JP6372778B2 - Refrigeration equipment - Google Patents

Description

  The present invention relates to a refrigeration apparatus including a refrigerant circuit having an auxiliary circuit that diverts a refrigerant discharged from a gas cooler and expands it with an auxiliary expansion valve for the purpose of improving performance.

  Conventionally, in this kind of refrigeration apparatus, a compressor, a gas cooler that cools the refrigerant discharged from the compressor, an expansion valve that expands the refrigerant that has exited the gas cooler, and an evaporator that evaporates the refrigerant that has passed through the expansion valve A refrigerant circuit is configured from the above. Also, for the purpose of improving the refrigerating capacity of the refrigeration system, for example, the refrigerant discharged from the gas cooler is diverted, and the diverted refrigerant is expanded by the auxiliary expansion valve and evaporated, so that the refrigerant before the diversion point or after the diversion is obtained. The thing which provided the auxiliary circuit which supercools the refrigerant | coolant of a main circuit is also developed (for example, refer patent document 1 and patent document 2).

  According to the refrigeration apparatus provided with such an auxiliary circuit, the high-pressure side refrigerant after passing through the gas cooler can be supercooled, so that the enthalpy difference can be expanded to improve the refrigeration capacity. Further, since the refrigerant that has passed through the auxiliary circuit is returned to the intermediate pressure portion of the compressor, the compression work of the compressor can be reduced and the operation efficiency can be improved.

JP 2013-155972 A JP 2011-133204 A

  However, in a high outside air temperature environment such as summer, the temperature of the refrigerant that has exited the gas cooler increases (because it can only be cooled to the outside air temperature), so the temperature of the refrigerant that is diverted to the auxiliary circuit also increases and flows into the expansion valve. The ability to supercool the refrigerant to be reduced is reduced. For this reason, when the amount of refrigerant flowing through the auxiliary circuit is increased, the pressure of the intermediate pressure portion of the compressor is increased, and the discharge pressure and temperature are also increased.

  The present invention has been made to solve the conventional technical problem, and an object of the present invention is to reliably obtain a performance improvement effect in a refrigeration apparatus including a refrigerant circuit having an auxiliary circuit. And

In order to solve the above-described problem, the refrigeration apparatus of the present invention includes a high-stage refrigerant circuit and a low-stage refrigerant circuit, and the low-stage refrigerant circuit supplies the refrigerant discharged from the compressor and passed through the gas cooler. The auxiliary circuit expands the divided refrigerant by the auxiliary expansion valve, and the high stage side refrigerant circuit evaporates the refrigerant and flows the refrigerant of the auxiliary circuit flowing into the auxiliary expansion valve of the low stage side refrigerant circuit. The low-stage refrigerant circuit is a first subcooling heat exchanger provided in the auxiliary circuit upstream of the auxiliary expansion valve, and is downstream of the gas cooler and is connected to the auxiliary circuit. And a second supercooling heat exchanger provided upstream from the branch point of the first stage, and the high stage refrigerant circuit includes a first cascade of the low stage refrigerant circuit and a first cascade. A first evaporator constituting a heat exchanger, and a second subcooling of the low-stage refrigerant circuit Characterized by comprising a second evaporator which constitutes the heat exchanger and the second cascade heat exchanger.

The refrigeration apparatus according to a second aspect of the present invention is characterized in that, in the above invention, the first evaporator is provided upstream of the second evaporator with respect to the refrigerant flow of the higher stage refrigerant circuit.

According to a third aspect of the present invention, there is provided the refrigeration apparatus according to the first or second aspect of the invention, wherein the auxiliary circuit is downstream of the second subcooling heat exchanger of the low-stage side refrigerant circuit by the refrigerant expanded by the auxiliary expansion valve. The refrigerant in the low-stage refrigerant circuit at the upstream side of the diversion point is cooled.

According to a fourth aspect of the present invention, there is provided the refrigeration apparatus according to the first or second aspect of the present invention, wherein the refrigerant in the low-stage refrigerant circuit is divided into the refrigerant flowing through the main circuit and the refrigerant flowing through the auxiliary circuit at the branch point. And the auxiliary circuit cools the refrigerant in the main circuit downstream from the branch point of the low-stage refrigerant circuit by the refrigerant expanded by the auxiliary expansion valve.

A refrigeration apparatus according to a fifth aspect of the invention is characterized in that, in the third or fourth aspect of the invention, the auxiliary circuit returns the refrigerant to the intermediate pressure portion of the compressor of the low stage side refrigerant circuit.

A refrigeration apparatus according to a sixth aspect of the invention is characterized in that, in the first or second aspect of the invention, the auxiliary circuit cools the compressor of the low-stage refrigerant circuit with the refrigerant expanded by the auxiliary expansion valve. .

In the refrigeration apparatus according to a seventh aspect of the present invention, in each of the above inventions, the refrigerant evaporation temperatures of the first and second evaporators of the higher stage refrigerant circuit are controlled to be lower than the temperature of the refrigerant that has passed through the gas cooler of the lower stage refrigerant circuit. It is characterized by that.

The refrigeration apparatus according to an eighth aspect of the present invention is characterized in that, in each of the above inventions, the operation of the high stage side refrigerant circuit is stopped in an environment where the outside air temperature is low.

The refrigeration apparatus of the invention of claim 9 is characterized in that, in each of the above inventions, the refrigerant in the low stage side refrigerant circuit is carbon dioxide.

The refrigeration apparatus of the present invention includes a high-stage refrigerant circuit and a low-stage refrigerant circuit, and the low-stage refrigerant circuit divides the refrigerant discharged from the compressor and passed through the gas cooler, and the divided refrigerant is Since it has an auxiliary circuit that is expanded by the auxiliary expansion valve, the high-stage refrigerant circuit evaporates the refrigerant and cools the refrigerant in the auxiliary circuit flowing into the auxiliary expansion valve of the low-stage refrigerant circuit. The refrigerant flowing through the auxiliary circuit for diverting the refrigerant that has passed through the gas cooler of the low stage side refrigerant circuit as in the inventions of claim 3 and claim 4 Since the refrigerant in the refrigerant circuit can be evaporated and cooled, the ability of the auxiliary circuit to improve the performance of the low-stage refrigerant circuit can be reliably obtained particularly in a high outside air temperature environment such as summer.
In this case, the low-stage refrigerant circuit is downstream of the first supercooling heat exchanger provided in the auxiliary circuit upstream of the auxiliary expansion valve and the gas cooler and upstream of the branch point of the auxiliary circuit. A first evaporation comprising a second subcooling heat exchanger provided, wherein the high stage side refrigerant circuit constitutes the first subcooling heat exchanger and the first cascade heat exchanger of the low stage side refrigerant circuit. And a second evaporator constituting the second subcooling heat exchanger of the low stage side refrigerant circuit and the second cascade heat exchanger, the refrigerant that has exited the gas cooler of the low stage side refrigerant circuit is also provided. It becomes possible to evaporate and cool the refrigerant in the higher stage side refrigerant circuit, thereby realizing further improvement in performance.

Further, when the compressor of the low-stage refrigerant circuit is cooled by the refrigerant expanded by the auxiliary expansion valve of the auxiliary circuit as in the invention of claim 6, the compressor is effectively cooled by the auxiliary circuit, A capability improvement effect can be obtained with certainty.

In particular, if the first evaporator is provided on the upstream side of the second evaporator with respect to the refrigerant flow of the high-stage refrigerant circuit as in the invention of claim 2 , the subcooling effect by the auxiliary circuit is surely implemented. Will be able to.

Further, as in the invention of claim 3 , the auxiliary circuit is downstream of the second subcooling heat exchanger of the low stage side refrigerant circuit by the refrigerant expanded by the auxiliary expansion valve, and upstream of the diversion point. By cooling the refrigerant in the lower stage refrigerant circuit, it becomes possible to flow a more stable refrigerant in the auxiliary circuit.

Further, as in the invention of claim 5 , the auxiliary circuit returns the refrigerant to the intermediate pressure portion of the compressor of the low stage side refrigerant circuit, thereby reducing the compression work in the compressor and improving the operation efficiency. become able to.

According to the seventh aspect of the present invention, the refrigerant evaporating temperature of the first and second evaporators of the high stage side refrigerant circuit is controlled to be lower than the temperature of the refrigerant passing through the gas cooler of the low stage side refrigerant circuit. The refrigerant in the auxiliary refrigerant circuit in the low-stage refrigerant circuit and the refrigerant that has passed through the gas cooler can be accurately cooled by the refrigerant in the refrigerant circuit on the side.

Further, the high stage side refrigerant circuit is stopped only in the case where the performance improvement effect by the auxiliary circuit of the low stage side refrigerant circuit is deteriorated by stopping the operation of the high stage side refrigerant circuit in the environment where the outside air temperature is low as in the invention of claim 8. To avoid unnecessary operation of the high-stage refrigerant circuit and to eliminate the deterioration of efficiency.

The refrigeration apparatus of each of the above inventions is particularly effective when carbon dioxide is used as the refrigerant in the low-stage refrigerant circuit as in the ninth aspect of the invention.

It is a refrigerant circuit figure of the freezing apparatus of one Example to which this invention is applied (Example 1). FIG. 2 is a Ph diagram of the refrigeration apparatus in FIG. 1. It is a refrigerant circuit figure of the freezing apparatus of the other Example to which this invention is applied (Example 2). It is a refrigerant circuit figure of the freezing apparatus of the other Example to which this invention is applied (Example 3). FIG. 5 is a Ph diagram of the refrigeration apparatus in FIG. 4. It is a refrigerant circuit figure of the freezing apparatus of another other Example to which this invention is applied (Example 4). FIG. 7 is a Ph diagram of the refrigeration apparatus in FIG. 6.

  Hereinafter, embodiments of the present invention will be described in detail.

  FIG. 1 is a refrigerant circuit diagram of a refrigerating apparatus 1 according to an embodiment to which the present invention is applied. The refrigeration apparatus 1 of this embodiment cools a showcase installed in a store such as a supermarket, and includes a high-stage refrigerant circuit 2 and a low-stage refrigerant circuit 3 that constitute independent refrigerant closed circuits. It is configured. The high-stage refrigerant circuit 2 includes a compressor 4, a gas cooler (or condenser) 6 connected to the discharge side of the compressor 4, an expansion valve 7 connected to the outlet side of the gas cooler 6, and an expansion valve 7 comprises a first evaporator 8 and a second evaporator 9 which are connected to the outlet side of 7.

  The outlet of the second evaporator 9 is connected to the suction side of the compressor 4, and an internal heat exchanger 11 is provided between the second evaporator 9 and the compressor 4. The internal heat exchanger 11 includes a first flow path 11A through which a high-pressure refrigerant flows from the gas cooler 6 toward the expansion valve 7 and a second flow through which the low-pressure refrigerant flows from the second evaporator 9 toward the compressor 4. A channel 11B is provided, and heat is exchanged between the refrigerants 11A and 11B between the refrigerants. And in this high stage side refrigerant circuit 2, natural refrigerants, such as carbon dioxide, or HFO refrigerant and HFC refrigerant, are enclosed as refrigerant.

  On the other hand, the low-stage refrigerant circuit 3 includes a two-stage compression compressor 12 including a first compression element 13 and a second compression element 14, and a discharge side of the second compression element 14 of the compressor 12. A gas cooler 16 connected to the gas cooler 16, a second subcooling heat exchanger 17 connected to the outlet side of the gas cooler 16, and an intermediate heat exchanger connected to the outlet side of the second subcooling heat exchanger 17 18 first flow paths 18A, a flow divider (diversion point) 19 connected to the outlet of the first flow path 18A of the intermediate heat exchanger 18, and a main circuit 21 branched from the flow divider 19 are connected in parallel. And a series circuit of an expansion valve (main expansion valve) 22 and an evaporator 23 connected to each other, and an auxiliary circuit 26 branched from the flow divider 19.

  The expansion valve 22 and the evaporator 23 of the low stage side refrigerant circuit 3 are respectively provided in a showcase S installed in a store (two in the embodiment), and each evaporator 23 is connected to the compressor 12. Connected to the suction side of the first compression element 13. All of the high stage side refrigerant circuit 2 and the equipment other than the expansion valve 22 and the evaporator 23 of the low stage side refrigerant circuit auxiliary circuit 3 are installed in a refrigerator installed outside the store. The branched main circuit 21 and the suction side of the first compression element 13 of the compressor 12 are connected to the expansion valve 22 and the evaporator 23 of each showcase S by refrigerant pipes 27 and 28.

  The auxiliary circuit 26 is a circuit for improving the refrigeration capacity of the low-stage refrigerant circuit 3 and is connected to the first subcooling heat exchanger 31 and the outlet side of the first subcooling heat exchanger 31. And the second flow path 18B of the intermediate heat exchanger 18 connected to the outlet side of the auxiliary expansion valve 32.

  Further, the compressor 12 includes an intercooler 33. The intercooler 33 cools (air-cools) the refrigerant discharged from the first compression element 13 of the compressor 12, and the refrigerant after passing through the intercooler 33 is sucked into the second compression element 14. And further compressed. That is, the intercooler 33 becomes an intermediate pressure portion of the compressor 12. The outlet side of the second flow path 18B of the auxiliary circuit 26 is connected to the outlet of the intercooler 33. The low-stage refrigerant circuit 3 contains a predetermined amount of carbon dioxide as a refrigerant.

  The first subcooling heat exchanger 31 of the auxiliary circuit 26 of the low-stage refrigerant circuit 3 is provided in a heat exchange relationship with the first evaporator 8 of the high-stage refrigerant circuit 2 to perform first cascade heat exchange. The device 36 is configured. The second subcooling heat exchanger 17 of the low stage side refrigerant circuit 3 is provided in a heat exchange relationship with the second evaporator 9 of the high stage side refrigerant circuit 2 so that the second cascade heat exchanger 37 is provided. Configure. In addition, each gas cooler 6 and 16 (similarly to the intercooler 33) is provided with a blower (not shown), and is configured to be air-cooled by each blower.

  In the figure, C is a controller as control means of the refrigeration apparatus 1. The controller C is connected to an outside air temperature sensor 39 that detects the outside air temperature. The controller C starts with the outside air temperature sensor 39 and outputs various sensors that detect the temperature and pressure of each part of the refrigeration apparatus 1. The compressors 4 and 12, the above-described blower, and the expansion valves 7 and 32 are controlled.

  The expansion valve 22 provided in the showcase S is controlled by a controller on the showcase S side. This controller operates in conjunction with the controller 38 or is controlled by a higher-level centralized controller. 38 will be controlled together.

  Next, the operation of the refrigeration apparatus 1 of the embodiment having the above configuration will be described. The controller C operates the compressor 12 of the low stage side refrigerant circuit 3 in response to an operation request from the showcase S side, but the outside air temperature sensor 39 detects the outside air of the compressor 4 of the high stage side refrigerant circuit 2. The operation is performed when the temperature rises to a predetermined high temperature (for example, + 30 ° C.), and the compressor 4 of the high-stage refrigerant circuit 2 is operated at an OFF temperature (for example, + 25 ° C.) or the like having a predetermined hysteresis. To stop.

  Assuming that the environment is a high outside air temperature environment higher than the predetermined high temperature, the controller C starts the compressor 12 of the low stage side refrigerant circuit 3 and the compressor 4 of the high stage side refrigerant circuit 2. The refrigerant compressed and discharged by the compressor 4 of the high stage side refrigerant circuit 2 flows into the gas cooler 6 where it is air-cooled. The refrigerant cooled by the gas cooler 6 flows into the expansion valve 7 through the first flow path 11A of the internal heat exchanger 11. The refrigerant is decompressed by the expansion valve 7 and expands, and first evaporates in the first evaporator 8 constituting the first cascade heat exchanger 36.

  The refrigerant that evaporates in the first evaporator 8 and exhibits the action of cooling the first subcooling heat exchanger 31 is then supplied to the second evaporator 9 that constitutes the second cascade heat exchanger 37. It flows in and evaporates, and exhibits the effect | action which cools the 2nd subcooling heat exchanger 17 there. The refrigerant evaporated in the second evaporator 9 is sucked into the compressor 4 again after cooling the high-pressure side refrigerant flowing in the first flow path 11A by the second flow path 11B of the internal heat exchanger 11. Compressed.

  On the other hand, the refrigerant (carbon dioxide) compressed by the first compression element 13 of the compressor 12 of the low stage side refrigerant circuit 3 first flows into the intercooler 33 and is air-cooled. The refrigerant cooled by the intercooler 33 returns to the intermediate pressure portion of the compressor 12 and is sucked into the second compression element 14. The refrigerant compressed in the second stage by the second compression element 14 flows into the gas cooler 16 where it is air-cooled.

  The refrigerant that has exited the gas cooler 16 then flows into the second subcooling heat exchanger 17 that constitutes the second cascade heat exchanger 37, where it is cooled from the second evaporator 9 of the high-stage refrigerant circuit 2. It is supercooled under the action. The refrigerant that has exited the second supercooling heat exchanger 17 reaches the flow divider 19 through the first flow path 18A of the intermediate heat exchanger 18. The refrigerant reaching the flow divider 19 is divided into the main circuit 21 and the auxiliary circuit 26.

  Among these, the refrigerant branched into the main circuit 21 reaches the expansion valve (main expansion valve) 22 of each showcase S through the refrigerant pipe 27 and is decompressed there to expand. The refrigerant that has passed through the expansion valve 22 enters the evaporator 23 and evaporates there. The inside of each showcase S is cooled by the endothermic action at this time. The refrigerant exiting the evaporator 23 is sucked into the first compression element 13 of the compressor 12 through the refrigerant pipe 28, and the first-stage compression is performed.

  On the other hand, the refrigerant divided into the auxiliary circuit 26 flows into the first subcooling heat exchanger 31 constituting the first cascade heat exchanger 36, where the first evaporator 8 in the high stage side refrigerant circuit 2 is supplied. Is cooled by receiving a cooling action. The refrigerant that has left the first supercooling heat exchanger 31 is decompressed by the auxiliary expansion valve 32 and expands. The refrigerant that has passed through the auxiliary expansion valve 32 flows into the second flow path 18B of the intermediate heat exchanger 18 and evaporates. The refrigerant flowing out of the second supercooling heat exchanger 17 and flowing into the first flow path 18A of the intermediate heat exchanger 18 is supercooled by the cooling action at this time.

  The refrigerant that has exited the second flow path 18B of the intermediate heat exchanger 18 merges with the refrigerant that has passed through the intercooler 33 at the outlet of the intercooler 33, and is then sucked into the second compression element 14 of the compressor 12. Compressed (second stage). That is, the refrigerant in the auxiliary circuit 26 is returned to the intermediate pressure portion of the compressor 12.

  The right side of FIG. 2 is a Ph diagram of the refrigeration apparatus 1 of FIG. 1, and the left side is a Ph diagram when there is no high stage side refrigerant circuit 2 and only the low stage side refrigerant circuit 3 is present. Show. The controller C controls the refrigeration apparatus 1 so that the evaporation temperature of the refrigerant in each of the evaporators 8 and 9 of the high-stage refrigerant circuit 2 is lower than the temperature of the refrigerant that has passed through the gas cooler 16 of the low-stage refrigerant circuit 3. . Thereby, for example, the high pressure side pressure (the discharge pressure of the compressor 4) of the high stage side refrigerant circuit 2 (L1 in FIG. 2) is about 9 MPa, and the low pressure side pressure (the suction pressure of the compressor 4) is about 6 MPa. The high pressure side pressure (the discharge pressure of the second compression element 14) of the refrigerant circuit 3 (L2 in FIG. 2) is 7 MPa, and the intermediate pressure (the suction pressure of the second compression element 14, that is, the discharge of the first compression element 13). The pressure) is 5 MPa, and the low-pressure side pressure (the suction pressure of the first compression element 13) is about 3 MPa. Moreover, although the temperature of the refrigerant | coolant which exited the gas cooler 16 of the low stage side refrigerant circuit 3 is about +30 degreeC, the temperature of the refrigerant | coolant which came out of the 2nd subcooling heat exchanger 17 falls to about +20 degreeC.

  On the other hand, in the case of only the low-stage refrigerant circuit 3 as shown on the left side in FIG. 2, the high-pressure side pressure is 8 MPa, the intermediate pressure is 5 MPa, and the low-pressure side pressure is about 3 MPa. As is clear from these figures, the refrigerant that has exited the gas cooler 16 of the low-stage refrigerant circuit 3 is supercooled by the second evaporator 9 of the high-stage refrigerant circuit 2 that constitutes the second cascade heat exchanger 37. By doing so, the high pressure side pressure of the low stage side refrigerant circuit 3 is suppressed.

  Further, the portion indicated by L3 in FIG. 2 is the supercooling effect of the refrigerant in the auxiliary circuit 26 by the first evaporator 8 of the higher stage refrigerant circuit 2 constituting the first cascade heat exchanger 36. Due to the supercooling of the refrigerant in the auxiliary circuit 26, the temperature of the refrigerant flowing into the second flow path 18B of the intermediate heat exchanger 18 is lowered, so that the supercooling effect of the refrigerant flowing through the first flow path 18A is improved. It will be. Therefore, the enthalpy difference of the refrigerant in the low stage side refrigerant circuit 3 can be increased. Furthermore, this prevents the amount of refrigerant that must be diverted to the auxiliary circuit 26 from increasing excessively.

  The controller C stops the compressor 4 of the high-stage refrigerant circuit 2 when the outside air temperature detected by the outside air temperature sensor 39 is lowered to the above-described OFF temperature as described above. Thereafter, only the low-stage refrigerant circuit 3 is operated. And when outside temperature rises to the high temperature mentioned above, the controller C starts the compressor 4 of the high stage side refrigerant circuit 2 again.

  As described above, the refrigeration apparatus 1 of the present invention includes the high-stage refrigerant circuit 2 and the low-stage refrigerant circuit 3, and the low-stage refrigerant circuit 3 is discharged from the compressor 12 and passes through the gas cooler 16. The auxiliary circuit 26 has an auxiliary circuit 26 that diverts the refrigerant and expands the divided refrigerant using the auxiliary expansion valve 32, and the high-stage refrigerant circuit 2 evaporates the refrigerant to the auxiliary expansion valve 32 of the low-stage refrigerant circuit 3. Since the refrigerant of the auxiliary circuit 26 that flows in is cooled, the refrigerant that has passed through the gas cooler 16 of the low-stage refrigerant circuit 3 is diverted and flows through the auxiliary circuit 26 for supercooling the refrigerant before the diversion. The refrigerant can be cooled by evaporating the refrigerant in the higher-stage refrigerant circuit 2. This makes it possible to reliably obtain the effect of improving the performance of the low-stage refrigerant circuit 3 by the auxiliary circuit 26, particularly in a high outside air temperature environment such as summer.

  In this case, the low-stage refrigerant circuit 3 includes the first subcooling heat exchanger 31 provided in the auxiliary circuit 26 upstream of the auxiliary expansion valve 32, the downstream of the gas cooler 16, and the flow divider 29 and the intermediate The second subcooling heat exchanger 17 provided on the upstream side of the heat exchanger 18 is provided, and the high stage side refrigerant circuit 2 is connected to the first subcooling heat exchanger 31 of the low stage side refrigerant circuit 3. The first evaporator 8 constituting the first cascade heat exchanger 36, the second subcooling heat exchanger 17 of the low stage side refrigerant circuit 3, and the second cascade heat exchanger 37 constituting the second cascade heat exchanger 37 Since the evaporator 9 is provided, the refrigerant that has exited the gas cooler 16 of the low-stage refrigerant circuit 3 can also be cooled by evaporating the refrigerant of the high-stage refrigerant circuit 2, thereby further improving the performance. can do.

  In particular, since the first evaporator 8 of the high stage side refrigerant circuit 2 is provided upstream of the second evaporator 9 with respect to the refrigerant flow of the high stage side refrigerant circuit 2, the expansion valve 7 is provided. The refrigerant that has come out first evaporates in the first evaporator 8 and supercools the refrigerant in the auxiliary circuit 26 that flows through the first supercooling heat exchanger 31. Thus, the refrigerant flowing into the auxiliary expansion valve 32 of the auxiliary circuit 26 is strongly subcooled compared to the case where the refrigerant evaporated in the second evaporator 9 evaporates in the first evaporator 8. Thus, the subcooling effect by the auxiliary circuit 26 in the intermediate heat exchanger 18 can be reliably implemented.

  The auxiliary circuit 26 of the low stage side refrigerant circuit 3 is downstream of the second subcooling heat exchanger 17 of the low stage side refrigerant circuit 3 by the refrigerant expanded by the auxiliary expansion valve 32, and is a shunt. Since the refrigerant in the low-stage refrigerant circuit 3 upstream of the refrigerant 19 is cooled, it becomes possible to flow the refrigerant that is more stable in temperature to the auxiliary circuit 26.

  Further, since the auxiliary circuit 26 of the low stage side refrigerant circuit 3 returns the refrigerant to the intermediate pressure portion of the compressor 12 of the low stage side refrigerant circuit 3, the compression work of the first compression element 13 in the compressor 12 is reduced. Therefore, it is possible to improve the operation efficiency.

  Further, since the controller C controls the refrigerant evaporation temperature of the first and second evaporators 8 and 9 of the high stage side refrigerant circuit 2 to be lower than the temperature of the refrigerant that has passed through the gas cooler 16 of the low stage side refrigerant circuit 3, The refrigerant in the high-stage refrigerant circuit 2 can accurately cool the refrigerant in the auxiliary circuit 26 in the low-stage refrigerant circuit 3 and the refrigerant that has passed through the gas cooler 16.

  Furthermore, since the controller C stops the operation of the compressor 4 of the high-stage refrigerant circuit 2 in an environment where the outside air temperature is low, the controller C increases only when the performance improvement effect by the auxiliary circuit 26 of the low-stage refrigerant circuit 3 deteriorates. By operating the side refrigerant circuit 2, it is possible to avoid unnecessary operation of the high-stage side refrigerant circuit 2 and to eliminate the deterioration of efficiency. The refrigeration apparatus 1 is particularly effective when carbon dioxide is used as the refrigerant in the low-stage refrigerant circuit 3.

  Next, FIG. 3 shows a refrigerant circuit diagram of another embodiment of the refrigeration apparatus 1 of the present invention. In this figure, the same reference numerals as those in FIG. 1 denote the same or similar functions. In this case, the flow divider 19 of the low-stage refrigerant circuit 3 is provided between the second subcooling heat exchanger 17 and the first flow path 18A of the intermediate heat exchanger 18.

  That is, in this embodiment, the refrigerant leaving the gas cooler 16 and passing through the second supercooling heat exchanger 17 is divided into the main circuit 21 and the auxiliary circuit 26 by the flow divider 19 and depressurized by the auxiliary expansion valve 32 of the auxiliary circuit 26. The expanded refrigerant evaporates in the second flow path 18B of the intermediate heat exchanger 18, and forms a form of supercooling the refrigerant in the main circuit 21 flowing through the first flow path 18A.

  Thus, the present invention is also effective in the case of the refrigeration apparatus 1 in which the auxiliary circuit 26 supercools the refrigerant in the main circuit 21 after being divided.

  Next, FIG. 4 shows a refrigerant circuit of another embodiment of the refrigeration apparatus 1 of the present invention. In this figure, the same reference numerals as those in FIG. 3 denote the same or similar functions. In the case of this embodiment, unlike FIG. 3, a single-stage compressor 12 </ b> A is used as the compressor of the low-stage refrigerant circuit 3 instead of the two-stage compression. Therefore, the auxiliary circuit 26 is configured to return the refrigerant to the suction side (low pressure side) of the compressor 12A.

  FIG. 5 shows a Ph diagram of the refrigeration apparatus 1 in this case. In the figure, L4 is the high-stage refrigerant circuit 2 and L5 is the low-stage refrigerant circuit 3 in this case, and L6 is a first subcooling heat exchanger 31 constituting the first cascade heat exchanger 36. Shows the supercooling effect. The present invention is also effective when a single-stage compressor 12 </ b> A is used as the compressor of the low-stage refrigerant circuit 3.

  Next, FIG. 6 shows a refrigerant circuit of still another embodiment of the refrigeration apparatus 1 of the present invention. In this figure, the same reference numerals as those in FIG. 4 denote the same or similar functions. In the case of this embodiment, unlike FIG. 4, the auxiliary circuit 26 is a so-called injection circuit. That is, the auxiliary circuit 26 of this embodiment decompresses the refrigerant diverted by the flow divider 19 with the auxiliary expansion valve 32, expands it, and returns it to the compressor 12A. Then, the compressor 12A is cooled by being evaporated in the compressor 12A.

  FIG. 7 shows a Ph diagram of the refrigeration apparatus 1 in this case. In the figure, L7 is the high-stage refrigerant circuit 2, L8 is the low-stage refrigerant circuit 3 in this case, and L9 is a first subcooling heat exchanger 31 that constitutes the first cascade heat exchanger 36. This shows the supercooling effect of the injection refrigerant. Thus, even when the refrigerant is injected into the compressor 12 </ b> A by the auxiliary circuit 26, the injection refrigerant can be subcooled by the first subcooling heat exchanger 31 constituting the first cascade heat exchanger 36. Therefore, the compressor 12 can be effectively cooled. As a result, the ability improvement effect by the auxiliary circuit 26 can be obtained with certainty.

  In the embodiment, the present invention is applied to the refrigeration apparatus 1 for cooling the showcase S. However, the present invention is not limited to this, and the present invention is also effective for a refrigeration apparatus used in a cooling storage, an air conditioner, or the like. In addition, the numerical values shown in the embodiments are merely examples and are not limited thereto.

DESCRIPTION OF SYMBOLS 1 Refrigeration apparatus 2 High stage side refrigerant circuit 3 Low stage side refrigerant circuit 4, 12, 12A Compressor 6, 16 Gas cooler 8 First evaporator 9 Second evaporator 17 Second supercooling heat exchanger 18 Intermediate heat Exchanger 19 Divider (Diversion point)
26 Auxiliary circuit 31 1st subcooling heat exchanger 32 Auxiliary expansion valve 36 1st cascade heat exchanger 37 2nd cascade heat exchanger

Claims (9)

A high-stage refrigerant circuit and a low-stage refrigerant circuit are provided. The low-stage refrigerant circuit divides the refrigerant discharged from the compressor and passed through the gas cooler, and expands the divided refrigerant using an auxiliary expansion valve. Has an auxiliary circuit,
The high-stage refrigerant circuit cools the refrigerant in the auxiliary circuit that evaporates the refrigerant and flows into the auxiliary expansion valve of the low-stage refrigerant circuit ,
The low-stage refrigerant circuit includes a first subcooling heat exchanger provided in the auxiliary circuit on the upstream side of the auxiliary expansion valve and a downstream side of the gas cooler and upstream of a branch point with the auxiliary circuit. A second subcooling heat exchanger provided on the side,
The high stage refrigerant circuit includes a first subcooling heat exchanger of the low stage refrigerant circuit, a first evaporator constituting a first cascade heat exchanger, and a second evaporator of the low stage refrigerant circuit. A refrigerating apparatus comprising: the subcooling heat exchanger and a second evaporator constituting a second cascade heat exchanger . 2. The refrigeration apparatus according to claim 1, wherein the first evaporator is provided upstream of the second evaporator with respect to the refrigerant flow of the high-stage refrigerant circuit . The auxiliary circuit includes the low-stage refrigerant on the downstream side of the second subcooling heat exchanger in the low-stage refrigerant circuit and upstream of the diversion point by the refrigerant expanded by the auxiliary expansion valve. The refrigerant | coolant of Claim 1 or Claim 2 which cools the refrigerant | coolant of a circuit . The refrigerant of the low stage side refrigerant circuit is divided into a refrigerant flowing in the main circuit at the diversion point and a refrigerant flowing in the auxiliary circuit,
The said auxiliary circuit cools the refrigerant | coolant of the said main circuit downstream from the branch point of the said low stage side refrigerant circuit with the refrigerant | coolant expanded by the said auxiliary | assistant expansion valve, The Claim 1 or Claim 2 characterized by the above-mentioned. The refrigeration apparatus described. The refrigeration apparatus according to claim 3 or 4, wherein the auxiliary circuit returns the refrigerant to an intermediate pressure portion of a compressor of the low-stage refrigerant circuit . 3. The refrigeration apparatus according to claim 1, wherein the auxiliary circuit cools a compressor of the low-stage refrigerant circuit with the refrigerant expanded by the auxiliary expansion valve . The refrigerant evaporating temperature of the first and second evaporators of the higher stage refrigerant circuit is controlled to be lower than the temperature of the refrigerant that has passed through the gas cooler of the lower stage refrigerant circuit. 6. The refrigeration apparatus according to claim 6. The refrigeration apparatus according to any one of claims 1 to 7, wherein the high-stage refrigerant circuit is stopped in an environment where the outside air temperature is low . The refrigeration apparatus according to any one of claims 1 to 8, wherein the refrigerant in the low-stage refrigerant circuit is carbon dioxide .

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