquid refrigerant that has exited the heat-source expansion valve 14 is decompressed by the subcooling expansion valve 15 whose opening degree is appropriately set, and becomes gas-liquid two-phase cooling gas. The cooling gas passes through the subcooling heat exchanger 16. At this time, the cooling gas cools the high-pressure liquid refrigerant and thereby gives a degree of subcooling. The cooling gas exits the subcooling heat exchanger 16, mixes with the low-pressure gas refrigerant that comes from the four-way switching valve 12, and is sucked by the compressor 11.
(3-1-2) Operation of Secondary-Side Cycle 40
The compressor 33 sucks low-pressure gas refrigerant that is the second refrigerant and discharges high-pressure gas refrigerant. The high-pressure gas refrigerant enters the second refrigerant passage 352 of the cascade heat exchanger 35 via the four-way switching valve 34. The cascade heat exchanger 35 condenses the high-pressure gas refrigerant and thereby produces high-pressure liquid refrigerant. At this time, the second refrigerant releases heat into the first refrigerant. The high-pressure liquid refrigerant exits the second refrigerant passage 352 and reaches the secondary-side expansion valve 32. The secondary-side expansion valve 32 whose opening degree is appropriately set decompresses the high-pressure liquid refrigerant and thereby produces low-pressure gas-liquid two-phase refrigerant. The low-pressure gas-liquid two-phase refrigerant passes through the liquid shutoff valve 38 and the secondary-side liquid connection pipe 41 and reaches the usage expansion valve 52. The usage expansion valve 52 whose opening degree is appropriately set further reduces the pressure of the low-pressure gas-liquid two-phase refrigerant. The low-pressure gas-liquid two-phase refrigerant reaches the usage heat exchanger 51. The usage heat exchanger 51 evaporates the low-pressure gas-liquid two-phase refrigerant and thereby produces low-pressure gas refrigerant. At this time, the refrigerant that is the second refrigerant absorbs heat from an environment in which a user is present. The low-pressure gas refrigerant exits the usage heat exchanger 51, passes through the secondary-side gas connection pipe 42 and the gas shutoff valve 39, and is sucked by the compressor 33 via the four-way switching valve 12.
(3-2) Heating Operation
(3-2-1) Operation of Primary-Side Cycle 20
The compressor 11 sucks low-pressure gas refrigerant that is the first refrigerant and discharges high-pressure gas refrigerant. The high-pressure gas refrigerant passes through the gas shutoff valve 19 and the primary-side gas connection pipe 22 via the four-way switching valve 12 and enters the first refrigerant passage 351 of the cascade heat exchanger 35. The cascade heat exchanger 35 condenses the high-pressure gas refrigerant and thereby produces high-pressure liquid refrigerant. At this time, the first refrigerant releases heat into the second refrigerant. The high-pressure liquid refrigerant passes through the primary-side expansion valve 31 that is full opened, then passes through the primary-side liquid connection pipe 21, the liquid shutoff valve 18, and the subcooling heat exchanger 16, and reaches the heat-source expansion valve 14. The heat-source expansion valve 14 whose opening degree is appropriately set decompresses the high-pressure liquid refrigerant and thereby produces low-pressure gas-liquid two-phase refrigerant. The low-pressure gas-liquid two-phase refrigerant reaches the heat-source heat exchanger 13. The heat-source heat exchanger 13 evaporates the low-pressure gas-liquid two-phase refrigerant and thereby produces low-pressure gas refrigerant. At this time, the refrigerant that is the first refrigerant absorbs heat from outside air. The low-pressure gas refrigerant passes through the four-way switching valve 12 and is sucked by the compressor 11.
(3-2-2) Operation of Secondary-Side Cycle 40
The compressor 33 sucks low-pressure gas refrigerant that is the second refrigerant and discharges high-pressure gas refrigerant. The high-pressure gas refrigerant passes through the gas shutoff valve 39 and the secondary-side gas connection pipe 42 via the four-way switching valve 34 and reaches the usage heat exchanger 51. The usage heat exchanger 51 condenses the high-pressure gas refrigerant and thereby produces high-pressure liquid refrigerant. At this time, the refrigerant that is the second refrigerant releases heat into an environment in which a user is present. The high-pressure liquid refrigerant reaches the usage expansion valve 52. The usage expansion valve 52 whose opening degree is appropriately set decompresses the high-pressure liquid refrigerant and thereby produces low-pressure gas-liquid two-phase refrigerant. The low-pressure gas-liquid two-phase refrigerant passes through the secondary-side liquid connection pipe 41 and the liquid shutoff valve 38 and reaches the secondary-side expansion valve 32. The secondary-side expansion valve 32 whose opening degree is appropriately set further reduces the pressure of the low-pressure gas-liquid two-phase refrigerant. The low-pressure gas-liquid two-phase refrigerant enters the second refrigerant passage 352 of the cascade heat exchanger 35. The cascade heat exchanger 35 evaporates the low-pressure gas-liquid two-phase refrigerant and thereby produces low-pressure gas refrigerant. At this time, the second refrigerant absorbs heat from the first refrigerant. The low-pressure gas refrigerant exits the second refrigerant passage 352, passes through the four-way switching valve 34, and is sucked by the compressor 33.
(4) Pipe Diameter of Secondary-Side Connection Pipe
Examples of the pipe diameter of the secondary-side connection pipe are presented in Table 1 to Table 6. In the fields of “HORSEPOWER” and “COOLING CAPACITY”, values of a capacity that should be achieved are indicated in different units. In the field of “SINGLE”, pipe diameters of the gas connection pipe and the liquid connection pipe that are required to achieve the capacity indicated by “REFRIGERATING CAPACITY” in a single cycle are indicated. In the field of “DUAL”, pipe diameters of the secondary-side gas connection pipe 42 and the secondary-side liquid connection pipe 41 that are required to achieve the capacity indicated by “REFRIGERATING CAPACITY” in a dual cycle are indicated.
The pipe diameter of the primary-side gas connection pipe 22 and the primary-side liquid connection pipe 21 in the dual cycle are the same as those indicated in the field of the “SINGLE”.
Regarding the pipe diameters, the values indicated in millimeter unit in the tables indicate pipes that are manufactured according to a standard based on inch unit. That is, the value 4.8 mm indicates 3/16 inches. The value 6.4 mm indicates ¼ inches. The value 7.9 mm indicates 5/16 inches. The value 9.5 mm indicates ⅜ inches. The value 12.7 mm indicates ½ inches. The value 15.9 mm indicates ⅝ inches. The value 19.1 mm indicates ¾ inches. The value 22.2 mm indicates ⅞ inches. The value 25.4 mm indicates 1 inch. The value 28.6 mm indicates 9/8 inches. The value 31.8 mm indicates 5/4 inches. The value 38.1 mm indicates 3/2 inches. The value 44.5 mm indicates 7/4 inches. The value 50.8 mm indicates 2 inches. The value 63.5 mm indicates 5/2 inches.
(4-1) When Refrigerant is Carbon Dioxide
In Table 1, pipe diameters of the secondary-side gas connection pipe 42 and the secondary-side liquid connection pipe 41 in the refrigerant cycle system 100 that uses carbon dioxide as refrigerant are indicated.

TABLE 1

PIPE DIAMETER OF SECONDARY-SIDE CONNECTION PIPE (REFRIGERANT: CO2)

SINGLE

DUAL

		GAS	LIQUID	GAS	LIQUID
		PIPE	PIPE	PIPE	PIPE
	COOLING	DIAM-	DIAM-	DIAM-	DIAM-
HORSEPOWER	CAPACITY	ETER	ETER	ETER	ETER
(HP)	(kW)	(mm)	(mm)	(mm)	(mm)

0.8	2.2	Φ7.9	Φ4.8	Φ7.9	Φ4.8
1	2.8	Φ7.9	Φ4.8	Φ7.9	Φ4.8
1.3	3.6	Φ7.9	Φ4.8	Φ7.9	Φ4.8
1.6	4.5	Φ7.9	Φ4.8	Φ7.9	Φ4.8
2	5.6	Φ9.5	Φ4.8	Φ7.9	Φ4.8
2.5	7.1	Φ9.5	Φ6.4	Φ9.5	Φ4.8
2.9	8	Φ12.7	Φ6.4	Φ9.5	Φ4.8
3.2	9	Φ12.7	Φ6.4	Φ9.5	Φ6.4
4	11.2	Φ12.7	Φ6.4	Φ12.7	Φ6.4
5	14	Φ12.7	Φ7.9	Φ12.7	Φ6.4
6	16	Φ12.7	Φ7.9	Φ12.7	Φ6.4
8	22.4	Φ15.9	Φ9.5	Φ12.7	Φ7.9
10	28	Φ15.9	Φ9.5	Φ15.9	Φ7.9
12	33.5	Φ19.1	Φ9.5	Φ15.9	Φ9.5
14	40	Φ19.1	Φ12.7	Φ15.9	Φ9.5
16	45	Φ19.1	Φ12.7	Φ19.1	Φ9.5
18	50	Φ19.1	Φ12.7	Φ19.1	Φ12.7
20	56	Φ22.2	Φ12.7	Φ19.1	Φ12.7
22	61.5	Φ22.2	Φ12.7	Φ19.1	Φ12.7
24	69	Φ22.2	Φ12.7	Φ22.2	Φ12.7
26	73	Φ22.2	Φ15.9	Φ22.2	Φ12.7
28	80	Φ22.2	Φ15.9	Φ22.2	Φ12.7
30	85	Φ25.4	Φ15.9	Φ22.2	Φ12.7
32	90	Φ25.4	Φ15.9	Φ22.2	Φ12.7
34	95	Φ25.4	Φ15.9	Φ22.2	Φ12.7
36	100	Φ25.4	Φ15.9	Φ22.2	Φ15.9
38	109	Φ25.4	Φ15.9	Φ25.4	Φ15.9
40	112	Φ25.4	Φ15.9	Φ25.4	Φ15.9
42	118	Φ28.6	Φ15.9	Φ25.4	Φ15.9
44	125	Φ28.6	Φ19.1	Φ25.4	Φ15.9
46	132	Φ28.6	Φ19.1	Φ25.4	Φ15.9
48	136	Φ28.6	Φ19.1	Φ25.4	Φ15.9
50	140	Φ28.6	Φ19.1	Φ25.4	Φ15.9
52	145	Φ28.6	Φ19.1	Φ25.4	Φ15.9
54	150	Φ28.6	Φ19.1	Φ28.6	Φ15.9

When the refrigerating capacity of the secondary-side cycle 40 is 4.5 kW or more and 5.6 kW or less, the pipe diameter of the secondary-side gas connection pipe 42 is 7.9 mm. This pipe diameter is smaller than the pipe diameter 9.5 mm of a gas connection pipe in a single cycle having the same capacity.
When the refrigerating capacity of the secondary-side cycle 40 is 7.1 kW or more and 9.0 kW or less, the pipe diameter of the secondary-side gas connection pipe 42 is 9.5 mm. This pipe diameter is smaller than the pipe diameter 12.7 mm of a gas connection pipe in a single cycle having the same capacity.
When the refrigerating capacity of the secondary-side cycle 40 is 16 kW or more and 22.4 kW or less, the pipe diameter of the secondary-side gas connection pipe 42 is 12.7 mm. This pipe diameter is smaller than the pipe diameter 15.9 mm of a gas connection pipe in a single cycle having the same capacity.
When the refrigerating capacity of the secondary-side cycle 40 is 5.6 kW or more and 8.0 kW or less, the pipe diameter of the secondary-side liquid connection pipe 41 is 4.8 mm. This pipe diameter is smaller than the pipe diameter 6.4 mm of a liquid connection pipe in a single cycle having the same capacity.
When the refrigerating capacity of the secondary-side cycle 40 is 11.2 kW or more and 16 kW or less, the pipe diameter of the secondary-side liquid connection pipe 41 is 6.4 mm. This pipe diameter is smaller than the pipe diameter 7.9 mm of a liquid connection pipe in a single cycle having the same capacity.
When the refrigerating capacity of the secondary-side cycle 40 is 16 kW or more and 28 kW or less, the pipe diameter of the secondary-side liquid connection pipe 41 is 7.9 mm. This pipe diameter is smaller than the pipe diameter 9.5 mm of a liquid connection pipe in a single cycle having the same capacity.
When the refrigerating capacity of the secondary-side cycle 40 is 33.5 kW or more and 45 kW or less, the pipe diameter of the secondary-side liquid connection pipe 41 is 9.5 mm. This pipe diameter is smaller than the pipe diameter 12.7 mm of a liquid connection pipe in a single cycle having the same capacity.
(4-2) When Refrigerant is R32
In table 2, pipe diameters of the secondary-side gas connection pipe 42 and the secondary-side liquid connection pipe 41 in the refrigerant cycle system 100 that uses R32 as refrigerant are indicated.

TABLE 2

PIPE DIAMETER OF SECONDARY-SIDE CONNECTION
PIPE (REFRIGERANT: R32)

SINGLE

DUAL

0.8	2.2	Φ9.5	Φ4.8	Φ9.5	Φ4.8
1	2.8	Φ9.5	Φ4.8	Φ9.5	Φ4.8
1.3	3.6	Φ9.5	Φ6.4	Φ9.5	Φ4.8
1.6	4.5	Φ12.7	Φ6.4	Φ12.7	Φ6.4
2	5.6	Φ12.7	Φ6.4	Φ12.7	Φ6.4
2.5	7.1	Φ12.7	Φ6.4	Φ12.7	Φ6.4
2.9	8	Φ12.7	Φ6.4	Φ12.7	Φ6.4
3.2	9	Φ12.7	Φ6.4	Φ12.7	Φ6.4
4	11.2	Φ15.9	Φ7.9	Φ15.9	Φ7.9
5	14	Φ15.9	Φ7.9	Φ15.9	Φ7.9
6	16	Φ15.9	Φ9.5	Φ15.9	Φ7.9
8	22.4	Φ19.1	Φ9.5	Φ15.9	Φ9.5
10	28	Φ19.1	Φ9.5	Φ19.1	Φ9.5
12	33.5	Φ22.2	Φ12.7	Φ19.1	Φ9.5
14	40	Φ22.2	Φ12.7	Φ22.2	Φ12.7
16	45	Φ25.4	Φ12.7	Φ22.2	Φ12.7
18	50	Φ25.4	Φ12.7	Φ22.2	Φ12.7
20	56	Φ25.4	Φ12.7	Φ22.2	Φ12.7
22	61.5	Φ25.4	Φ12.7	Φ25.4	Φ12.7
24	69	Φ25.4	Φ12.7	Φ25.4	Φ12.7
26	73	Φ28.6	Φ15.9	Φ25.4	Φ12.7
28	80	Φ28.6	Φ15.9	Φ25.4	Φ12.7
30	85	Φ28.6	Φ15.9	Φ28.6	Φ15.9
32	90	Φ28.6	Φ15.9	Φ28.6	Φ15.9
34	95	Φ28.6	Φ15.9	Φ28.6	Φ15.9
36	100	Φ28.6	Φ15.9	Φ28.6	Φ15.9
38	109	Φ31.8	Φ15.9	Φ28.6	Φ15.9
40	112	Φ31.8	Φ15.9	Φ28.6	Φ15.9
42	118	Φ31.8	Φ15.9	Φ31.8	Φ15.9
44	125	Φ31.8	Φ15.9	Φ31.8	Φ15.9
46	132	Φ31.8	Φ15.9	Φ31.8	Φ15.9
48	136	Φ38.1	Φ19.1	Φ31.8	Φ15.9
50	140	Φ38.1	Φ19.1	Φ31.8	Φ15.9
52	145	Φ38.1	Φ19.1	Φ31.8	Φ15.9
54	150	Φ38.1	Φ19.1	Φ31.8	Φ15.9

When the refrigerating capacity of the secondary-side cycle 40 is 16 kW or more and 22.4 kW or less, the pipe diameter of the secondary-side gas connection pipe 42 is 15.9 mm. This pipe diameter is smaller than the pipe diameter 19.1 mm of a gas connection pipe in a single cycle having the same capacity.
When the refrigerating capacity of the secondary-side cycle 40 is 2.8 kW or more and 3.6 kW or less, the pipe diameter of the secondary-side liquid connection pipe 41 is 4.8 mm. This pipe diameter is smaller than the pipe diameter 6.4 mm of a liquid connection pipe in a single cycle having the same capacity.
When the refrigerating capacity of the secondary-side cycle 40 is 14 kW or more and 16 kW or less, the pipe diameter of the secondary-side liquid connection pipe is 7.9 mm. This pipe diameter is smaller than the pipe diameter 9.5 mm of a liquid connection pipe in a single cycle having the same capacity.
When the refrigerating capacity of the secondary-side cycle 40 is 28 kW or more and 33.5 kW or less, the pipe diameter of the secondary-side liquid connection pipe is 9.5 mm. This pipe diameter is smaller than the pipe diameter 12.7 mm of a liquid connection pipe in a single cycle having the same capacity.
(4-3) When Refrigerant is R454B
In Table 3, pipe diameters of the secondary-side gas connection pipe 42 and the secondary-side liquid connection pipe 41 in the refrigerant cycle system 100 that uses R454B as refrigerant are indicated.

TABLE 3

PIPE DIAMETER OF SECONDARY-SIDE CONNECTION
PIPE (REFRIGERANT: R454B)

SINGLE

DUAL

0.8	2.2	Φ12.7	Φ6.4	Φ12.7	Φ6.4
1	2.8	Φ12.7	Φ6.4	Φ12.7	Φ6.4
1.3	3.6	Φ12.7	Φ6.4	Φ12.7	Φ6.4
1.6	4.5	Φ12.7	Φ6.4	Φ12.7	Φ6.4
2	5.6	Φ12.7	Φ6.4	Φ12.7	Φ6.4
2.5	7.1	Φ15.9	Φ9.5	Φ15.9	Φ9.5
2.9	8	Φ15.9	Φ9.5	Φ15.9	Φ9.5
3.2	9	Φ15.9	Φ9.5	Φ15.9	Φ9.5
4	11.2	Φ19.1	Φ9.5	Φ15.9	Φ9.5
5	14	Φ19.1	Φ9.5	Φ19.1	Φ9.5
6	16	Φ19.1	Φ9.5	Φ19.1	Φ9.5
8	22.4	Φ22.2	Φ12.7	Φ19.1	Φ9.5
10	28	Φ22.2	Φ12.7	Φ22.2	Φ12.7
12	33.5	Φ25.4	Φ12.7	Φ22.2	Φ12.7
14	40	Φ25.4	Φ12.7	Φ25.4	Φ12.7
16	45	Φ28.6	Φ12.7	Φ25.4	Φ12.7
18	50	Φ28.6	Φ15.9	Φ25.4	Φ12.7
20	56	Φ28.6	Φ15.9	Φ28.6	Φ12.7
22	61.5	Φ28.6	Φ15.9	Φ28.6	Φ15.9
24	69	Φ31.8	Φ15.9	Φ28.6	Φ15.9
26	73	Φ31.8	Φ15.9	Φ28.6	Φ15.9
28	80	Φ31.8	Φ15.9	Φ31.8	Φ15.9
30	85	Φ31.8	Φ15.9	Φ31.8	Φ15.9
32	90	Φ38.1	Φ19.1	Φ38.1	Φ15.9
34	95	Φ38.1	Φ19.1	Φ38.1	Φ15.9
36	100	Φ38.1	Φ19.1	Φ38.1	Φ15.9
38	109	Φ38.1	Φ19.1	Φ38.1	Φ15.9
40	112	Φ38.1	Φ19.1	Φ38.1	Φ19.1
42	118	Φ38.1	Φ19.1	Φ38.1	Φ19.1
44	125	Φ38.1	Φ19.1	Φ38.1	Φ19.1
46	132	Φ38.1	Φ19.1	Φ38.1	Φ19.1
48	136	Φ38.1	Φ19.1	Φ38.1	Φ19.1
50	140	Φ44.5	Φ19.1	Φ38.1	Φ19.1
52	145	Φ44.5	Φ19.1	Φ38.1	Φ19.1
54	150	Φ44.5	Φ19.1	Φ38.1	Φ19.1

When the refrigerating capacity of the secondary-side cycle 40 is 9.0 kW or more and 11.2 kW or less, the pipe diameter of the secondary-side gas connection pipe 42 is 15.9 mm. This pipe diameter is smaller than the pipe diameter 19.1 mm of a gas connection pipe in a single cycle having the same capacity.
When the refrigerating capacity of the secondary-side cycle 40 is 16.0 kW or more and 22.4 kW or less, the pipe diameter of the secondary-side gas connection pipe 42 is 19.1 mm. This pipe diameter is smaller than the pipe diameter 22.2 mm of a gas connection pipe in a single cycle having the same capacity.
When the refrigerating capacity of the secondary-side cycle 40 is 16 kW or more and 22.4 kW or less, the pipe diameter of the secondary-side liquid connection pipe 41 is 9.5 mm. This pipe diameter is smaller than the pipe diameter 12.7 mm of a liquid connection pipe in a single cycle having the same capacity.
When the refrigerating capacity of the secondary-side cycle 40 is 45 kW or more and 56 kW or less, the pipe diameter of the secondary-side liquid connection pipe 41 is 12.7 mm. This pipe diameter is smaller than the pipe diameter 15.9 mm of a liquid connection pipe in a single cycle having the same capacity.
When the refrigerating capacity of the secondary-side cycle 40 is 85 kW or more and 109 kW or less, the pipe diameter of the secondary-side liquid connection pipe 41 is 15.9 mm. This pipe diameter is smaller than the pipe diameter 19.1 mm of a liquid connection pipe in a single cycle having the same capacity.
(4-4) When Refrigerant is R1234yf
In Table 4, pipe diameters of the secondary-side gas connection pipe 42 and the secondary-side liquid connection pipe 41 in the refrigerant cycle system 100 that uses R1234yf as refrigerant are indicated.

TABLE 4

PIPE DIAMETER OF SECONDARY-SIDE CONNECTION
PIPE (REFRIGERANT: R1234yf)

SINGLE

DUAL

0.8	2.2	Φ12.7	Φ6.4	Φ12.7	Φ6.4
1	2.8	Φ15.9	Φ6.4	Φ15.9	Φ6.4
1.3	3.6	Φ15.9	Φ6.4	Φ15.9	Φ6.4
1.6	4.5	Φ19.1	Φ6.4	Φ15.9	Φ6.4
2	5.6	Φ19.1	Φ9.5	Φ19.1	Φ6.4
2.5	7.1	Φ19.1	Φ9.5	Φ19.1	Φ9.5
2.9	8	Φ22.2	Φ9.5	Φ19.1	Φ9.5
3.2	9	Φ22.2	Φ9.5	Φ22.2	Φ9.5
4	11.2	Φ22.2	Φ9.5	Φ22.2	Φ9.5
5	14	Φ25.4	Φ9.5	Φ22.2	Φ9.5
6	16	Φ25.4	Φ12.7	Φ25.4	Φ9.5
8	22.4	Φ28.6	Φ12.7	Φ28.6	Φ12.7
10	28	Φ31.8	Φ12.7	Φ28.6	Φ12.7
12	33.5	Φ38.1	Φ12.7	Φ31.8	Φ12.7
14	40	Φ38.1	Φ15.9	Φ38.1	Φ12.7
16	45	Φ38.1	Φ15.9	Φ38.1	Φ15.9
18	50	Φ38.1	Φ15.9	Φ38.1	Φ15.9
20	56	Φ44.5	Φ15.9	Φ38.1	Φ15.9
22	61.5	Φ44.5	Φ15.9	Φ38.1	Φ15.9
24	69	Φ44.5	Φ19.1	Φ44.5	Φ15.9
26	73	Φ44.5	Φ19.1	Φ44.5	Φ15.9
28	80	Φ44.5	Φ19.1	Φ44.5	Φ15.9
30	85	Φ44.5	Φ19.1	Φ44.5	Φ19.1
32	90	Φ50.8	Φ19.1	Φ44.5	Φ19.1
34	95	Φ50.8	Φ19.1	Φ44.5	Φ19.1
36	100	Φ50.8	Φ19.1	Φ44.5	Φ19.1
38	109	Φ50.8	Φ19.1	Φ50.8	Φ19.1
40	112	Φ50.8	Φ19.1	Φ50.8	Φ19.1
42	118	Φ50.8	Φ22.2	Φ50.8	Φ19.1
44	125	Φ63.5	Φ22.2	Φ50.8	Φ19.1
46	132	Φ63.5	Φ22.2	Φ50.8	Φ19.1
48	136	Φ63.5	Φ22.2	Φ50.8	Φ19.1
50	140	Φ63.5	Φ22.2	Φ50.8	Φ19.1
52	145	Φ63.5	Φ22.2	Φ63.5	Φ22.2
54	150	Φ63.5	Φ22.2	Φ63.5	Φ22.2

(4-5) When Refrigerant is R1234ze
In Table 5, pipe diameters of the secondary-side gas connection pipe 42 and the secondary-side liquid connection pipe 41 in the refrigerant cycle system 100 that uses R1234ze as refrigerant are indicated.

TABLE 5

PIPE DIAMETER OF SECONDARY-SIDE CONNECTION
PIPE (REFRIGERANT: R1234ze)

SINGLE

DUAL

0.8	2.2	Φ15.9	Φ6.4	Φ15.9	Φ6.4
1	2.8	Φ15.9	Φ6.4	Φ15.9	Φ6.4
1.3	3.6	Φ15.9	Φ6.4	Φ15.9	Φ6.4
1.6	4.5	Φ19.1	Φ6.4	Φ19.1	Φ6.4
2	5.6	Φ19.1	Φ9.5	Φ19.1	Φ6.4
2.5	7.1	Φ22.2	Φ9.5	Φ19.1	Φ9.5
2.9	8	Φ22.2	Φ9.5	Φ22.2	Φ9.5
3.2	9	Φ22.2	Φ9.5	Φ22.2	Φ9.5
4	11.2	Φ25.4	Φ9.5	Φ22.2	Φ9.5
5	14	Φ25.4	Φ9.5	Φ25.4	Φ9.5
6	16	Φ28.6	Φ12.7	Φ25.4	Φ9.5
8	22.4	Φ31.8	Φ12.7	Φ28.6	Φ12.7
10	28	Φ38.1	Φ12.7	Φ31.8	Φ12.7
12	33.5	Φ38.1	Φ12.7	Φ38.1	Φ12.7
14	40	Φ38.1	Φ12.7	Φ38.1	Φ12.7
16	45	Φ44.5	Φ15.9	Φ38.1	Φ12.7
18	50	Φ44.5	Φ15.9	Φ38.1	Φ15.9
20	56	Φ44.5	Φ15.9	Φ44.5	Φ15.9
22	61.5	Φ44.5	Φ15.9	Φ44.5	Φ15.9
24	69	Φ44.5	Φ15.9	Φ44.5	Φ15.9
26	73	Φ50.8	Φ15.9	Φ44.5	Φ15.9
28	80	Φ50.8	Φ19.1	Φ44.5	Φ15.9
30	85	Φ50.8	Φ19.1	Φ50.8	Φ15.9
32	90	Φ50.8	Φ19.1	Φ50.8	Φ15.9
34	95	Φ50.8	Φ19.1	Φ50.8	Φ19.1
36	100	Φ50.8	Φ19.1	Φ50.8	Φ19.1
38	109	Φ63.5	Φ19.1	Φ50.8	Φ19.1
40	112	Φ63.5	Φ19.1	Φ50.8	Φ19.1
42	118	Φ63.5	Φ19.1	Φ50.8	Φ19.1
44	125	Φ63.5	Φ19.1	Φ63.5	Φ19.1
46	132	Φ63.5	Φ19.1	Φ63.5	Φ19.1
48	136	Φ63.5	Φ19.1	Φ63.5	Φ19.1
50	140	Φ63.5	Φ22.2	Φ63.5	Φ19.1
52	145	Φ63.5	Φ22.2	Φ63.5	Φ19.1
54	150	Φ63.5	Φ22.2	Φ63.5	Φ19.1

(4-6) When Refrigerant is Mixture Refrigerant
In Table 6, pipe diameters of the secondary-side gas connection pipe 42 and the secondary-side liquid connection pipe 41 in the refrigerant cycle system 100 that uses, as refrigerant, mixture refrigerant constituted by R32, R1234yf, and R1123 are indicated. Here, percentages of R32, R1234yf, and R1123 in the mixture refrigerant are 21.5%, 18.5%, and 60%, respectively.

TABLE 6

PIPE DIAMETER OF SECONDARY-SIDE CONNECTION
PIPE (REFRIGERANT: R32/R1234yf/R1123 (21.5%/18.5%/60%) MIXTURE)

SINGLE

DUAL

0.8	2.2	Φ12.7	Φ6.4	Φ12.7	Φ6.4
1	2.8	Φ12.7	Φ6.4	Φ12.7	Φ6.4
1.3	3.6	Φ12.7	Φ6.4	Φ12.7	Φ6.4
1.6	4.5	Φ12.7	Φ6.4	Φ12.7	Φ6.4
2	5.6	Φ12.7	Φ9.5	Φ12.7	Φ6.4
2.5	7.1	Φ15.9	Φ9.5	Φ15.9	Φ9.5
2.9	8	Φ15.9	Φ9.5	Φ15.9	Φ9.5
3.2	9	Φ15.9	Φ9.5	Φ15.9	Φ9.5
4	11.2	Φ19.1	Φ9.5	Φ15.9	Φ9.5
5	14	Φ19.1	Φ9.5	Φ19.1	Φ9.5
6	16	Φ19.1	Φ12.7	Φ19.1	Φ9.5
8	22.4	Φ22.2	Φ12.7	Φ19.1	Φ12.7
10	28	Φ22.2	Φ12.7	Φ22.2	Φ12.7
12	33.5	Φ25.4	Φ12.7	Φ22.2	Φ12.7
14	40	Φ25.4	Φ15.9	Φ25.4	Φ12.7
16	45	Φ28.6	Φ15.9	Φ25.4	Φ12.7
18	50	Φ28.6	Φ15.9	Φ25.4	Φ15.9
20	56	Φ28.6	Φ15.9	Φ25.4	Φ15.9
22	61.5	Φ28.6	Φ15.9	Φ28.6	Φ15.9
24	69	Φ31.8	Φ15.9	Φ28.6	Φ15.9
26	73	Φ31.8	Φ19.1	Φ28.6	Φ15.9
28	80	Φ31.8	Φ19.1	Φ28.6	Φ15.9
30	85	Φ31.8	Φ19.1	Φ31.8	Φ15.9
32	90	Φ38.1	Φ19.1	Φ31.8	Φ15.9
34	95	Φ38.1	Φ19.1	Φ31.8	Φ19.1
36	100	Φ38.1	Φ19.1	Φ31.8	Φ19.1
38	109	Φ38.1	Φ19.1	Φ31.8	Φ19.1
40	112	Φ38.1	Φ19.1	Φ38.1	Φ19.1
42	118	Φ38.1	Φ19.1	Φ38.1	Φ19.1
44	125	Φ38.1	Φ22.2	Φ38.1	Φ19.1
46	132	Φ38.1	Φ22.2	Φ38.1	Φ19.1
48	136	Φ38.1	Φ22.2	Φ38.1	Φ19.1
50	140	Φ44.5	Φ22.2	Φ38.1	Φ19.1
52	145	Φ44.5	Φ22.2	Φ38.1	Φ19.1
54	150	Φ44.5	Φ22.2	Φ38.1	Φ19.1

(5) Features
(5-1)
The pipe diameter of the connection pipe in the secondary-side cycle 40 is smaller than the pipe diameter of the connection pipe in the primary-side cycle 20. Consequently, it is possible to increase the flow speed of refrigerant in the secondary-side cycle. Therefore, a refrigerating-machine oil that has flowed out from the compressor easily returns to the compressor.
(5-2)
The pipe diameter of the secondary-side gas connection pipe 42 may be less than or equal to 90% of the pipe diameter of the primary-side gas connection pipe 22, or the pipe diameter of the secondary-side liquid connection pipe 41 may be less than or equal to 90% of the pipe diameter of the primary-side liquid connection pipe 21.
(5-3)
The compression ratio of the secondary-side cycle 40 may be smaller than the compression ratio of the primary-side cycle 20.
(6) Modifications
In the embodiments described above, the refrigerant cycle system 100 includes the one heat source unit 10, the one cascade unit 30, and the one usage unit 50. Instead of this, the refrigerant cycle system 100 may include the one heat source unit 10, a plurality of the cascade units 30, and a plurality of the usage units 50.

CONCLUSION

Although the disclosure has been described with respect to only a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that various other embodiments may be devised without departing from the scope of the present disclosure. Accordingly, the scope of the disclosure should be limited only by the attached claims.

REFERENCE SIGNS LIST

10 heat source unit
13 heat-source heat exchanger
20 primary-side cycle
21 primary-side liquid connection pipe
22 primary-side gas connection pipe
30 cascade unit
35 cascade heat exchanger
40 secondary-side cycle
41 secondary-side liquid connection pipe
42 secondary-side gas connection pipe
50 usage unit
52 usage expansion valve
100 refrigerant cycle system

PATENT LITERATURE

PTL 1: Japanese Patent Application Laid-Open Publication No. 2014-74508

Claims

1. A refrigerant cycle system comprising:

a primary-side cycle of a vapor compression type, wherein the primary-side cycle circulates a first refrigerant;

a secondary-side cycle of a vapor compression type, wherein the secondary-side cycle circulates a second refrigerant; and

a cascade heat exchanger that exchanges heat between the first refrigerant and the second refrigerant, wherein

the primary-side cycle comprises:

a heat-source heat exchanger for giving cold or heat to the first refrigerant; and

a primary-side connection pipe that connects the cascade heat exchanger and the heat-source heat exchanger,

the secondary-side cycle comprises:

a usage heat exchanger for using the cold or the heat obtained by the second refrigerant from the cascade heat exchanger; and

a secondary-side connection pipe that connects the cascade heat exchanger and the usage heat exchanger,

the primary-side connection pipe comprises:

a primary-side gas connection pipe; and

a primary-side liquid connection pipe,

the secondary-side connection pipe comprises:

a secondary-side gas connection pipe; and

a secondary-side liquid connection pipe, and

at least one of the following is satisfied:

a pipe diameter of the secondary-side gas connection pipe is smaller than a pipe diameter of the primary-side gas connection pipe, and

a pipe diameter of the secondary-side liquid connection pipe is smaller than a pipe diameter of the primary-side liquid connection pipe.

2. The refrigerant cycle system according to claim 1, wherein

the second refrigerant is carbon dioxide,

a refrigerating capacity of the secondary-side cycle is 4.5 kW or more and 5.6 kW or less, and

the pipe diameter of the secondary-side gas connection pipe is 5/16 inch.

3. The refrigerant cycle system according to claim 1, wherein

the second refrigerant is carbon dioxide,

a refrigerating capacity of the secondary-side cycle is 7.1 kW or more and 9.0 kW or less, and

the pipe diameter of the secondary-side gas connection pipe is ⅜ inch.

4. The refrigerant cycle system according to claim 1, wherein

the second refrigerant is carbon dioxide,

a refrigerating capacity of the secondary-side cycle is 16 kW or more and 22.4 kW or less, and

the pipe diameter of the secondary-side gas connection pipe is ½ inch.

5. The refrigerant cycle system according to claim 1, wherein

the second refrigerant is carbon dioxide,

a refrigerating capacity of the secondary-side cycle is 5.6 kW or more and 8.0 kW or less, and

the pipe diameter of the secondary-side liquid connection pipe is 3/16 inch.

6. The refrigerant cycle system according to claim 1, wherein

the second refrigerant is carbon dioxide,

a refrigerating capacity of the secondary-side cycle is 11.2 kW or more and 16 kW or less, and

the pipe diameter of the secondary-side liquid connection pipe is ¼ inch.

7. The refrigerant cycle system according to claim 1, wherein

the second refrigerant is carbon dioxide,

a refrigerating capacity of the secondary-side cycle is 16 kW or more and 28 kW or less, and

the pipe diameter of the secondary-side liquid connection pipe is 5/16 inch.

8. The refrigerant cycle system according to claim 1, wherein

the second refrigerant is carbon dioxide,

a refrigerating capacity of the secondary-side cycle is 33.5 kW or more and 45 kW or less, and

the pipe diameter of the secondary-side liquid connection pipe is ⅜ inch.

9. The refrigerant cycle system according to claim 1, wherein

the second refrigerant is R32,

the pipe diameter of the secondary-side gas connection pipe is ⅝ inch.

10. The refrigerant cycle system according to claim 1, wherein

the second refrigerant is R32,

a refrigerating capacity of the secondary-side cycle is 2.8 kW or more and 3.6 kW or less, and

the pipe diameter of the secondary-side liquid connection pipe is 3/16 inch.

11. The refrigerant cycle system according to claim 1, wherein

the second refrigerant is R32,

a refrigerating capacity of the secondary-side cycle is 14 kW or more and 16 kW or less, and

the pipe diameter of the secondary-side liquid connection pipe is 5/16 inch.

12. The refrigerant cycle system according to claim 1, wherein

the second refrigerant is R32,

a refrigerating capacity of the secondary-side cycle is 28 kW or more and 33.5 kW or less, and

the pipe diameter of the secondary-side liquid connection pipe is ⅜ inch.

13. The refrigerant cycle system according to claim 1, wherein

the second refrigerant is R454B,

a refrigerating capacity of the secondary-side cycle is 9.0 kW or more and 11.2 kW or less, and

the pipe diameter of the secondary-side gas connection pipe is ⅝ inch.

14. The refrigerant cycle system according to claim 1, wherein

the second refrigerant is R454B,

a refrigerating capacity of the secondary-side cycle is 16.0 kW or more and 22.4 kW or less, and

the pipe diameter of the secondary-side gas connection pipe is ¾ inch.

15. The refrigerant cycle system according to claim 1, wherein

the second refrigerant is R454B,

the pipe diameter of the secondary-side liquid connection pipe is ⅜ inch.

16. The refrigerant cycle system according to claim 1, wherein

the second refrigerant is R454B,

a refrigerating capacity of the secondary-side cycle is 45 kW or more and 56 kW or less, and

the pipe diameter of the secondary-side liquid connection pipe is ½ inch.

17. The refrigerant cycle system according to claim 1, wherein

the second refrigerant is R454B,

a refrigerating capacity of the secondary-side cycle is 85 kW or more and 109 kW or less, and

the pipe diameter of the secondary-side liquid connection pipe is ⅝ inch.

18. The refrigerant cycle system according to claim 1, wherein at least one of the following is satisfied:

the pipe diameter of the secondary-side gas connection pipe is less than or equal to 90% of the pipe diameter of the primary-side gas connection pipe, and

the pipe diameter of the secondary-side liquid connection pipe is less than or equal to 90% of the pipe diameter of the primary-side liquid connection pipe.

19. The refrigerant cycle system according to claim 1, wherein a compression ratio of the secondary-side cycle is smaller than a compression ratio of the primary-side cycle.