JP6543450B2 - Refrigeration system - Google Patents

Description

  The present invention relates to a refrigeration apparatus, and more particularly to a refrigeration apparatus that condenses a refrigerant discharged from a compressor and then evaporates it in an evaporator to exhibit a cooling function.

  DESCRIPTION OF RELATED ART Conventionally, the freezing apparatus which can cool the inside of a storage to ultra-low temperature below -80 degrees C is known (for example, refer patent document 1). In such a freezing apparatus, an azeotropic mixture (R508A), an azeotropic mixture (R508B), etc. were used as a refrigerant.

JP, 2011-112351, A

  The refrigeration system is required to have a small load on the global environment. For this reason, it is desirable that the refrigerant used for the refrigeration system not only has refrigeration performance capable of cooling the inside of the refrigerator to a target temperature, but also has a small global-warming potential (GWP). Further, with the trend of energy saving in recent years, energy saving is also required for the refrigeration system. In order to save energy of the refrigeration system, it is desirable to further improve the refrigeration performance of the refrigerant.

  The present invention has been made in view of these circumstances, and an object thereof is to provide a technology for realizing a refrigeration system having a small load on the global environment and high energy saving performance.

  In order to solve the above-mentioned subject, one mode of the present invention is a freezer. The refrigeration system includes a refrigerant circuit in which a compressor, a condenser, a pressure reducer, and an evaporator are annularly connected in this order. The refrigerant circuit has a heat exchanger that performs heat exchange between the refrigerant traveling from the evaporator to the compressor and the refrigerant in the pressure reducer and cools the refrigerant in the pressure reducer. Further, the refrigerant circuit has a first refrigerant containing at least one of difluoroethylene (R1132a) and ethane (R170) as a refrigerant, and a boiling point lower than the boiling point of the first refrigerant, and the boiling point in the pressure reducing device is thermal And a second refrigerant having a temperature equal to or higher than a temperature reached by the refrigerant in the pressure reducer by heat exchange in the exchanger.

  Another aspect of the present invention is also a refrigeration system. The refrigeration system includes a high temperature side refrigerant circuit in which a first compressor, a first condenser, a first pressure reducer and a first evaporator are annularly connected in this order, a second compressor, a second condenser, And a low temperature side refrigerant circuit in which a second pressure reducer and a second evaporator are annularly connected in this order. In the refrigeration system, a cascade heat exchanger is configured by the first evaporator and the second condenser, and in the cascade heat exchanger, heat exchange is performed between the refrigerant of the high temperature side refrigerant circuit and the refrigerant of the low temperature side refrigerant circuit. As a result, the refrigerant of the low temperature side refrigerant circuit is cooled. The low temperature side refrigerant circuit has a first refrigerant containing at least one of difluoroethylene (R1132a) and ethane (R170) as a refrigerant, a boiling point lower than the boiling point of the first refrigerant, and a boiling point in the second condenser And a second refrigerant whose temperature is equal to or higher than the temperature reached by the refrigerant in the second condenser by heat exchange in the cascade heat exchanger.

  According to the present invention, it is possible to provide a technology for realizing a refrigeration system having a small load on the global environment and high energy saving performance.

It is a side view which shows schematic structure of the cryogenic storage which mounts the freezing apparatus which concerns on embodiment. FIG. 1 is a refrigerant circuit diagram of a refrigeration apparatus according to Embodiment 1; It is a schematic diagram which shows schematic structure of a heat exchanger. FIG. 7 is a refrigerant circuit diagram of a refrigeration apparatus according to Embodiment 2. FIG. 10 is a refrigerant circuit diagram of a refrigeration apparatus according to Embodiment 3. FIG. 16 is a refrigerant circuit diagram of a refrigeration apparatus according to Embodiment 4. It is a graph which shows chamber internal temperature at the time of making content of a 2nd refrigerant | coolant different, and a pull-down time.

  Hereinafter, the present invention will be described based on preferred embodiments with reference to the drawings. The embodiments do not limit the invention and are merely examples, and all the features and combinations thereof described in the embodiments are not necessarily essential to the invention.

Embodiment 1
FIG. 1 is a side view showing a schematic structure of a cryogenic storage equipped with a refrigeration system according to the embodiment. The ultra low temperature storage 1 is used, for example, for ultra low temperature storage of frozen food, living tissue or a sample. The cryogenic storage 1 has a heat insulation box 2 whose upper surface is opened, and a machine room (not shown) which is located in the lower part of the heat insulation box 2 and in which the refrigeration apparatus of the present embodiment is installed. .

  The heat insulation box 2 includes an outer case 3 and an inner case 4 whose upper surfaces are open, a breaker 5 connecting the upper ends of the outer case 3 and the inner case 4, an outer case 3, an inner case 4 and a breaker 5. And a heat insulating material 7 filled in the enclosed space. The heat insulating material 7 is, for example, a polyurethane resin, and can be filled by an on-site foaming method. The space in the inner box 4 constitutes a storage room 8. The target temperature in the storage chamber 8 (hereinafter appropriately referred to as the storage temperature) is, for example, −80 ° C. or less. For this reason, the heat insulation box 2 is required to have a large heat insulation capacity as compared to a low temperature storage where the temperature in the storage is near 0 ° C. Therefore, in the case where the heat insulating ability is ensured only by the heat insulating material 7 made of polyurethane resin, the thickness of the heat insulating material 7 becomes extremely large, and it is difficult to sufficiently ensure the storage amount of the storage chamber 8. On the other hand, by arranging a vacuum insulating material made of glass wool on the inner wall surface of the outer case 3, the thickness dimension of the heat insulating material 7 can be reduced, and the storage amount of the storage room 8 can be secured.

  The breaker 5 has a stepped upper surface, and the heat insulating door 9 is provided on the upper surface of the breaker 5 via the packing 11. One end of the heat insulation door 9 is fixed to the heat insulation box 2, and the heat insulation door 9 is provided rotatably about the one end. Thereby, the opening of storage room 8 is closed openably and closably. At the other end of the heat insulating door 9, a handle 10 for opening and closing the heat insulating door 9 is provided. An evaporator 13 described later of the refrigeration system is attached to the circumferential surface of the inner case 4 on the heat insulating material 7 side. Thereby, the inside of the storage chamber 8 can be cooled by evaporation of the refrigerant in the evaporator 13.

  FIG. 2 is a refrigerant circuit diagram of the refrigeration apparatus according to the first embodiment. Refrigeration system R1 which concerns on this Embodiment is provided with the refrigerant circuit 12 of single unit single stage. The refrigerant circuit 12 mainly includes a compressor 14 (compressor), a condenser 15 (condenser), a capillary tube 18 as a pressure reducer, and an evaporator 13, which are annularly connected in this order. The compressor 14 is, for example, a motor-driven compressor using a one-phase or three-phase AC power supply. A desuper heater 20 is connected to the compressor 14. The refrigerant compressed by the compressor 14 is once discharged to the desuperheater 20 to be dissipated, and then returned to the inside of the hermetic container of the compressor 14. Then, the refrigerant is discharged to the refrigerant discharge pipe 31 connected to the discharge side of the compressor 14. The desuper heater 20 may not be provided.

  The refrigerant discharge pipe 31 is connected to the auxiliary condenser 21 (pre-condenser). A frame pipe 22 is connected to the auxiliary condenser 21 via a refrigerant pipe, and a condenser 15 is connected to the frame pipe 22. The frame pipe 22 is a member for heating the opening edge of the storage chamber 8 to prevent dew attachment. The auxiliary condenser 21 and the condenser 15 are configured as an integral condenser, and are cooled by the condensing fan 29. A dehydrator 17 (dry core) is connected to the condenser 15. The dehydrator 17 is a member for removing moisture in the refrigerant circuit 12. A condensing pipe 23 is connected to the dehydrator 17. The condensing pipe 23 constitutes a heat exchanger 16 together with a part of the suction pipe 32 which comes out of the evaporator 13 and returns to the compressor 14.

  The capillary tube 18 is connected to the condensing pipe 23. The capillary tube 18 is inserted into a suction pipe 32 through which the refrigerant that exits the evaporator 13 and returns to the compressor 14 passes. Therefore, the capillary tube 18 constitutes a double pipe together with the suction pipe 32. Moreover, the heat exchanger 25 is comprised by this double pipe | tube. In the heat exchanger 25, heat is exchanged between the refrigerant traveling from the evaporator 13 to the compressor 14 and the refrigerant in the capillary tube 18, and the refrigerant in the capillary tube 18 is cooled. The double tube structure of the heat exchanger 25 will be described in detail later. An evaporator 13 is connected to the capillary tube 18. The suction pipe 32 is connected to the evaporator 13. The suction pipe 32 passes from the evaporator 13 through the header 26 to the heat exchanger 25. The suction pipe 32 which has left the heat exchanger 25 is connected to the suction side of the compressor 14 through the heat exchanger 16, the check valve 27, and the accumulator 28 in this order.

(Double pipe structure)
The double tube structure of the heat exchanger 25 will be described in detail. FIG. 3 is a schematic view showing a schematic structure of a heat exchanger having a double pipe structure. The capillary tube 18 is inserted into the pipe 32A which is located on the outlet side of the header 26 and on the upstream side of the heat exchanger 16 and which constitutes a part of the suction pipe 32, heat exchange of the double pipe structure Container 25 is configured. The heat exchanger 25 exchanges heat between the refrigerant flowing in the pipe 32A which is the outside of the double pipe and the refrigerant flowing in the capillary tube 18 which is the inside of the double pipe.

  The heat exchanger 25 can be formed, for example, as follows. That is, the straight tubular capillary tube 18 is inserted into the straight tubular pipe 32A larger in diameter than the capillary tube 18, and a double tube is formed. Next, the double tube is spirally wound multiple times. At this time, the center of the axis of the pipe 32A and the center of the axis of the capillary tube 18 are wound as closely as possible, and a uniform gap is formed between the inner wall surface of the pipe 32A and the outer wall surface of the capillary tube 18 Be done. By making the heat exchanger 25 into a spiral double pipe structure, it is possible to suppress the upsizing of the heat exchanger 25 and hence the refrigeration system R1 while sufficiently securing the length of the heat exchanger 25.

  Subsequently, connection pipes 36 are attached to both ends of the pipe 32A. The connection pipe 36 is a member formed by welding one end of the end pipe 37 to one side end 36A of the T-shaped pipe, and constitutes a part of the suction pipe 32. The other end 36B of the connection pipe 36 is welded to the end of the pipe 32A. When the connection pipe 36 is attached, the end of the capillary tube 18 is drawn out from the opening at the other end of the end tube 37. Then, the other end of the end tube 37 is sealed by welding. Further, the suction pipe 32 connected to the outlet side of the evaporator 13 is connected to the lower end 36C of one of the connection pipes 36. Furthermore, a suction pipe 32 leading to the heat exchanger 16 is connected to the lower end 36C of the other connection pipe 36. Thereafter, the entire outer periphery of the heat exchanger 25 is wrapped with the heat insulating material 35 (see FIG. 1).

  In the heat exchanger 25 having such a double-pipe structure, the refrigerant passing through the capillary tube 18 and the refrigerant passing through the pipe 32A of the suction pipe 32 are heated via the entire circumferential wall surface of the capillary tube 18 Exchange. Therefore, the heat exchange efficiency can be improved as compared with the structure in which the capillary tube is wound around the outer peripheral surface of the suction pipe. Moreover, the whole outer periphery of the heat exchanger 25 is wrapped with the heat insulating material 35, so that the heat exchanger 25 is less susceptible to the influence of external heat. Thereby, heat exchange between the refrigerant in the capillary tube 18 and the refrigerant in the pipe 32A can be further promoted.

  Further, in the capillary tube 18 inside the double tube and in the pipe 32A outside the double tube, the flow of the refrigerant is in the opposite direction to each other. Thereby, the heat exchange capacity of the heat exchanger 25 can be further improved. The heat exchanger 25 is disposed in the heat insulating material 7 of the cryogenic storage 1 (see FIG. 1). Specifically, it is accommodated in the heat insulating material 7 located on the back side of the inner box 4 and located below the heat exchanger 16 so as to be able to be taken out and taken in and out. The heat exchanger 16 may also have a double ring structure.

(Refrigerant)
In the refrigerant circuit 12, a refrigerant composition including a first refrigerant and a second refrigerant is sealed as a refrigerant. The first refrigerant contains at least one of difluoroethylene (R1132a) and ethane (R170), 1,1,1,3,3-pentafluoropropane (R245fa) and butane (R600). R1132a has a standard boiling point of -85.7 ° C and a GWP of 10. Further, R170 has a standard boiling point of -88.8 ° C and a GWP of 3. Therefore, both are earth-friendly refrigerants capable of achieving a storage temperature below -80 ° C. R245fa has a boiling point of + 15.3 ° C, and R600 has a boiling point of -0.5 ° C. These refrigerants have a function of condensing the first refrigerant and the second refrigerant mixed together. Further, R 600 has a function of returning the lubricating oil of the compressor 14 and the mixed water that can not be absorbed by the dehydrator 17 back to the compressor 14 in a state of being dissolved therein. Although R600 is a flammable substance, it can be handled as a nonflammable mixture by mixing it with the nonflammable R245fa in a predetermined ratio. The mixing ratio of R245fa and R600 is, for example, R245fa / R600 = 70/30. The mixing ratio of each refrigerant in the refrigerant composition in the present embodiment, the first refrigerant 24 mass% For example, the second refrigerant is 12% by mass. Since the refrigerant composition contains the first refrigerant, the refrigerant composition can have refrigeration performance for keeping the temperature in the cold storage at -80 ° C. or lower, and the GWP can be reduced.

  The first refrigerant is preferably at least one selected from the group consisting of hexafluoroethane (R116), trifluoromethane (R23), an azeotropic mixture (R508A) and an azeotropic mixture (R508B) (hereinafter referred to as appropriate) 1a) is further included. R116 has a standard boiling point of -78.4 ° C. and is flame retardant than R1132a and R170, but has a high GWP of 12200. R23 has a standard boiling point of −82.1 ° C. and is flame retardant than R1132 a and R170, but has a GWP as high as 14800. R508A is an azeotropic mixture in which 39% by mass of trifluoromethane (R23) and 61% by mass of hexafluoroethane (R116) are mixed. Although R508A has a standard boiling point of −85.7 ° C. and is flame retardant than R1132 a and R170, GWP is as high as 13214. R508B is an azeotropic mixture in which 46% by mass of trifluoromethane (R23) and 54% by mass of hexafluoroethane (R116) are mixed. R508B has a standard boiling point of −86.9 ° C. and is flame retardant than R1132a and R170, but has a GWP as high as 13396.

  The 1ath refrigerant is contained for the purpose of further improving the refrigeration performance of the refrigerant composition by the azeotropic effect with R1132a and / or R170. Further, since the 1ath refrigerant is more flame retardant than R1132a and R170, the inclusion of the 1ath refrigerant can increase the flame retardancy of the refrigerant composition.

  The content of the 1ath refrigerant is 95% by mass or less, preferably 80% by mass or less, and more preferably 60% by mass or less based on the total mass of the first refrigerant. The content of the 1ath refrigerant is more than 0% by mass, preferably more than 20% by mass, and more preferably more than 40% by mass, with respect to the total mass of the first refrigerant. By setting the content of the 1ath refrigerant to 0% by mass or more and 95% by mass or less, the refrigeration performance of the refrigerant composition can be improved. Further, by setting the content of the 1ath refrigerant to more than 0% by mass and 80% by mass or less, it is possible to achieve both improvement in refrigeration performance and reduction in GWP. Further, by setting the content of the 1ath refrigerant to more than 20% by mass and 95% by mass or less, it is possible to achieve both good refrigeration performance and good flame retardancy. Further, by setting the content of the 1ath refrigerant to more than 20% by mass and 80% by mass or less, it is possible to realize good refrigeration performance, good flame retardancy and good GWP. Furthermore, by setting the content of the 1ath refrigerant to more than 40% by mass and 60% by mass or less, higher refrigeration performance can be obtained while achieving good flame retardancy and good GWP.

  The second refrigerant is a refrigerant having a boiling point (standard boiling point) lower than the boiling point (standard boiling point) of the first refrigerant. In addition, the second refrigerant is a refrigerant whose boiling point in the capillary tube 18 as a pressure reducer is equal to or higher than the temperature reached by the refrigerant in the capillary tube 18 by heat exchange in the heat exchanger 25, ie, heat exchange in the heat exchanger 25 Is a refrigerant that condenses in the capillary tube 18. As such a 2nd refrigerant | coolant, tetrafluoromethane (R14), ethylene (R1150), etc. can be mentioned. The second refrigerant preferably contains at least one selected from the group consisting of tetrafluoromethane (R14) and ethylene (R1150).

  R14 has a normal boiling point of -127.9 ° C, and R1150 has a standard boiling point of -103.7 ° C. The second refrigerant has a boiling point lower than that of the first refrigerant, and therefore, by including the second refrigerant in the refrigerant composition, the refrigeration performance of the refrigerant composition can be further improved. As a result, it is possible to shorten the time required to reach a desired internal temperature, that is, the pull-down time, so that the energy saving performance of the refrigeration system R1 can be improved. Further, since the second refrigerant has a boiling point which condenses in the capillary tube 18, the refrigeration performance can be more reliably exhibited in the evaporator 13.

  The GWP of R14 is 6500, and the GWP of R1150 is 20 or less. The content of the second refrigerant is preferably 30% by mass or less based on the total mass of the refrigerant composition. By setting the content of the refrigerant composition to 30% by mass or less, the entire amount of the second refrigerant can be more reliably condensed without increasing the size of the heat exchanger 25. Therefore, the amount of the second refrigerant that is wasted without condensation can be more reliably reduced, and it is possible to more reliably achieve both the improvement in the refrigeration performance of the refrigerant composition and the reduction in GWP.

  The content of the second refrigerant is more than 0% by mass, preferably more than 5% by mass, based on the total mass of the refrigerant composition. By setting the content of the second refrigerant to more than 5% by mass, it is possible to further reduce the internal temperature in addition to shortening the pull-down time.

  The refrigerant composition further preferably includes a third refrigerant containing at least one of carbon dioxide (R744) and nitrous oxide (R744A). R744 has a standard boiling point of −78.4 ° C. and a GWP of 1. R744A has a normal boiling point of -88.5 ° C and a GWP of 310. In R744 and R744A, since the GWP of each of R744 and R744A is smaller than the GWP of the second refrigerant (R744 is smaller than the GWP of the first refrigerant), the third refrigerant is contained in the refrigerant composition to further add the refrigerant composition. The GWP can be reduced.

  Moreover, the thermal conductivity of the refrigerant composition can be improved by containing the third refrigerant in the refrigerant composition. The improvement of the thermal conductivity of the refrigerant composition can improve the refrigeration capacity of the refrigerant composition. In addition, the density of the refrigerant composition sucked into the compressor 14 can be increased. Furthermore, an azeotropic effect with the first refrigerant can also be expected. Therefore, the refrigeration performance of the refrigerant composition can be further improved.

  Here, the boiling point of R744 is higher than the boiling points of the first refrigerant and the second refrigerant. Therefore, R744 may be sent out to the suction pipe 32 as liquid or wet vapor without evaporating even in the evaporator 13. Therefore, the refrigerant leaving the evaporator 13 tends to have a high ratio of R744. In addition, the refrigerant leaving the evaporator 13 is at a cryogenic temperature of -85 ° C or less. For this reason, in the refrigerant | coolant which came out of the evaporator 13, R744 is in the state which is easy to dry-ice. On the other hand, in the connection pipe 36 of the heat exchanger 25, the flow direction of the refrigerant changes substantially at right angles along its shape (see the regions X1 and X2 in FIG. 3). Therefore, when the refrigerant passes through the inside of the connection pipe 36, a pressure loss is likely to occur.

  When the refrigerant in a state where R744 tends to dry ice reaches the regions X1 and X2 where pressure loss of the heat exchanger 25 is likely to occur, there is a possibility that the R744 solidifies in the regions X1 and X2 to become dry ice. The generated dry ice may be clogged in the connection pipe 36 and the circulation of the refrigerant in the refrigerant circuit 12 may be inhibited. On the other hand, R744A is explosive because it is a refrigerant having nitrogen (N).

  For this reason, it is preferable that content of a 3rd refrigerant | coolant is more than 0 mass% and 40 mass% or less with respect to the total mass of a refrigerant | coolant composition. By setting the content of R744 to 40% by mass or less, it is possible to suppress the possibility that R744 is solidified and the refrigerant circulation is inhibited. In addition, it is possible to provide a heater in the connection piping 36 and to heat area | region X1, X2 as a method of suppressing solidification of R744. Even in this case, the content of R744 is preferably 40% by mass or less in order to more reliably suppress the solidification of R744. In addition, by setting the content of R744A to 40% by mass or less, the danger of explosion can be suppressed.

  In addition, when the third refrigerant contains R744, the refrigerant composition preferably further includes a fourth refrigerant having a solubility with R744 at a temperature lower than the boiling point of R744. Solidification of R 744 can also be suppressed by including the fourth refrigerant in the refrigerant composition. Further, since the solidification of R 744 can be suppressed without providing the above-described heater or the like, the refrigerant circuit 12 can be suppressed from being complicated or enlarged. In addition, solidification of R744 can be suppressed more by the combination of addition of the 4th refrigerant | coolant to a refrigerant | coolant composition, and setting content of R744 to 40 mass% or less.

  As the fourth refrigerant, difluoromethane (R32), 1,1,1,2-tetrafluoroethane (R134a), n-pentane (R600), isobutane (R600a), 1,1,1,2,3-pentafluoromethane Penten (HFO-1234ze) and 1,1,1,2-tetrafluoropentene (HFO-1234yf) etc. can be mentioned.

  Furthermore, from the viewpoint of suppressing solidification of R744, the content of R744 is more preferably 20% by mass or less with respect to the total mass of the refrigerant composition. By making content of R744 into 20 mass% or less, solidification of R744 can be suppressed irrespective of installation of a heater, or addition of a 4th refrigerant | coolant. In addition, solidification of R744 can be suppressed further by the combination of setting content of R744 to 20 mass% or less, and addition of the 4th refrigerant | coolant to a refrigerant | coolant composition. Further, from the viewpoint of suppressing the risk of explosion of R744A, the content of R744A is more preferably 20% by mass or less with respect to the total mass of the refrigerant composition. As mentioned above, it is more preferable that content of a 3rd refrigerant | coolant is 20 mass% or less with respect to the total mass of a refrigerant | coolant composition.

  The circulation of the refrigerant in the refrigerant circuit 12 will be described with reference to FIG. In FIG. 2, the flow of the refrigerant is indicated by an arrow. The refrigerant is compressed in the compressor 14 to be a high temperature gaseous refrigerant. The refrigerant is discharged from the closed container of the compressor 14 toward the desuperheater 20. After the refrigerant dissipates heat in the desuperheater 20, it returns to the inside of the closed container again. Thereby, the inside of the closed container can be cooled.

  Next, the refrigerant is discharged to the refrigerant discharge pipe 31, passes through the auxiliary condenser 21, the frame pipe 22, and the condenser 15, and in the process, the refrigerant condenses and is liquefied. The condensed refrigerant has the water contained in the dehydrator 17 removed and flows into the heat exchanger 16. In the heat exchanger 16, the refrigerant flowing from the condenser 15 side exchanges heat with the low temperature refrigerant flowing in the suction pipe 32. Thus, the refrigerant flowing from the condenser 15 side is cooled, and a part of the first refrigerant in the refrigerant is condensed.

  Thereafter, the refrigerant flows into the capillary tube 18. The refrigerant flowing into the capillary tube 18 is decompressed and exchanges heat with the low temperature refrigerant flowing in the pipe 32A constituting the heat exchanger 25. Thereby, the refrigerant in the capillary tube 18 is further cooled. By this cooling, the remaining part of the first refrigerant and the second refrigerant in the refrigerant composition used as the refrigerant are almost completely condensed. Then, the refrigerant flows into the evaporator 13.

  In the evaporator 13, the refrigerant takes heat from the surroundings and evaporates. Thereby, the cooling action of the refrigerant is exhibited, and the periphery of the evaporator 13 is cooled to an extremely low temperature of about -90.degree. Since the evaporator 13 is disposed along the heat insulating material 7 side of the inner box 4, the temperature in the storage chamber 8 can be reduced to −85 ° C. or less by the cooling of the evaporator 13. The refrigerant evaporated in the evaporator 13 is discharged to the suction pipe 32, and returns to the compressor 14 through the header 26, the heat exchanger 25, the heat exchanger 16, the check valve 27 and the accumulator 28.

  As described above, the refrigeration apparatus R1 according to the present embodiment performs heat exchange between the refrigerant traveling from the evaporator 13 to the compressor 14 and the refrigerant in the capillary tube 18, and the refrigerant in the capillary tube 18 The heat exchanger 25 cools the The refrigerating apparatus R1 has a first refrigerant containing at least one of R1132a and R170 as a refrigerant, and a boiling point lower than the boiling point of the first refrigerant, and the boiling point in the capillary tube 18 is the heat exchanger 25. A refrigerant composition including a second refrigerant whose temperature is equal to or higher than the temperature reached by the refrigerant in the capillary tube 18 by heat exchange is used.

  The first refrigerant has a low GWP and a very low boiling point of -85 ° C or less. In addition, the second refrigerant has a boiling point lower than that of the first refrigerant. Then, the second refrigerant condenses in the capillary tube 18 by heat exchange in the heat exchanger 25. Thereby, the refrigeration performance of the refrigerant can be improved while the GWP of the refrigerant is reduced. And, by improving the refrigeration performance, it is possible to shorten the pull-down time. Thus, energy saving of the refrigeration system R1 can be achieved. Therefore, according to the refrigeration system R1 of the present embodiment, it is possible to realize a refrigeration system having a small load on the global environment and high energy saving performance.

  Moreover, the temperature around the evaporator 13 can be cooled to a lower temperature by the improvement of the refrigeration performance of the refrigerant. For this reason, a compressor having a lower compression capacity than that of the conventional one can be used as the compressor 14. Thereby, the power consumption of refrigeration system R1 can be reduced, and energy saving of refrigeration system R1 can be attained also from this point. In addition, the refrigeration system R1 can be miniaturized. Furthermore, ultra-low temperature can be realized by a single-stage refrigeration system without using a multistage refrigeration system. Therefore, the refrigeration system can be simplified, and the cost can be reduced.

  In addition, the refrigerant used for the refrigeration system R1 may further include a third refrigerant including at least one of R744 and R744A. Thereby, it is possible to further reduce the GWP of the refrigerant. In addition, the first refrigerant has an azeotropic effect with R1132a and / or R170, and has a content of 95% by mass or less with respect to the total mass of the first refrigerant, and the 1a refrigerant having lower combustibility than these It may further include. Thereby, the refrigeration performance of the refrigerant can be further enhanced, and as a result, further energy saving of the refrigeration system R1 becomes possible. Moreover, since the flame retardance of a refrigerant | coolant can be improved, the handleability of freezing apparatus R1 can be improved.

  Further, the heat exchanger 25 is constituted by a double pipe in which the capillary tube 18 is inserted into the suction pipe 32. Thereby, the heat exchange efficiency between the refrigerant in the suction pipe 32 and the refrigerant in the capillary tube 18 can be improved. Therefore, the refrigerant, particularly the second refrigerant, can be more reliably condensed in the capillary tube 18, and energy saving of the refrigeration system R1 can be realized more reliably. In addition, the double pipe structure can reduce the size of the heat exchanger 25 required to achieve the desired heat exchange. For this reason, it is possible to suppress an increase in size of the heat exchanger 25 and hence the refrigeration system R1.

Second Embodiment
The refrigeration system according to the second embodiment has a configuration that is substantially in common with the refrigeration system R1 according to the first embodiment except that the refrigeration system according to the second embodiment has a multiple single-stage refrigeration system. In the description of the present embodiment, the description of the same configuration as that of the first embodiment will be omitted as appropriate. FIG. 4 is a refrigerant circuit diagram of the refrigeration apparatus according to the second embodiment. In the present embodiment, a binary single-stage refrigerant circuit will be described as an example of the multiple single-stage refrigerant circuit.

  Refrigeration system R2 which concerns on this Embodiment is equipped with the high temperature side refrigerant circuit 52 and the low temperature side refrigerant circuit 82 which comprise a respectively independent refrigerant | coolant closed circuit. The high temperature side refrigerant circuit 52 mainly includes a first compressor 54, a first condenser 55, a capillary tube 58 as a first decompressor, and a first evaporator 59, which are annularly connected in this order. . The first compressor 54 is, for example, an electric compressor similar to the compressor 14. A desuperheater 60 is connected to the first compressor 54. Further, a refrigerant discharge pipe 71 is connected to the first compressor 54. The refrigerant discharge pipe 71 is connected to the auxiliary condenser 61, and the frame pipe 62 is connected to the auxiliary condenser 61. An oil cooler 84C of the second compressor 84 in the low temperature side refrigerant circuit 82 and the first condenser 55 are connected to the frame pipe 62 in this order.

  To the first condenser 55, a dehydrator 57 is connected, and subsequently, a capillary tube 58 is connected. The capillary tube 58 is inserted into a suction line 72 which exits the first evaporator 59 and returns to the first compressor 54. Specifically, the capillary tube 58 is inserted into the pipe 72A which is located on the discharge side of the evaporator 59 and on the suction side of the accumulator 68 and which constitutes a part of the suction pipe 72, thereby a double The tube is constructed. Moreover, the heat exchanger 67 is comprised by this double pipe | tube. The heat exchanger 67 exchanges heat between the refrigerant flowing in the capillary tube 58 and the refrigerant flowing in the pipe 72A. The structure and formation method of the double tube are the same as the heat exchanger 25.

  The first evaporator 59 is connected to the capillary tube 58. The first evaporator 59 is provided so as to be heat exchangeable with the second condenser 85 of the low temperature side refrigerant circuit 82. Therefore, the cascade heat exchanger 56 is configured by the first evaporator 59 and the second condenser 85. A suction pipe 72 is connected to the first evaporator 59. The suction pipe 72 passes from the first evaporator 59 through the header 66 to the heat exchanger 67. The suction pipe 72 that has left the heat exchanger 67 is connected to the suction side of the first compressor 54 through the accumulator 68 and the check valve 69 in this order.

(High temperature side refrigerant)
In the high temperature side refrigerant circuit 52, for example, a mixed refrigerant (R404A) is sealed as a refrigerant. R404A is a mixture of pentafluoroethane (R125), 1,1,1-trifluoroethane (R143a), and 1,1,1,2-tetrafluoroethane (R134a). The proportion of each refrigerant in R404A is 44% by mass for R125, 52% by mass for R143a, and 4% by mass for R134a. The standard boiling point of each refrigerant is -48.5 ° C for R125, -47.8 ° C for R143a, -26.1 ° C for R134a, and -46.5 ° C for R404A. Alternatively, another refrigerant such as a mixed refrigerant (R704C) may be sealed in the high temperature side refrigerant circuit 52. R407C is a mixture obtained by mixing R134a, difluoromethane (R32) and R125.

  The circulation of the refrigerant in the high temperature side refrigerant circuit 52 will be described with reference to FIG. In FIG. 4, the flow of the refrigerant in the high temperature side refrigerant circuit 52 is indicated by a broken arrow. The refrigerant is compressed in the first compressor 54 to be a high temperature gaseous refrigerant. The high temperature gaseous refrigerant is discharged from the first compressor 54 to the desuperheater 60, dissipates heat, and returns to the first compressor 54 again. Thereby, the first compressor 54 can be cooled. Next, the refrigerant is discharged to the refrigerant discharge pipe 71, passes through the auxiliary condenser 61, the frame pipe 62, the oil cooler 84C and the first condenser 55, and is condensed and liquefied in the process. The condensed refrigerant is dewatered by the dehydrator 57 and flows into the capillary tube 58.

  The refrigerant flowing into the capillary tube 58 is decompressed and exchanges heat with the low temperature refrigerant flowing in the pipe 72A constituting the heat exchanger 67. Thereby, the refrigerant in the capillary tube 58 is cooled. Then, the refrigerant flows into the first evaporator 59. In the first evaporator 59, the refrigerant absorbs heat from the refrigerant flowing in the second condenser 85 of the cascade heat exchanger 56 and evaporates. The evaporation of the refrigerant cools the refrigerant flowing in the second condenser 85. The refrigerant evaporated in the first evaporator 59 is discharged to the suction pipe 72 and flows into the heat exchanger 67 through the header 66. The refrigerant exchanges heat with the refrigerant flowing in the capillary tube 58 in the heat exchanger 67, and then returns to the first compressor 54 through the accumulator 68 and the check valve 69.

  The low temperature side refrigerant circuit 82 mainly includes a second compressor 84, a second condenser 85, a capillary tube 88 as a second pressure reducer, and a second evaporator 83, which are annularly connected in this order. . The second compressor 84 is an electric compressor similar to the first compressor 54. A desuperheater 90 is connected to the second compressor 84. Further, the refrigerant discharge pipe 101 is connected to the second compressor 84. The refrigerant discharge pipe 101 is connected to the auxiliary condenser 91, and an oil separator 92 is connected to the auxiliary condenser 91. An oil return pipe 103 returning to the second compressor 84 is connected to the oil separator 92.

  The refrigerant pipe exiting the oil separator 92 reaches the internal heat exchanger 93. In the internal heat exchanger 93, heat exchange is performed between the high pressure side refrigerant on the way from the second compressor 84 to the capillary tube 88 and the low pressure side refrigerant on the way from the second evaporator 83 to the second compressor 84. Ru. The refrigerant pipe that has passed through the internal heat exchanger 93 is connected to the second condenser 85. The second condenser 85 constitutes a cascade heat exchanger 56 together with the first evaporator 59. A dehydrator 87 is connected to the second condenser 85, and then a capillary tube 88 is connected.

  The capillary tube 88 is inserted into the suction pipe 102 that exits the second evaporator 83 and returns to the second compressor 84. Specifically, the capillary tube 88 is inserted into the pipe 102A which is located on the discharge side of the second evaporator 83 and on the suction side of the internal heat exchanger 93 and which constitutes a part of the suction pipe 102. , This constitutes a double pipe. Moreover, the heat exchanger 95 is comprised by this double pipe | tube. In the heat exchanger 95, the refrigerant flowing in the capillary tube 88 exchanges heat with the refrigerant flowing in the pipe 102A. The structure and formation method of the double tube are the same as the heat exchanger 25. Similar to the heat exchanger 25, the heat exchanger 95 is encased in the heat insulating material 105 over the entire outer circumference, and is accommodated in the heat insulating material 7 of the cryogenic storage 1 so as to be able to be taken in and out (see FIG. 1).

  The second evaporator 83 is connected to the capillary tube 88. The 2nd evaporator 83 is attached to the peripheral surface by the side of the heat insulating material 7 of the inner case 4 similarly to the evaporator 13 (refer FIG. 1). The suction pipe 102 is connected to the second evaporator 83. The suction pipe 102 is connected to the suction side of the second compressor 84 through the heat exchanger 95 and the internal heat exchanger 93. The refrigerant pipe 106 is connected to the second compressor 84. An expansion tank 107 is connected to the refrigerant pipe 106 via a capillary tube 108. The expansion tank 107 is a tank that stores the refrigerant when the second compressor 84 stops.

(Low temperature side refrigerant)
In the low temperature side refrigerant circuit 82, a refrigerant composition similar to that of the first embodiment is enclosed as a refrigerant. That is, the low temperature side refrigerant circuit 82 has a first refrigerant containing at least one of R1132a and R170, and a boiling point lower than the boiling point of the first refrigerant, and the boiling point in the capillary tube 88 is the thermal energy in the heat exchanger 95. And a second refrigerant having a temperature equal to or higher than a temperature reached by the refrigerant in the capillary tube 88 by the exchange.

  The first refrigerant is preferably contained as a main refrigerant in the refrigerant composition. The content of the first refrigerant is preferably 50% by mass or more based on the total mass of the refrigerant composition. Since the refrigerant composition contains the first refrigerant, the refrigerant composition can have refrigeration performance for keeping the temperature in the cold storage at -80 ° C. or lower, and the GWP can be reduced.

  The first refrigerant is preferably at least one type 1a refrigerant selected from the group consisting of hexafluoroethane (R116), trifluoromethane (R23), an azeotropic mixture (R508A) and an azeotropic mixture (R508B), It further contains in 95 mass% or less with respect to the total mass of a 1st refrigerant | coolant. The second refrigerant includes at least one selected from the group consisting of tetrafluoromethane (R14) and ethylene (R1150). The content of the second refrigerant is preferably less than 50% by mass, more preferably 30% by mass or less, based on the total mass of the refrigerant composition. Further, the content of the second refrigerant is preferably more than 5% by mass with respect to the total mass of the refrigerant composition.

  The second refrigerant is preferably contained as an auxiliary refrigerant in the refrigerant composition. The content of the second refrigerant is preferably less than 50% by mass, more preferably 30% by mass or less, based on the total mass of the refrigerant composition. By setting the content of the second refrigerant to less than 50% by mass, it is possible to suppress the increase in the GWP of the refrigerant composition.

  The refrigerant composition further preferably includes a third refrigerant containing at least one of carbon dioxide (R744) and nitrous oxide (R744A). The content of the third refrigerant is preferably 40% by mass or less based on the total mass of the refrigerant composition. The refrigerant composition preferably further includes a fourth refrigerant having a solubility with the third refrigerant at a temperature lower than the boiling point of the third refrigerant. Furthermore, the content of the third refrigerant is preferably 20% by mass or less based on the total mass of the refrigerant composition.

  The circulation of the refrigerant in the low temperature side refrigerant circuit 82 will be described with reference to FIG. In FIG. 4, the flow of the refrigerant in the low temperature side refrigerant circuit 82 is indicated by a solid arrow. The refrigerant is compressed in the second compressor 84 to be a high temperature gaseous refrigerant. The refrigerant is discharged from the second compressor 84 to the desuperheater 90, dissipates heat, and returns to the second compressor 84 again. Thereby, the second compressor 84 can be cooled. Next, the refrigerant is discharged to the refrigerant discharge pipe 101, dissipated in the auxiliary condenser 91, and then flows into the oil separator 92. In the oil separator 92, most of the lubricating oil of the second compressor 84 mixed with the refrigerant and a part of the refrigerant condensed by the auxiliary condenser 91 pass through the oil return pipe 103 and the second compressor 84. Return to As a result, a refrigerant of higher purity flows on the downstream side of the oil separator 92, and the cooling efficiency is improved. Therefore, the storage capacity of the ultra low temperature storage 1 can be expanded while maintaining the performance of the first compressor 54 and the second compressor 84.

  The remaining refrigerant is discharged from the oil separator 92, passes through the internal heat exchanger 93, and the second condenser 85 constituting the cascade heat exchanger 56, and condenses in the process. By heat exchange in the cascade heat exchanger 56, heat exchange is performed between the refrigerant flowing in the first evaporator 59 of the high temperature side refrigerant circuit 52 and the refrigerant flowing in the second condenser 85 of the low temperature side refrigerant circuit 82 The refrigerant of the side refrigerant circuit 82 is cooled. This cooling condenses a part of the first refrigerant in the refrigerant composition used as the refrigerant. The condensed refrigerant is dewatered by the dehydrator 87 and flows into the capillary tube 88.

  The refrigerant flowing into the capillary tube 88 is decompressed and exchanges heat with the low temperature refrigerant flowing in the pipe 102A constituting the heat exchanger 95. Thereby, the refrigerant in the capillary tube 88 is further cooled, and the remaining portion of the first refrigerant and the second refrigerant condense almost completely. Then, the refrigerant flows into the second evaporator 83. In the second evaporator 83, the refrigerant takes heat from the surroundings and evaporates. Thereby, the cooling action of the refrigerant is exhibited, and the periphery of the second evaporator 83 is cooled to an extremely low temperature of −90 ° C. or less. By the cooling of the second evaporator 83, the temperature in the storage chamber 8 can be set to −85 ° C. or less. The refrigerant evaporated by the second evaporator 83 is discharged to the suction pipe 102, passes through the heat exchanger 95 and the internal heat exchanger 93, and is returned to the second compressor 84.

  The second compressor 84 is controlled to switch between ON and OFF by a control device (not shown) based on the internal temperature of the storage chamber 8. When the operation of the second compressor 84 is stopped by the controller, the refrigerant of the low temperature side refrigerant circuit 82 is recovered from the refrigerant pipe 106 through the capillary tube 108 to the expansion tank 107. Thereby, the rise of the pressure in the low temperature side refrigerant circuit 82 can be suppressed. Further, when the operation of the second compressor 84 is started by the control device, the refrigerant in the expansion tank 107 is gradually returned to the second compressor 84 through the capillary tube 108. Thereby, the starting load of the second compressor 84 can be reduced.

  As described above, the refrigeration apparatus R2 according to the present embodiment includes the high temperature side refrigerant circuit 52 and the low temperature side refrigerant circuit 82. Further, a cascade heat exchanger 56 is configured by the first evaporator 59 of the high temperature side refrigerant circuit 52 and the second condenser 85 of the low temperature side refrigerant circuit 82. In the cascade heat exchanger 56, the refrigerant of the high temperature side refrigerant circuit 52 And the refrigerant of the low temperature side refrigerant circuit 82 exchange heat. The low temperature side refrigerant circuit 82 has a boiling point lower than that of the first refrigerant and the first refrigerant as refrigerants, and the boiling point in the second condenser 85 is exchanged by heat exchange in the cascade heat exchanger 56. (2) A refrigerant composition including a second refrigerant which is equal to or higher than the temperature reached by the refrigerant composition in the condenser 85 is used. Even with such a configuration, the same effect as that of the first embodiment can be obtained. In addition, the refrigeration apparatus R2 has the same features as those of the first embodiment in the other composition of the refrigerant composition and the double pipe structure, and can exhibit the same effect.

  The second refrigerant has a boiling point lower than the boiling point of the first refrigerant, and a temperature at which the boiling point in the second condenser 85 reaches the refrigerant in the second condenser 85 by heat exchange in the cascade heat exchanger 56 The refrigerant which is more than may be sufficient. Even in this case, the second refrigerant can be more reliably condensed in the front stage of the second evaporator 83, and the same effect as that of the first embodiment can be obtained.

Third Embodiment
The refrigeration system according to the third embodiment has a configuration that is generally in common with the refrigeration system according to the first or second embodiment except that it has a single-stage multistage refrigeration system. In the description of the present embodiment, the description of the same configuration as that of the first embodiment or 2 will be omitted as appropriate. FIG. 5 is a refrigerant circuit diagram of the refrigeration apparatus according to the third embodiment. In the present embodiment, as an example of the single-stage multistage refrigerant circuit, a single-stage two-stage refrigerant circuit will be described.

  The refrigeration system R3 according to the present embodiment includes a refrigerant circuit 112 and a refrigerant circuit 152. The refrigerant circuit 112 and the refrigerant circuit 152 have similar single-unit two-stage circuit configurations and are circuits independent of each other. Therefore, the other refrigerant circuit can be used as a backup when one refrigerant circuit fails. By arranging two independent refrigerant circuits 112 and 152 in parallel, the low temperature state in the storage chamber 8 can be maintained more stably. As a result, the reliability of the ultra low temperature storage 1 equipped with the refrigerant circuit R3 can be improved.

  Hereinafter, the configuration of the refrigerant circuit provided in the refrigeration system R3 will be described. The refrigerant circuit 112 and the refrigerant circuit 152 have the same configuration, and the same refrigerant is used. Therefore, the refrigerant circuit 112 will be described in detail below, and the description of the refrigerant circuit 152 will be omitted. In the refrigerant circuit 152, those to which the same reference numerals as those of the refrigerant circuit 112 are attached have the same effects.

  The compressor 114 of the refrigerant circuit 112 is, for example, an electric compressor similar to the compressor 14. The refrigerant discharge pipe 131 connected to the discharge side of the compressor 114 is connected to the auxiliary condenser 121. A frame pipe 122 is connected to the auxiliary condenser 121, and an oil cooler 114C is connected to the frame pipe 122. A condenser 115 is connected to the oil cooler 114C. The auxiliary condenser 121 and the condenser 115 are configured as an integral condenser, and are cooled by the condensing fan 129.

  The dehydrator 117 is connected to the condenser 115, and then the gas-liquid separator 130 is connected. The gas-liquid separator 130 separates the refrigerant condensed and liquefied in the process of passing through the auxiliary condenser 121, the flame pipe 122 and the condenser 115, and the refrigerant which is not condensed but remains in a gas state. A gas phase pipe 133 is connected to the gas-liquid separator 130. The gas phase pipe 133 is a pipe for taking out the non-condensed gas phase refrigerant separated by the gas liquid separator 130. The gas phase piping 133 is connected to the condensation pipe 123.

  In addition, a liquid phase pipe 134 is connected to the gas-liquid separator 130. The liquid-phase pipe 134 is a pipe for taking out the condensed liquid-phase refrigerant separated by the gas-liquid separator 130. The liquid phase piping 134 is connected to the auxiliary evaporator 136 via a capillary tube 135. The condensing pipe 123 and the auxiliary evaporator 136 constitute an intermediate heat exchanger 116. In the intermediate heat exchanger 116, the liquid phase refrigerant which is depressurized by the capillary tube 135 and flows into the auxiliary evaporator 136 is evaporated, whereby the gas phase refrigerant flowing in the condensation pipe 123 is cooled and condensed. A capillary tube 118 as a pressure reducer is connected to the condensation pipe 123. The capillary tube 118 is a capillary tube of the final stage.

  The capillary tube 118 is inserted into a suction line 132 which exits the evaporator 113 and returns to the compressor 114. Specifically, the capillary tube 118 is inserted into a pipe 132A which is located on the discharge side of the evaporator 113 and on the suction side of the intermediate heat exchanger 116 and which constitutes a part of the suction pipe 132. Form a double pipe. Moreover, the heat exchanger 125 is comprised by this double pipe | tube. In the heat exchanger 125, heat is exchanged between the refrigerant flowing in the capillary tube 118 and the refrigerant flowing in the pipe 132A, and the refrigerant in the capillary tube 118 is cooled. The structure and formation method of the double tube are the same as the heat exchanger 25. Similar to the heat exchanger 25, the heat exchanger 125 is encased in the heat insulating material 140 over the entire outer circumference, and is housed in the heat insulating material 7 of the cryogenic storage 1 so as to be able to be inserted and extracted (see FIG. 1).

  An evaporator 113 is connected to the capillary tube 118. The evaporator 113 is attached to the circumferential surface of the inner case 4 on the side of the heat insulating material 7 in the same manner as the evaporator 13 (see FIG. 1). The suction pipe 132 is connected to the evaporator 113. The suction pipe 132 is connected to the auxiliary evaporator 136 through the pipe 132A of the heat exchanger 125. The suction pipe 132 leaving the auxiliary evaporator 136 is connected to the suction side of the compressor 114. An expansion tank 137 is connected between the auxiliary evaporator 136 and the compressor 114 in the suction pipe 132 via a capillary tube 138. The expansion tank 137 is a tank for storing the refrigerant when the compressor 114 is stopped.

(Refrigerant)
In the refrigerant circuit 112, a refrigerant composition similar to that of Embodiment 1 is enclosed as a refrigerant. That is, in the refrigerant circuit 112, the first refrigerant containing at least one of R1132a and R170, 1,1,1,3,3-pentafluoropropane (R245fa) and butane (R600), and the boiling point of the first refrigerant And a second refrigerant having a low boiling point, and having a boiling point in the capillary tube 118 equal to or higher than a temperature reached by the refrigerant in the capillary tube 118 by heat exchange in the heat exchanger 125. The first refrigerant is preferably at least one type 1a refrigerant selected from the group consisting of hexafluoroethane (R116), trifluoromethane (R23), an azeotropic mixture (R508A) and an azeotropic mixture (R508B), It further contains in 95 mass% or less with respect to the total mass of a 1st refrigerant | coolant.

  The second refrigerant includes at least one selected from the group consisting of tetrafluoromethane (R14), ethylene (R1150), methane (R50) and argon (R740). R50 has a normal boiling point of -164 ° C, and R740 has a standard boiling point of -185.8 ° C. In the present embodiment, since the refrigerant circuit 112 has a two-stage circuit configuration, R50 and R740 can be more reliably condensed. The content of the second refrigerant is preferably 30% by mass or less based on the total mass of the refrigerant composition. Further, the content of the second refrigerant is more than 0% by mass, preferably more than 5% by mass, with respect to the total mass of the refrigerant composition.

  The refrigerant composition further preferably includes a third refrigerant containing at least one of carbon dioxide (R744) and nitrous oxide (R744A). The content of the third refrigerant is preferably 40% by mass or less based on the total mass of the refrigerant composition. When the third refrigerant contains R744, the refrigerant composition preferably further includes a fourth refrigerant having a solubility with R744 at a temperature lower than the boiling point of R744. Furthermore, the content of the third refrigerant is preferably 20% by mass or less based on the total mass of the refrigerant composition.

  The circulation of the refrigerant in the refrigerant circuit 112 will be described with reference to FIG. In FIG. 5, the flow of the refrigerant is indicated by an arrow. Further, the case where a refrigerant composition containing R245fa, R600, R1132a and R14 is used as the refrigerant will be described as an example. The refrigerant is compressed in the compressor 114 to be a high temperature gaseous refrigerant. The refrigerant is discharged to the refrigerant discharge pipe 131, and passes through the auxiliary condenser 121, the frame pipe 122, the oil cooler 114C, and the condenser 115 in this order. In this process, R245fa and R600, which have relatively high boiling points, are mainly condensed. Then, the refrigerant that has passed through the condenser 115 is dewatered by the dehydrator 117 and flows into the gas-liquid separator 130. R1132a and R14 have extremely low boiling points. Therefore, at the time when the refrigerant flows into the gas-liquid separator 130, R1132a and R14 are still gaseous without being condensed. Therefore, in the gas-liquid separator 130, R1132a and R14 are mainly discharged to the gas phase pipe 133, and R245fa and R600 are mainly discharged to the liquid phase pipe 134, respectively.

  The refrigerant that has flowed into the gas phase piping 133 flows into the condensation pipe 123 that constitutes the intermediate heat exchanger 116. The refrigerant flowing into the liquid phase piping 134 is depressurized by the capillary tube 135 and then flows into the auxiliary evaporator 136 which constitutes the intermediate heat exchanger 116. Then, the refrigerant flowing into the auxiliary evaporator 136 is evaporated in the auxiliary evaporator 136 to cool the refrigerant flowing through the condensing pipe 123. Further, the refrigerant flowing through the condensing pipe 123 is also cooled by the refrigerant returning from the evaporator 113. As a result, the refrigerant that has not been condensed when reaching the gas-liquid separator 130 is cooled and condensed. Here, a part of R1132a condenses. Then, the refrigerant that has passed through the intermediate heat exchanger 116 flows into the capillary tube 118.

  In the capillary tube 118, the refrigerant is depressurized and exchanges heat with the low temperature refrigerant passing through the inside of the pipe 132A constituting the heat exchanger 125. Thereby, the refrigerant in the capillary tube 118 is further cooled. By this cooling, the remainder of R1132a and R14 condense almost completely. Then, the refrigerant flows into the evaporator 113. In the evaporator 113, the refrigerant takes heat from the surroundings and evaporates. Thereby, the cooling action of the refrigerant is exhibited, and the periphery of the evaporator 113 is cooled to an extremely low temperature of -90 ° C or less. By cooling the evaporator 113, the temperature in the storage chamber 8 can be set to −85 ° C. or less. The refrigerant evaporated by the evaporator 113 is discharged to the suction pipe 132, passes through the heat exchanger 125, and reaches the intermediate heat exchanger 116. In the auxiliary evaporator 136 of the intermediate heat exchanger 116, the refrigerant joins with the refrigerant flowing into the auxiliary evaporator 136 through the liquid phase pipe 134. Thereafter, the refrigerant returns to the compressor 114.

  The compressor 114 is switched between ON and OFF by a control device (not shown) based on the internal temperature of the storage room 8. When the operation of the compressor 114 is stopped by the controller, the refrigerant is recovered to the expansion tank 137 via the capillary tube 138. Also, when the operation of the compressor 114 is started by the controller, the refrigerant in the expansion tank 137 is gradually returned to the compressor 114 through the capillary tube 138.

  As described above, the refrigeration apparatus R3 according to the present embodiment includes the single-stage multistage refrigerant circuit 112 and the refrigerant circuit 152. Each refrigerant circuit has a heat exchanger 125 which performs heat exchange between the refrigerant directed from the evaporator 113 to the compressor 114 and the refrigerant in the capillary tube 118 and cools the refrigerant in the capillary tube 118. Each refrigerant circuit has a first refrigerant and a boiling point lower than the boiling point of the first refrigerant as refrigerants, and the boiling point in the capillary tube 118 is exchanged in the capillary tube 118 by heat exchange in the heat exchanger 125. And a second refrigerant having a temperature equal to or higher than the temperature reached by Thereby, the same effect as that of the first embodiment can be obtained. In addition, the refrigeration apparatus R3 has the same features as those of the first embodiment regarding the other composition of the refrigerant composition and the double tube structure, and can exert the same effect. The refrigeration system R3 may include only one of the refrigerant circuit 112 and the refrigerant circuit 152.

Embodiment 4
The refrigeration apparatus according to the fourth embodiment has a configuration that is generally common to the refrigeration apparatus according to any of the first to third embodiments except that the refrigeration system according to the fourth embodiment has a multistage refrigeration system. In the description of the present embodiment, the description of the same configuration as any of the first to third embodiments will be omitted as appropriate. FIG. 6 is a refrigerant circuit diagram of the refrigeration apparatus according to the fourth embodiment. In the present embodiment, a binary multi-stage refrigerant circuit will be described as an example of the multi-stage refrigerant circuit.

  Refrigeration system R4 which concerns on this Embodiment is provided with the high temperature side refrigerant circuit 212 and the low temperature side refrigerant circuit 252 which comprise a respectively independent refrigerant | coolant closed circuit. The first compressor 214 of the high temperature side refrigerant circuit 212 is an electric compressor similar to the compressor 14. The refrigerant discharge pipe 231 connected to the discharge side of the first compressor 214 is connected to the first auxiliary condenser 221. A frame pipe 222 is connected to the first auxiliary condenser 221, and an oil cooler 214C is connected to the frame pipe 222. The second auxiliary condenser 215 is connected to the oil cooler 214C. After the oil cooler 254C of the second compressor 254 in the low temperature side refrigerant circuit 252 is connected to the second auxiliary condenser 215, the first condenser 223 is connected. The first auxiliary condenser 221, the second auxiliary condenser 215, and the first condenser 223 are configured as an integral condenser, and are cooled by the condensing fan 229.

  A dehydrator 217 is connected to the first condenser 223, and subsequently, a capillary tube 218 as a first pressure reducer is connected. The first evaporator 213 is connected to the capillary tube 218. The first evaporator 213 constitutes a cascade heat exchanger 216 together with a condensation pipe 255 as a second condenser of the low temperature side refrigerant circuit 252. The suction pipe 232 is connected to the first evaporator 213. The suction pipe 232 is connected to the suction side of the first compressor 214 via the accumulator 228.

(High temperature side refrigerant)
In the high temperature side refrigerant circuit 212, a non-azeotropic refrigerant in which R407D and n-pentane are mixed as a refrigerant is sealed. R407D is a refrigerant formed by mixing R32, R125, and R134a. The proportion of each refrigerant in R407D is 15% by mass for R32, 15% by mass for R125, and 70% by mass for R134a. The standard boiling point of R32 is -51.8 ° C, the standard boiling point of R407D is -38.7 ° C, and the standard boiling point of n-pentane is + 36.1 ° C.

  The circulation of the refrigerant in the high temperature side refrigerant circuit 212 will be described with reference to FIG. The refrigerant is compressed by the first compressor 214 to be a high temperature gaseous refrigerant. The refrigerant is discharged to the refrigerant discharge pipe 231, and passes through the first auxiliary condenser 221, the frame pipe 222, the oil cooler 214C, the second auxiliary condenser 215, the oil cooler 254C, and the first condenser 223 in this order, It condenses in the process. The condensed refrigerant is dewatered by the dehydrator 217 and flows into the capillary tube 218. The refrigerant is depressurized in the capillary tube 218 and then flows into the first evaporator 213.

  In the first evaporator 213, R32, R125 and R134a in the refrigerant absorb heat from the refrigerant flowing in the condensation pipe 255 of the cascade heat exchanger 216 and evaporate. Thus, the refrigerant flowing in the condensation pipe 255 is cooled. Thereafter, the refrigerant is discharged to the suction pipe 232 and returns to the first compressor 214 through the accumulator 228.

  The compression performance of the first compressor 214 is, for example, 1.5 HP, and the temperature reached by the cooling in the first evaporator 213 is about −27 ° C. to about −35 ° C. Under such low temperature, n-pentane in the refrigerant does not evaporate in the first evaporator 213. Therefore, n-pentane does not contribute to the cooling of the refrigerant in the condensing pipe 255 in the cascade heat exchanger 216. On the other hand, n-pentane can dissolve the lubricating oil of the first compressor 214 and the residual water that can not be removed by the dehydrator 217, and has the function of returning them to the first compressor 214. Further, n-pentane evaporates in the first compressor 214 to cool the first compressor 214.

  The second compressor 254 of the low temperature side refrigerant circuit 252 is an electric compressor similar to the compressor 14. The refrigerant discharge pipe 281 connected to the discharge side of the second compressor 254 is connected to the radiator 259. The radiator 259 is configured by, for example, a wire capacitor. An oil separator 260 is connected to the radiator 259. An oil return pipe 287 returning to the second compressor 254 is connected to the oil separator 260. Further, a condensation pipe 255 is connected to the oil separator 260. The condensing pipe 255 constitutes a cascade heat exchanger 216 together with the first evaporator 213.

  The first gas-liquid separator 261 is connected to the condensing pipe 255 via the dehydrator 257. A gas phase pipe 283 and a liquid phase pipe 284 are connected to the first gas-liquid separator 261. The gas phase pipe 283 is a pipe for taking out the uncondensed gas phase refrigerant separated by the first gas / liquid separator 261. The liquid phase pipe 284 is a pipe for taking out the condensed liquid phase refrigerant separated in the first gas-liquid separator 261. The gas phase pipe 283 is connected to the second gas-liquid separator 265 through the first intermediate heat exchanger 262. The liquid phase pipe 284 is connected to the first intermediate heat exchanger 262 via the dehydrator 263 and the capillary tube 264. The first intermediate heat exchanger 262 has a function of cooling and condensing the gas phase refrigerant flowing in the gas phase pipe 283 by evaporation of the liquid phase refrigerant decompressed by the capillary tube 264.

  A gas phase piping 285 and a liquid phase piping 286 are connected to the second gas-liquid separator 265. The gas phase pipe 285 is a pipe for taking out the uncondensed gas phase refrigerant separated by the second gas liquid separator 265. The liquid phase pipe 286 is a pipe for taking out the condensed liquid phase refrigerant separated by the second gas-liquid separator 265. The gas phase pipe 285 is connected to the third intermediate heat exchanger 270 via the second intermediate heat exchanger 266. The liquid phase piping 286 is connected to the second intermediate heat exchanger 266 via the dehydrator 267 and the capillary tube 268. The second intermediate heat exchanger 266 has a function of cooling and condensing the gas phase refrigerant flowing in the gas phase pipe 285 by the evaporation of the liquid phase refrigerant decompressed by the capillary tube 268.

  The fourth intermediate heat exchanger 272 is connected to the third intermediate heat exchanger 270. A dehydrator 274 and a capillary tube 258 as a second pressure reducer are connected to the fourth intermediate heat exchanger 272 in this order. The third intermediate heat exchanger 270 and the fourth intermediate heat exchanger 272 are heat for performing heat exchange between the refrigerant directed to the capillary tube 258 and the refrigerant returned from the second evaporator 253 to the second compressor 254. It is an exchanger.

  The capillary tube 258 is inserted into a suction line 282 that exits the second evaporator 253 and returns to the second compressor 254. Specifically, it is located on the discharge side of the second evaporator 253 and on the side closer to the second evaporator 253 than the fourth intermediate heat exchanger 272, and in the pipe 282A that constitutes a part of the suction pipe 282. , And the capillary tube 258 is inserted, thereby forming a double tube. Moreover, the heat exchanger 295 is comprised by this double pipe | tube. The heat exchanger 295 exchanges heat between the refrigerant flowing in the capillary tube 258 and the refrigerant flowing in the pipe 282A. The structure and formation method of the double tube are the same as the heat exchanger 25. Similar to the heat exchanger 25, the heat exchanger 295 is encased in the heat insulating material 297 around the entire outer periphery, and is housed in the heat insulating material 7 of the cryogenic storage 1 so as to be able to be taken in and out (see FIG. 1). The first intermediate heat exchanger 262 to the fourth intermediate heat exchanger 272 may have a double-pipe structure as well as the heat exchanger 295.

  The second evaporator 253 is connected to the capillary tube 258. The 2nd evaporator 253 is attached to the peripheral surface by the side of the heat insulating material 7 of the inner case 4 similarly to the evaporator 13 (refer FIG. 1). A suction pipe 282 is connected to the second evaporator 253. The suction pipe 282 passes through the heat exchanger 295, the fourth intermediate heat exchanger 272, the third intermediate heat exchanger 270, the second intermediate heat exchanger 266 and the first intermediate heat exchanger 262, and Connected to the suction side. An expansion tank 288 is connected to the suction pipe 282 via a capillary tube 289 between the first intermediate heat exchanger 262 and the second compressor 254. The expansion tank 288 is a tank that stores the refrigerant when the second compressor 254 is stopped. A check valve 290 is connected in parallel with the capillary tube 289 between the suction pipe 282 and the expansion tank 288. The check valve 290 is connected such that the direction toward the expansion tank 288 is a forward direction.

(Low temperature side refrigerant)
In the low temperature side refrigerant circuit 252, a refrigerant composition similar to that of the first embodiment is enclosed as a refrigerant. That is, the low temperature side refrigerant circuit 252 has a first refrigerant containing at least one of R1132a and R170, and a boiling point lower than the boiling point of the first refrigerant, and the boiling point in the capillary tube 258 is the heat in the heat exchanger 295 And a second refrigerant having a temperature equal to or higher than a temperature reached by the refrigerant in the capillary tube 258 by exchange. The first refrigerant is preferably at least one type 1a refrigerant selected from the group consisting of hexafluoroethane (R116), trifluoromethane (R23), an azeotropic mixture (R508A) and an azeotropic mixture (R508B), It further contains in 95 mass% or less with respect to the total mass of a 1st refrigerant | coolant.

  The second refrigerant includes at least one selected from the group consisting of tetrafluoromethane (R14), ethylene (R1150), methane (R50) and argon (R740). In the present embodiment, since the low temperature side refrigerant circuit 252 has a multistage circuit configuration, R50 and R740 can be condensed more reliably. The content of the second refrigerant is preferably 30% by mass or less based on the total mass of the refrigerant composition. Further, the content of the second refrigerant is more than 0% by mass, preferably more than 5% by mass, with respect to the total mass of the refrigerant composition.

  The refrigerant composition further preferably includes a third refrigerant containing at least one of carbon dioxide (R744) and nitrous oxide (R744A). The content of the third refrigerant is preferably 40% by mass or less based on the total mass of the refrigerant composition. In addition, when the third refrigerant contains R744, the refrigerant composition preferably further includes a fourth refrigerant having a solubility with R744 at a temperature lower than the boiling point of R744. Furthermore, the content of the third refrigerant is preferably 20% by mass or less based on the total mass of the refrigerant composition.

  The circulation of the refrigerant in the low temperature side refrigerant circuit 252 will be described with reference to FIG. Here, the case where a refrigerant composition containing R245fa, R600, R404A, R1132a, R14, R50 and R740 is used as a refrigerant is described as an example. The refrigerant is compressed in the second compressor 254 to be a high temperature gaseous refrigerant. The refrigerant is discharged to the refrigerant discharge pipe 281 and dissipated by the radiator 259. Due to the heat radiation, R245fa having a relatively high boiling point and R600 having a relatively high boiling point and good oil compatibility are condensed. R600 functions as an oil carrier refrigerant.

  The refrigerant that has passed through the radiator 259 flows into the oil separator 260. In the oil separator 260, most of the lubricating oil of the second compressor 254 mixed with the refrigerant and a part of the refrigerant condensed by the radiator 259 are supplied to the second compressor 254 via the oil return pipe 287. I will return. As a result, the refrigerant of higher purity flows on the downstream side of the oil separator 260, and the cooling efficiency is improved. The gaseous refrigerant separated by the oil separator 260 flows into the condensation pipe 255 of the cascade heat exchanger 216.

  The refrigerant flowing into the condensing pipe 255 is cooled by the radiator 259. For this reason, it is possible to reduce the load applied to the first compressor 214 in order to cool the refrigerant of the low temperature side refrigerant circuit 252 by the cascade heat exchanger 216. Further, since the refrigerant in the low temperature side refrigerant circuit 252 can be efficiently cooled in the cascade heat exchanger 216, the load on the second compressor 254 can also be reduced. As a result, the operating efficiency of the entire refrigeration system R4 can be improved.

  In the cascade heat exchanger 216, the refrigerant in the condensing pipe 255 is cooled to about -40 ° C to -30 ° C. Thereby, a part of R404A and R1132 in a refrigerant condenses. Then, the refrigerant that has passed through the condensing pipe 255 flows into the first gas-liquid separator 261 through the dehydrator 257. At this point, the remainder of R1132a, R14, R50, R740 are still gaseous without condensation. Therefore, in the first gas-liquid separator 261, a part of R404A and R1132a is mainly discharged to the liquid phase pipe 284 and the remaining part of R1132a, and R14, R50 and R740 are mainly discharged to the gas phase pipe 283.

  The refrigerant flowing into the liquid phase pipe 284 passes through the dehydrator 263 and is depressurized by the capillary tube 264 and then flows into the first intermediate heat exchanger 262. The refrigerant flowing into the gas phase pipe 283 is cooled in the first intermediate heat exchanger 262 by evaporation of the refrigerant decompressed by the capillary tube 264. Further, the refrigerant exchanges heat with the refrigerant returned from the second evaporator 253 and is cooled. As a result, the intermediate temperature of the first intermediate heat exchanger 262 is approximately −60 ° C., and the remaining portion of R 1132 a in the gas phase pipe 283 is condensed. R14, R50 and R740 are still in the gaseous state. The refrigerant that has passed through the first intermediate heat exchanger 262 flows into the second gas-liquid separator 265. Here, the intermediate temperature of the intermediate heat exchanger refers to the temperature of the pipe at the center of the intermediate heat exchanger.

  In the second gas-liquid separator 265, the R 1132 a condensed in the first intermediate heat exchanger 262 is discharged to the liquid phase pipe 286, and R 14, R 50, and R 740 are discharged to the gas phase pipe 285. The refrigerant flowing into the liquid phase piping 286 passes through the dehydrator 267 and is depressurized by the capillary tube 268 and then flows into the second intermediate heat exchanger 266. The refrigerant flowing into the gas phase pipe 285 is cooled in the second intermediate heat exchanger 266 by evaporation of the refrigerant decompressed by the capillary tube 268. Further, the refrigerant exchanges heat with the refrigerant returned from the second evaporator 253 and is cooled. As a result, the intermediate temperature of the second intermediate heat exchanger 266 becomes about −90 ° C., and the R 14 in the gas phase pipe 285 condenses. R50 and R740 are still in the gaseous state. The refrigerant that has passed through the second intermediate heat exchanger 266 flows into the third intermediate heat exchanger 270.

  The refrigerant flowing into the third intermediate heat exchanger 270 exchanges heat with the refrigerant returning from the second evaporator 253 to be cooled, and flows into the fourth intermediate heat exchanger 272. The refrigerant flowing into the fourth intermediate heat exchanger 272 exchanges heat with the refrigerant returned from the second evaporator 253 to be cooled, and flows through the dehydrator 274 into the capillary tube 258. The heat exchange in the third intermediate heat exchanger 270 and the fourth intermediate heat exchanger 272 cools the refrigerant, and R50 condenses. The intermediate temperature of the fourth intermediate heat exchanger 272 is approximately -130.degree.

  In the capillary tube 258, the refrigerant is depressurized and exchanges heat with the low temperature refrigerant passing through the inside of the pipe 282A constituting the heat exchanger 295. Thereby, the refrigerant in the capillary tube 258 is further cooled. This cooling condenses R740. Then, the refrigerant flows into the second evaporator 253. In the second evaporator 253, the refrigerant takes heat from the surroundings and evaporates. Thereby, the cooling action of the refrigerant is exhibited, and the periphery of the second evaporator 253 is cooled to an extremely low temperature of about -160 ° C to -157 ° C. By cooling the evaporator 253, the temperature in the storage chamber 8 can be set to about -152 ° C. As described above, in the low temperature side refrigerant circuit 252, since the refrigerant in the gas phase is condensed one after another by utilizing the difference in the boiling points of the respective refrigerants, the extremely low temperature in the second evaporator 253 of the final stage is obtained. Can be achieved.

  The refrigerant evaporated in the second evaporator 253 is discharged to the suction pipe 282, and the heat exchanger 295, the fourth intermediate heat exchanger 272, the third intermediate heat exchanger 270, the second intermediate heat exchanger 266, and the first intermediate The heat flows into the heat exchanger 262 sequentially. And when passing through the 2nd middle heat exchanger 266 and the 1st middle heat exchanger 262, it joins with the refrigerant evaporated in each, and returns to the 2nd compressor 254.

  The second compressor 254 is switched on and off by a control device (not shown) based on the internal temperature of the storage chamber 8. When the operation of the compressor 254 is stopped by the controller, the refrigerant is recovered to the expansion tank 288 via the check valve 290. By passing through the check valve 290, the refrigerant can be recovered more quickly than in the case of passing through the capillary tube 289. Also, when the operation of the compressor 254 is started by the controller, the refrigerant in the expansion tank 288 is gradually returned into the second compressor 254 via the capillary tube 289. By rapidly recovering the refrigerant when the second compressor 254 is stopped, the pressure in the low temperature side refrigerant circuit 252 can be quickly equilibrated. As a result, the second compressor 254 can be smoothly restarted. Therefore, it is possible to shorten the time until the inside of the low temperature side refrigerant circuit 252 reaches the equilibrium pressure after the second compressor 254 is started. As a result, since the pull-down time can be shortened, the energy saving performance of the ultra low temperature storage 1 and the convenience can be improved.

  As described above, the refrigeration apparatus R4 according to the present embodiment includes the high temperature side refrigerant circuit 212 and the low temperature side refrigerant circuit 252. In addition, the low temperature side refrigerant circuit 252 performs heat exchange between the refrigerant traveling from the second evaporator 253 to the second compressor 254 and the refrigerant in the capillary tube 258 to cool the refrigerant in the capillary tube 258. A switch 295 is provided. The low temperature side refrigerant circuit 252 has a boiling point lower than the boiling points of the first refrigerant and the first refrigerant as refrigerants, and the boiling point in the capillary tube 258 exchanges heat in the capillary tube 258 by heat exchange in the heat exchanger 295. And a second refrigerant which is equal to or higher than the temperature reached by the second refrigerant. Thereby, the same effect as that of the first embodiment can be obtained. In addition, the refrigeration apparatus R4 has the same features as those of the first embodiment with respect to the other composition of the refrigerant composition and the double tube structure, and can exhibit the same effect.

  The second refrigerant has a boiling point lower than the boiling point of the first refrigerant, and the boiling point in the condensing pipe 255 is equal to or higher than the temperature reached by the refrigerant in the condensing pipe 255 by heat exchange in the cascade heat exchanger 216. It may be

  The present invention is not limited to the above-described embodiments, and it is possible to combine the embodiments or to add further modifications such as various design changes based on the knowledge of those skilled in the art. Embodiments in which such combinations or further modifications are added are also included in the scope of the present invention. The combination of each embodiment mentioned above and the new embodiment which arises by addition of modification to each embodiment mentioned above combine the embodiment combined and the effect of each modification.

  Hereinafter, the present invention will be described in detail based on examples, but the present invention is not limited to these examples.

<Evaluation of Refrigerant Performance of Refrigerant Composition>
First, a plurality of refrigerant compositions different in composition were produced. Specifically, a first refrigerant containing R1132a and R116 in a mass ratio of 1: 1 was prepared. And this 1st refrigerant | coolant was divided into plurality, R14 as a 2nd refrigerant | coolant was mixed with each in a different quantity, and the several refrigerant | coolant composition was obtained. The content of R14 in each refrigerant composition was 5% by mass, 10% by mass, and 15% by mass with respect to the entire refrigerant composition. Moreover, the refrigerant | coolant composition (R14: 0 mass%) which consists only of a 1st refrigerant | coolant was also prepared. Each of these refrigerant compositions was filled in the refrigeration apparatus R2 shown in the second embodiment described above, and the temperature inside the storage chamber 8 and the pull-down time were measured. The inside temperature was the central temperature of the storage room 8. The pull-down time was measured as the time for the inside temperature to reach room temperature (30 ° C.) to -80 ° C., and was taken as a relative value when the pull-down time for a refrigerant composition in which R14 is 0 mass% was 100. .

  The results are shown in FIG. FIG. 7 is a graph showing the internal temperature and the pull-down time when the content of the second refrigerant is made different. As shown in FIG. 7, the internal temperature of each refrigerant composition having a content of R 14 of 0, 5, 10, 15% by mass is −89.2 ° C., −89.3 ° C., −89. It was 7 ° C and -90.5 ° C. Moreover, the pull-down time of each was 100, 94, 87, 82. From these results, it was confirmed that the pull-down time is shortened in the refrigerant composition containing R14 as compared to the refrigerant composition not containing R14. Moreover, it was confirmed that the pull-down time is further shortened as the content of R14 is larger. Furthermore, when the content of R14 exceeds 5% by mass, it is confirmed that not only the pull-down time can be shortened but also the internal temperature can be further lowered.

<Evaluation of Performance Change of First Refrigerant Due to Containing of 1a Refrigerant>
As the first refrigerant contained in the low temperature side refrigerant used in the refrigeration apparatus R2 described in the second embodiment described above, samples 1 to 6 in which the mass ratio of R1132a and R116 were made different were prepared. Then, these samples were filled in the refrigeration system R2 shown in the second embodiment, and the temperature inside the storage chamber 8 was measured to evaluate the refrigeration performance of the first refrigerant. The inside temperature was the central temperature of the storage room 8. In the evaluation of the refrigeration performance, assuming that the internal temperature when the first refrigerant is R1132a alone is the reference temperature, and the internal temperature is higher than the reference temperature (specifically, more than -89 ° C and -88 ° C or less) “A” when relatively lower than the reference temperature and relatively lower than the reference temperature (specifically more than −90 ° C. and not more than −89 ° C.), and relatively higher (specifically −90 ° C or less) "AA". The results are shown in Table 1.

  Moreover, based on the research report on the combustibility of the refrigerant, the combustibility was predicted from the mixing ratio of the refrigerant in each sample, and the combustibility of the first refrigerant was evaluated. In the evaluation of flammability, “low level combustibility”, which has a relatively high level of flammability, “slight burn”, which is less flammable than “low level burn”, and burnt than “slight burn” In the case of “low level flammable”, it was classified as “B”, in the case of “slightly flammable” as “A”, and in the case of “non-combustible” as “AA”. The results are shown in Table 1. Moreover, based on the evaluation report by IPCC, GWP of each sample was calculated, and the environmental performance of the 1st refrigerant was evaluated. In the evaluation of environmental performance, a case where the GWP exceeds 10000 is referred to as “B”, a case of more than 2500 and 10000 or less is referred to as “A”, and a case of 2500 or less is referred to as “AA”. The results are shown in Table 1.

  As shown in Table 1, Samples 2 to 6 in which the content of R116 is more than 0% by mass and 95% by mass or less based on the total mass of the first refrigerant are samples 1 and 7 in which the content is out of this range. It is confirmed that the refrigeration performance is improved compared to the above. Moreover, samples 3 to 6 in which the content of R116 is more than 0% by mass and 80% by mass or less with respect to the total mass of the first refrigerant are compared with samples 1, 2 and 7 in which the content is out of this range. It was confirmed to combine good refrigeration performance with good environmental performance. Further, samples 2 to 5 in which the content of R116 is more than 20% by mass and 95% by mass or less with respect to the total mass of the first refrigerant are compared to samples 1, 6 and 7 in which the content is out of this range, It was confirmed to combine good refrigeration performance and good flame retardancy.

  Further, samples 3 to 5 in which the content of R116 is more than 20% by mass and 80% by mass or less with respect to the total mass of the first refrigerant are compared to samples 1, 2, 6, 7 where the content is out of this range. It has been confirmed that they have good refrigeration performance, good flame retardancy and good environmental performance. Furthermore, Sample 4 having a content of R116 of more than 40% by mass and 60% by mass or less with respect to the total mass of the first refrigerant has good flame retardancy with respect to the other samples 1 to 3 and 5 to 7 It was confirmed to have higher refrigeration performance while having a good GWP.

  The evaluations of the refrigeration performance, the combustibility and the environmental performance described above are for the first refrigerant. Therefore, even if it is the 1st refrigerant determined with "B" in any performance evaluation, the effect explained by the embodiment mentioned above can be exhibited by combination with the 2nd refrigerant. Moreover, in the evaluation of environmental performance, the case where GWP exceeds 10000 was evaluated as "B", but even if it is Samples 1 and 2 evaluated as "B", the conventional refrigerant which uses R508A and R508B as a main refrigerant It was good enough compared with.

  R1, R2, R3, R4 Refrigeration system, 12, 112, 152 Refrigerant circuit, 13, 113 Evaporator, 14, 114 Compressor, 15, 115 Condenser, 18, 58, 88, 118, 218, 258 Capillary tube, 25, 95, 125, 295 heat exchanger, 52, 212 high temperature side refrigerant circuit, 54, 214 first compressor, 55, 223 first condenser, 56, 216 cascade heat exchanger, 59, 213 first evaporator 82, 252 low temperature side refrigerant circuit, 83, 253 second evaporator, 84, 254 second compressor, 85 second condenser.

Claims (11)

A refrigerant circuit in which a compressor, a condenser, a pressure reducer and an evaporator are annularly connected in this order;
The refrigerant circuit has a heat exchanger that performs heat exchange between the refrigerant traveling from the evaporator to the compressor and the refrigerant in the decompressor, and cools the refrigerant in the decompressor,
As the refrigerant , the first refrigerant and a boiling point lower than the boiling point of the first refrigerant, and the boiling point in the decompressor is equal to or higher than the temperature reached by the refrigerant in the decompressor by heat exchange in the heat exchanger Using a refrigerant composition containing a certain second refrigerant ,
The refrigeration apparatus according to claim 1, wherein the first refrigerant includes difluoroethylene (R1132a) and at least one of ethane (R170) and hexafluoroethane (R116) . A high temperature side refrigerant circuit in which a first compressor, a first condenser, a first pressure reducer and a first evaporator are annularly connected in this order;
A low temperature side refrigerant circuit in which a second compressor, a second condenser, a second pressure reducer and a second evaporator are annularly connected in this order;
A cascade heat exchanger is constituted by the first evaporator and the second condenser, and heat exchange is performed between the refrigerant of the high temperature side refrigerant circuit and the refrigerant of the low temperature side refrigerant circuit in the cascade heat exchanger. The refrigerant of the low temperature side refrigerant circuit is cooled,
The low temperature side refrigerant circuit has a boiling point lower than the boiling point of the first refrigerant and the first refrigerant as the refrigerant, and the boiling point in the second condenser is the heat exchange in the cascade heat exchanger. (2) using a refrigerant composition containing a second refrigerant which is equal to or higher than the temperature reached by the refrigerant in the condenser ;
The refrigeration apparatus according to claim 1, wherein the first refrigerant includes difluoroethylene (R1132a) and at least one of ethane (R170) and hexafluoroethane (R116) .   The refrigeration system according to claim 1 or 2, wherein the refrigerant composition further includes a third refrigerant containing at least one of carbon dioxide (R744) and nitrous oxide (R744A). Wherein the first refrigerant is at least one selected from the group consisting of trifluoromethane (R23), azeotrope (R508A) and azeotrope (R508B), 95 mass relative to the total weight of the first refrigerant The refrigeration apparatus according to any one of claims 1 to 3, further comprising a content of% or less.   The said 2nd refrigerant | coolant contains at least 1 sort (s) selected from the group which consists of tetrafluoromethane (R14), ethylene (R1150), methane (R50), and argon (R740) in any one of Claim 1 thru | or 4 Refrigerating apparatus as described.   The refrigeration apparatus according to any one of claims 1 to 5, wherein the content of the second refrigerant is more than 5% by mass with respect to the total mass of the refrigerant composition.   The refrigeration apparatus according to claim 6, wherein a content of the second refrigerant is 30% by mass or less with respect to a total mass of the refrigerant composition.   The refrigeration apparatus according to claim 3, wherein a content of the third refrigerant is 40% by mass or less with respect to a total mass of the refrigerant composition. The third refrigerant includes the R744,
The refrigeration apparatus according to claim 3, further comprising a fourth refrigerant having a solubility with the R744 at a temperature lower than the boiling point of the R744.   The refrigeration apparatus according to any one of claims 3, 8 and 9, wherein the content of the third refrigerant is 20% by mass or less with respect to the total mass of the refrigerant composition.   The refrigeration system according to claim 1, wherein the heat exchanger is a double pipe in which the pressure reducer is inserted into a pipe through which a refrigerant flowing from the evaporator to the compressor passes.

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