JP2011112351A - Refrigerating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a refrigerating device effectively cooling the inside of the refrigerating device down to ultralow temperature. <P>SOLUTION: In the refrigerating device R1, a refrigerant delivered from a compressor 14 is condensed, and then, is decompressed by a capillary tube 18, and is evaporated by an evaporator 13 so as to exhibit cooling action. The capillary tube 18 is inserted into suction piping 32 through which the refrigerant returning from the evaporator 13 to the compressor 14 passes, and a double tube structure is provided. The suction piping 32 (piping 32A) in which the capillary tube 18 is inserted in order to obtain the double tube structure, is surrounded by a heat insulating material 35. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a refrigeration apparatus that condenses refrigerant discharged from a compressor and then evaporates it in an evaporator to exert a cooling action.

Conventionally, the cryogenic freezer used for the storage of frozen food for long-term cryopreservation and the ultra-low temperature preservation of living tissues and specimens is a non-copolymer containing butane, ethylene and R14 (carbon tetrafluoride: CF ₄ ). A boiling mixed refrigerant or a non-azeotropic mixed refrigerant containing butane, ethane and R14 is sealed in a refrigerant circuit, and the refrigerant in the refrigeration apparatus due to the operability at room temperature of butane having a high boiling point in the non-azeotropic mixed refrigerant gas. As a result, the temperature in the storage chamber was set to an ultra-low temperature of −60 ° C. or less by evaporating ethane or ethylene having a very low boiling point with an evaporator.

JP 2007-107858 A

  However, in order to realize a desired ultra-low temperature, a compressor having a larger capacity has to be selected. In such a case, there are problems associated with an increase in the size of the apparatus and an increase in cost. In addition, as the capacity of the compressor to be used increases, the amount of power consumption increases, so it has been desired to develop a refrigeration apparatus that can cool the storage chamber to an ultra-low temperature more efficiently.

  Therefore, the present invention has been made to solve the conventional technical problems, and an object of the present invention is to provide a refrigeration apparatus that can cool the storage chamber to an ultra-low temperature more efficiently.

  In the refrigeration apparatus according to the first aspect of the present invention, the refrigerant discharged from the compressor is condensed and then depressurized by a capillary tube and evaporated by an evaporator to exert a cooling action. A capillary tube is inserted into a suction pipe through which the refrigerant returning to the pipe passes, and a double pipe structure is formed.

  In the refrigeration apparatus according to the second aspect of the present invention, the refrigerant discharged from the compressor is condensed, decompressed by the capillary tube, evaporated by the evaporator, and constitutes an independent refrigerant closed circuit that exhibits a cooling action. Side refrigerant circuit and low temperature side refrigerant circuit, and a cascade heat exchanger is configured by the evaporator of the high temperature side refrigerant circuit and the condenser of the low temperature side refrigerant circuit, and finally cooling is performed by the evaporator of the low temperature side refrigerant circuit. It has a double-pipe structure by inserting the capillary tube of the low-temperature side refrigerant circuit into the suction pipe through which the refrigerant returning from the evaporator of the low-temperature side refrigerant circuit to the compressor passes. Features.

  According to a third aspect of the present invention, there is provided a refrigeration apparatus comprising a compressor, a condenser, an evaporator, a single or plural intermediate heat exchangers connected so that a return refrigerant from the evaporator flows, and a plurality of capillary tubes A plurality of types of non-azeotropic refrigerant mixture are enclosed, and the condensed refrigerant in the refrigerant that has passed through the condenser is joined to the intermediate heat exchanger via the capillary tube, and the uncondensed refrigerant in the refrigerant in the intermediate heat exchanger The refrigerant having a lower boiling point is condensed by cooling the refrigerant, and the refrigerant having the lowest boiling point is evaporated in the evaporator via the capillary tube in the final stage, and the cooling action is exhibited. The final stage capillary tube is inserted into the suction pipe through which the refrigerant returning to the pipe passes, thereby forming a double pipe structure.

  In the refrigeration apparatus according to the fourth aspect of the present invention, the refrigerant discharged from the compressor is condensed, decompressed by the capillary tube, evaporated by the evaporator, and constitutes an independent refrigerant closed circuit that exhibits a cooling action. Side refrigerant circuit and low temperature side refrigerant circuit, and this low temperature side refrigerant circuit includes a compressor, a condenser, an evaporator, and a single or a plurality of intermediate heats connected so that the return refrigerant from the evaporator flows. An exchanger and a plurality of capillary tubes are filled with a plurality of types of non-azeotropic refrigerant mixture, and the condensed refrigerant in the refrigerant that has passed through the condenser is joined to the intermediate heat exchanger via the capillary tube, and the intermediate heat By cooling the uncondensed refrigerant in the refrigerant with the exchanger, the refrigerant with the lower boiling point is condensed, and the refrigerant with the lowest boiling point is evaporated in the evaporator via the capillary tube at the final stage, and the cooling effect is exhibited. A cascade heat exchanger is constituted by the evaporator of the high temperature side refrigerant circuit and the condenser of the low temperature side refrigerant circuit, and exhibits a final cooling action in the evaporator of the low temperature side refrigerant circuit. A double-pipe structure is formed by inserting the capillary tube at the final stage of the low-temperature side refrigerant circuit into the suction pipe through which the refrigerant returning from the evaporator of the circuit passes to the compressor.

  In the refrigeration apparatus according to the fifth aspect of the present invention, the capillary tube of the high temperature side refrigerant circuit is placed in the suction pipe through which the refrigerant returning from the evaporator of the high temperature side refrigerant circuit passes to the compressor in the invention of the second or fourth aspect. It is characterized by having a double-pipe structure.

  A refrigeration apparatus according to a sixth aspect of the present invention is characterized in that, in each of the above-described inventions, the suction pipe into which the capillary tube is inserted to form a double pipe structure is surrounded by a heat insulating material.

  A refrigeration apparatus according to a seventh aspect of the present invention is characterized in that, in each of the above-described inventions, the flow of the refrigerant in the capillary tube and the flow of the refrigerant passing through the suction pipe outside the capillary tube are used as counterflows.

  According to the first aspect of the present invention, in the refrigeration apparatus that condenses the refrigerant discharged from the compressor, depressurizes it with a capillary tube, evaporates it with an evaporator, and exhibits a cooling action. Since the capillary tube is inserted into the suction pipe through which the returning refrigerant passes, a double-pipe structure is adopted, improving the heat exchange efficiency between the refrigerant in the suction pipe and the refrigerant in the capillary tube, and improving performance. It becomes possible to plan.

  In particular, the capillary tube is inserted into the suction pipe immediately after coming out of the evaporator to form a double pipe structure so that heat exchange is possible by heat conduction that transmits the entire wall surface of the capillary tube. With this return refrigerant, the refrigerant having the lowest boiling point is efficiently cooled, and the performance can be significantly improved.

  According to invention of Claim 2, after condensing the refrigerant | coolant discharged from the compressor, respectively, it pressure-reduces with a capillary tube, It evaporates with an evaporator, The high temperature side which comprises the independent refrigerant | coolant closed circuit which exhibits a cooling effect | action A refrigerant circuit and a low-temperature side refrigerant circuit are provided, and a cascade heat exchanger is configured by the evaporator of the high-temperature side refrigerant circuit and the condenser of the low-temperature side refrigerant circuit, and the final cooling action is performed by the evaporator of the low-temperature side refrigerant circuit In the refrigeration apparatus that exhibits the above, since the capillary tube of the low-temperature side refrigerant circuit is inserted into the suction pipe through which the refrigerant returning from the evaporator of the low-temperature side refrigerant circuit passes to the compressor, the suction pipe It is possible to improve the performance by improving the heat exchange efficiency between the refrigerant in the capillary tube and the refrigerant in the capillary tube.

  In particular, the capillary tube of the low-temperature side refrigerant circuit is inserted into the suction pipe immediately after exiting the evaporator to form a double tube structure so that heat can be exchanged by heat conduction that transmits the entire wall surface of the capillary tube. Thus, the refrigerant having the lowest boiling point is efficiently cooled by the return refrigerant from the evaporator of the low-temperature side refrigerant circuit, and the performance can be significantly improved.

  According to the invention of claim 3, the compressor, the condenser, the evaporator, the single or plural intermediate heat exchangers connected so that the return refrigerant from the evaporator flows, and the plural capillary tubes Multiple types of non-azeotropic refrigerant mixture are enclosed, condensed refrigerant in the refrigerant that has passed through the condenser is joined to the intermediate heat exchanger via the capillary tube, and uncondensed refrigerant in the refrigerant is removed by this intermediate heat exchanger. By cooling, the refrigerant having a lower boiling point is condensed, and the refrigerant having the lowest boiling point is evaporated in the evaporator via the capillary tube in the final stage to return to the compressor from the evaporator. Since the final stage capillary tube is inserted into the suction pipe through which the refrigerant to be passed has a double pipe structure, the efficiency of heat exchange between the refrigerant in the suction pipe and the refrigerant in the capillary tube is improved. It is possible to achieve good.

  In particular, the capillary tube is inserted into the suction pipe immediately after coming out of the evaporator to form a double pipe structure so that heat exchange is possible by heat conduction that transmits the entire wall surface of the capillary tube. With this return refrigerant, the refrigerant having the lowest boiling point is efficiently cooled, and the performance can be significantly improved.

  According to invention of Claim 4, after condensing the refrigerant | coolant discharged from the compressor, respectively, it decompresses with a capillary tube, it evaporates with an evaporator, The high temperature side which comprises the independent refrigerant | coolant closed circuit which exhibits a cooling effect | action A refrigerant circuit and a low-temperature side refrigerant circuit, the low-temperature side refrigerant circuit comprising a compressor, a condenser, an evaporator, and a single or a plurality of intermediate heat exchanges connected so that the return refrigerant from the evaporator flows. And a plurality of capillary tubes filled with multiple types of non-azeotropic refrigerant mixture, and the condensed refrigerant in the refrigerant that has passed through the condenser is merged with the intermediate heat exchanger via the capillary tube, and intermediate heat exchange is performed. By cooling the uncondensed refrigerant in the refrigerant in the evaporator, the refrigerant having a lower boiling point is condensed, and the refrigerant having the lowest boiling point is evaporated in the evaporator via the capillary tube in the final stage, and the cooling action is exhibited. High In the refrigeration system in which a cascade heat exchanger is configured by the evaporator of the low-temperature side refrigerant circuit and the condenser of the low-temperature side refrigerant circuit, and exhibits the final cooling action in the evaporator of the low-temperature side refrigerant circuit, Since the capillary tube at the final stage of the low-temperature side refrigerant circuit is inserted into the suction pipe through which the refrigerant returning from the evaporator to the compressor passes, the refrigerant in the suction pipe and the refrigerant in the capillary tube are formed. The heat exchange efficiency can be improved and the performance can be improved.

  In particular, the capillary tube of the low-temperature side refrigerant circuit is inserted into the suction pipe immediately after exiting the evaporator to form a double tube structure so that heat can be exchanged by heat conduction that transmits the entire wall surface of the capillary tube. Thus, the refrigerant having the lowest boiling point is efficiently cooled by the return refrigerant from the evaporator of the low-temperature side refrigerant circuit, and the performance can be significantly improved.

  According to the invention of claim 5, in the invention of claim 2 or claim 4, the capillary tube of the high temperature side refrigerant circuit is placed in the suction pipe through which the refrigerant returning from the evaporator of the high temperature side refrigerant circuit passes to the compressor. Since it is inserted into a double pipe structure, it is possible to further improve the performance of the refrigeration system by further improving the heat exchange efficiency between the refrigerant in the suction pipe and the refrigerant in the capillary tube even in the high temperature side refrigerant circuit. become able to.

  In each of the above inventions, the heat exchange efficiency can be further improved by enclosing the suction pipe having a double tube structure through which the capillary tube is inserted as in the invention of claim 6 with a heat insulating material. It becomes like this.

  Further, in each of the above-described inventions, if the refrigerant flow in the capillary tube and the refrigerant flow passing through the suction pipe outside the capillary tube are made to counter flow as in the invention of claim 7, further heat exchange capability It will be possible to improve.

It is a side view of the ultra-low temperature storage which applied the freezing apparatus. It is a refrigerant circuit figure in the Example of the ultra-low-temperature storage of FIG. It is a figure for demonstrating the double pipe structure of the heat exchanger formed by inserting a capillary tube in the suction piping of this invention shown in FIG. It is a graph regarding each data at the time of making the weight of the mixed refrigerant | coolant of R245fa and R600, and R14 constant, and changing the weight of R23. It is a graph regarding each data at the time of changing the weight of R14, making the weight of the mixed refrigerant | coolant of R245fa and R600, and R23 constant. It is a refrigerant circuit figure in 2nd Example (Example 2). It is a refrigerant circuit figure in 3rd Example (Example 3). It is a refrigerant circuit figure in 4th Example (Example 4).

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a side view of an ultra-low temperature storage 1 to which the refrigeration apparatus of the present invention is applied. The ultra-low temperature storage 1 is used, for example, for storage of frozen foods for long-term low-temperature storage, and for ultra-low temperature storage of biological tissues, specimens, and the like. The main body is constituted by a machine room (not shown) in which the compressor 14 and the like constituting the refrigerant circuit of the refrigeration apparatus R1 of the present embodiment are installed.

  The heat insulating box 2 includes a steel plate outer box 3 and an inner box 4 each having an open upper surface, a synthetic resin breaker 5 connecting the upper ends of both boxes 3 and 4, and the outer box 3, The space enclosed by the inner box 4 and the breaker 5 is composed of a polyurethane resin heat insulating material 7 filled by an in-situ foaming method, and the inside of the inner box 4 serves as a storage chamber 8 opened on the upper surface.

  In this embodiment, in order to set the target temperature in the storage chamber 8 (hereinafter referred to as the internal temperature) to, for example, −80 ° C. or less, the heat insulating box 2 that partitions the storage chamber 8 from the outside air is A large heat insulation capacity is required as compared with a low temperature chamber in which the internal temperature is set to around 0 ° C. Therefore, in order to ensure the heat insulation capability only by the polyurethane resin heat insulating material 7 as described above, it must be formed to have a considerable thickness, and with the limited main body dimensions, the storage capacity of the storage chamber 8 is sufficient. There is a problem that cannot be secured. Thereby, as for the heat insulation box 2 in a present Example, the vacuum heat insulating material made from glass wool is arrange | positioned on the inner wall surface of the outer case 3, and according to the heat insulation capability by the said vacuum heat insulating material, the polyurethane resin heat insulating material 7 The thickness dimension is small.

  Further, the upper surface of the breaker 5 is formed in a stepped shape, and a heat insulating door 9 is provided therethrough via a packing 11 so as to be rotatable about the rear end in this embodiment. Thereby, the upper surface opening of the storage chamber 8 is closed by the heat insulating door 9 so as to be freely opened and closed. Moreover, the handle part 10 is provided in the other end of the heat insulation door 9, and a front end in the present Example, and the heat insulation door 9 is opened and closed by operating the handle part 10. Further, an evaporator (refrigerant pipe) 13 constituting the refrigerant circuit of the refrigeration apparatus R1 is attached to the peripheral surface of the inner box 4 on the heat insulating material 7 side in a heat exchange (heat exchange) manner.

  Next, the refrigerant circuit of the refrigeration apparatus R1 of the present embodiment will be described with reference to FIG. The refrigerant circuit of the refrigeration apparatus R1 of the present embodiment is configured by a single-unit single-stage refrigerant circuit 12. The compressor (compressor) 14 constituting the refrigerant circuit 12 is an electric compressor using a one-phase or three-phase AC power source. The compressor 14 is connected to a dissuperheater 20, and after the refrigerant compressed by the compressor 14 is once discharged to the outside to dissipate heat, it is returned to the shell of the hermetic container, and again the refrigerant discharge pipe. It is set as the structure discharged to 31. A refrigerant discharge pipe 31 connected to the discharge side of the compressor 14 is connected to an auxiliary condenser (pre-condenser) 21. The auxiliary condenser 21 is connected to a condenser (condenser) 15 after being connected to a frame pipe 22 for heating the opening edge of the storage chamber 8 to prevent dew condensation.

  The refrigerant pipe exiting the condenser 15 is connected to the dry core 17 and the condensation pipe 23. The dry core 17 is a moisture removing means for removing moisture in the refrigerant circuit 12. Further, the condensing pipe 23 constitutes the heat exchanger 16 together with a part of the suction pipe 32 that exits from the evaporator (evaporator) 13 and returns to the compressor 14.

  The refrigerant pipe exiting the condensing pipe 23 is connected to an evaporator (evaporator) 13 through a capillary tube 18 as a decompression device. The capillary tube 18 is inserted into a part of the suction pipe 32 (pipe 32A) that exits the evaporator 13 and returns to the compressor 14. Specifically, a pipe 32 </ b> A that is a discharge side (exit side) of the header 26 provided on the discharge side of the evaporator 13 and is a part of the suction pipe 32 located on the suction side of the heat exchanger 16. A double tube structure is formed by inserting the capillary tube 18 into the tube as shown in FIG. With such a double pipe structure, the refrigerant flowing through the capillary tube 18 that is the inner side of the double pipe 25 (hereinafter referred to as the double pipe structure), and the refrigerant from the evaporator 13 that flows through the pipe 32A that is the outer side thereof. Is configured to be capable of heat exchange.

  Here, the manufacturing method of the said double-pipe structure 25 is demonstrated. First, the straight tubular capillary tube 18 is inserted into the relatively large diameter straight tubular pipe 32A. Next, the double pipe is spirally wound in a plurality of stages. At this time, winding is performed so that the center of the axis of the pipe 32A and the center of the axis of the capillary tube 18 coincide as much as possible to form a spiral double pipe. Thus, a gap is formed as consistently as possible between the inner wall surface of the pipe 32A and the outer wall surface of the capillary tube 18. Thus, the double tube is wound in a plurality of stages to form a spiral double tube structure, so that the length of the capillary tube 18 is sufficiently secured and the heat of the double tube structure is obtained. It is possible to reduce the size while sufficiently securing the replacement part.

  Next, cap-shaped connection pipes (not shown) having holes on both sides and sides are attached to both ends of the pipe 32A, and the end portions of the capillary tubes 18 are respectively drawn out from the side holes, and then Seal the hole by welding. Furthermore, one end of the connection pipe attached to one end of the pipe 32A and the connection part of the pipe 32A are welded, and the suction pipe 32 connected to the discharge side of the evaporator 13 is connected to the other end of the connection pipe. This connection is welded. Similarly, one end of the connection pipe attached to the other end of the pipe 32A is welded to the connection portion of the pipe 32A, and the suction pipe 32 reaching the heat exchanger 16 is connected to the other end of the connection pipe. Weld the parts. And the double pipe structure 25 of a present Example can be comprised by surrounding the piping 32A made into the double pipe structure with the heat insulating material 35. FIG.

  By the way, in the conventional refrigeration apparatus, when the capillary tube and the suction pipe exiting from the evaporator are formed so as to be capable of heat exchange, the outer wall of the capillary tube and the outer wall of the suction pipe are in heat exchange contact with each other. The capillary tube was attached to the outer peripheral surface of the suction pipe. In this case, the suction pipe and the capillary tube are only in line contact. For this reason, heat exchange performance was poor and heat exchange could not be performed sufficiently.

  On the other hand, the refrigerant passing through the capillary tube 18 and the suction pipe 32 are passed by inserting the capillary tube 18 into the suction pipe 32 (pipe 32A) to form a double pipe structure as in the present invention. The refrigerant exchanges heat by heat conduction transmitted through the wall surface of the entire circumference of the capillary tube 18. Thereby, compared with the conventional structure, heat exchange performance can be improved significantly. In particular, as described above, the entire outer periphery of the pipe 32A having the double-pipe structure is surrounded by the heat insulating material 35, so that it is difficult to be affected by the heat from the outside, and the refrigerant in the pipe 32A and the refrigerant in the capillary tube 18 It becomes possible to further improve the heat exchange capacity.

  Further, in the capillary tube 18 that is the inner side of the double-pipe structure and in the suction pipe 32 (pipe 32A) outside the capillary tube 18, the refrigerant is caused to flow in a counterflow, so that The heat exchange capability in the heavy pipe structure 25 can be further improved.

  The double pipe structure 25 is arranged in the heat insulating member 7. Specifically, as shown in FIG. 1, it is housed in a heat insulating material 7 on the back side of the inner box 4 and below the heat exchanger 16 so as to be put in and out.

  On the other hand, the suction pipe 32 exiting the double pipe structure 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. In the present embodiment, the auxiliary condenser 21 and the condenser 15 are configured as an integrated condenser, and are cooled by a condensing fan 29 as a condenser blower.

In this embodiment, the refrigerant circuit 12 is filled with a mixed refrigerant composed of R245fa and R600, and a non-azeotropic mixed refrigerant composed of R23 and R14. R245fa is 1,1,1, -3,3-pentafluoropropane (CF ₃ CH ₂ CHF ₂ ) and has a boiling point of + 15.3 ° C. R600 is butane (C ₄ H ₁₀ ) and has a boiling point of −0.5 ° C. The R600 has a function of returning the mixed water that could not be absorbed by the lubricating oil of the compressor 14 or the dryer 17 to the compressor 14 in a state where the mixed water was dissolved therein. However, since this R600 is a flammable substance, it can be treated as nonflammable by mixing it with a nonflammable R245fa at a predetermined ratio, in this embodiment R245fa./R600=70/30. Become. R23 is trifluoromethane (CHF ₃ ) and has a boiling point of −82.1 ° C. R14 is tetrafluoromentane (CF ₄ ) and has a boiling point of −127.9 ° C.

  The composition of these mixed refrigerants in this example is 64% by weight of the mixed refrigerant of R245fa and R600, 24% by weight of R23, and 12% by weight of R14.

  In FIG. 2, the arrows indicate the flow of the refrigerant circulating in the refrigerant circuit 12. More specifically, the high-temperature gaseous refrigerant discharged from the compressor 14 is once discharged from the sealed container to the desuperheater 20 through the refrigerant discharge pipe on the desuperheater 20 side, radiated, and then again. Return to the shell of the sealed container. Thereby, it can cool with the refrigerant | coolant which thermally radiated the inside of the shell of the airtight container with the desuper heater 20, and the temperature fell. Then, the high-temperature gaseous refrigerant is discharged from the sealed container through the refrigerant discharge pipe 31, condensed in the auxiliary condenser 21, the frame pipe 22, and the condenser 15 to be radiated liquid, and then contained in the dry core 17. Is removed and flows into the heat exchanger 16. In this heat exchanger 16, the refrigerant from the condenser 15 exchanges heat with a low-temperature refrigerant in the suction pipe 32 that is exchanged heat-exchanged, thereby cooling the uncondensed refrigerant to condensate and liquefying, It flows into the capillary tube 18.

  Here, in the capillary tube 18, the refrigerant exchanges heat with the refrigerant passing through the suction pipe 32 provided on the entire circumference of the capillary tube 18 and the heat conduction transmitted through the wall surface of the entire circumference of the capillary tube 18, Further, the pressure is reduced while the temperature is lowered, and then flows into the evaporator 13. In the evaporator 13, the refrigerants R <b> 14 and R <b> 23 take heat from the surroundings and evaporate. At this time, the refrigerants R14 and R23 evaporate in the evaporator 13, thereby exhibiting a cooling action and cooling the periphery of the evaporator 13 to an ultra-low temperature of -85 ° C. In this case, as described above, the evaporator (refrigerant pipe) 13 is configured to be heat-heated along the heat insulating material 7 side of the inner box 4. It becomes possible to set the inside of one storage chamber 8 to an internal temperature of −80 ° C. or lower.

  Then, the refrigerant evaporated in the evaporator 13 is then discharged from the evaporator 13 through the suction pipe 32, and the header 26, the double pipe structure 25, the heat exchanger 16, the check valve 27, and the accumulator. It returns to the compressor 14 through 28.

  At this time, the final reached temperature of the evaporator 13 during the operation of the compressor 14 becomes −100 ° C. to −60 ° C. Under such a low temperature, R245fa in the refrigerant has a boiling point of + 15.3 ° C., and R600 has a boiling point of −0.5 ° C., so that it does not evaporate in the evaporator 13 and remains in a liquid state. Hardly contributes. However, the R600 has a function of returning the mixed oil that could not be absorbed by the lubricating oil of the compressor 14 or the dry core 17 to the compressor 14 in a state of being dissolved therein, and evaporation of the liquid refrigerant in the compressor 14. Thus, the function of reducing the temperature of the compressor 14 is achieved.

  The evaporation temperature in the evaporator 13 varies depending on the composition ratio of the non-azeotropic mixed refrigerant sealed in the refrigerant circuit 12. Hereinafter, the evaporator temperature, the internal temperature, the high-pressure side pressure, and the low-pressure side pressure with respect to the composition ratio of each refrigerant will be described in detail based on each experimental result. FIG. 4 is a graph showing the evaporator inlet temperature, the internal temperature, the high pressure side pressure, and the low pressure side pressure when the mixed refrigerant of R245fa and R600 and the weight of R14 are constant and the weight of R23 is changed. FIG. 5 is a graph showing the evaporator inlet temperature, the internal temperature, the high-pressure side pressure, and the low-pressure side pressure when the mixed refrigerant of R245fa and R600 and the weight of R23 are constant and the weight of R14 is changed.

  The experimental results in FIG. 4 are obtained by increasing the weight ratio of R23 to the total refrigerant weight enclosed from 20.0 wt% to 42.0 wt%. According to this, at 20.0% by weight, which is the minimum amount in this experiment, the inlet temperature of the evaporator 13 was −88.0 ° C., and the internal temperature for this was −71.0 ° C. On the other hand, when the weight ratio of R23 is 21.3% by weight, the inlet temperature of the evaporator 13 is suddenly lowered to -95.9 ° C., and the internal temperature for this is also reduced to -87.5 ° C. It is falling. Thereafter, as the weight ratio of R23 is increased to 42.0% by weight, the inside temperature can be reduced to about −85 ° C. or less only by a slight temperature rise.

  Further, the experimental results in FIG. 5 are obtained by increasing the weight ratio of R14 to 0.01% by weight to 14.1% by weight with respect to the total weight of the refrigerant enclosed. According to this, 0.0% by weight which is the minimum amount in such an experiment, that is, the inlet temperature of the evaporator 13 when R14 is not included is −66.1 ° C., and the internal temperature is −66. It was 9 ° C. On the other hand, when the weight ratio of R14 is 1.8% by weight, the inlet temperature of the evaporator 13 is suddenly lowered to −80.2 ° C., and the internal temperature for this is also reduced to −74.1 ° C. Declined. In this experiment, the inlet temperature of the evaporator 13 is reduced to -98.9 ° C., and the internal temperature for this is also −90%. It has dropped to 0 ° C. Since the boiling point of R14 is −129.7 ° C., it is expected that the temperature of the evaporator 13 and the internal temperature will further decrease when the weight ratio of R14 is increased thereafter.

  However, as can be seen from the graph of FIG. 5, as the weight ratio of R14 increases, the high-pressure side pressure increases. Therefore, when the weight ratio of R14 is further increased to 20% by weight or more, there arises a problem that the high pressure side pressure becomes too high, for example, to 3 MPa or more. The increase in the high-pressure side pressure has a problem that causes damage to equipment for the compressor 14 and the like, and a problem that the startability of the compressor 14 deteriorates. Therefore, in order to suitably set the target internal temperature to −75 ° C. or less, it is preferable that the weight ratio of R14 is 3% by weight to 20% by weight.

  As described above, the boiling point of R23 is −82.1 ° C. Therefore, only the R23 cannot achieve the temperature of the evaporator 13 below the boiling point. However, by adding a predetermined amount, for example, about 5% by weight or more of R14 having a remarkably low boiling point as in the present invention, the evaporating temperature in the evaporator 13 is constantly realized at an extremely low temperature of −80 ° C. or less by the cooling action of R14. It becomes possible to do.

  From the above experimental results, the non-azeotropic mixed refrigerant sealed in the refrigerant circuit 12 has a total weight of the combined refrigerant of R245fa and R600 of 40% to 80% by weight and R23 of the total weight with respect to the total weight. By setting 15% to 47% by weight and R14 to 3% to 20% by weight, it is possible to realize an ultra-low temperature with the non-azeotropic non-azeotropic refrigerant mixture having an internal temperature of −70 ° C. or lower. Become. In particular, the non-azeotropic mixed refrigerant sealed in the refrigerant circuit 12 has a total weight of 49 to 70% by weight of R245fa and R600 combined with R245fa and 21% by weight of R23 with respect to the total weight. By setting 42 wt% and R14 to 9 wt% to 20 wt%, it becomes possible to realize an ultra-low temperature with the in-chamber temperature being −85 ° C. or less by the nonflammable non-azeotropic mixed refrigerant.

  Thereby, long-term preservation | save of a foodstuff, a biological tissue, a specimen, etc. can be stabilized more, and the improvement of reliability can be aimed at. In addition, since the non-azeotropic refrigerant mixture is nonflammable, it can be used safely, improving handling, and damaging the refrigerant piping, etc., causing inconvenience of burning when the refrigerant mixture leaks. It can be avoided.

  In particular, when the composition ratio of each component of the non-azeotropic refrigerant mixture is 64 wt% for the mixed refrigerant of R245fa and R600, 24 wt% for R23, and 12 wt% for R14, the internal temperature is − An ultra-low temperature of 80 ° C. or lower can be realized. As a result, food, living tissue, specimens, etc. can be stored for a long period of time more stably, and the reliability of the device can be improved.

The R23 is not limited to this. For example, R116 (hexafluoroethane: CF ₃ CF ₃ ) having a boiling point of −78.4 ° C., or R23 and R116 are mixed at a predetermined ratio. R508A (R23 / R116 = 39/61, boiling point: −85.7 ° C.) and R508B (R23 / R116 = 46/54, boiling point: −86.9 ° C.) exhibit the same effect. It is possible.

  In addition, by using a non-azeotropic refrigerant mixture such as in this example, the performance can be maintained with almost no change to the conventional refrigeration circuit accompanying the change in refrigerant composition, and the ozone layer is destroyed. It is possible to deal with environmental problems.

  Furthermore, the capillary tube 18 is inserted into the suction pipe 32 (pipe 32A) through which the refrigerant returning from the evaporator 13 to the compressor 14 passes as in the present invention, thereby forming a double pipe structure. The heat exchange efficiency between the refrigerant inside and the refrigerant inside the capillary tube 18 can be improved, and the performance can be improved. In particular, the capillary tube 18 is inserted into the pipe 32A of the suction pipe 32 immediately after exiting the evaporator 13 as in the present invention to form a double pipe structure, and heat is transferred by heat conduction that transmits the wall surface of the entire circumference of the capillary tube 18. By configuring so as to be exchangeable, the refrigerant having the lowest boiling point is efficiently cooled by the return refrigerant from the evaporator 13, and the performance can be significantly improved.

  Furthermore, the heat exchange efficiency can be further improved by surrounding the pipe 32A having the double tube structure through which the capillary tube 18 is inserted with the heat insulating material 35. Furthermore, by making the flow of the refrigerant in the capillary tube 18 and the flow of the refrigerant passing through the pipe 32A outside the capillary tube 18 as a counter flow, the heat exchange capability can be further improved.

  As a result, energy savings of about 15% to 20% can be achieved as compared with conventional refrigeration apparatuses that are used in the same manner. In addition, the temperature around the evaporator 13 can also be lower than that of the prior art. Thereby, even if it is a case where it changes to the compressor with smaller capacity than the compressor used conventionally, it becomes possible to ensure sufficient performance. Thereby, further reduction of power consumption and size reduction of an apparatus can be achieved.

  In general, according to the present invention, an ultra-low temperature can be realized by a single-stage refrigeration system as in this embodiment without using a so-called multi-stage refrigeration system, so that the apparatus can be simplified. Cost can be reduced.

  Note that the refrigeration apparatus of the present invention is not limited to the refrigeration apparatus R1 of the embodiment. After condensing the refrigerant discharged from the compressor, the refrigerant is decompressed by a capillary tube and evaporated by an evaporator to provide a cooling action. The present invention is effective as long as it exhibits. In this embodiment, when the heat exchanger 16 is not used, the temperature of the compressed gas is cooled to these temperature ranges by using other well-known cooling means so that the intended condensation process proceeds. Also good.

  Further, in this embodiment, the refrigerant circuit 12 includes a non-azeotropic mixed refrigerant including R245fa, R600, R23, and R14, or a non-azeotropic mixed refrigerant including R245fa, R600, R116, and R14, or R245fa, R600, and R508A. , The non-azeotropic refrigerant mixture including R14, or the non-azeotropic refrigerant mixture including R245fa, R600, R508B, and R14 has been described. However, the present invention is effective.

  Next, a refrigeration apparatus according to another embodiment of the present invention will be described with reference to FIG. FIG. 6 is a refrigerant circuit diagram of another embodiment constituting the refrigeration apparatus of the ultra-low temperature storage 1 of FIG. In this case, the compressors 54, 84, etc. constituting the refrigerant circuit of the refrigeration apparatus R 2 are installed in a machine room (not shown) located below the heat insulating box 2 of the ultra-low temperature storage 1, and an evaporator (refrigerant pipe) 83 is installed. Is attached to the peripheral surface of the inner box 4 on the side of the heat insulating material 7 in a heat exchange manner, similarly to the evaporator 13 of the first embodiment.

  The refrigerant circuit of the refrigeration apparatus R2 according to the present embodiment includes a high-temperature side refrigerant circuit 52 and a low-temperature side refrigerant circuit 82 that form independent refrigerant closed circuits as multi-component (binary) single-stage refrigerant circuits. The compressor 54 constituting the high temperature side refrigerant circuit 52 is an electric compressor using a one-phase or three-phase AC power source. The compressor 54 is connected to a dissuperheater 60, and after the refrigerant compressed by the compressor 54 is once discharged to the outside to dissipate heat, it is returned to the shell of the hermetic container, and again the refrigerant discharge pipe. It is set as the structure discharged to 71. A refrigerant discharge pipe 71 connected to the discharge side of the compressor 54 is connected to an auxiliary condenser (pre-condenser) 61. The auxiliary condenser 61 is connected to a frame pipe 62 for heating the opening edge of the storage chamber 8 to prevent dew condensation. The refrigerant pipe exiting the frame pipe 62 is connected to an oil cooler 84 </ b> C of the compressor 84 constituting the low temperature side refrigerant circuit 82, and then connected to a condenser (condenser) 55.

  The refrigerant pipe exiting the condenser 55 is connected to a high temperature side dehydrator (dry core) 57 and a capillary tube 58. The dehydrator 57 is a moisture removing means for removing moisture in the high temperature side refrigerant circuit 52. The capillary tube 58 is inserted into a part (72 </ b> A) of the suction pipe 72 that comes out of the high-temperature side evaporator 59 of the cascade heat exchanger 56 and returns to the compressor 54.

  Specifically, the capillary tube 58 is inserted into a pipe 72A which is a part of the suction pipe 72 located on the discharge side of the evaporator 59 and on the suction side of the accumulator 68, as shown in FIG. Has a double-pipe structure. With such a double pipe structure, the refrigerant flowing through the capillary tube 58 that is the inner side of the double pipe 67 (hereinafter referred to as the double pipe structure), and the refrigerant from the evaporator 83 that flows through the pipe 72A that is the outer side of the double pipe 67 Is configured to be capable of heat exchange.

  The double pipe structure 67 is manufactured in the same manner as the double pipe structure 25 described in the first embodiment. That is, first, the straight tubular capillary tube 58 is inserted into the relatively large diameter straight tubular pipe 72A. Next, the double pipe is spirally wound in a plurality of stages. At this time, it is wound so that the center of the axis of the pipe 72A and the center of the axis of the capillary tube 58 coincide as much as possible to form a spiral double pipe. Thus, a gap is formed as consistently as possible between the inner wall surface of the pipe 72A and the outer wall surface of the capillary tube 58. In this way, the double tube is wound in a plurality of stages to form a spiral double tube structure, so that a sufficient length of the capillary tube 58 is ensured and the heat of the double tube structure is obtained. It is possible to reduce the size while sufficiently securing the replacement part.

  Next, cap-shaped connection pipes (not shown) having holes on both sides and the sides are attached to both ends of the pipe 72A, and the end portions of the capillary tubes 58 are respectively drawn out from the side holes. Seal the hole by welding. Furthermore, one end of the connection pipe attached to one end of the pipe 72A and the connection portion of the pipe 72A are welded, and the other end of the connection pipe is connected to the suction pipe 72 connected to the discharge side of the evaporator 59, This connection is welded. Similarly, one end of the connection pipe attached to the other end of the pipe 72A is welded to the connection portion of the pipe 72A, and the suction pipe 72 reaching the accumulator 68 is connected to the other end of the connection pipe. Weld. And the double pipe structure 67 of a present Example can be comprised by surrounding the outer periphery of the piping 72A made into the double pipe structure with a heat insulating material (not shown).

  As described above, the capillary tube 58 is inserted into the suction pipe 72 (pipe 72A) to form a double pipe structure, whereby the refrigerant passing through the capillary tube 58 and the refrigerant passing through the suction pipe 72 (pipe 72A). The heat exchange is performed by heat conduction that transmits the wall surface of the entire circumference of the capillary tube 58. Thereby, compared with the structure which attached the capillary tube to the outer peripheral surface of the conventional suction piping, it becomes possible to improve heat exchange performance markedly.

  Further, as described above, by surrounding the entire outer periphery of the pipe 72A having a double-pipe structure with a heat insulating material, it becomes difficult to be affected by heat from the outside, and the refrigerant in the pipe 72A and the refrigerant in the capillary tube 58 are not affected. The heat exchange capability can be further improved. Furthermore, in the capillary tube 58 that is the inner side of the double-pipe structure and in the suction pipe 72 (pipe 72A) outside the capillary tube 58, the refrigerant is caused to flow in a counterflow, The heat exchange capability in the double pipe structure 67 can be further improved.

  The refrigerant pipe exiting the capillary tube 58 is connected to a high temperature side evaporator 59 provided in heat exchange with the condenser 85 of the low temperature side refrigerant circuit 82. The high temperature side evaporator 59 constitutes a cascade heat exchanger 56 together with the condenser 85 of the low temperature side refrigerant circuit 82.

  The suction pipe 72 exiting from the high temperature side evaporator 59 is connected to the suction side of the compressor 54 through the high temperature side header 66, the double pipe structure 67, the accumulator 68, and the check valve 69 in this order.

In the high temperature side refrigerant circuit 52, R404A is enclosed as a refrigerant. The R404A includes R125 (pentafluoroethane: CHF ₂ CF ₃ ), R143a (1,1,1-trifluoroethane: CH ₃ CF ₃ ), and R134a (1,1,1,2-tetrafluoroethane: CH ₂ FCF ₃ ), and the composition thereof is 44% by weight of R125, 52% by weight of R143a, and 4% by weight of R134a. The mixed refrigerant has a boiling point of −46.5 ° C.

In addition, the refrigerant | coolant enclosed in the high temperature side refrigerant circuit 52 is not limited to R404A mentioned above. For example, the present invention is effective even when R407C composed of a three-type mixed refrigerant of R134a, R32 (difluoromethane: CH ₂ F ₂ ), and R125 is sealed as a refrigerant.

  In FIG. 6, the broken line arrows indicate the flow of the refrigerant circulating in the high temperature side refrigerant circuit 52. That is, the high-temperature gaseous refrigerant discharged from the compressor 54 is once discharged from the sealed container to the desuperheater 60 via the refrigerant discharge pipe on the side of the desuperheater 60, and after being dissipated, the shell of the sealed container is again formed. Return inside. Thereby, it can cool with the refrigerant | coolant which thermally radiated the inside of the shell of the airtight container with the desuper heater 60, and the temperature fell. Then, the high-temperature gaseous refrigerant is discharged from the sealed container through the refrigerant discharge pipe 71, and the auxiliary condenser 61, the frame pipe 62, the oil cooler 84 </ b> C of the compressor 84 of the low-temperature side refrigerant circuit 82, and the condenser 55. After being condensed and converted into heat dissipation liquid, moisture contained in the dehydrator 57 is removed and flows into the capillary tube 58 of the double-pipe structure 67.

  Here, in the capillary tube 58, the refrigerant is heated by the heat passing through the suction pipe 72 (pipe 72A) provided on the entire circumference of the capillary tube 58 and the wall surface of the entire circumference of the capillary tube 58. The pressure is reduced while the temperature is further lowered and flows into the evaporator 59. In the evaporator 59, R204A evaporates by absorbing heat from the refrigerant flowing in the condenser 85 of the cascade heat exchanger 56. At this time, the refrigerant flowing through the condenser 85 is cooled by evaporating the R204A refrigerant.

  The refrigerant evaporated in the evaporator 59 then exits the high temperature side evaporator 59 via the suction pipe 72 and flows into the double pipe structure 67 through the high temperature side header 66, and the capillary tube described above. After exchanging heat with the refrigerant flowing in 58, the refrigerant returns to the compressor 54 through the accumulator 68 and the check valve 69.

  On the other hand, the compressor 84 constituting the low-temperature side refrigerant circuit 82 is an electric compressor that uses a one-phase or three-phase AC power source, like the compressor 54 of the high-temperature side refrigerant circuit 52. The compressor 84 is connected to a dissuperheater 90, and once the refrigerant compressed by the compressor 84 is discharged to the outside to dissipate heat, it is returned to the shell of the hermetic container, and again the refrigerant discharge pipe 101 is discharged. The refrigerant discharge pipe 101 connected to the discharge side of the compressor 84 is connected to an auxiliary condenser (pre-condenser) 91. The refrigerant pipe exiting the auxiliary condenser 91 is connected to the oil separator 92. An oil return pipe 103 that returns to the compressor 84 is connected to the oil separator 92.

  The refrigerant pipe exiting the oil separator 92 reaches the internal heat exchanger 93. The internal heat exchanger 93 is compressed by the compressor 84, evaporates in the evaporator 86 on the way to the capillary tube 88 and evaporates in the evaporator 86, and exchanges heat between the low-pressure side refrigerant on the way back to the compressor 84. It is a heat exchanger.

  The refrigerant pipe on the high pressure side that has passed through the internal heat exchanger 93 is connected to the condenser 85. The condenser 85 constitutes the cascade heat exchanger 56 together with the high temperature side evaporator 59 of the high temperature side refrigerant circuit 52 as described above. The refrigerant pipe exiting from the condenser 85 is connected to a low temperature side dehydrator (dry core) 87 and a capillary tube 88. The dehydrator 87 is water removal means for removing water in the low temperature side refrigerant circuit 82. The capillary tube 88 is inserted into a part of the suction pipe 102 (pipe 102A) that exits the evaporator 83 and returns to the compressor 84.

  Specifically, the capillary tube 88 is inserted into a pipe 102A which is a part of the suction pipe 102 located on the discharge side of the evaporator 83 and on the suction side of the internal heat exchanger 93, and is shown in FIG. As shown in FIG. With such a double pipe structure, the refrigerant flowing through the capillary tube 88 that is the inner side of the double pipe 95 (hereinafter referred to as a double pipe structure), and the refrigerant from the evaporator 83 that flows through the pipe 102A that is the outer side of the double pipe 95 Is configured to be capable of heat exchange.

  The double pipe structure 95 is manufactured by the same method as the double pipe structure 25 described in the first embodiment. That is, first, the straight tubular capillary tube 88 is inserted into the relatively large straight pipe 102A. Next, the double pipe is spirally wound in a plurality of stages. At this time, winding is performed so that the center of the axis of the pipe 102A and the center of the axis of the capillary tube 88 coincide as much as possible to form a spiral double pipe. Thus, a gap is formed as consistently as possible between the inner wall surface of the pipe 102A and the outer wall surface of the capillary tube 88. In this way, the double tube is wound in a plurality of stages to form a spiral double tube structure, so that the length of the capillary tube 88 is sufficiently secured and the heat of the double tube structure is obtained. It is possible to reduce the size while sufficiently securing the replacement part.

  Next, cap-shaped connection pipes (not shown) having holes on both sides and the sides are attached to both ends of the pipe 102A, and the end portions of the capillary tubes 88 are respectively drawn out from the side holes. Seal the hole by welding. Furthermore, one end of the connection pipe attached to one end of the pipe 102A and the connection portion of the pipe 102A are welded, and the other end of the connection pipe is connected to the suction pipe 102 connected to the discharge side of the evaporator 83, This connection is welded. Similarly, one end of the connection pipe attached to the other end of the pipe 102A and the connection portion of the pipe 102A are welded, and the other end of the connection pipe is connected to the suction pipe 102 leading to the internal heat exchanger 93. Weld the connection. And the double pipe structure 95 of a present Example can be comprised by surrounding the outer periphery of the piping 102A made into the double pipe structure with the heat insulating material 105. FIG.

  As described above, the capillary tube 88 is inserted into the suction pipe 102 (pipe 102A) to form a double pipe structure, whereby the refrigerant passing through the capillary tube 88 and the refrigerant passing through the suction pipe 102 (pipe 102A). The heat exchange is performed by heat conduction that transmits the wall surface of the entire circumference of the capillary tube 88. Thereby, compared with the structure which attached the capillary tube to the outer peripheral surface of the conventional suction piping, it becomes possible to improve heat exchange performance markedly.

  Further, as described above, the entire outer periphery of the pipe 102A having the double-pipe structure is surrounded by the heat insulating material 105, so that it is difficult to be affected by heat from the outside, and the refrigerant in the pipe 102A and the refrigerant in the capillary tube 88 are It becomes possible to further improve the heat exchange capacity. Furthermore, in the capillary tube 88 that is the inner side of the double-pipe structure and in the suction pipe 102 (pipe 102A) outside the capillary tube 88, the refrigerant is caused to flow in a counterflow, The heat exchange capacity in the double pipe structure 95 can be further improved.

  Similar to the double pipe structure 25 of the first embodiment, the double pipe structure 95 is accommodated in the heat insulating material 7 located on the lower side of the back surface of the inner box 4 so as to be put in and out.

  On the other hand, the suction pipe 102 exiting the double pipe structure 95 is connected to the suction side of the compressor 84 via the internal heat exchanger 93. A refrigerant pipe 106 is further connected to the compressor 84, and an expansion tank 107 that stores the refrigerant when the compressor 84 is stopped is connected to the refrigerant pipe 106 via a capillary tube 108 as a decompression device.

On the other hand, in the low temperature side refrigerant circuit 82, R508A is enclosed as a refrigerant. The R508A is composed of R23 (trifluoromethane: CHF ₃ ) and R116 (hexafluoroethane: CF ₃ CF ₃ ), and the composition thereof is 39% by weight for R23 and 61% by weight for R116. The mixed refrigerant has a boiling point of −85.7 ° C.

  In addition, the refrigerant | coolant enclosed in the low temperature side refrigerant circuit 82 is not limited to R508A demonstrated in the present Example. For example, the present invention is effective even when R508B (R23 / R116: 46/54) having a different mixing ratio of R23 and R116 is used instead of R508A.

  In FIG. 6, the solid line arrows indicate the flow of the refrigerant circulating in the low temperature side refrigerant circuit 82. Specifically, the flow of the refrigerant in the low-temperature side refrigerant circuit 82 will be described. The high-temperature gaseous refrigerant discharged from the compressor 84 is once removed from the sealed container through the refrigerant discharge pipe on the side of the desuperheater 90. After being discharged to 90 and dissipated, it returns again into the shell of the sealed container. Thereby, the inside of the shell of the hermetic container can be cooled by the refrigerant whose temperature is reduced by dissipating heat in the dissuperheater 90. Then, the high-temperature gaseous refrigerant is discharged from the sealed container through the refrigerant discharge pipe 101, radiates heat in the auxiliary condenser 91, and then flows into the oil separator 92.

  Most of the lubricating oil of the compressor 84 mixed with the refrigerant in the oil separator 92 and a part of the refrigerant condensed and liquefied in the auxiliary condenser 91 are returned to the compressor 84 through the oil return pipe 103. On the other hand, the refrigerant discharged from the oil separator 92 is condensed by the internal heat exchanger 93 and the condenser 85 to be radiated liquid, and then the moisture contained in the low temperature side dehydrator 87 is removed and flows into the capillary tube 88.

  Here, in the capillary tube 88, the refrigerant is heated by the heat passing through the suction pipe 102 (pipe 102 </ b> A) provided on the entire circumference of the capillary tube 88 and the wall surface of the entire circumference of the capillary tube 88. The pressure is reduced while the temperature is further lowered and flows into the evaporator 83. In the evaporator 83, the refrigerant R508A evaporates by taking heat from the surroundings. At this time, the refrigerant R508 evaporates in the evaporator 83, thereby exerting a cooling action, and the periphery of the evaporator 83 is cooled to an extremely low temperature of −86 ° C. to −87 ° C. In this case, as described above, the evaporator (refrigerant pipe) 83 is configured to be heat-heated along the heat insulating material 7 side of the inner box 4. It becomes possible to set the inside of one storage chamber 8 to an internal temperature of −80 ° C. or lower.

  The refrigerant evaporated in the evaporator 83 then exits the evaporator 83 through the suction pipe 102 and returns to the compressor 84 through the double pipe structure 95 and the internal heat exchanger 93 described above.

  On the other hand, the compressor 84 constituting the low-temperature side refrigerant circuit 82 is ON / OFF controlled by a control device (not shown) based on the internal temperature in the storage chamber 8. In this case, when the operation of the compressor 84 is stopped by the control device, the mixed refrigerant in the low temperature side refrigerant circuit 82 is recovered from the refrigerant pipe 106 into the expansion tank 107 via the capillary tube 108.

  Thereby, it is possible to prevent the pressure in the refrigerant circuit 82 from rising. Further, when the compressor 84 is started by the control device, the starting load on the compressor 84 can be reduced by gradually returning the refrigerant from the expansion tank 107 into the compressor 84 via the capillary tube 108. It becomes possible.

  As described above in detail, the capillary tube 88 is inserted into the suction pipe 102 (pipe 102A) through which the refrigerant returning from the evaporator 83 to the compressor 84 passes, thereby forming a double pipe structure. The heat exchange efficiency between the refrigerant and the refrigerant in the capillary tube 88 can be improved, and the performance can be improved.

  In particular, the capillary tube 88 is inserted into the pipe 102A of the suction pipe 102 immediately after exiting the evaporator 83 as in the present invention to form a double pipe structure, and heat is transmitted by heat conduction that transmits the entire wall surface of the capillary tube 88. By configuring so as to be replaceable, the refrigerant having the lowest boiling point is efficiently cooled by the return refrigerant from the evaporator 83, and the performance can be significantly improved. Therefore, it is particularly effective in the ultra-low temperature storage 1 as in the present embodiment.

  Furthermore, the heat exchange efficiency can be further improved by surrounding the pipe 102A having a double tube structure through which the capillary tube 88 is inserted with the heat insulating material 105. Furthermore, by making the flow of the refrigerant in the capillary tube 88 and the flow of the refrigerant passing through the pipe 102 </ b> A outside the capillary tube 88 a counter flow, the heat exchange capability can be further improved.

  Furthermore, in the present embodiment, the capillary tube 58 as the pressure reducing means of the high temperature side refrigerant circuit 52 is also formed in a double tube structure like the capillary tube 88 of the low temperature side refrigerant circuit 82, and the pipe 72A having such a double tube structure is provided. Surrounded by insulation. Furthermore, the flow of the refrigerant becomes a counterflow in the capillary tube 58 that is the inner side of the double-pipe structure and in the suction pipe 72 (the pipe 72A) outside the capillary tube 58. Thereby, the refrigerant in the capillary tube 58 can be efficiently cooled by the return refrigerant from the evaporator 59. Thereby, the heat exchange efficiency can be further improved to further improve the performance.

  In general, the ultra-low temperature storage 1 capable of efficiently cooling the inside of the storage chamber 8 to a desired ultra-low temperature can be realized by the present invention. In particular, according to the present invention, energy saving of about 15% to 20% can be achieved as compared with a conventional refrigeration apparatus of similar use. Further, the temperature around the evaporator 13 is conventionally about −83 ° C. However, by using the structure of the present invention described above, a low temperature of −86 ° C. to −87 ° C. can be realized. . As a result, sufficient performance can be ensured even when the compressor of the 200 V specification that has been used as the compressor of the low-temperature side refrigerant circuit 82 is changed to a 115 V specification compressor having a small capacity. It becomes. Thereby, further reduction of power consumption and size reduction of an apparatus can be achieved.

  Next, a refrigerating apparatus according to another embodiment of the present invention will be described with reference to FIG. FIG. 7 is a refrigerant circuit diagram of another example constituting the refrigeration apparatus of the ultra-low temperature storage 1 of FIG. In this case, the compressor 114 and the like constituting the refrigerant circuit of the refrigeration apparatus R3 are installed in a machine room (not shown) located below the heat insulation box 2 of the ultra-low temperature storage 1, and an evaporator (refrigerant pipe) 113 is It is attached to the peripheral surface of the inner box 4 on the heat insulating material 7 side by heat exchange.

  The refrigerant circuit of the refrigeration apparatus R3 of the present embodiment includes a compressor 114, a condenser 115, an evaporator 113, a single intermediate heat exchanger 116 connected so that a return refrigerant from the evaporator 113 flows, and The unit is composed of a single-unit multi-stage (two-stage) refrigerant circuit 112 having a plurality of capillary tubes 118 and 135. The compressor 114 constituting the refrigerant circuit 112 is an electric compressor using a one-phase or three-phase AC power source as in the above embodiments. The refrigerant discharge pipe 131 connected to the discharge side of the compressor 114 is connected to an auxiliary condenser (pre-condenser) 121. The auxiliary condenser 121 is connected to a frame pipe 122 for heating the opening edge of the storage chamber 8 to prevent dew condensation and an oil cooler 114C of the compressor 114, and then connected to a condenser (condenser) 115. . In the present embodiment, the auxiliary condenser 121 and the condenser 115 are configured as an integrated condenser and are cooled by a condensing fan 129 as a condenser blower.

  The refrigerant pipe exiting the condenser 115 is connected to the flow divider 130 via a dehydrator (dry core) 117. The dehydrator 117 is a moisture removing means for removing moisture in the refrigerant circuit 112. The flow divider 130 is a refrigerant (condensed refrigerant) condensed and liquefied in the process of passing through the auxiliary condenser 121, the frame pipe 122, and the condenser 115, and a refrigerant that has not been condensed yet (a non-condensed refrigerant). Is a gas-liquid separator. A gas phase pipe 133 connected to the discharge side (exit side) of the flow divider 130 and for taking out the gas phase refrigerant (uncondensed refrigerant) separated by the flow divider 130 is connected to the condensing pipe 123.

  The condensing pipe 123 forms an intermediate heat exchanger 116 together with the auxiliary evaporator 136. The intermediate heat exchanger 116 depressurizes the liquid-phase refrigerant (condensed refrigerant) separated by the flow divider 130 in the capillary tube 135, and then flows it to the auxiliary evaporator 136 of the intermediate heat exchanger 116 for evaporation there. Thus, the gas-phase refrigerant (uncondensed refrigerant) flowing through the condensation pipe 123 is cooled and condensed. The refrigerant pipe exiting from the condensing pipe 123 is connected to an evaporator (evaporator) 113 via a capillary tube (final stage capillary tube) 118.

  The capillary tube 118 is inserted into a part of the suction pipe 132 (pipe 132A) that exits the evaporator 113 and returns to the compressor 114. Specifically, the capillary tube 118 is inserted into a pipe 132A that is a part of the suction pipe 132 that is located on the discharge side of the evaporator 113 and on the suction side of the intermediate heat exchanger 116, as shown in FIG. As shown in FIG. With such a double pipe structure, the refrigerant flowing through the capillary tube 118 that is the inner side of the double pipe 125 (hereinafter referred to as a double pipe structure), and the refrigerant from the evaporator 113 that flows through the pipe 132A that is the outer side thereof Is configured to be capable of heat exchange.

  The double pipe structure 125 is manufactured by the same method as the double pipe structure 25 described in the first embodiment. That is, first, the straight tubular capillary tube 118 is inserted into the relatively large diameter straight tubular pipe 132A. Next, the double pipe is spirally wound in a plurality of stages. At this time, it is wound so that the center of the axis of the pipe 132A and the center of the axis of the capillary tube 118 coincide as much as possible to form a spiral double pipe. Thereby, a gap is formed as consistently as possible between the inner wall surface of the pipe 132A and the outer wall surface of the capillary tube 118. In this way, the double tube is wound in a plurality of stages to form a spiral double tube structure, so that the length of the capillary tube 118 is sufficiently secured and the heat of the double tube structure is obtained. It is possible to reduce the size while sufficiently securing the replacement part.

  Next, cap-shaped connection pipes (not shown) having holes on both sides and the sides are attached to both ends of the pipe 132A, and the end portions of the capillary tubes 118 are respectively pulled out from the side holes. Seal the hole by welding. Furthermore, one end of the connection pipe attached to one end of the pipe 132A and the connection portion of the pipe 132A are welded, and the suction pipe 102 connected to the discharge side of the evaporator 113 is connected to the other end of the connection pipe. This connection is welded. Similarly, one end of a connection pipe attached to the other end of the pipe 132A is welded to a connection portion of the pipe 132A, and the suction pipe 102 reaching the intermediate heat exchanger 116 is connected to the other end of the connection pipe. Weld the connection. And the double pipe structure 125 of a present Example can be comprised by surrounding the outer periphery of the piping 132A made into the double pipe structure with the heat insulating material 140. FIG.

  As described above, the capillary tube 118 is inserted into the suction pipe 132 to form a double pipe structure, so that the refrigerant passing through the capillary tube 118 and the refrigerant passing through the suction pipe 132 are all of the capillary tube 118. Heat exchange is performed by heat conduction transmitted through the circumferential wall surface. Thereby, compared with the structure which attached the capillary tube to the outer peripheral surface of the conventional suction piping, it becomes possible to improve heat exchange performance markedly.

  Furthermore, as described above, by surrounding the entire outer periphery of the pipe 132A having a double-pipe structure with the heat insulating material 140, it becomes difficult to be affected by heat from the outside, and the refrigerant in the pipe 132A and the refrigerant in the capillary tube 118 It becomes possible to further improve the heat exchange capacity. Furthermore, in the capillary tube 118 that is the inner side of the double-pipe structure and in the suction pipe 132 (pipe 132A) outside the capillary tube 118, the refrigerant is caused to flow in a counterflow, The heat exchange capability in the double pipe structure 125 can be further improved.

  The double pipe structure 125 is accommodated in the heat insulating material 7 below the back side of the inner box 4 in a manner similar to the double pipe structures 25 and 95 of the respective embodiments.

  On the other hand, the suction pipe 132 exiting the evaporator 113 is connected to the auxiliary evaporator 136 through the pipe 132A of the double pipe structure 125 described above. The suction pipe 132 exiting the auxiliary evaporator 136 is connected to the suction side of the compressor 114. Between the compressor 114 and the auxiliary evaporator 136 of the suction pipe 132, an expansion tank 137 for storing a refrigerant when the compressor 114 is stopped is further connected via a capillary tube 138 as a decompression device.

In the refrigerant circuit 112, a non-azeotropic mixed refrigerant composed of a plurality of types of mixed refrigerants having different boiling points is enclosed as a refrigerant. In this example, as in Example 1, R245fa (1,1,1, -3,3-pentafluoropropane: CF ₃ CH ₂ CHF ₂ ), R600 (butane: CH ₃ CH ₂ CH ₂ CH ₃ ) A non-azeotropic refrigerant mixture composed of R23 (trifluoromethane: CHF ₃ ) and R14 (tetrafluoromentane: CF ₄ ) is enclosed.

  In addition, the refrigerant | coolant enclosed with the refrigerant circuit 112 is not limited to the non-azeotropic refrigerant mixture containing R245fa, R600, R23, R14 mentioned above. For example, a non-azeotropic refrigerant mixture including R245fa, R600, R116, and R14, a non-azeotropic refrigerant mixture including R245fa, R600, R508A, and R14, or a non-azeotropic refrigerant mixture including R245fa, R600, R508B, and R14 The present invention is effective even when the refrigerant is used or other refrigerant is used.

  In FIG. 7, arrows indicate the flow of the refrigerant circulating in the refrigerant circuit 112. Specifically, the high-temperature gaseous refrigerant discharged from the compressor 114 is discharged from the sealed container through the refrigerant discharge pipe 131, and the auxiliary condenser 121, the frame pipe 122, the oil cooler 114C of the compressor 114, and the condensation. Pass through the vessel 115 sequentially. The high-temperature gaseous refrigerant discharged from the compressor 114 dissipates heat in the process of passing through the auxiliary condenser 121, the frame pipe 122, the oil cooler 114C, and the condenser 115, and the refrigerant having a high boiling point in the mixed refrigerant (R245fa, R600) condensates.

  Then, the mixed refrigerant that has exited the condenser 115 is freed of moisture contained in the dehydr 117 and flows into the flow divider 130. At this time, R23 and R14 in the mixed refrigerant are not condensed yet because they have a very low boiling point, and are in a gas state. Since R245fa and R600 having a high boiling point are condensed and liquefied, R23 and R14 are vapor phase pipes 133. In addition, R245fa and R600 are separated into the liquid phase pipe 134. The refrigerant mixture that has flowed into the gas phase pipe 133 flows into the condensation pipe 123 that constitutes the intermediate heat exchanger 116.

  The mixed refrigerant flowing into the liquid phase pipe 134 is decompressed by the capillary tube 135 and then flows into the auxiliary evaporator 136 constituting the intermediate heat exchanger 116 together with the condensing pipe 123, and returns from the evaporator 113. R23 and R14 which flow through the condensing pipe 123 together with the cold refrigerant coming are cooled. Thereby, R23 and R14 which flow through the condensation pipe 123 are condensed and liquefied. In the intermediate heat exchanger 116, the condensed R 23 and R 14 then exit the condensation pipe 123 and flow into the capillary tube 118.

  Here, in the capillary tube 118, the refrigerant is heated by the heat passing through the suction pipe 132 (pipe 132 </ b> A) provided on the entire circumference of the capillary tube 118 and the wall surface of the entire circumference of the capillary tube 118. The pressure is reduced while the temperature is further lowered and flows into the evaporator 113. Then, in the evaporator 113, the refrigerants R14 and R23 take heat from the surroundings and evaporate. At this time, the refrigerants R14 and R23 evaporate in the evaporator 113, thereby exhibiting a cooling action and cooling the periphery of the evaporator 113 to an ultra-low temperature of -85 ° C. In this case, as described above, the evaporator (refrigerant pipe) 113 is configured to be heat-exchanged along the heat insulating material 7 side of the inner box 4, so that the evaporator 113 is cooled to cool the cryogenic storage. The inside of one storage chamber 8 can be set to an internal temperature of −80 ° C. or lower.

  Then, the refrigerant evaporated in the evaporator 113 exits from the evaporator 113 via the suction pipe 132 and flows into the auxiliary evaporator 136 of the intermediate heat exchanger 116 through the double pipe structure 125 described above. The refrigerant having a high boiling point (R245fa, R600) evaporated by the auxiliary evaporator 136 is joined. Thereafter, the refrigerant leaves the auxiliary condenser 136 and returns to the compressor 114.

  On the other hand, the compressor 114 constituting the refrigerant circuit 112 is ON / OFF controlled by a control device (not shown) based on the internal temperature in the storage chamber 8. In this case, when the operation of the compressor 114 is stopped by the control device, the mixed refrigerant in the low temperature side refrigerant circuit 112 is recovered in the expansion tank 137 via the capillary tube 138.

  Thereby, it is possible to prevent the pressure in the refrigerant circuit 112 from increasing. Further, when the compressor 114 is started by the control device, the starting load of the compressor 114 can be reduced by gradually returning the refrigerant from the expansion tank 137 into the refrigerant circuit 112 via the capillary tube 138. It becomes possible.

  By inserting the capillary tube 118 into the suction pipe 132 (pipe 132A) through which the refrigerant returning from the evaporator 113 to the compressor 114 passes as in the present embodiment detailed above, a double pipe structure is obtained. It is possible to improve the performance by improving the heat exchange efficiency between the refrigerant in the pipe 132A and the refrigerant in the capillary tube 118. In particular, the capillary tube 118 is inserted into the pipe 132A of the suction pipe 132 immediately after exiting the evaporator 113 as in the present invention to form a double pipe structure, and heat is transmitted by heat conduction that transmits the entire wall surface of the capillary tube 118. By configuring so as to be exchangeable, the refrigerant having the lowest boiling point is efficiently cooled by the return refrigerant from the evaporator 113, and the performance can be significantly improved. Therefore, it is particularly effective in the ultra-low temperature storage 1 as in the present embodiment.

  Furthermore, the heat exchange efficiency can be further improved by surrounding the pipe 132A having the double tube structure through which the capillary tube 118 is inserted with the heat insulating material 140. Furthermore, by making the flow of the refrigerant in the capillary tube 118 and the flow of the refrigerant passing through the suction pipe 132A outside the capillary tube 118 a counter flow, the heat exchange capability can be further improved. .

  In general, according to the present invention, it is possible to realize the ultra-low temperature storage 1 capable of efficiently cooling the interior of the storage chamber 8 to a desired ultra-low temperature. In particular, according to the present invention, energy saving of about 15% to 20% can be achieved as compared with a conventional refrigeration apparatus of similar use. In addition, the temperature around the evaporator 113 can also be made lower than before. Thereby, even if it is a case where it changes to the compressor with a smaller capacity than the conventional compressor, it becomes possible to ensure sufficient performance. Thereby, further reduction of power consumption and size reduction of an apparatus can be achieved.

  In this embodiment, the refrigeration apparatus R3 of the ultra-low temperature storage 1 may be configured by only the refrigerant circuit 112 described above. However, in addition to the refrigerant circuit 112, as shown in FIG. The refrigerant circuit 152 having the same circuit configuration as that described above may be provided in parallel, and the two refrigerant circuits 112 and 152 may constitute the refrigeration apparatus R3 of the ultra-low temperature storage 1. Since the circuit configuration of the refrigerant circuit 152 and the flow of the refrigerant are the same as those of the refrigerant circuit 112 described above, the same reference numerals as those of the members constituting the refrigerant circuit 112 are given. That is, since the thing with the same code | symbol as the refrigerant circuit 112 has the same or similar effect or effect | action, description is abbreviate | omitted here.

  Like the compressor 114 of the refrigerant circuit 112, the compressor 114 and the like constituting the refrigerant circuit 152 are installed in a machine room (not shown) located below the heat insulating box 2 of the ultra-low temperature storage 1. Similarly to the evaporator 113 of the refrigerant circuit 112, the evaporator 113 is also attached to the peripheral surface of the inner box 4 on the heat insulating material 7 side in a heat exchange manner. Furthermore, since the refrigerant sealed in the refrigerant circuit 152 and the circulation of the refrigerant are the same as those of the refrigerant circuit 112 described above, the description thereof is omitted here.

  As described above, when the refrigeration apparatus R3 of the low temperature storage 1 is configured by arranging two independent refrigerant circuits 112 and 152 having substantially the same performance in parallel, the other refrigerant circuit is used as a backup when one refrigerant circuit fails. A refrigerant circuit can be used. That is, for example, even when the refrigerant circuit 112 fails, the refrigerant circuit 152 can be operated without any trouble, and the inside of the storage chamber 8 can be maintained at an extremely low temperature by the evaporator 113 of the refrigerant circuit 152. As a result, the reliability of the ultra-low temperature storage 1 can be improved.

  In this embodiment, each refrigerant circuit constituting the refrigeration apparatus has a single intermediate heat connected so that the compressor 114, the condenser 115, the evaporator 113, and the return refrigerant from the evaporator 113 circulate. The exchanger 116 and a plurality of, specifically, two capillary tubes 135, 118 are filled with a plurality of types of non-azeotropic mixed refrigerant, and the condensed refrigerant in the refrigerant having passed through the condenser 115 is replaced with the capillary tube 135. The intermediate heat exchanger 116 is joined to the intermediate heat exchanger 116, and the uncondensed refrigerant in the refrigerant is cooled by the intermediate heat exchanger 116, thereby condensing the refrigerant having a lower boiling point and passing through the capillary tube 118 at the final stage. The single-stage two-stage refrigeration apparatus R3 that evaporates the boiling-point refrigerant in the evaporator 113 and exerts the cooling action has been described. However, the present invention is not limited to this. No problem even as constituting the circuit of the intermediate heat exchanger connected in series.

  Next, a refrigerating apparatus according to still another embodiment of the present invention will be described with reference to FIG. FIG. 8 is a refrigerant circuit diagram of still another embodiment constituting the refrigeration apparatus of the ultra-low temperature storage 1 of FIG. In this case, the compressors 214, 254, etc. constituting the refrigerant circuit of the refrigeration apparatus R4 are installed in a machine room (not shown) located below the heat insulating box 2 of the ultra-low temperature storage 1, and an evaporator (refrigerant pipe) 253 is installed. Is attached to the peripheral surface of the inner box 4 on the side of the heat insulating material 7 in a heat exchange manner, similarly to the evaporators 13, 83, and 113 of the above embodiments.

  The refrigerant circuit of the refrigerating apparatus R4 of the present embodiment is configured as a multi-stage multi-stage refrigerant circuit by a high-temperature side refrigerant circuit 212 that constitutes an independent refrigerant closed circuit and a binary two-stage refrigerant circuit of a low-temperature side refrigerant circuit 252. Has been. The compressor 214 constituting the high temperature side refrigerant circuit 212 is an electric compressor using a one-phase or three-phase AC power supply, and the refrigerant discharge pipe 231 connected to the discharge side of the compressor 214 is connected to the auxiliary condenser 221. Connected. The auxiliary condenser 26 is connected to a frame pipe 222 for heating the opening edge of the storage chamber 8 to prevent dew condensation.

  This frame pipe 222 is connected to the condenser 215 after being connected to the oil cooler 214 </ b> C of the compressor 214. The refrigerant pipe exiting the condenser 215 is connected to the oil cooler 254C of the compressor 254 constituting the low temperature side refrigerant circuit 252, and then connected to the condenser 223. The refrigerant pipe exiting the condenser 223 is The high temperature side evaporator 213 as an evaporator constituting the evaporator of the high temperature side refrigerant circuit 212 is sequentially connected through a dryer (dry core) 217 and a capillary tube 218 as a decompression device.

  The high temperature side evaporator 213 constitutes a cascade heat exchanger 216 together with a condensation pipe 255 as a condenser of the low temperature side refrigerant circuit 252. An accumulator 228 serving as a refrigerant liquid reservoir is connected to the suction pipe 232 exiting from the auxiliary evaporator 213, and the suction pipe 232 exiting from the accumulator 228 is connected to the suction side of the compressor 214. In addition, the auxiliary condenser 221 and the condensers 215 and 223 in the present embodiment are configured as an integrated condenser, and are cooled by a condensing fan 229 as a condenser blower.

The high temperature side refrigerant circuit 212 is filled with a refrigerant composed of R407D and n-pentane as a non-azeotropic refrigerant having different boiling points. R407D is composed of R32 (difluoromethane: CH ₂ F ₂ ), R125 (pentafluoroethane: CHF ₂ CF ₃ ), and R134a (1,1,1,2-tetrafluoroethane: CH ₂ FCF ₃ ). The composition of R32 is 15% by weight, R125 is 15% by weight, and R134a is 70% by weight. The boiling point of each refrigerant is −321.8 ° C. for R32, −48.57 ° C. for R125, and −26.16 ° C. for R134a. The boiling point of n-pentane is + 36.1 ° C.

  In such a configuration, the high-temperature gaseous refrigerant discharged from the compressor 214 includes the auxiliary condenser 221, the frame pipe 222, the oil cooler 214C, the condenser 215, the oil cooler 254C of the compressor 254 of the low-temperature side refrigerant circuit 252, and the condenser. After being condensed at 223 and converted into a heat radiation liquid, moisture contained in the dryer 217 is removed and flows into the capillary tube 218. Then, the refrigerant decompressed by the capillary tube 218 flows into the high temperature side evaporator 213 constituting the cascade heat exchanger 216. In the high temperature side evaporator 213, the refrigerants R32, R125, and R134a evaporate by absorbing heat from the refrigerant flowing in the condensation pipe 255. At this time, in the cascade heat exchanger 216, the refrigerant in the high temperature side evaporator 213 of the high temperature side refrigerant circuit 212 evaporates, whereby the refrigerant in the low temperature side refrigerant circuit 252 flowing in the condensation pipe 255 is cooled.

  The refrigerant evaporated in the high temperature side evaporator 213 then exits the evaporator 213 via the suction pipe 232 and returns to the compressor 214 via the accumulator 228.

  At this time, the capacity of the compressor 214 is, for example, 1.5 HP, and the final temperature reached by the high-temperature side evaporator 213 during operation is −27 ° C. to −35 ° C. Under such a low temperature, the boiling point of n-pentane in the refrigerant is + 36.1 ° C., so that it does not evaporate in the evaporator 213 and remains in a liquid state, and therefore hardly contributes to cooling. The function of returning the mixed moisture that could not be absorbed by the dryer 217 to the compressor 214 while being dissolved therein and the evaporation of the liquid refrigerant in the compressor 214 reduce the temperature of the compressor 214. Play a function.

  On the other hand, the low-temperature side refrigerant circuit 252 includes a compressor 254, a condensing pipe (condenser) 255, an evaporator 253, and a plurality of intermediate heat exchangers 262 and 266 connected so that the return refrigerant from the evaporator 253 flows. 270, 272 and a plurality of capillary tubes 264, 268, 258. Specifically, the compressor 254 constituting the low-temperature side refrigerant circuit 252 is an electric compressor that uses a one-phase or three-phase AC power source similarly to the compressor 214, and is connected to the discharge side of the compressor 254. An oil separator 260 is connected to the refrigerant discharge pipe 281 via a heat radiator 259 composed of a wire condenser. The oil separator 260 is connected to an oil return pipe 287 that returns to the compressor 254. The refrigerant pipe connected to the discharge side of the oil separator 260 is connected to a condensing pipe 255 as a condenser constituting the cascade heat exchanger 216 together with the high temperature side evaporator 213.

  The refrigerant pipe connected to the discharge side of the condensing pipe 255 is connected to the first gas-liquid separator 261 via a dryer (dry core) 257. The gas-phase refrigerant (uncondensed refrigerant) separated by the gas-liquid separator 261 passes through the first intermediate heat exchanger 262 via the gas-phase pipe 283 and flows into the second gas-liquid separator 265. . On the other hand, the liquid-phase refrigerant (condensed refrigerant) separated by the first gas-liquid separator 261 passes through the liquid-phase pipe 284, the dryer 263, and the capillary tube 268 as a decompression device, so that the first intermediate heat exchanger. Flows into H.262. The first intermediate heat exchanger 262 joins the liquid-phase refrigerant (condensed refrigerant) separated by the first gas-liquid separator 261 to the intermediate heat exchanger 262 via the capillary tube 264, where the gas By cooling the gas-phase refrigerant (uncondensed refrigerant) flowing through the phase pipe 283, the refrigerant having a lower boiling point is condensed.

  The liquid-phase refrigerant separated by the second gas-liquid separator 265 passes through the dryer 267 through the liquid-phase piping 286 and then flows into the second intermediate heat exchanger 266 through the capillary tube 268 as a decompression device. . Further, the gas-phase refrigerant separated by the second gas-liquid separator 265 passes through the second intermediate heat exchanger 266 via the gas-phase pipe 285. The second intermediate heat exchanger 266 joins the liquid-phase refrigerant (condensed refrigerant) separated by the second gas-liquid separator 265 to the intermediate heat exchanger 266 via the capillary tube 268, where the gas By cooling the gas-phase refrigerant (uncondensed refrigerant) flowing through the phase piping 285, the refrigerant having a lower boiling point is condensed.

  The gas phase piping 285 that has passed through the second intermediate heat exchanger 266 is then passed through the third intermediate heat exchanger 270, the fourth intermediate heat exchanger 272, and the dryer 274, and a capillary tube as a decompression device. Flows into H.258.

  The capillary tube 258 is inserted into a part of the suction pipe 282 (pipe 282A) that returns from the evaporator 253 and returns to the compressor 254. Specifically, the capillary tube 258 is inserted into a pipe 282A which is a part of the suction pipe 282 located on the discharge side of the evaporator 253 and on the suction side of the fourth intermediate heat exchanger 272. As shown in FIG. 3, a double tube structure is formed. With such a double pipe structure, the refrigerant flowing through the capillary tube 258 inside the double pipe 295 (hereinafter referred to as a double pipe structure), and the refrigerant from the evaporator 253 flowing through the pipe 282A as the outside Is configured to be capable of heat exchange.

  The double pipe structure 295 is manufactured by the same method as the double pipe structure 25 described in the first embodiment. That is, first, the straight tubular capillary tube 258 is inserted into the relatively large diameter straight tubular pipe 282A. Next, the double pipe is spirally wound in a plurality of stages. At this time, winding is performed so that the center of the axis of the pipe 282A and the center of the axis of the capillary tube 258 coincide as much as possible to form a spiral double tube. Thus, a gap is formed as consistently as possible between the inner wall surface of the pipe 282A and the outer wall surface of the capillary tube 258. In this way, the double tube is wound in a plurality of stages to form a spiral double tube structure, so that a sufficient length of the capillary tube 258 is secured and the heat of the double tube structure is obtained. It is possible to reduce the size while sufficiently securing the replacement part.

  Next, cap-shaped connection pipes (not shown) having holes on both sides and laterally are attached to both ends of the pipe 282A, and the end portions of the capillary tubes 258 are respectively pulled out from the horizontal holes, and then Seal the hole by welding. Furthermore, one end of the connection pipe attached to one end of the pipe 282A and the connection portion of the pipe 282A are welded, and the suction pipe 282 connected to the discharge side of the evaporator 253 is connected to the other end of the connection pipe. This connection is welded. Similarly, one end of the connection pipe attached to the other end of the pipe 282A and the connection portion of the pipe 282A are welded, and the suction pipe 282 leading to the fourth intermediate heat exchanger 272 is connected to the other end of the connection pipe. And weld this connection. And the double pipe structure 295 of a present Example can be comprised by surrounding the outer periphery of the piping 282A made into the double pipe structure with the heat insulating material 297.

  In this way, the capillary tube 258 is inserted into the suction pipe 282 to form a double pipe structure, so that the refrigerant passing through the capillary tube 258 and the refrigerant passing through the suction pipe 282 are all of the capillary tube 258. Heat exchange is performed by heat conduction transmitted through the circumferential wall surface. Thereby, compared with the structure which attached the capillary tube to the outer peripheral surface of the conventional suction piping, it becomes possible to improve heat exchange performance markedly.

  Further, as described above, the entire outer periphery of the pipe 282A having the double-pipe structure is surrounded by the heat insulating material 297, so that it is difficult to be affected by heat from the outside, and the refrigerant in the pipe 282A and the refrigerant in the capillary tube 258 It becomes possible to further improve the heat exchange capacity. Furthermore, in the capillary tube 258 that is the inner side of the double-pipe structure and in the suction pipe 282 (pipe 282A) outside the capillary tube 258, the refrigerant is caused to flow in a counterflow, The heat exchange capacity in the double pipe structure 295 can be further improved.

  Similar to the double tube structure 25 of the first embodiment, the double tube structure 295 is accommodated in the heat insulating material 7 on the lower side of the back side of the inner box 4 so as to be put in and out.

  On the other hand, the suction pipe 282 exiting the double-pipe structure 295 includes a fourth intermediate heat exchanger 272, a third intermediate heat exchanger 270, a second intermediate heat exchanger 266, and a first intermediate heat exchange. After being connected to the compressor 262 one after another, it is connected to the suction side of the compressor 254. Between the compressor 254 and the first intermediate heat exchanger 262 of the suction refrigerant pipe 282, an expansion tank 288 that stores refrigerant when the compressor 254 is stopped is connected via a capillary tube 289 as a decompression device. ing. The capillary tube 289 is connected in parallel with a check valve 290 having the expansion tank 288 in the forward direction.

On the other hand, a non-azeotropic refrigerant mixture including R245fa, R600, R404A, R508, R14, R50, and R740 is enclosed in the low temperature side refrigerant circuit 252 as seven types of mixed refrigerants having different boiling points. R245fa is 1,1,1, -3,3-pentafluoropropane (CF ₃ CH ₂ CHF ₂ ), and R600 is butane (CH ₃ CH ₂ CH ₂ CH ₃ ). The boiling point of R245fa is + 15.3 ° C., and the boiling point of R600 is −0.5 ° C. Therefore, by mixing these at a predetermined ratio, it can be used as a substitute for R21 having a boiling point of + 8.9 ° C., which has been conventionally used.

  Since R600 is a flammable substance, it is mixed with the nonflammable R245fa at a predetermined ratio, in this embodiment, at a ratio of R245fa / R600: 70/30, so that it is sealed in the refrigerant circuit 38 as nonflammable. And In this embodiment, R245fa is set to 70% by weight based on the total weight of R245fa and R600, but if it is more than that, it becomes nonflammable, so it may be more than that.

R404A includes R125 (pentafluoroethane: CHF ₂ CF ₃ ), R143a (1,1,1-trifluoroethane: CH ₃ CF ₃ ), and R134a (1,1,1,2-tetrafluoroethane: CH ₂ FCF ₃ ), and the composition thereof is 44% by weight of R125, 52% by weight of R143a, and 4% by weight of R134a. The mixed refrigerant has a boiling point of −46.48 ° C. Therefore, it can be used as a substitute for R22 having a boiling point of −40.8 ° C. which has been conventionally used.

R508 is composed of R23 (trifluoromethane: CHF ₃ ) and R116 (hexafluoroethane: CF ₃ CF ₃ ), and the composition thereof is 39% by weight for R23 and 61% by weight for R116. The mixed refrigerant has a boiling point of −88.64 ° C.

R14 is tetrafluoromethane (carbon tetrafluoride: CF ₄ ), R50 is methane (CH ₄ ), and R740 is argon (Ar). As for these boiling points, R14 is −127.9 ° C., R50 is −161.5 ° C., and R740 is −185.86 ° C. Although R50 has a danger of causing an explosion when combined with oxygen, mixing with R14 eliminates the danger of an explosion. Therefore, even if a mixed refrigerant leakage accident occurs, no explosion occurs.

  These refrigerants as described above are once mixed with R245fa and R600 and R14 and R50 in advance to be incombustible state, then mixed with R245fa and R600, R404A, R508A, R14 and R50. The mixed refrigerant and R740 are mixed in advance and sealed in the refrigerant circuit 252. Alternatively, they are sealed in the order of R245fa and R600, then R404A, R5080A, R14 and R50, and finally R740 in descending order of boiling point. The composition of each refrigerant is, for example, 10.3% by weight of a mixed refrigerant of R245fa and R600, 28% by weight of R404A, 29.2% by weight of R508A, 26.4% by weight of a mixed refrigerant of R14 and R50, and R740. It shall be 5.1% by weight.

  In this embodiment, 4% by weight of n-pentane (in the range of 0.5 to 2% by weight with respect to the total weight of the non-azeotropic refrigerant) may be added to R404A.

  Next, the circulation of the refrigerant in the low temperature side refrigerant circuit 252 will be described. The high-temperature and high-pressure gaseous mixed refrigerant discharged from the compressor 254 flows into the radiator 259 via the refrigerant discharge pipe 281 and is radiated there, and the oil having a high boiling point in the mixed refrigerant and good oil compatibility. A part of n-pentane or R600 as a carrier refrigerant condenses.

  The mixed refrigerant that has passed through the radiator 259 flows into the oil separator 260, and most of the lubricating oil of the compressor 254 mixed with the refrigerant and part of the refrigerant condensed and liquefied by the radiator 259 (n-pentane). , A part of R600) is returned to the compressor 254 through the oil return pipe 287. Thereby, a low-boiling-point refrigerant with higher purity flows through the refrigerant circuit 252 subsequent to the cascade heat exchanger 216, and it is possible to efficiently obtain an ultra-low temperature. As a result, even in the case of the compressors 214 and 254 having the same capacity, the inside of the storage chamber 8 that is a cooling target having a larger volume can be cooled to a predetermined ultra-low temperature, and the entire refrigeration apparatus R is increased in size. It is possible to increase the storage capacity without doing so.

  Here, in the present embodiment, since the refrigerant flowing into the oil separator 260 is once cooled by the radiator 259, the temperature of the refrigerant entering the cascade heat exchanger 216 can be lowered. Specifically, in the present embodiment, it is possible to reduce the refrigerant temperature flowing into the cascade heat exchanger 216 from about + 65 ° C. to about + 45 ° C. in the present embodiment.

  Therefore, in the cascade heat exchanger 216, the load applied to the compressor 214 of the high temperature side refrigerant circuit 212 for cooling the refrigerant in the low temperature side refrigerant circuit 252 can be reduced. In addition, since the refrigerant in the low temperature side refrigerant circuit 252 can be effectively cooled, it is possible to reduce the load applied to the compressor 254 constituting the low temperature side refrigerant circuit 252. This makes it possible to improve the operation efficiency of the entire refrigeration apparatus R4.

  Other mixed refrigerants themselves are cooled to about −40 ° C. to −30 ° C. from the high-temperature side evaporator 213 by the cascade heat exchanger 216, and some of the refrigerants having high boiling points in the mixed refrigerant (R245fa, R600, R404A, R508). Part of the liquid). Then, the mixed refrigerant that has exited the condensation pipe 255 of the cascade heat exchanger 216 flows into the first gas-liquid separator 261 through the dryer 257. At this time, R14, R50, and R740 in the mixed refrigerant are not condensed yet because they have a very low boiling point, and are in a gas state, and only a part of R245fa, R600, R404A, and R508 is condensed and liquefied. , R50 and R740 are separated into the gas phase piping 283, and R245fa, R600, R404A and R508A are separated into the liquid phase piping 284.

  The refrigerant mixture flowing into the gas phase pipe 283 is condensed by exchanging heat with the first intermediate heat exchanger 262 and then reaching the second gas-liquid separator 265. Here, the low-temperature refrigerant returned from the evaporator (refrigerant pipe) 253 flows into the first intermediate heat exchanger 262, and the liquid refrigerant that has flowed into the liquid-phase pipe 284 passes through the dryer 263 and is then capillary tube. In order to contribute to cooling by flowing into the first intermediate heat exchanger 262 and evaporating there after being depressurized by H.264, cooling a part of uncondensed R14, R50, R740, and R508, The intermediate temperature of the first intermediate heat exchanger 262 is about −60 ° C. Accordingly, R508 in the mixed refrigerant that has passed through the gas-phase pipe 283 is completely condensed and liquefied, and is divided into the second gas-liquid separator 265. R14, R50, and R740 are still in a gas state because of their lower boiling points.

  In the second intermediate heat exchanger 266, R508 separated by the second gas-liquid separator 265 is dehydrated by the dryer 267 and decompressed by the capillary tube 268, and then the second intermediate heat exchanger 266. R14, R50, and R740 in the gas-phase pipe 285 are cooled together with the low-temperature refrigerant returned to the evaporator 253, and among them, R14 having the highest evaporation temperature is condensed. As a result, the intermediate temperature of the second intermediate heat exchanger 266 is about −90 ° C.

  The gas-phase pipe 285 passing through the second intermediate heat exchanger 226 passes through the fourth intermediate heat exchanger 272 via the third intermediate heat exchanger 270. Here, the refrigerant immediately returned from the evaporator 253 through the double pipe structure 295 is returned to the fourth intermediate heat exchanger 272, and according to an experiment, the intermediate temperature of the fourth intermediate heat exchanger 272 is It reaches a temperature as low as -130 ° C.

  Here, in the capillary tube 258, the refrigerant is heated by the heat passing through the suction pipe 282 (pipe 282 </ b> A) provided in the entire circumference of the capillary tube 258 and the wall surface of the entire circumference of the capillary tube 258. The pressure is reduced while the temperature is further lowered and flows into the evaporator 253. Then, in the evaporator 253, the refrigerant takes heat from the surroundings and evaporates. According to experiments, at this time, the temperature around the evaporator 253 became an extremely low temperature of −160.3 ° C. to −157.3 ° C.

  In this way, by using the difference in the evaporation temperature of each refrigerant in the low-temperature side refrigerant circuit 252, the refrigerant that is still in the gas phase is successively condensed in each intermediate heat exchanger 262, 266, 270, 272, and the final stage An extremely low temperature of −150 ° C. or lower can be achieved in the evaporator 253. Therefore, the said evaporator 253 is comprised by heat-exchanged along the heat insulating material 7 side of the inner box 4, and the inside of the storage chamber 8 can implement | achieve the internal temperature of -152 degrees C or less. It becomes possible.

  The refrigerant evaporated in the evaporator 253 then exits the evaporator 253 via the suction pipe 282, and the double pipe structure 295, the fourth intermediate heat exchanger 272, and the third intermediate heat exchanger described above. 270, the second intermediate heat exchanger 266, and the first intermediate heat exchanger 262 one after another, merge with the refrigerant evaporated in each heat exchanger, and return to the compressor 254.

  Most of the oil mixed and discharged from the compressor 254 is separated by the oil separator 260 and returned to the compressor 254. However, the oil is discharged from the oil separator 260 together with the refrigerant in the form of a mist. What has been removed is returned to the compressor 254 in a state of being dissolved in R600 having high compatibility with oil. Thereby, poor lubrication and locking of the compressor 254 can be prevented. Further, since R600 returns to the compressor 254 in a liquid state and is evaporated in the compressor 254, the discharge temperature of the compressor 254 can be reduced.

  The compressor 254 constituting the low temperature side refrigerant circuit 252 is ON / OFF controlled by a control device (not shown) based on the internal temperature in the storage chamber 8. In this case, when the operation of the compressor 254 is stopped by the control device, the mixed refrigerant in the low-temperature side refrigerant circuit 252 enters the expansion tank 288 via the check valve 290 whose forward direction is the expansion tank 288 direction. Collected.

  Therefore, when the compressor 254 is stopped, the refrigerant in the refrigerant circuit 252 is recirculated through the check valve 290 significantly more quickly than when the refrigerant is collected in the expansion tank 288 via the capillary tube 289. It can be recovered in 288.

  Thereby, it is possible to prevent the pressure in the refrigerant circuit 252 from rising, and when the compressor 254 is activated by the control device, the refrigerant circuit 252 gradually enters the refrigerant circuit 252 from the expansion tank 288 via the capillary tube 289. It is possible to reduce the starting load of the compressor 254 by returning the refrigerant to the initial position.

  Therefore, by quickly collecting the refrigerant into the expansion tank 288 when the compressor 254 is stopped, the pressure in the refrigerant circuit 252 can be quickly balanced, and when the compressor 254 is restarted, the compression is performed. The compressor 254 can be restarted smoothly without imposing a load on the machine 254. Thereby, the operating efficiency of the compressor 252 can be improved by significantly reducing the time required for the inside of the refrigerant circuit 252 to reach the equilibrium pressure when the compressor is started. For example, the time required for the pull-down operation is reduced. It is possible to improve convenience.

  As in the present invention described above in detail, by inserting the capillary tube 258 into the suction pipe 282 (pipe 282A) through which the refrigerant returning from the evaporator 253 to the compressor 254 passes, a double pipe structure is obtained. The heat exchange efficiency between the refrigerant in the pipe 282A and the refrigerant in the capillary tube 258 can be improved to improve performance. In particular, the capillary tube 258 is inserted into the pipe 282A of the suction pipe 282 immediately after exiting the evaporator 253 as in the present invention to form a double pipe structure, and heat is transferred by heat conduction that transmits the entire wall surface of the capillary tube 258. By being configured to be replaceable, the refrigerant having the lowest boiling point is efficiently cooled by the return refrigerant from the evaporator 253, and the performance can be significantly improved. Therefore, it is particularly effective in the ultra-low temperature storage 1 as in the present embodiment.

  Furthermore, the heat exchange efficiency can be further improved by surrounding the pipe 282A in which the capillary tube 258 is inserted into the double pipe structure with the heat insulating material 297. Furthermore, by making the flow of the refrigerant in the capillary tube 258 and the flow of the refrigerant passing through the suction pipe 282A outside the capillary tube 258 counterflow, it is possible to further improve the heat exchange capability. .

  In general, according to the present invention, it is possible to realize the ultra-low temperature storage 1 capable of efficiently cooling the interior of the storage chamber 8 to a desired ultra-low temperature. In particular, according to the present invention, energy saving of about 15% to 20% can be achieved as compared with a conventional refrigeration apparatus of similar use. Also, the temperature around the evaporator 253 can be made lower than before. Thereby, even if it is a case where it changes to the compressor with a smaller capacity than the conventional compressor, it becomes possible to ensure sufficient performance. Thereby, further reduction of power consumption and size reduction of an apparatus can be achieved.

  In the present embodiment, only the capillary tube 258 at the final stage of the low temperature side refrigerant circuit 252 has the double tube structure of the present invention. However, the present invention is not limited to this, and the capillary tube 218 of the high temperature side refrigerant circuit 212 similarly has a high temperature. The present invention is also effective when a double pipe structure is inserted through a part of the suction pipe 232 through which the refrigerant returning from the evaporator 213 of the side refrigerant circuit 212 returns to the compressor 214 passes. In this case, also in the high temperature side refrigerant circuit 212, the heat exchange capability between the refrigerant in the suction pipe 232 and the refrigerant in the capillary tube 218 can be improved. Thereby, the performance of the refrigeration apparatus R4 can be further improved.

  Further, in this embodiment, the refrigerant circuit constituting the refrigeration apparatus condenses the refrigerant discharged from the compressor 214 or 254, respectively, and then depressurizes and evaporates it in the evaporator 213 or 253 to exert a cooling action. The low-temperature side refrigerant circuit 252 includes a compressor 254, a condensing pipe 255, an evaporator 253, and the evaporator 253. A plurality of, specifically, four intermediate heat exchangers 262, 266, 270, 272, and a plurality, specifically, three capillary tubes 264, 268, connected in series so that the return refrigerant flows. 258, and a plurality of types of non-azeotropic refrigerant mixtures are enclosed, and the condensed refrigerant in the refrigerant that has passed through the condensation pipe 255 is joined to each intermediate heat exchanger via each capillary tube. Then, by cooling the non-condensed refrigerant in the refrigerant in each intermediate heat exchanger, the refrigerant having a lower boiling point is condensed sequentially, and the refrigerant having the lowest boiling point is evaporated through the final capillary tube 258 by the evaporator 253. In addition to exerting the cooling action, the evaporator 213 of the high temperature side refrigerant circuit 212 and the condensing pipe 255 of the low temperature side refrigerant circuit 252 constitute a cascade heat exchanger 216, and the evaporator 253 of the low temperature side refrigerant circuit 252 Although it is described as the obtained two-stage multi-stage refrigeration apparatus R4, the present invention is not limited to this and may be a multi-element multi-stage refrigeration apparatus. Further, the present invention is effective even if the gas-liquid separator and the intermediate heat exchanger are one binary single-stage refrigeration apparatus.

R Refrigeration equipment 1 Ultra-low temperature freezer 2 Heat insulation box 7 Heat insulation material 8 Storage room 9 Heat insulation door 12 Refrigerant circuit 13 Evaporator (evaporator)
14 Compressor
15 Condenser
16 Heat exchanger (cascade capacitor)
18 Capillary tube 21 Auxiliary condenser (pre-condenser)
22 Frame pipe 23 Condensation pipe 25 Double pipe structure 31 Refrigerant discharge pipe 32 Suction pipe 32A pipe (constitutes a part of the suction pipe)
35 Insulation

Claims (7)

In the refrigeration system that condenses the refrigerant discharged from the compressor, depressurizes with a capillary tube, evaporates with an evaporator, and exhibits a cooling action.
A refrigerating apparatus, wherein the capillary tube is inserted into a suction pipe through which a refrigerant returning from the evaporator to the compressor passes to form a double pipe structure. After the refrigerant discharged from the compressor is condensed, the high-pressure side refrigerant circuit and the low-temperature side refrigerant circuit, which constitute an independent refrigerant closed circuit that exhibits a cooling action by depressurizing with a capillary tube and evaporating with an evaporator, A refrigeration system comprising a cascade heat exchanger composed of the evaporator of the high temperature side refrigerant circuit and the condenser of the low temperature side refrigerant circuit, and exhibiting a final cooling action in the evaporator of the low temperature side refrigerant circuit ,
2. A refrigeration apparatus comprising a double-pipe structure in which a capillary tube of the low-temperature side refrigerant circuit is inserted into a suction pipe through which refrigerant returning from the evaporator of the low-temperature side refrigerant circuit passes to the compressor. A compressor, a condenser, an evaporator, a single or a plurality of intermediate heat exchangers connected so that a return refrigerant from the evaporator flows, and a plurality of capillary tubes, and a plurality of types of non-azeotropic mixing Refrigerant is sealed, condensed refrigerant in the refrigerant that has passed through the condenser is joined to the intermediate heat exchanger via the capillary tube, and by cooling the uncondensed refrigerant in the refrigerant in the intermediate heat exchanger, In a refrigeration apparatus that condenses a refrigerant having a lower boiling point and evaporates the refrigerant having the lowest boiling point in the evaporator via the capillary tube in the final stage to exert a cooling action.
A refrigeration apparatus comprising a double-pipe structure in which a capillary tube in the final stage is inserted into a suction pipe through which a refrigerant returning from the evaporator to the compressor passes. After the refrigerant discharged from the compressor is condensed, the high-pressure side refrigerant circuit and the low-temperature side refrigerant circuit, which constitute an independent refrigerant closed circuit that exhibits a cooling action by depressurizing with a capillary tube and evaporating with an evaporator, The low-temperature side refrigerant circuit includes the compressor, the condenser, the evaporator, the single or plural intermediate heat exchangers connected so that the return refrigerant from the evaporator flows, and the plural capillaries A plurality of types of non-azeotropic refrigerant mixture, and the condensed refrigerant in the refrigerant that has passed through the condenser is joined to the intermediate heat exchanger via the capillary tube, and the intermediate heat exchanger By cooling the uncondensed refrigerant in the refrigerant, the refrigerant having a lower boiling point is condensed, and the refrigerant having the lowest boiling point is evaporated in the evaporator via the capillary tube in the final stage, thereby exhibiting a cooling action. , The condenser and the cascade heat exchanger of the evaporator and the low temperature side refrigerant circuit of the high-temperature side refrigerant circuit is constituted, in the refrigeration system to exhibit ultimate cooling effect at the evaporator of the low temperature side refrigerant circuit,
A refrigeration having a double-pipe structure in which a capillary tube at the final stage of the low-temperature side refrigerant circuit is inserted into a suction pipe through which the refrigerant returning from the evaporator of the low-temperature side refrigerant circuit passes to the compressor. apparatus.   The double tube structure according to claim 2, wherein a capillary tube of the high temperature side refrigerant circuit is inserted into a suction pipe through which the refrigerant returning from the evaporator of the high temperature side refrigerant circuit passes to the compressor. The refrigeration apparatus according to claim 4.   The refrigerating apparatus according to any one of claims 1 to 5, wherein a suction pipe having a double-pipe structure through which the capillary tube is inserted is surrounded by a heat insulating material.   7. The refrigerant flow in the capillary tube and the refrigerant flow passing through the suction pipe outside the capillary tube are set as counterflows. Refrigeration equipment.

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