JP2021011985A - Two-stage refrigerator - Google Patents

Abstract

To provide a two-stage refrigerator capable of suppressing an increase in pressure loss generated when a high-stage refrigerant is circulated in a route in which a low-stage refrigerant in a low-stage side cooling circuit is condensed by the high-stage refrigerant cooled by a heat exchanger in a high-stage side cooling circuit.SOLUTION: A two-stage refrigerator 100 includes: a first heat exchanger 4 evaporating a high-stage refrigerant expanded by a high-stage side expansion valve 33 and condensing a low-stage refrigerant caused to flow out from a low-stage side compressor 11; and a second heat exchanger 5 cooling the high-stage refrigerant caused to flow out from a high-stage side condenser 32 by using a low-stage refrigerant caused to flow out from a low-stage side evaporator 14. The high-stage side cooling circuit 3 includes a connection pipeline 34 directly connecting the high-stage side condenser 32 and the second heat exchanger 5 without interposing a valve.SELECTED DRAWING: Figure 1

Description

The present invention relates to a dual refrigerator, and more particularly to a dual refrigerator including a low source side cooling circuit and a high source side cooling circuit.

Conventionally, a dual refrigerator including a low-source side cooling circuit and a high-source side cooling circuit is known (see, for example, Patent Document 1).

Patent Document 1 discloses a dual refrigeration cycle (dual refrigerating machine) including a low source side circuit (low source side cooling circuit) and a high source side circuit (high source side cooling circuit). The high-source side circuit includes a first compressor, a condenser, and a first expansion valve. The low source side circuit includes a second compressor, a second expansion valve, and an evaporator.

The dual refrigeration cycle of Patent Document 1 includes a cascade heat exchanger and a heat exchanger. The cascade heat exchanger is provided across the low-source side circuit and the high-source side circuit. The cascade heat exchanger is configured to exchange heat between the refrigerant flowing out from the condenser of the high-source side circuit and the refrigerant flowing out from the second compressor of the low-source side circuit. The heat exchanger is provided across the low-source side circuit and the high-source side circuit. The heat exchanger is configured to exchange heat between the refrigerant flowing out of the condenser of the high-source side circuit and the refrigerant flowing out of the evaporator of the low-source side circuit. That is, the heat exchanger is configured to supply the refrigerant after cooling the refrigerant flowing out from the condenser of the high-source side circuit to the cascade heat exchanger.

The high-source side circuit of Patent Document 1 includes a first pipeline, a second pipeline, a first solenoid valve, and a second solenoid valve. The first pipeline connects the condenser and the heat exchanger. The second line connects the condenser and the cascade heat exchanger. The first solenoid valve and the second solenoid valve are arranged in the first pipeline and the second pipeline, respectively.

In the dual refrigeration cycle of Patent Document 1, the refrigerant flows through the first pipeline by switching the open / closed state of the first solenoid valve and the second solenoid valve, and the refrigerant is supplied to the cascade heat exchanger via the heat exchanger. It is configured to switch between supplying or flowing the refrigerant through the second pipeline and supplying the refrigerant directly from the condenser to the cascade heat exchanger.

International Publication No. 2018/008053

However, in the dual refrigeration cycle (dual refrigerating machine) of Patent Document 1, the refrigerant flows through the first pipeline by opening the first solenoid valve and switching the second solenoid valve to the closed state. There is a disadvantage that the flow path resistance increases due to the provision of the first solenoid valve when the refrigerant flows through the first pipeline. Therefore, in this dual refrigeration cycle, in the high-source side circuit (high-source side cooling circuit) including the first pipeline and the first electromagnetic valve, the low-source is reduced by the refrigerant cooled by the heat exchanger (high-source refrigerant). There is a problem that the pressure loss generated when the refrigerant (high source refrigerant) is circulated in the path for condensing the refrigerant (low source refrigerant) of the side circuit (low source side cooling circuit) increases.

The present invention has been made to solve the above-mentioned problems, and one object of the present invention is to cool the low-source side by a high-source refrigerant cooled by a heat exchanger in the high-source side cooling circuit. It is an object of the present invention to provide a dual refrigerator capable of suppressing an increase in pressure loss generated when the high-source refrigerant is circulated in a path for condensing the low-source refrigerant in the circuit.

The dual refrigerator according to one aspect of the present invention includes a low source side compressor, a low source side expansion valve for expanding the low source side refrigerant, and a low source side evaporator for evaporating the low source side refrigerant. The main cooling circuit, the high source side compressor, the high source side condenser that condenses the high source side refrigerant that has a larger pressure loss than the low source side refrigerant, and the high source side expansion valve that expands the high source side refrigerant. The high-source side cooling circuit including the above, the high-source side cooling circuit, and the low-source side cooling circuit are provided, and the high-source side refrigerant expanded by the high-source side expansion valve is evaporated from the low-source side compressor. The first heat exchanger that condenses the spilled low-source refrigerant is provided across the high-source side cooling circuit and the low-source side cooling circuit, and the low-source refrigerant that flows out from the low-source side evaporator provides high yuan. It is equipped with a second heat exchanger that cools the high-source refrigerant flowing out of the side condenser, and the high-source side cooling circuit directly connects the high-source side condenser and the second heat exchanger without using a valve. Includes connecting pipelines. The high-source side cooling circuit is a cooling circuit that takes heat from the refrigerant of the other cooling circuit as the refrigerant of one cooling circuit evaporates in the two cooling circuits. The low-source side cooling circuit is a cooling circuit that wastes heat of condensation to the refrigerant of the other cooling circuit as the refrigerant of one cooling circuit condenses in the two cooling circuits.

In the dual refrigerator according to one aspect of the present invention, as described above, the connection pipeline that directly connects the high source side condenser and the second heat exchanger to the high source side cooling circuit without using a valve. Is provided. As a result, it is possible to suppress an increase in flow path resistance due to the arrangement of the valve between the high source side condenser and the second heat exchanger. As a result, in the high-source side cooling circuit, the pressure loss generated when the high-source refrigerant is circulated in the path for condensing the low-source refrigerant in the low-source side cooling circuit by the high-source refrigerant cooled by the heat exchanger increases. Can be suppressed. Further, since it is possible to suppress an increase in flow path resistance due to the arrangement of the valve between the high source side condenser and the second heat exchanger, the high source side refrigerant is circulated in the high source side cooling circuit. It is possible to improve the energy efficiency when making it. Further, by providing the second heat exchanger in the cooling circuit on the high source side, the low source refrigerant can be cooled and condensed by the lower temperature high source refrigerant. As a result, the degree of supercooling of the low-source refrigerant can be improved. Further, since the degree of supercooling of the low-source refrigerant can be improved only by providing a second heat exchanger in the high-source side cooling circuit, supercooling can be suppressed while suppressing the complexity and size of the high-source side cooling circuit. The degree can be improved.

In the dual refrigerator according to the above one aspect, preferably, the length of the path through which the high-source refrigerant flows in the high-source side cooling circuit is shorter than the length of the path through which the low-source refrigerant flows in the low-source side cooling circuit. .. With this configuration, the pressure loss that occurs in the low-source side cooling circuit can be suppressed, so that the low-source refrigerant can be efficiently circulated in the low-source side cooling circuit.

In the two-dimensional refrigerator according to the above one aspect, preferably, the high-source refrigerant and the low-source refrigerant have R1234yf and carbon dioxide, respectively. With this configuration, R1234yf has a higher coefficient of performance than carbon dioxide, so that carbon dioxide can be cooled with high efficiency. Further, since R1234yf is used in the high source side cooling circuit in a state where the pressure is lower than the carbon dioxide in the low source side cooling circuit, pressure loss is likely to occur due to the density of R1234yf being smaller than that of carbon dioxide. However, by circulating R1234yf as the high-source refrigerant in the high-source side cooling circuit that suppresses the increase in pressure loss as described above, the increase in pressure loss caused by R1234yf can be suppressed as much as possible. Therefore, it is possible to suppress an increase in the driving force of the high-source side compressor due to the circulation of R1234yf. As a result, carbon dioxide can be cooled with high efficiency, and the coefficient of performance of the dual refrigerator as a whole can be improved by suppressing an increase in the driving force of the high-source compressor. .. Further, since the carbon dioxide can be cooled with high efficiency, the carbon dioxide can be supercooled without making the carbon dioxide a critical state. R1234yf is one of the non-fluorocarbon refrigerants classified as hydrofluoroolefins. The coefficient of performance is a numerical value representing the ratio of the heat taken from the low-temperature heat source to the work of the compressor.

In this case, preferably, a compressor cooling circuit provided separately from the low-source side cooling circuit and including a third heat exchanger that cools carbon dioxide as the low-source side refrigerant flowing out of the low-source side compressor. Further, the low-source compressor includes a low-stage compressor that compresses carbon dioxide from low pressure to intermediate pressure and a high-stage compressor that compresses carbon dioxide from intermediate pressure to high pressure. The carbon dioxide compressed to an intermediate pressure by the low-stage compressor is cooled by the third heat exchanger, and then the carbon dioxide cooled by the high-stage compressor is compressed. With this configuration, when carbon dioxide is compressed by the low source side compressor to a high temperature and high pressure, the carbon dioxide compressed to the intermediate pressure by the low stage compressor is cooled by the third heat exchanger, so that the low source side is used. It is possible to prevent the pressure rise of carbon dioxide caused by the side compressor from being saturated. As a result, carbon dioxide can be efficiently converted into a desired high-temperature and high-pressure superheated steam.

In the two-dimensional refrigerator according to the above one aspect, preferably, the high-source refrigerant has a higher coefficient of performance than the low-source refrigerant, and the pressure when it flows out from the first heat exchanger in the high-source side cooling circuit. However, it is composed of a refrigerant having a pressure loss that is lower than the pressure of the low-source refrigerant when it flows out from the low-source side evaporator in the low-source side cooling circuit. With this configuration, the high-source refrigerant is used in the high-source side cooling circuit at a lower pressure than the low-source refrigerant in the low-source side cooling circuit, and therefore the high-source refrigerant is used rather than the low-source refrigerant. Pressure loss is likely to occur due to the decrease in the density of the refrigerant, but it is caused by the high-source refrigerant by circulating the high-source refrigerant in the high-source side cooling circuit that suppresses the increase in pressure loss as described above. The increase in pressure loss can be suppressed as much as possible. Therefore, it is possible to suppress an increase in the driving force of the high-source side compressor due to the circulation of the high-source refrigerant. Further, since the high-source refrigerant has a higher coefficient of performance than the low-source refrigerant, the low-source refrigerant can be cooled with high efficiency. As a result, the low-source refrigerant can be cooled with high efficiency, and the increase in the driving force of the high-source compressor can be suppressed, so that the coefficient of performance of the dual refrigerator as a whole is improved. Can be made to.

In the dual refrigerator according to the above one aspect, preferably, the high source side cooling circuit and the low source side cooling circuit are provided so as to be provided, and the high source refrigerant and the first heat on the upstream side of the first heat exchanger. A fourth heat exchanger that exchanges heat with the low-source refrigerant downstream of the exchanger is further provided, and the high-source side cooling circuit is a branch pipe that branches from the connection pipeline and is connected to the fourth heat exchanger. It further includes a path and a branch-side expansion valve provided in the branch pipeline to expand the high-source refrigerant flowing through the branch pipeline. With this configuration, heat can be taken from the low-source refrigerant on the downstream side of the first heat exchanger by the low-temperature low-pressure high-source refrigerant expanded by the branch-side expansion valve in the fourth heat exchanger. As a result, the degree of supercooling of the low-source refrigerant in the liquid phase condensed in the first heat exchanger can be further improved.

In the dual refrigerator according to the above one aspect, preferably, the low-source refrigerant flowing from the low-source side compressor to the low-source side expansion valve is caused by the low-source side refrigerant flowing from the low-source side evaporator to the low-source side compressor. A fifth heat exchanger for cooling the air is further provided. With this configuration, unlike the case where the heat exchanger is provided in the high-source side cooling circuit, the liquid phase condensed in the first heat exchanger by the fifth heat exchanger without extending the path of the high-source side cooling circuit. It is possible to further improve the degree of supercooling of the low-source refrigerant. As a result, it is possible to suppress an increase in the driving force of the high-source side compressor by suppressing an increase in pressure loss caused by the high-source refrigerant, and to further improve the degree of supercooling of the low-source refrigerant. Therefore, the coefficient of performance of the dual refrigerator can be improved.

According to the present invention, as described above, in the high-source side cooling circuit, the high-source refrigerant is circulated in the path for condensing the low-source refrigerant in the low-source side cooling circuit by the high-source refrigerant cooled by the heat exchanger. It is possible to suppress an increase in pressure loss that occurs when the refrigerant is generated.

It is an overall view which showed the high-source side cooling circuit and the low-source side cooling circuit of the dual refrigerator by 1st Embodiment. It is a Moriel diagram of the high-source side cooling circuit of the dual refrigerator according to the first embodiment. It is a Moriel diagram of the low-source side cooling circuit of the dual refrigerator according to the first embodiment. It is an overall view which showed the high-source side cooling circuit and the low-source side cooling circuit of the dual refrigerator by 2nd Embodiment. It is an overall view which showed the high-source side cooling circuit and the low-source side cooling circuit of the dual refrigerator by the 1st modification of 1st Embodiment. It is an overall view which showed the high-source side cooling circuit and the low-source side cooling circuit of the dual refrigerator by the 2nd modification of 1st Embodiment. It is an overall view which showed the high-source side cooling circuit and the low-source side cooling circuit of the dual refrigerator by the 3rd modification of 2nd Embodiment. It is an overall view which showed the high-source side cooling circuit and the low-source side cooling circuit of the dual refrigerator by the 4th modification of 2nd Embodiment.

Hereinafter, embodiments embodying the present invention will be described with reference to the drawings.

[First Embodiment]
First, the configuration of the dual refrigerator 100 according to the first embodiment will be described with reference to FIGS. 1 to 3. The dual refrigerator 100 is configured as a cooling device for cooling (freezing / refrigerating) fresh foods and the like in the showcase 110.

Specifically, as shown in FIG. 1, the dual refrigerator 100 includes a low source side cooling circuit 1, a compressor cooling circuit 2, a high source side cooling circuit 3, and a first heat exchanger 4. , A second heat exchanger 5 is provided. A low-source refrigerant and a high-source refrigerant flow through the low-source side cooling circuit 1 and the high-source side cooling circuit 3, respectively. That is, the high-source refrigerant and the low-source refrigerant have R1234yf and carbon dioxide (R744), respectively.

The low-source side cooling circuit 1 constitutes a cooling circuit for cooling the inside of the showcase 110. Specifically, the low-source side cooling circuit 1 includes a low-source side compressor 11, a low-source side radiator 12, a low-source side expansion valve 13, and a low-source side evaporator 14.

The low-source side compressor 11 is configured to compress the low-source refrigerant. The low source side compressor 11 is controlled by an inverter (not shown). As a result, the low source side compressor 11 is configured so that the flow rate of the refrigerant discharged from the low source side compressor 11 can be adjusted. The low-source side radiator 12 is configured to pre-cool the high-temperature and high-pressure low-source refrigerant flowing out of the low-source side compressor 11 before flowing it to the first heat exchanger 4. The low source side expansion valve 13 is configured to expand the low source side refrigerant. The lower expansion valve 13 is composed of, for example, a needle valve. The opening degree of the low source side expansion valve 13 is adjusted by a stepping motor (not shown) attached to the low source side expansion valve 13. The low-source side evaporator 14 is configured to evaporate the low-source refrigerant.

The compressor cooling circuit 2 is provided separately from the low-source side cooling circuit 1. The compressor cooling circuit 2 includes an oil separator 21 and a third heat exchanger 22. The oil separator 21 is configured to separate the gas phase and the liquid phase portion of the low source refrigerant discharged from the low source side compressor 11. The third heat exchanger 22 is configured to cool carbon dioxide as a low-source refrigerant flowing out of the low-source side compressor 11. Here, in the third heat exchanger 22, the low-source refrigerant is wasted into the liquid-phase low-source refrigerant separated in the oil separator 21. As a result, the liquid-phase low-source refrigerant is heated. Then, the heated low-source refrigerant is resupplied to the low-source compressor 11 and compressed.

Here, the low-source side compressor 11 has a low-stage compression unit 11a and a high-stage compression unit 11b. The low-stage compression unit 11a and the high-stage compression unit 11b are driven by a common drive source in such a manner that the rotation speed ratio of each is constant. The low-stage compression unit 11a is configured to compress the sucked low-source refrigerant from a low pressure to an intermediate pressure. The high-stage compression unit 11b is configured to compress the low-source refrigerant compressed to an intermediate pressure and compress it from an intermediate pressure to a high pressure. In this way, the low-end compressor 11 cools the carbon dioxide compressed to the intermediate pressure by the low-stage compressor 11a with the third heat exchanger 22, and then compresses the carbon dioxide cooled by the high-stage compressor 11b. Is configured to

(High source side cooling circuit)
Further, the high-source side cooling circuit 3 is configured to improve the cooling performance of the low-source side cooling circuit 1 that cools the inside of the showcase 110 by cooling the low-source refrigerant flowing through the low-source side cooling circuit 1. Has been done. In detail, the high source side compressor 31, the high source side condenser 32, and the high source side expansion valve 33 are included.

The high-source side compressor 31 is configured to compress the high-source refrigerant. The high source side compressor 31 is controlled by an inverter (not shown). As a result, the high-source side compressor 31 is configured so that the flow rate of the high-source refrigerant discharged from the high-source side compressor 31 can be adjusted. The high-source side condenser 32 is configured to condense the high-source refrigerant. The high source side condenser 32 is composed of, for example, a capacitor. The high-source side expansion valve 33 is configured to expand the high-source refrigerant. The high-source side expansion valve 33 is composed of, for example, a needle valve. The opening degree of the high source side expansion valve 33 is adjusted by a stepping motor (not shown) attached to the high source side expansion valve 33.

The first heat exchanger 4 is composed of, for example, a plate heat exchanger. The first heat exchanger 4 is composed of a latent heat type heat exchanger. The first heat exchanger 4 is provided across the high-source side cooling circuit 3 and the low-source side cooling circuit 1, and evaporates the high-source refrigerant expanded by the high-source side expansion valve 33 to compress the low-source side. It is configured to condense the low-source refrigerant that has flowed out of the machine 11. That is, in the first heat exchanger 4, the high-source refrigerant has changed from the liquid phase to the gas phase. In the first heat exchanger 4, the low-source refrigerant is changed from the gas phase to the liquid phase. As described above, in the first heat exchanger 4, the high-source refrigerant and the low-source refrigerant flow inside in a gas-liquid two-layer state.

The second heat exchanger 5 is configured to precool the high-source refrigerant before flowing into the first heat exchanger 4. Specifically, the second heat exchanger 5 is provided straddling the high-source side cooling circuit 3 and the low-source side cooling circuit 1, and is generated by the low-source refrigerant flowing out from the low-source side evaporator 14. It is configured to cool the high-source refrigerant that has flowed out of the side condenser 32. That is, in the second heat exchanger 5, the liquid-phase high-source refrigerant flowing out from the high-source side condenser 32 flows in, and the high-source refrigerant flows out while maintaining the liquid phase. In the second heat exchanger 5, the low-source refrigerant containing the vapor phase evaporated in the low-source evaporator flows in, and the low-source refrigerant takes heat from the high-source refrigerant and flows out.

The high-source side cooling circuit 3 of the first embodiment includes a connection line 34 that directly connects the high-source side condenser 32 and the second heat exchanger 5 without a valve. That is, in the high-source side cooling circuit 3, the high-source side condenser 32 and the second heat exchanger 5 are connected only by the connection pipe line 34. The connection pipeline 34 is formed in a shape capable of suppressing the flow path resistance with respect to the high-source refrigerant. That is, it is preferable that the connecting pipeline 34 is formed in a substantially linear shape.

The high-source side cooling circuit 3 has a structure for suppressing a pressure loss with respect to the high-source refrigerant flowing inside. That is, the length of the path through which the high-source refrigerant flows in the high-source side cooling circuit 3 is shorter than the length of the path through which the low-source refrigerant flows in the low-source side cooling circuit 1. Here, the length of the path of the portion of the high source side cooling circuit 3 through which the high source refrigerant of the liquid phase flows is the length of the path of the portion of the high source side cooling circuit 3 through which the high source refrigerant of the gas phase flows. It is preferable that it is smaller than the size. The high-source side cooling circuit 3 preferably has a bent portion bent at a smooth angle. The layout of the high-source side cooling circuit 3 is preferably larger in the horizontal direction than in the vertical direction.

Here, the high-source refrigerant is a refrigerant capable of removing heat with higher efficiency than the low-source refrigerant. That is, the high-source refrigerant has a coefficient of performance equivalent to that of R410A and R404A. The low-source refrigerant is a refrigerant that takes heat less efficiently than the high-source refrigerant, but has a smaller environmental load than the high-source refrigerant. The high-source refrigerant is a refrigerant having a smaller global warming potential than R410A and R404A. The low yuan refrigerant is a refrigerant having a smaller global warming potential than the high yuan refrigerant. The global warming potential is a numerical value indicating the degree of the greenhouse effect.

Further, in the state of low-pressure and high-temperature steam, the low-source refrigerant is a refrigerant having a smaller pressure loss with respect to the length of the path through which the refrigerant flows than R410A and R404A. That is, in the state of low-pressure and high-temperature steam, the low-source refrigerant is a refrigerant having a higher pressure (density) than R410A and R404A. In the state of low-pressure and high-temperature steam, the high-source refrigerant is a refrigerant having a larger pressure loss with respect to the length of the path through which the refrigerant flows than R410A and R404A. That is, in the state of low-pressure and high-temperature steam, the high-source refrigerant is a refrigerant having a lower pressure (density) than R410A and R404A.

As described above, as shown in FIGS. 2 and 3, when the high-source refrigerant has a higher coefficient of performance than the low-source refrigerant and flows out from the first heat exchanger 4 in the high-source side cooling circuit 3. The pressure of the refrigerant is lower than the pressure of the low-source refrigerant when it flows out from the low-source side evaporator 14 in the low-source side cooling circuit 1.

(Refrigeration cycle of high-source side cooling circuit and refrigeration cycle of low-source side cooling circuit)
Here, the refrigeration cycle of the high-source side cooling circuit 3 will be described with reference to FIGS. 2 and 3. The dotted line indicates the conventional refrigeration cycle on the high source side. The conventional refrigeration cycle on the high source side refers to the refrigeration cycle on the high source side of the normal dual refrigeration cycle. The solid line shows the refrigeration cycle on the high-source side and the low-source side of the first embodiment. The alternate long and short dash line indicates the saturated liquid line. The alternate long and short dash line indicates the saturated steam line. The vertical axis represents pressure, and the horizontal axis represents specific enthalpy.

The high-source side compressor 31 compresses the high-source refrigerant in cycle A1. As a result, the high-source refrigerant becomes a high-temperature and high-pressure gas-phase high-source refrigerant. The high-source side condenser 32 condenses the high-source refrigerant in cycle A2. As a result, the high-source refrigerant becomes a low-temperature, high-pressure liquid-phase high-source refrigerant. The second heat exchanger 5 further cools the high-source refrigerant condensed in the high-source side condenser 32 in the cycle A2 with the low-source refrigerant. As a result, the low-temperature and high-pressure high-source refrigerant becomes a low-temperature and high-pressure liquid-phase high-source refrigerant. The high-source side expansion valve 33 expands the high-source refrigerant in cycle A3. As a result, the low-temperature and high-pressure high-source refrigerant becomes a low-temperature and low-pressure gas-liquid two-phase high-source refrigerant. The first heat exchanger 4 evaporates the high-source refrigerant in the cycle A4. As a result, it becomes a high-temperature and low-pressure gas-phase high-source refrigerant. Then, the cycle A1 is returned and the same cycle is repeated.

The degree of supercooling of the refrigeration cycle on the high source side of the first embodiment is larger by the degree of supercooling C1 than the degree of supercooling of the conventional refrigeration cycle on the high source side by the second heat exchanger 5. .. Further, the refrigeration cycle on the high source side of the first embodiment is lower in the cycle A4 due to the high source refrigerant having a liquid phase lower than that of the conventional refrigeration cycle on the high source side by the degree of supercooling C1. The amount of heat taken from the original refrigerant is increasing. In this way, the refrigeration cycle on the high source side of the first embodiment improves the coefficient of performance as compared with the conventional refrigeration cycle on the high source side.

The low-source side compressor 11 compresses the low-source refrigerant in cycle B1. As a result, the low-source refrigerant becomes a high-temperature, high-pressure gas-phase low-source refrigerant. The first heat exchanger 4 condenses the low-source refrigerant in cycle B2. As a result, the low-source refrigerant becomes a low-temperature, high-pressure liquid-phase low-source refrigerant. The low source side expansion valve 13 expands the low source side refrigerant in cycle B3. As a result, the low-temperature and high-pressure low-source refrigerant becomes a low-temperature and low-pressure gas-liquid two-phase low-source refrigerant. The low source side evaporator 14 evaporates the high source side refrigerant in cycle B4. As a result, it becomes a high-temperature and low-pressure gas-phase high-source refrigerant. The second heat exchanger 5 further heats the low-source refrigerant evaporated in the low-source side evaporator 14 in the cycle B4 with the high-source refrigerant. As a result, the high-temperature and low-pressure high-source refrigerant becomes a higher-temperature, high-temperature and low-pressure gas-phase high-source refrigerant. Then, it returns to cycle B1 and repeats the same cycle.

The supercooling degree of the refrigeration cycle on the low source side of the first embodiment is larger by the supercooling degree C1 than the supercooling degree of the conventional refrigeration cycle on the high source side by the second heat exchanger 5. As a result, the supercooling degree C2 is larger than the supercooling degree of the conventional refrigeration cycle on the high source side. As a result, the refrigeration cycle on the low source side of the first embodiment is performed in cycle B2 by the low source refrigerant having a liquid phase that is lower by the degree of supercooling C2 as compared with the conventional refrigeration cycle on the low source side. The amount of heat taken away by the high-temperature refrigerant is increasing. Further, the refrigeration cycle on the low source side of the first embodiment shows in cycle B4 by the low source refrigerant having a liquid phase lower by the degree of supercooling C2 as compared with the conventional refrigeration cycle on the low source side. The amount of heat taken from the air in the case 110 is increasing. In this way, the refrigeration cycle on the low source side of the first embodiment improves the coefficient of performance as compared with the conventional refrigeration cycle on the low source side.

Such a refrigeration cycle on the high source side is performed in a pressure region near 1 MPa. Further, the refrigeration cycle on the low source side is performed in a pressure region higher than 1 MPa. The refrigeration cycle on the high source side is a refrigeration cycle performed in a pressure region higher than the refrigeration cycle on the low source side. That is, the cycle B2 on the high source side is located in a pressure region lower than the pressure of the cycle B4 on the low source side. Further, the cycle A4 on the high source side is performed in a pressure region lower than that of the cycle B4 on the low source side.

(Effect of the first embodiment)
In the first embodiment, the following effects can be obtained.

In the first embodiment, as described above, the high-source side cooling circuit 3 is provided with a connection line 34 for directly connecting the high-source side condenser 32 and the second heat exchanger 5 without using a valve. As a result, it is possible to suppress an increase in flow path resistance due to the arrangement of the valve between the high source side condenser 32 and the second heat exchanger 5. As a result, in the high-source side cooling circuit 3, when the high-source refrigerant is circulated in the path for condensing the low-source refrigerant in the low-source side cooling circuit 1 by the high-source refrigerant cooled by the second heat exchanger 5. The increase in pressure loss that occurs can be suppressed. Further, since it is possible to suppress an increase in flow path resistance due to the arrangement of the valve between the high source side condenser 32 and the second heat exchanger 5, the high source side cooling circuit 3 is used for high source. It is possible to improve the energy efficiency when circulating the refrigerant. Further, by providing the second heat exchanger 5 in the high source side cooling circuit 3, the low source refrigerant can be cooled and condensed by the lower temperature high source refrigerant. As a result, the degree of supercooling of the low-source refrigerant can be improved. Further, since the degree of supercooling of the low-source refrigerant can be improved only by providing the second heat exchanger 5 in the high-source side cooling circuit 3, it is possible to suppress the complexity and size of the high-source side cooling circuit 3. At the same time, the degree of supercooling can be improved.

Further, in the first embodiment, as described above, the length of the path through which the high-source refrigerant flows in the high-source side cooling circuit 3 is larger than the length of the path through which the low-source refrigerant flows in the low-source side cooling circuit 1. shorten. As a result, the pressure loss that occurs in the low-source side cooling circuit 1 can be suppressed, so that the low-source refrigerant can be efficiently circulated in the low-source side cooling circuit 1.

Further, in the first embodiment, as described above, the high-source refrigerant and the low-source refrigerant are R1234yf and carbon dioxide, respectively. As a result, R1234yf has a higher coefficient of performance than carbon dioxide, so that carbon dioxide can be cooled with high efficiency. Further, since R1234yf is used in the high source side cooling circuit 3 in a state where the pressure is lower than the carbon dioxide of the low source side cooling circuit 1, the pressure loss is caused by the density of R1234yf being smaller than that of carbon dioxide. Although it is likely to occur, the increase in pressure loss caused by R1234yf can be suppressed as much as possible by circulating R1234yf as the refrigerant for high source in the high source side cooling circuit 3 which suppresses the increase in pressure loss as described above. Therefore, it is possible to suppress an increase in the driving force of the high-source side compressor 31 due to the circulation of R1234yf. As a result, carbon dioxide can be cooled with high efficiency, and the coefficient of performance of the dual refrigerator 100 as a whole can be improved by suppressing an increase in the driving force of the high-source side compressor 31. Can be done. Further, since the carbon dioxide can be cooled with high efficiency, the carbon dioxide can be supercooled without making the carbon dioxide a critical state.

Further, in the first embodiment, as described above, the low-stage compressor 11 is compressed to an intermediate pressure by the low-stage compression unit 11a, and then the carbon dioxide is cooled by the third heat exchanger 22, and then the high-stage compression unit is used. It is configured to compress the carbon dioxide cooled by 11b. As a result, when carbon dioxide is compressed by the low-source side compressor 11 to a high temperature and high pressure, the carbon dioxide compressed to the intermediate pressure by the low-stage compressor 11a is cooled by the third heat exchanger 22, so that the low-source side is cooled. It is possible to prevent the pressure rise of carbon dioxide caused by the compressor 11 from being saturated. As a result, carbon dioxide can be efficiently converted into a desired high-temperature and high-pressure superheated steam.

Further, in the first embodiment, as described above, when the high-source refrigerant has a higher coefficient of performance than the low-source refrigerant and flows out from the first heat exchanger 4 in the high-source side cooling circuit 3. It is composed of a refrigerant whose pressure is lower than the pressure of the low-source refrigerant when it flows out from the low-source side evaporator 14 in the low-source side cooling circuit 1 and has a larger pressure loss than the low-source refrigerant. As a result, in the high-source side cooling circuit 3, the high-source refrigerant is used in a state where the pressure is lower than that of the low-source side cooling circuit 1, so that the density of the high-source refrigerant is higher than that of the low-source refrigerant. Pressure loss is likely to occur due to the decrease in pressure, but the pressure generated by the high-source refrigerant by circulating the high-source refrigerant in the high-source side cooling circuit 3 that suppresses the increase in pressure loss as described above. The increase in loss can be suppressed as much as possible. Therefore, it is possible to suppress an increase in the driving force of the high-source side compressor 31 due to the circulation of the high-source refrigerant. Further, since the high-source refrigerant has a higher coefficient of performance than the low-source refrigerant, the low-source refrigerant can be cooled with high efficiency. As a result, the low-source refrigerant can be cooled with high efficiency, and the increase in the driving force of the high-source side compressor 31 can be suppressed. Therefore, the coefficient of performance of the dual refrigerator 100 as a whole can be suppressed. Can be improved.

Further, in the first embodiment, as described above, the low-source refrigerant containing the gas phase or the liquid phase that has flowed out from the low-source side evaporator 14 in the second heat exchanger 5 flows out from the high-source side condenser 32. When cooling the high-source refrigerant, it is possible to remove not only sensible heat but also latent heat from the high-source refrigerant. As a result, it is possible to lower the temperature of the high-source refrigerant to a temperature lower than the temperature on the inflow side of the low-source side evaporator 14.

[Second Embodiment]
The dual refrigerator 200 of the second embodiment will be described with reference to FIG. In this second embodiment, unlike the dual refrigerator 100 of the first embodiment, the dual refrigerator 200 further provided with the fourth heat exchanger 206 will be described. In the figure, the same configurations as those in the first embodiment are designated by the same reference numerals.

As shown in FIG. 4, the dual refrigerator 200 of the second embodiment includes a low source side cooling circuit 1, a compressor cooling circuit 2, a high source side cooling circuit 3, and a first heat exchanger 4. , A second heat exchanger 5 is provided. Here, the compressor cooling circuit 2 includes a third heat exchanger 22. The dual refrigerator 200 of the second embodiment includes a fourth heat exchanger 206.

A low-source refrigerant and a high-source refrigerant flow through the low-source side cooling circuit 1 and the high-source side cooling circuit 3, respectively. That is, the high-source refrigerant and the low-source refrigerant have R1234yf and carbon dioxide (R744), respectively.

(High source side cooling circuit)
Further, the high source side cooling circuit 3 includes a high source side compressor 31, a high source side condenser 32, a high source side expansion valve 33, and a branch side expansion valve 235. Further, the high source side cooling circuit 3 includes a branch line 236 that branches from the connection line 34 and is connected to the fourth heat exchanger 206.

The branch side expansion valve 235 is provided in the branch line 236. The branch-side expansion valve 235 is configured to expand the high-source refrigerant. The branch side expansion valve 235 is composed of, for example, a needle valve. The opening degree of the branch side expansion valve 235 is adjusted by a stepping motor (not shown) attached to the branch side expansion valve 235.

The fourth heat exchanger 206 is provided separately from the second heat exchanger 5 and is configured to precool the high-source refrigerant before flowing into the first heat exchanger 4. Specifically, the fourth heat exchanger 206 is provided so as to straddle the high-source side cooling circuit 3 and the low-source side cooling circuit 1, and is provided with the high-source refrigerant on the upstream side of the first heat exchanger 4 and the first 1 It is configured to exchange heat with the low-source refrigerant on the downstream side of the heat exchanger 4. The other configurations of the second embodiment are the same as those of the first embodiment.

Here, the flow of the high-source refrigerant in the high-source side cooling circuit 3 will be described. Since the flow of the high-source refrigerant other than the flow of the high-source refrigerant that has flowed into the branch line 236 is the same as that of the dual refrigerator 100 of the first embodiment, the description thereof will be omitted.

A low-temperature, high-pressure liquid-phase high-source refrigerant flowing from the high-source side condenser 32 toward the second heat exchanger 5 flows into the branch line 236. In the branch line 236, the high-temperature refrigerant for the low-temperature and high-pressure liquid phase becomes the high-source refrigerant for the low-temperature and low-pressure liquid phase by being expanded by the branch-side expansion valve 235. This low-temperature, low-pressure liquid-phase high-source refrigerant flows into the fourth heat exchanger 206. In the fourth heat exchanger 206, the liquid-phase high-source refrigerant flowing out from the branch-side expansion valve 235 flows in, and the high-source refrigerant takes latent heat from the low-source refrigerant and vaporizes it. In the fourth heat exchanger 206, the high-temperature and low-pressure gas-phase high-source refrigerant flows out. Then, in the first heat exchanger 4, the high-temperature and low-pressure liquid-phase high-source refrigerant cooled in the second heat exchanger 5 and the high-temperature and low-pressure gas-phase high-source heated in the fourth heat exchanger 206 are used. Refrigerant flows in.

(Effect of the second embodiment)
In the second embodiment, the following effects can be obtained.

In the second embodiment, as described above, the high-source side cooling circuit 3 is provided with a connection line 34 for directly connecting the high-source side condenser 32 and the second heat exchanger 5 without using a valve. As a result, it is possible to suppress an increase in flow path resistance due to the arrangement of the valve between the high source side condenser 32 and the second heat exchanger 5. As a result, in the high-source side cooling circuit 3, when the high-source refrigerant is circulated in the path for condensing the low-source refrigerant in the low-source side cooling circuit 1 by the high-source refrigerant cooled by the second heat exchanger 5. The increase in pressure loss that occurs can be suppressed.

Further, in the second embodiment, as described above, the dual refrigerator 200 is provided across the high-source side cooling circuit 3 and the low-source side cooling circuit 1, and is provided on the upstream side of the first heat exchanger 4. A fourth heat exchanger 206 is provided to exchange heat between the high-source refrigerant and the low-source refrigerant downstream of the first heat exchanger 4. The high source side cooling circuit 3 is provided with a branch line 236 that branches from the connection line 34 and is connected to the fourth heat exchanger 206, and a high source refrigerant that is provided in the branch line 236 and flows through the branch line 236. A branch-side expansion valve 235 is provided to expand the valve. As a result, heat can be taken from the low-temperature and low-pressure high-source refrigerant expanded by the branch-side expansion valve 235 in the fourth heat exchanger 206 from the low-source refrigerant on the downstream side of the first heat exchanger 4. As a result, the degree of supercooling of the low-source refrigerant in the liquid phase condensed in the first heat exchanger 4 can be further improved. The other effects of the second embodiment are the same as those of the first embodiment.

[Modification example]
It should be noted that the embodiments disclosed this time are exemplary in all respects and are not considered to be restrictive. The scope of the present invention is shown by the scope of claims rather than the description of the above-described embodiment, and further includes all modifications (modifications) within the meaning and scope equivalent to the scope of claims.

For example, in the first embodiment, the dual refrigerator 100 includes a low source side cooling circuit 1, a compressor cooling circuit 2, a high source side cooling circuit 3, a first heat exchanger 4, and a second. Although an example including the heat exchanger 5 is shown, the present invention is not limited to this. In the present invention, the dual refrigerator may further include a low source side internal heat exchanger. Here, the low-source internal heat exchanger cools the low-source refrigerant flowing from the low-source side compressor to the low-source side expansion valve by the low-source refrigerant flowing from the low-source side evaporator to the low-source side compressor. It is configured to do. For example, as in the first modification of the first embodiment shown in FIG. 5, the low source side internal heat exchanger 307 includes the low source side refrigerant flowing out from the low source side radiator 12 and the second heat exchanger 5. It may be configured to exchange heat with the low-source refrigerant flowing out from. As a result, unlike the case where the heat exchanger is provided in the high source side cooling circuit 3, the low source refrigerant of the liquid phase condensed in the first heat exchanger 4 is low without extending the path of the high source side cooling circuit 3. The degree of supercooling can be further improved by the original internal heat exchanger 307. As a result, the increase in the driving force of the high-source side compressor 31 can be suppressed by suppressing the increase in the pressure loss caused by the high-source refrigerant, and the degree of supercooling of the low-source refrigerant can be further improved. Therefore, the coefficient of performance of the dual refrigerator 100 can be improved. The low source side internal heat exchanger 307 is an example of the "fifth heat exchanger" in the claims.

Further, as in the second modification of the first embodiment shown in FIG. 6, the low source side internal heat exchanger 407 includes the low source side refrigerant flowing out from the first heat exchanger 4 and the low source side evaporator 14. It may be configured to exchange heat with the low-source refrigerant flowing out from. The low source side internal heat exchanger 407 is an example of the "fifth heat exchanger" in the claims.

Further, in the second embodiment, the dual refrigerator 200 includes a low source side cooling circuit 1, a compressor cooling circuit 2, a high source side cooling circuit 3, a first heat exchanger 4, and a second. Although an example including the heat exchanger 5, the third heat exchanger 22, and the fourth heat exchanger 206 is shown, the present invention is not limited to this. In the present invention, the dual refrigerator may further include a low source side internal heat exchanger. Here, the low-source internal heat exchanger cools the low-source refrigerant flowing from the low-source side compressor to the low-source side expansion valve by the low-source refrigerant flowing from the low-source side evaporator to the low-source side compressor. It is configured to do. For example, as in the third modification shown in FIG. 7, the low source side internal heat exchanger 507 contains the low source refrigerant flowing out from the low source side radiator 12 and the low source side outflow from the second heat exchanger 5. It may be configured to exchange heat with the refrigerant for use. The low source side internal heat exchanger 507 is an example of the "fifth heat exchanger" in the claims.

Further, as in the fourth modification shown in FIG. 8, the low source side internal heat exchanger 607 is used for the low source refrigerant flowing out from the fourth heat exchanger and the low source side evaporator 14 flowing out. It may be configured to exchange heat with the refrigerant. The low source side internal heat exchanger 607 is an example of the "fifth heat exchanger" in the claims.

Further, in the first and second embodiments, the high-source refrigerant and the low-source refrigerant have R1234yf and carbon dioxide (R744), respectively, but the present invention is not limited to this. .. In the present invention, the high-source refrigerant and the low-source refrigerant may be refrigerants other than R1234yf and carbon dioxide, respectively, as long as the coefficient of performance, global warming potential, and pressure loss satisfy the desired conditions.

1 Low-source side cooling circuit 2 Compressor cooling circuit 3 High-source side cooling circuit 4 First heat exchanger 5 Second heat exchanger 11 Low-source side compressor 11a Low-stage compressor 11b High-stage compression section 13 Low-source side Expansion valve 14 Low source side evaporator 22 Third heat exchanger 31 High source side compressor 32 High source side condenser 33 High source side expansion valve 34 Connection pipeline 100, 200 Dual refrigerator 206 No. 4 heat exchanger 235 Branch side expansion valve 236 Branch pipeline 307, 407, 507, 607 Low source side internal heat exchanger (fifth heat exchanger)

Claims (7)

A low source side cooling circuit including a low source side compressor, a low source side expansion valve for expanding the low source side refrigerant, and a low source side evaporator for evaporating the low source side refrigerant.
A high source side compressor including a high source side compressor, a high source side condenser for condensing a high source side refrigerant having a larger pressure loss than the low source side refrigerant, and a high source side expansion valve for expanding the high source side refrigerant. Side cooling circuit and
The low source side cooling circuit and the low source side cooling circuit are provided so as to evaporate the high source side refrigerant expanded by the high source side expansion valve and flow out from the low source side compressor. The first heat exchanger that condenses the original refrigerant,
The high-source refrigerant that is provided across the high-source side cooling circuit and the low-source side cooling circuit and that flows out from the high-source side condenser due to the low-source refrigerant that flows out from the low-source side evaporator. Equipped with a second heat exchanger to cool the
The high-source side cooling circuit is a dual refrigerator including a connection line for directly connecting the high-source side condenser and the second heat exchanger without a valve. The dual refrigeration according to claim 1, wherein the length of the path through which the high-source refrigerant flows in the high-source side cooling circuit is shorter than the length of the path through which the low-source refrigerant flows in the low-source side cooling circuit. Machine. The dual refrigerator according to claim 1 or 2, wherein the high-source refrigerant and the low-source refrigerant have R1234yf and carbon dioxide, respectively. A compressor cooling circuit that is provided separately from the low-source side cooling circuit and includes a third heat exchanger that cools the carbon dioxide as the low-source side refrigerant flowing out of the low-source side compressor is further provided. ,
The low source side compressor is
A low-stage compression unit that compresses carbon dioxide from low pressure to intermediate pressure,
It includes a high-stage compression unit that compresses the carbon dioxide from an intermediate pressure to a high pressure.
The low-source compressor is such that the carbon dioxide compressed to an intermediate pressure by the low-stage compressor is cooled by the third heat exchanger, and then the carbon dioxide cooled by the high-stage compressor is compressed. The dual refrigerator according to claim 3, which is configured. The high-source refrigerant has a higher coefficient of performance than the low-source refrigerant, and the pressure when it flows out from the first heat exchanger in the high-source side cooling circuit is the low in the low-source side cooling circuit. The invention according to any one of claims 1 to 4, wherein the refrigerant is composed of a refrigerant having a pressure lower than the pressure of the low-source refrigerant when flowing out from the main evaporator and a larger pressure loss than the low-source refrigerant. Dual refrigerator. The high-source side cooling circuit and the low-source side cooling circuit are provided so as to straddle the high-source side cooling circuit, the high-source refrigerant on the upstream side of the first heat exchanger, and the low on the downstream side of the first heat exchanger. Further equipped with a fourth heat exchanger that exchanges heat with the original refrigerant,
The high-source side cooling circuit
A branch line that branches off from the connection line and is connected to the fourth heat exchanger.
The dual refrigerator according to any one of claims 1 to 5, further comprising a branch-side expansion valve provided in the branch pipeline and expanding the high-source refrigerant flowing through the branch pipeline. A fifth heat exchanger that cools the low-source refrigerant flowing from the low-source side compressor to the low-source side expansion valve by the low-source refrigerant flowing from the low-source side evaporator to the low-source side compressor. The dual refrigerator according to any one of claims 1 to 6, further comprising.

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