JP6300519B2 - Cooling system using CO2 refrigerant - Google Patents

Description

  The present invention relates to a cooling system that can prevent generation of flash gas in a piping system that sends CO2 refrigerant to a load-side cooler.

  Development of CNG (Compressed Natural Gas) vehicles, fuel cell vehicles, and the like using gas fuels such as hydrogen has been actively conducted as vehicles that respond to environmental problems in recent years. In order to promote the spread of vehicles that run using such gas fuel, it is necessary to stably and efficiently fill the vehicle-mounted tank mounted on the vehicle with the gas fuel.

  Therefore, the present applicants first cooled the gas fuel with a refrigerator using CO2 refrigerant and filled the vehicle tank in a high-pressure gas filling facility for filling the vehicle tank mounted on the vehicle with gas fuel at a high pressure. A cooling system is proposed (Patent Document 1). This refrigerator is configured by combining a primary refrigerant circuit that uses alternative chlorofluorocarbon, NH3, or the like as a primary refrigerant with a secondary refrigerant circuit that uses CO2 as a secondary refrigerant via a cascade capacitor, and the latent heat of vaporization of the primary refrigerant using the cascade capacitor Is used to cool and liquefy the CO2 refrigerant.

Patent Document 2 discloses a configuration in which, in the cooling system, CO2 refrigerant liquefied by a cascade condenser is temporarily stored in a receiver and separated into gas and liquid, and then the CO2 refrigerant liquid is sent to a load side cooler by a liquid pump. Yes.
In the piping system that sends the CO2 refrigerant liquid from the receiver to the load side cooler, if flash gas is generated due to heat intrusion or pressure loss, the supply amount of the CO2 refrigerant liquid becomes unstable, so it is necessary to increase the total head of the liquid pump. Occurs. Therefore, there is a problem in that the liquid pump is increased in size and the amount of heat for the power of the liquid pump is added to the CO 2 refrigerant liquid, so that the cooling capacity is reduced. In particular, if the receiver and the load side cooler are separated, the pressure loss of the piping system increases and the amount of heat penetration increases, so that flash gas is likely to be generated.

In Patent Document 2, a cooling coil that cools the CO2 refrigerant in the receiver and supercools the CO2 refrigerant liquid in order to prevent cavitation from occurring in the liquid pump due to a pressure change in the receiver due to a load fluctuation of the load side cooler. Is provided.
Further, in Patent Document 3, in order to improve COP in a heat pump device, a refrigerant flow path from a condenser to an expansion valve and a refrigerant flow path to an evaporator or a compressor are separated by a partition wall having a circular cross section. A configuration is disclosed in which the double pipes are formed, and the refrigerant flowing through the inner flow path and the outer flow path of the double pipes exchange heat with each other.

JP 2013-148197 A JP 2007-155315 A JP 2006-183889 A

As in the cooling system disclosed in Patent Document 2, if a cooling coil is provided inside the receiver in which the CO2 refrigerant is stored, the capacity of the receiver increases and the size of the receiver increases, and it is necessary to provide a supercooling device outside the receiver. This is contrary to downsizing and cost reduction of the device.
Further, in the piping system that sends the CO 2 refrigerant stored in the receiver to the load-side cooler, if the forward path and the return path are independent paths, a large installation space is required. This is a problem due to restrictions on the layout of the apparatus.

  The present invention has been made in view of the above-mentioned problems, and when sending CO2 refrigerant to a load-side cooler, the generation of flash gas, heat input, etc. are eliminated by low-cost means, and the loss of cooling capacity is suppressed. The purpose is to do.

  The cooling system of the present invention includes a primary refrigerant circuit in which a primary refrigerant flows to constitute a refrigeration cycle, a secondary refrigerant circuit that is connected to the primary refrigerant circuit via a cascade capacitor, and in which CO2 refrigerant flows as a secondary refrigerant, and a secondary refrigerant. A receiver provided in the circuit for temporarily storing the CO2 refrigerant liquefied by the cascade capacitor and separating the gas and liquid; a forward path for introducing the CO2 refrigerant liquid stored in the receiver into the load side cooler; and the load side cooler. The present invention is applied to a cooling system using a CO2 refrigerant having a CO2 piping system composed of a return path for returning a CO2 refrigerant in a gas-liquid mixed state after cooling an object to be cooled to a receiver.

In order to achieve the above object, the CO2 piping system is a region between the liquid pump and the load side cooler provided in the forward path, and the forward path and the return path are double walls, and the inner flow path and the outer flow path are provided. In this double tube, the CO2 refrigerant liquid flowing in the forward path flows through the inner flow path, and the gas-liquid mixed state CO2 refrigerant flowing in the return path flows in the outer flow path. Yes.
In addition, the said double pipe shall include what is arrange | positioned mutually concentrically and what is arrange | positioned eccentrically.

In the present invention, the CO2 refrigerant flowing in the return path is depressurized by the pressure loss of the pipe as compared with the CO2 refrigerant flowing in the forward path, so that the temperature also decreases somewhat. By flowing the low-temperature CO2 refrigerant flowing in the return path to the outer flow path, the heat insulation of the CO2 refrigerant in the forward path is effectively performed, so that generation of flash gas and loss of cooling capacity can be effectively suppressed. Therefore, even if the piping system becomes long, generation of flash gas can be reliably prevented.
In addition, since the CO2 piping system is a double pipe, the installation space can be reduced and restrictions on the installation space can be cleared. Furthermore, by making the outer channel a return channel for the CO2 refrigerant in a gas-liquid mixed state having a small heat transfer coefficient and a large volume, heat input from the outside can be effectively suppressed and two channels can be used. Can be distributed in a well-balanced manner.

Further, since the CO2 refrigerant in a gas-liquid mixed state in which the pressure slightly changes with respect to the CO2 refrigerant liquid flowing through the inner flow path flows through the outer flow path, it is necessary to provide pressure resistance performance to the partition walls forming the inner flow path. In addition, the thickness can be reduced and a low-cost material can be used.
Therefore, the cooling system can be made compact and low in cost without increasing the capacity of the receiver.
Furthermore, since the temperature of the CO2 refrigerant flowing through the outer flow path is somewhat lower than that of the CO2 refrigerant flowing through the inner flow path, there is also an effect of cooling the CO2 refrigerant flowing through the inner flow path with the CO2 refrigerant flowing through the outer flow path.

  As an embodiment of the present invention, the outer periphery of the double pipe can be surrounded by a heat insulating wall. As a result, heat input from the outside can be cut off, so that it is possible to prevent a loss in cooling capacity and a decrease in thermal efficiency of the cooling system.

  As an embodiment of the present invention, the outer periphery of the double tube can be surrounded by a heat insulating space of vacuum pressure. Also by this, since the heat input from the outside can be cut off, it is possible to prevent a loss in cooling capacity and a decrease in thermal efficiency of the cooling system.

In one embodiment of the present invention, the primary refrigerant circuit is provided with a compressor, a condenser, and an expansion valve, and a refrigerant introduction space is formed in the double pipe. And it branches from the primary refrigerant circuit at the outlet of the condenser and is connected to the primary refrigerant branch forward path connected to one end of the refrigerant introduction space, the other end of the refrigerant introduction space, and the primary refrigerant circuit of the compressor inlet A refrigerant branch return path, and the primary refrigerant can be introduced into the refrigerant introduction space via the primary refrigerant branch forward path.
As a result, the primary refrigerant can be introduced into the refrigerant introduction space where the double pipe is formed, and the double pipe can be cooled with the primary refrigerant, so that heat input from the outside to the double pipe can be effectively suppressed, and the flash gas Generation can be suppressed.

In the above embodiment, if the refrigerant introduction space is formed so as to surround the outer peripheral surface of the double pipe, heat input from the outside to the double pipe can be effectively suppressed, and generation of flash gas can be suppressed.
In addition, pressure fluctuations in the cascade capacitor and the receiver may occur due to increase / decrease in the load, and these pressure fluctuations may lower the suction head of the liquid pump and lead to cavitation. In this embodiment, by precooling the CO2 refrigerant in the return path with the primary refrigerant, the increased load can be precooled in advance, and the pressure fluctuation can be suppressed.

  Or depending on the case, you may form the said refrigerant | coolant introduction space between an inner side flow path and an outer side flow path. As a result, it is possible to effectively insulate the inner flow path that forms the forward path.

In one embodiment of the present invention, the load-side cooler is provided in a high-pressure gas filling facility that fills a vehicle-mounted tank of a vehicle with gas fuel, and cools the gas fuel mounted on the vehicle-mounted tank from the high-pressure gas filling facility. is there.
Thereby, the temperature rise of the gas fuel due to the high-pressure filling can be suppressed, and the vehicle can be efficiently filled with the gas fuel.

  According to the present invention, when CO2 refrigerant is sent to a load-side cooler in a cooling system, generation of flash gas, heat input, and the like can be eliminated by low-cost and space-saving means, and loss of cooling capacity can be effectively suppressed. .

1 is an overall configuration diagram of a cooling system according to a first embodiment of the present invention. It is a longitudinal cross-sectional view of the double pipe in the said 1st Embodiment. It is sectional drawing which follows the AA line in FIG. It is a Mollier diagram of the cooling system of the present invention. It is a schematic diagram of the cooling system of this invention for demonstrating FIG. It is a cross-sectional view of a double pipe according to a second embodiment of the present invention. It is a whole block diagram of the cooling system which concerns on 3rd Embodiment of this invention. It is sectional drawing which follows the BB line in FIG. It is a schematic diagram of the conventional cooling system. It is a Mollier diagram of the conventional cooling system.

  Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in this embodiment are not intended to limit the scope of the present invention to that unless otherwise specified.

(Embodiment 1)
A cooling system according to a first embodiment of the present invention will be described with reference to FIGS. In FIG. 1, a cooling system 10 </ b> A according to this embodiment includes a primary refrigerant circuit 12, a secondary refrigerant circuit 14, and a load side cooler 16.
In the primary refrigerant circuit 12, the primary refrigerant circulates. As the primary refrigerant, for example, a natural refrigerant such as NH3 or hydrocarbon, or a fluorocarbon refrigerant is used. The primary refrigerant circuit 12 is provided with a compressor 18, a condenser 20, an expansion valve 22, and a cascade capacitor 24. For example, a reciprocating compressor or the like is used as the compressor 18, and a shell and plate heat exchanger or the like is used as the cascade condenser 24.

  The gaseous primary refrigerant is compressed by the compressor 18 and then condensed by the condenser 20 to be liquid. The liquefied primary refrigerant is depressurized by the expansion valve 22, the cascade condenser 24 cools the CO2 refrigerant, and the primary refrigerant evaporates.

  In the secondary refrigerant circuit 14, CO2 refrigerant is circulated. A receiver 30 is interposed in the secondary refrigerant circuit 14, and the cascade capacitor 24 and the receiver 30 are connected by a CO 2 circulation path 32. The CO 2 refrigerant gas in the receiver 30 is sent to the cascade condenser 24 and is cooled and liquefied by the cascade condenser 24. The CO 2 refrigerant liquid liquefied by the cascade condenser 24 descends due to gravity and returns to the receiver 30.

  The secondary refrigerant circuit 14 includes an outward path 14a and a return path 14b. A liquid supply amount variable liquid pump 34 is provided in the forward path 14 a on the outlet side of the receiver 30. The secondary refrigerant circuit 14 is led to the load side cooler 16. The load side cooler 16 is provided in a hydrogen station 42 in which hydrogen gas is stored at a high pressure. In the hydrogen station 42, hydrogen gas is stored in a storage tank (not shown) in a high pressure state. The load-side cooler 16 is provided with a hydrogen gas conduit 44, and the hydrogen gas is cooled in advance when the hydrogen gas is supplied to a vehicle-mounted tank of the vehicle.

A flow rate adjustment valve 36 is provided in the forward path 14 a at the outlet of the receiver 30, and a pressure adjustment valve 38 is provided in the forward path 14 a at the inlet of the load side cooler 16. The forward path 14 a is connected to the inlet of a heat transfer tube provided inside the load side cooler 16, and the return path 14 b is connected to the outlet of the heat transfer pipe of the load side cooler 16.
The forward path 14a and the return path 14b between the flow rate regulating valve 36 and the pressure regulating valve 38 are constituted by a double pipe 40A. Hereinafter, the configuration of the double tube 40A will be described with reference to FIGS.

2 and 3, the double tube 40 </ b> A is composed of two inner tubes 46 and outer tubes 48 having a circular cross section and different diameters. The inner tube 46 and the outer tube 48 are arranged concentrically. The inner pipe 46 is connected to the forward path 14a, and an inner flow path F1 is formed inside the inner pipe 46. The outer pipe 48 is connected to the return path 14b, and an outer flow path F2 is formed inside the outer pipe 48. The inner tube 46 and the outer tube 48 may be made of Al having good thermal conductivity or Al alloy containing Al as a main component.
The outer peripheral surface of the outer tube 48 is surrounded by a heat insulating layer 50 made of a heat insulating material. The heat insulating material constituting the heat insulating layer 50 is a known heat insulating material such as polyurethane foam, for example.

In such a configuration, −40 ° C. CO 2 refrigerant liquid is sent from the forward path 14 a to the load-side cooler 16, and 45 to 50 ° C. hydrogen gas is sent to the hydrogen gas pipe 44. In the load side cooler 16, the −2 ° C. CO 2 refrigerant liquid cools the hydrogen gas to −33 ° C. to −37 ° C., and the CO 2 refrigerant enters a gas-liquid mixed state and is discharged from the return path 14b. The ratio of the gas and liquid is set to, for example, about 1.5 to 3 times the necessary amount of refrigerant circulating for evaporation. Since the CO2 refrigerant flowing through the return path 14b is decompressed by the pressure loss in the piping such as the load-side cooler 16 as compared with the CO2 refrigerant flowing through the forward path 14a, the temperature is also somewhat lowered to, for example, about -42 ° C.
Here, the state change of the CO2 refrigerant in the conventional cooling system in which the forward path 14a and the return path 14b are not double pipes and the cooling system of the present embodiment will be described with reference to FIGS.

FIG. 9 schematically shows a conventional cooling system, and FIG. 10 shows a Mollier diagram of the conventional cooling system.
In the conventional cooling system, the CO2 refrigerant flowing in the forward path 14a approaches the saturated liquid line at the position e due to intrusion heat and pressure loss between e → d. Therefore, if the pump pressure of the liquid pump 34 is not increased, vaporization occurs at the e position. Further, the enthalpy at the inlet (d position) of the load-side cooler 16 is also increased, and unless the pump pressure of the liquid pump 34 is further increased, the CO2 refrigerant is sent to the load-side cooler 16 in a vaporized state. Therefore, the refrigerant supply amount becomes uneasy, the pressure loss in the load side cooler 16 increases, the latent heat per refrigerant circulation amount (kg / s) decreases, and the cooling capacity decreases.

FIG. 4 shows a Mollier diagram of the cooling system 10A, and FIG. 5 schematically shows the cooling system 10A for explaining the Mollier diagram of FIG.
In the present embodiment, the CO2 refrigerant flowing in the forward path 14a needs to consider the pressure loss of the CO2 refrigerant between e → d, but is not vaporized because it is cooled by the CO2 refrigerant flowing in the return path 14b. Therefore, since only the pressure loss needs to be taken into consideration, the pump pressure of the liquid pump 34 can be reduced.

According to the present embodiment, in the double pipe 40A, the CO2 refrigerant flowing through the inner flow path F1 is effectively insulated by flowing a CO2 refrigerant having a temperature lower than that of the CO2 refrigerant liquid flowing through the inner flow path F1 into the outer flow path F2. To be done. Therefore, it is possible to effectively suppress the generation of flash gas of the CO2 refrigerant liquid flowing through the forward path 14a and the loss of cooling capacity. Therefore, even if the CO2 refrigerant piping system becomes long, generation of flash gas can be reliably prevented.
In addition, since the CO2 piping system is the double pipe 40A, the installation space can be reduced, and the restrictions on the installation space can be cleared. Furthermore, by making the outer flow path F2 a flow path through which a CO2 refrigerant in a gas-liquid mixed state with a small heat transfer coefficient and a large volume flows, heat input from the outside can be effectively suppressed, and two flow paths Can be distributed in a well-balanced manner.

Further, since the CO2 refrigerant in a gas-liquid mixed state whose pressure changes only slightly to the CO2 refrigerant liquid flowing in the inner flow path F1 flows in the outer flow path F2, the inner pipe 46 forming the inner flow path F1 has a pressure resistance. Costs can be reduced without the need for performance. For example, by using a flexible pipe such as a polyethylene pipe for the inner pipe 46, the number of pipe installation steps can be reduced and the pipe material cost can be reduced.
Moreover, the heat input from the outside can be shut off by surrounding the outer periphery of the double pipe 40A with the heat insulating layer 50, and therefore, the loss of the cooling capacity and the decrease in the thermal efficiency of the cooling system 10A can be prevented.
Further, since the temperature of the CO2 refrigerant flowing through the outer flow path F2 is somewhat lower than that of the CO2 refrigerant flowing through the inner flow path F1, the effect of cooling the CO2 refrigerant flowing through the inner flow path F1 with the CO2 refrigerant flowing through the outer flow path F2 is also achieved. is there.

Furthermore, the load-side cooler 16 is provided in the hydrogen station 42 that fills the vehicle-mounted tank of the vehicle with hydrogen gas, and the vehicle-mounted tank is charged with high pressure to cool the hydrogen gas mounted on the vehicle-mounted tank of the vehicle from the hydrogen station 42. The temperature rise of the generated hydrogen gas can be suppressed, and the charging efficiency of the hydrogen gas into the vehicle can be increased.
In the present embodiment, the inner tube 46 and the outer tube 48 are arranged concentrically, but the present invention is not limited to this arrangement. That is, the inner tube 46 and the outer tube 48 may be arranged eccentrically.

(Embodiment 2)
Next, a second embodiment of the present invention will be described with reference to FIG. The triple pipe 40B according to this embodiment is concentric with these pipes on the outer side of a double pipe composed of an inner pipe 46 that forms an inner flow path F1 and an outer pipe 48 that forms an outer flow path F2. Is provided with a circular cross-section tube 52. Inside the tube 52, a heat insulating space s maintained at a vacuum pressure is formed. A pipe line 49 communicating with the heat insulating space s is provided, and an open / close valve 51 is provided in the pipe line 49. The pipe line 49 is connected to a decompression device (not shown) such as a vacuum pump. By evacuating the pipe 49 through the pressure reducing device, the heat insulating space s can be made almost vacuum. The heat insulation space s may be divided into a plurality of partitions in the tube axis direction by a partition plate, and the pipe line 49 may be connected to each heat insulation space s. Other configurations are the same as those of the first embodiment.

  According to this embodiment, the heat insulation performance with respect to the inner flow path F1 and the outer flow path F2 can be further improved by forming the heat insulation space s held at the vacuum pressure outside the outer flow path F2. Therefore, generation of flash gas of the CO2 refrigerant liquid flowing in the forward path 14a and loss of cooling capacity can be effectively suppressed, and the precooling effect of the CO2 refrigerant flowing in the return path 14b can be further exhibited.

(Embodiment 3)
Next, a third embodiment of the present invention will be described with reference to FIGS. In the cooling system 10B according to the present embodiment, as shown in FIG. 8, the flow path forming the forward path 14a and the return path 14b of the CO 2 refrigerant is constituted by a triple pipe 40C.
The triple pipe 40C is arranged concentrically with these pipes on the outer side of the double pipe formed by the inner pipe 46 forming the inner flow path F1 and the outer pipe 48 forming the outer flow path F2. A tube 54 is provided. A refrigerant introduction space r for introducing a primary refrigerant is formed inside the pipe 54, and the outer peripheral surface of the pipe 54 is surrounded by a heat insulating layer 50 similar to that of the first embodiment.

  Moreover, as shown in FIG. 7, in the primary refrigerant circuit 12, in addition to the structure of the primary refrigerant circuit 12 of 1st Embodiment, the following structure is further added. That is, the primary refrigerant branch forward path 56 branched from the primary refrigerant circuit 12 at the outlet of the condenser 20 and connected to one end of the refrigerant introduction space r (the end on the side close to the liquid pump 34), and other refrigerant introduction space r A primary refrigerant branch return path 58 connected to the end and the primary refrigerant circuit 12 at the inlet of the compressor 18. An expansion valve 57 is provided in the primary refrigerant branch forward path 56. Other configurations are the same as those of the first embodiment.

  In such a configuration, during the operation of the cooling system 10 </ b> B, the primary refrigerant is introduced into the refrigerant introduction space r through the primary refrigerant branch forward path 56. The primary refrigerant flowing through the primary refrigerant branch forward path 56 passes through the expansion valve 57 and fills the refrigerant introduction space r. The primary refrigerant filled in the refrigerant introduction space r is vaporized by absorbing the latent heat of evaporation from the CO2 refrigerant flowing in the outer and outer flow paths F2 and F1. Thereafter, the refrigerant is returned to the primary refrigerant circuit 12 at the inlet of the compressor 18 via the primary refrigerant branch return path 58.

According to this embodiment, since the inner flow path F1 and the outer flow path F2 can be cooled from the outside by the latent heat of evaporation of the primary refrigerant, heat input from the outside to these flow paths can be effectively suppressed.
Further, pressure fluctuations in the cascade capacitor 24 and the receiver 30 occur due to increase / decrease in the load, and these pressure fluctuations may lower the suction head of the liquid pump 34 and lead to cavitation. By pre-cooling the CO2 refrigerant of 14b, the increased load can be pre-cooled and the pressure fluctuation can be suppressed.
Further, in the triple tube 40C, the CO2 refrigerant flowing through the outer flow path F2 and the primary refrigerant flowing through the refrigerant introduction space r flow counter-currently, so that the cooling effect of the CO2 refrigerant by the primary refrigerant can be further enhanced.

  In this embodiment, the refrigerant introduction space r is arranged outside the outer tube 48, but the refrigerant introduction space r may be arranged between the inner tube 46 and the outer tube 48.

  According to the present invention, when CO2 refrigerant is sent to the load side cooler in the cooling system, generation of flash gas and heat input are eliminated by cost-saving and space-saving means, and loss of cooling capacity is effectively suppressed. it can.

10A, 10B Cooling system 12 Primary refrigerant circuit 14 Secondary refrigerant circuit 14a Outward path 14b Return path 16 Load side cooler 18 Compressor 20 Condenser 22, 57 Expansion valve 24 Cascade capacitor 36 Flow rate adjustment valve 30 Receiver 32 CO2 circulation path 34 Liquid pump 38 Pressure regulating valve 40A Double pipe 40B, 40C Triple pipe 42 Hydrogen station (high-pressure gas filling equipment)
44 conduit 46 inner pipe 48 outer pipe 49 pipe 50 heat insulation layer 51 on-off valve 52, 54 pipe 56 primary refrigerant branch forward path 58 primary refrigerant branch return path F1 inner flow path F2 outer flow path r refrigerant introduction space s heat insulation space

Claims (6)

A primary refrigerant circuit in which a primary refrigerant flows and forms a refrigeration cycle;
A secondary refrigerant circuit that is connected to the primary refrigerant circuit via a cascade capacitor and through which CO2 refrigerant flows as a secondary refrigerant;
A receiver that is provided in the secondary refrigerant circuit, temporarily stores the CO2 refrigerant liquefied by the cascade condenser, and performs gas-liquid separation;
CO2 comprising a forward path for introducing the CO2 refrigerant liquid stored in the receiver to the load-side cooler, and a return path for returning the CO2 refrigerant in a gas-liquid mixed state after the object to be cooled is cooled by the load-side cooler to the receiver A cooling system using a CO2 refrigerant having a piping system,
The CO2 piping system is
In the region between the liquid pump provided in the forward path and the load-side cooler, the forward path and the return path are constituted by a double pipe in which an inner flow path and an outer flow path are formed by a double wall,
In the double pipe, the CO2 refrigerant liquid flowing through the forward path flows through the inner flow path, and the gas-liquid mixed CO2 refrigerant flowing through the return path is configured to flow through the outer flow path ,
The double pipe is changed from a saturated liquid state in the receiver to a supercooled state via the liquid pump so that the CO2 refrigerant liquid flowing through the inner flow path flows into the load side cooler in the supercooled state. In addition, the CO2 refrigerant that is configured to flow the CO2 refrigerant in the gas-liquid mixed state in the load-side cooler to the outer flow path toward the receiver is used. Cooling system.   The cooling system using CO2 refrigerant according to claim 1, wherein an outer periphery of the double pipe is surrounded by a heat insulating wall.   The cooling system using a CO2 refrigerant according to claim 1 or 2, wherein an outer periphery of the double pipe is surrounded by a heat insulating space having a vacuum pressure. The primary refrigerant circuit is provided with a compressor, a condenser and an expansion valve,
A refrigerant introduction space is formed in the double pipe,
Branched from the primary refrigerant circuit at the outlet of the condenser, and connected to one end of the refrigerant introduction space, a primary refrigerant branch forward path;
A primary refrigerant branch return path connected to the other end of the refrigerant introduction space and the primary refrigerant circuit at the compressor inlet;
The cooling system using CO2 refrigerant according to claim 1, wherein the primary refrigerant is introduced into the refrigerant introduction space via the primary refrigerant branch forward path.   The cooling system using a CO2 refrigerant according to claim 4, wherein the refrigerant introduction space is formed so as to surround an outer peripheral surface of the double pipe. The load side cooler is:
2. The high-pressure gas filling facility for filling the on-vehicle tank of the vehicle with gas fuel, and cooling the gas fuel mounted on the on-vehicle tank from the high-pressure gas filling facility. Cooling system using CO2 refrigerant.

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