JP2006329503A - Internal heat exchanger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To positively maintain airtightness of the respective openings of high pressure side refrigerant piping and low pressure side refrigerant piping regarding an internal heat exchanger in which the high pressure side refrigerant piping of a refrigerant cooling circuit is mounted inside the low pressure side refrigerant piping. <P>SOLUTION: The internal heat exchanger comprises a first fastening member 144A inserting the high pressure side refrigerant piping 141 through inside and brazed with airtightness to the end of the low pressure side refrigerant piping 142 and the outer peripheral surface of the high pressure side refrigerant piping 141, and a second fastening member 144B provided divided from the first fastening member 144A to insert the high pressure side refrigerant piping 141 through inside and brazed with airtightness to the end of the high pressure side refrigerant piping 141 and the inner peripheral surface of a port pipe 141c disposed at the end. Brazing is therefore performed divided into the first fastening member 144A side and the second fastening member 144B side. As a result, the influence of mutual heating is prevented in brazing work, and a fastening failure at the respective openings of the high pressure side refrigerant piping 141 and low pressure side refrigerant piping 142 is eliminated to positively maintain airtightness. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is provided, for example, in a refrigerant cooling circuit that forms a refrigerant circulation path for cooling the interior of a heat-insulating housing, and performs internal heat exchange between the high-pressure side and the low-pressure side of the refrigerant circulation path. It relates to an exchanger.

  2. Description of the Related Art Conventionally, for example, a refrigerant cooling circuit for cooling the inside of a refrigerator of a heat insulating housing such as a vending machine, a refrigerator, a freezer showcase / refrigerated showcase, or a beverage dispenser is known. The refrigerant cooling circuit forms a refrigerant circulation path for circulating the refrigerant mainly through the compressor, the radiator, the throttle unit, and the evaporator. As the refrigerant circulating in the refrigerant cooling circuit, a refrigerant having little influence on the global environment is used. For example, carbon dioxide is used as a refrigerant in that it has nonflammability, safety, and non-corrosion properties, and has little influence on the ozone layer.

  In the refrigerant cooling circuit, between the radiator on the high pressure side from the outlet side of the compressor through the radiator to the inlet side of the throttle unit and the throttle unit, from the outlet side of the throttle unit to the inlet side of the compressor through the evaporator An internal heat exchanger is provided between the evaporator and the compressor on the low pressure side. This internal heat exchanger is arranged so that the high-pressure side refrigerant pipe and the low-pressure side refrigerant pipe flow in a non-contact counterflow with a distance allowing heat exchange with each other. Thereby, while the refrigerant | coolant obtained from a radiator becomes easy to liquefy, the refrigerant | coolant vaporized from the evaporator is supplied to a compressor (for example, refer patent document 1).

JP 2004-54424 A

  By the way, when carbon dioxide is used as the refrigerant in the refrigerant cooling circuit, the critical temperature of the carbon dioxide is as low as about 31 ° C., so that it is far more than when a conventional refrigerant (for example, HFC refrigerant (hydrofluorocarbon)) is used. Pressure increases. In the conventional refrigerant cooling circuit described above, the internal heat exchanger is simply provided at a distance that allows heat exchange between the high-pressure side refrigerant pipe and the low-pressure side refrigerant pipe. For this reason, the heat exchange efficiency in an internal heat exchanger is bad, and there exists a problem that the carbon dioxide which passed the evaporator is supplied to a compressor with a part liquefied.

  Further, if the heat exchange efficiency of the internal heat exchanger is poor at an ambient temperature of 27 ° C. or higher, the temperature of the radiator may exceed the critical temperature of carbon dioxide (about 31 ° C.). In this case, it becomes a supercritical pressure state in which carbon dioxide does not liquefy while being vaporized in the radiator. If the carbon dioxide is partially vaporized, the pressure increase on the high pressure side cannot be suppressed.

  Further, in the compressor, it is difficult to completely seal the refrigerating machine oil therein, and the refrigerating machine oil is discharged from the compressor during the circulation operation of the refrigerant circulation path. If the heat exchange efficiency of the internal heat exchanger is poor, it is difficult to circulate the refrigeration oil discharged from the compressor through the refrigerant circulation path and return it to the compressor.

  Therefore, an internal heat exchanger that performs heat exchange between the low-pressure side refrigerant pipe and the high-pressure side refrigerant pipe as a double-pipe structure that is built inside the low-pressure side refrigerant pipe that is a large-sized high-pressure side refrigerant pipe. Can be considered. In this case, between the both ends of the low-pressure refrigerant pipe that is a large pipe and the outer surface of the high-pressure refrigerant pipe that is a narrow pipe, or both ends of the high-pressure refrigerant pipe that is a thin pipe and the inner surface of the mouth pipe provided at the both ends If a brazing failure occurs between the two, the airtightness is insufficient and refrigerant leakage occurs. For this reason, it is desirable to reliably maintain the airtightness in the above-mentioned part.

  In view of the above circumstances, the present invention relates to an internal heat exchanger having a double-pipe structure in which a high-pressure side refrigerant pipe of a refrigerant cooling circuit is housed inside a low-pressure side refrigerant pipe. It aims at providing the internal heat exchanger which can maintain the airtightness in each mouth reliably.

  In order to achieve the above object, an internal heat exchanger according to claim 1 of the present invention includes a compressor that compresses a refrigerant, a radiator that dissipates the refrigerant supplied from the compressor, and the radiator. Provided in a refrigerant cooling circuit that forms a refrigerant circulation path having a throttle part for adjusting the flow rate of the supplied refrigerant and an evaporator for evaporating the refrigerant supplied from the throttle part and returning it to the compressor; In the internal heat exchanger for exchanging heat between the high-pressure side and the low-pressure side of the refrigerant circulation path, a high-pressure side refrigerant pipe is built inside the low-pressure side refrigerant pipe, and the high-pressure side refrigerant pipe is inserted through A first fixing member fixed in an airtight manner to an end portion of the low-pressure side refrigerant pipe and an outer peripheral surface of the high-pressure side refrigerant pipe; and the high-pressure side refrigerant pipe provided separately from the first fixing member Through the end of the high-pressure side refrigerant pipe and the end Characterized in that a second fixing member which is fixed to the inner peripheral surface of the placed mouth tube having airtightness.

  An internal heat exchanger according to a second aspect of the present invention is characterized in that, in the first aspect, the first fixing member and the second fixing member are separated from each other to expose an outer peripheral surface of the high-pressure side refrigerant pipe. And

  According to a third aspect of the present invention, the internal heat exchanger according to the first or second aspect, wherein a plurality of the high-pressure side refrigerant pipes are housed inside the low-pressure side refrigerant pipe, and the first fixing member and the first The two fixing members are fixed to each of the high-pressure side refrigerant pipes, the low-pressure side refrigerant pipes, and the mouth pipes so as to be airtight.

  The internal heat exchanger according to claim 4 of the present invention is characterized in that, in any one of claims 1 to 3, the refrigerant is carbon dioxide.

  In the internal heat exchanger according to the present invention, the high-pressure side refrigerant pipe is internally provided in the low-pressure side refrigerant pipe, and the end of the low-pressure side refrigerant pipe and the outer peripheral surface of the high-pressure side refrigerant pipe are inserted through the high-pressure side refrigerant pipe. A first fixing member fixed in an airtight manner and a first fixing member which is provided separately from the first fixing member and is inserted into the end portion of the high-pressure side refrigerant pipe through the high-pressure side refrigerant pipe and the port disposed at the end portion And a second fixing member fixed to the inner peripheral surface of the tube with airtightness. For this reason, the first fixing member side and the second fixing member side are separately fixed. As a result, it is possible to prevent the influence of mutual heating in the fixing operation, so that the fixing failure does not occur at the mouths of the high-pressure side refrigerant pipe and the low-pressure side refrigerant pipe, and the airtightness can be reliably maintained. .

  By separating the first fixing member and the second fixing member and exposing the outer peripheral surface of the high pressure side refrigerant pipe, the first fixing member is fixed to the portion exposed from the end of the low pressure side refrigerant pipe, About 2 adhering members, the site | part exposed from the opening edge part of the mouth tube is adhering. As a result, since the work can be performed while visually checking the fixed part in the fixing work, the fixing work can be easily and reliably performed.

  Exemplary embodiments of an internal heat exchanger according to the present invention will be described below in detail with reference to the accompanying drawings. Note that the present invention is not limited to the embodiments.

  FIG. 1 is a schematic view showing an embodiment of a refrigerant cooling circuit to which an internal heat exchanger according to the present invention is applied. 1 mainly includes a compressor 1, a gas cooler (heat radiator) 2, an electronic expansion valve (throttle portion) 3, and an evaporator 4 to connect a refrigerant circulation path through which refrigerant can be circulated. Formed. In the present embodiment, for example, carbon dioxide is used as the refrigerant. Carbon dioxide is a refrigerant that has non-flammability, safety, and non-corrosion properties, and has little influence on the ozone layer.

  The compressor 1 compresses the carbon dioxide returned from the evaporator 4 to bring it into a high temperature and high pressure state. In this embodiment, the compressor 1 performs a two-stage compression operation via the intermediate heat exchanger 10. Specifically, the compressor 1 includes a first compressor 1a that performs a first-stage compression operation and a second compressor 1b that performs a second-stage compression operation in a two-stage compression operation. . And the intermediate heat exchanger 10 is provided between the 1st compressor 1a and the 2nd compressor 1b. After the first stage compression operation by the first compressor 1a, the intermediate heat exchanger 10 cools the carbon dioxide compressed by the first compressor 1a and returns it to the second compressor 1b. In this way, the compressor 1 performs a two-stage compression operation via the intermediate heat exchanger 10, thereby obtaining high compression efficiency with low power consumption and compressing carbon dioxide to a desired high temperature and high pressure state. It becomes possible to do. In this embodiment, carbon dioxide is compressed to about 6 MPa by the first stage compression in the first compressor 1a, and carbon dioxide is compressed to about 9 MPa by the second stage compression in the second compressor 1b. .

  An oil separator 11 is connected to the compressor 1. The oil separator 11 is for returning the refrigeration oil discharged from the compressor 1 to the compressor 1. The refrigerating machine oil prevents friction and refrigerant leakage in the compressor 1, but it is difficult to completely seal the refrigerating machine oil inside the compressor 1. In particular, the compressor 1 compresses carbon dioxide to a high pressure as described above, and this pressure is much higher than when a conventional refrigerant (for example, HFC refrigerant (hydrofluorocarbon)) is used. The amount of refrigeration oil discharged from the machine 1 increases. Therefore, in the present embodiment, in the compressor 1, the oil separator 11 is connected between the outlet side of the second compressor 1b and the inlet side of the first compressor 1a, and discharged from the second compressor 1b. The refrigerating machine oil thus returned is returned to the first compressor 1a.

  The compressor 1 includes a reciprocating compressor, a rotary compressor, a scroll compressor, or an inverter compressor that can adjust the compression capacity thereof. And what is necessary is just to apply suitably the compressor corresponding to the object which arrange | positions a refrigerant | coolant cooling circuit, an environment, or the cost of a refrigerant | coolant cooling circuit.

  The gas cooler 2 is for liquefying carbon dioxide by releasing heat from high-temperature and high-pressure carbon dioxide supplied from the compressor 1. The gas cooler 2 in the present embodiment uses a fin tube type composed of, for example, a copper tube and an aluminum fin. The gas cooler 2 is provided with a fan 21. The fan 21 is for blowing the gas cooler 2 and is driven by a fan motor 22.

  The electronic expansion valve 3 is for reducing the pressure of carbon dioxide supplied from the gas cooler 2 and controlling the evaporation temperature and flow rate.

  The evaporator 4 is for cooling the ambient temperature by absorbing ambient heat when the liquid carbon dioxide supplied from the electronic expansion valve 3 evaporates. The evaporator 4 in the present embodiment uses a fin tube type composed of, for example, a copper tube and an aluminum fin. The evaporator 4 is provided with a fan 41. The fan 41 is for blowing the evaporator 4 and is driven by a fan motor 42.

  The evaporator 4 is arrange | positioned inside the refrigerator of the heat insulation housing | casing in a vending machine, a refrigerator, a freezer showcase, a refrigerated showcase, or a drink dispenser etc., for example. In particular, in this embodiment, for example, in an automatic vending machine, in order to cool a plurality of (three rooms in the embodiment) refrigerators (product storage units) independently, the evaporators 4 (4a, 4a, 4b, 4c) are arranged respectively. That is, the evaporators 4a, 4b, and 4c are connected to respective paths branched from the electronic expansion valve 3 in three directions. Further, electromagnetic valves 12a, 12b, and 12c are provided on the inlet sides of the evaporators 4a, 4b, and 4c in the respective paths. And carbon dioxide from the electronic expansion valve 3 is supplied to each evaporator 4a, 4b, 4c by selectively open | releasing each solenoid valve 12a, 12b, 12c. Further, the outlet-side paths of the evaporators 4a, 4b, and 4c are gathered together and connected to the first compressor 1a of the compressor 1. The solenoid valves 12a, 12b, and 12c in the present embodiment are configured so that the valve body is seated by utilizing a pressure difference between the inlet side and the outlet side (for example, the inlet side is high pressure and the output side is low pressure) and spring elastic force. A configuration is adopted in which the valve body is separated from the valve seat and opened when the electromagnetic coil portion is energized from this state.

  The decompression means 13a is connected to each of the evaporators 4a, 4b, and 4c from the electronic expansion valve 3 and between each of the solenoid valves 12a, 12b, and 12c and each of the evaporators 4a, 4b, and 4c. , 13b, 13c are provided. The decompression means 13a, 13b, and 13c act as throttles that provide pressure resistance in the path between the electromagnetic valves 12a, 12b, and 12c and the evaporators 4a, 4b, and 4c. The decompression means 13a, 13b, and 13c in the present embodiment are formed as orifices provided in the respective paths. The decompression means 13a, 13b, and 13c are not limited to orifices as long as they function as a throttle that provides pressure resistance in the path.

  For example, in the carbon dioxide circulation operation, when only the solenoid valve 12a is opened, the evaporators 4b and 4c provided in the path having the solenoid valves 12b and 12c in the closed state perform the circulation operation. The evaporator 4a and the outlet side of the refrigerant circulation path are gathered. For this reason, the pressure difference between the inlet side and the outlet side of the electromagnetic valves 12b and 12c in the closed state is substantially equal. At this time, since the decompression means 13a, 13b, and 13c are provided, in the path having the closed electromagnetic valves 12b and 12c, the decompression means 13b and 13c act as a throttle that provides pressure resistance in the path, The outlet side of the solenoid valves 12b and 12c in the closed state becomes low pressure, and the inlet side becomes high pressure. Accordingly, a pressure difference is generated between the inlet side and the outlet side of the electromagnetic valves 12b and 12c in the closed state, and the closed state of the electromagnetic valves 12b and 12c is assisted by the pressure difference between the inlet side and the outlet side. The closed state of the electromagnetic valves 12b and 12c is maintained.

  Further, with respect to the evaporator 4 provided inside the cooler of the heat insulating housing, dew condensation water or the like is generated as drainage during the refrigerant circulation operation to the refrigerant circulation path. Then, the waste water is led to the evaporation means 15 located outside the cooler and provided with the compressor 1, the gas cooler 2, and the like. The evaporation means 15 is provided between the compressor 1 (second compressor 1 b) and the gas cooler 2 and in a path between the outlet side of the oil separator 11 and the inlet side of the gas cooler 2. Although not clearly shown in the figure, the evaporating means 15 includes an evaporating dish into which drainage is guided, an evaporating pipe disposed inside the evaporating dish, and a water-absorbing evaporating sheet that contacts the evaporating pipe. . The evaporation pipe is connected to a path between the outlet side of the oil separator 11 and the inlet side of the gas cooler 2, and high-temperature and high-pressure carbon dioxide discharged from the compressor 1 passes therethrough. That is, the waste water led to the evaporating dish is absorbed by the evaporating sheet and is heated and evaporated by the evaporating pipe through which the high-temperature and high-pressure carbon dioxide passes. At this time, carbon dioxide passing through the evaporation pipe is pre-cooled by drainage.

  By the way, when carbon dioxide is used as a refrigerant, the temperature of the gas cooler 2 may exceed the critical temperature of carbon dioxide (about 31 ° C.) in summer when the outside air temperature becomes high. In this case, the gas cooler 2 is in a supercritical pressure state in which carbon dioxide is not vaporized while being vaporized. On the other hand, it is desirable that all the carbon dioxide that has passed through the evaporator 4 is vaporized. If the carbon dioxide that has passed through the evaporator 4 is supplied to the compressor 1 while being partially liquefied, the compressor 1 may cause liquid compression and damage the cylinder.

  Therefore, an internal heat exchanger 14 is provided between the gas cooler 2 and the electronic expansion valve 3 and between the evaporator 4 and the compressor 1 (first compressor 1a). 2 is a perspective view showing an internal heat exchanger, FIG. 3 is a cross-sectional view showing the internal heat exchanger, FIG. 4 is a perspective view showing a high-pressure side refrigerant pipe of the internal heat exchanger, and FIG. 5 is a cross-section of the internal heat exchanger. FIG.

  The internal heat exchanger 14 is for exchanging heat between the high pressure side and the low pressure side of the refrigerant circulation path. The high pressure side of the refrigerant circulation path is from the outlet side (after compression) of the compressor 1 through the gas cooler 2 to the inlet side of the electronic expansion valve 3. The low pressure side of the refrigerant circulation path is from the outlet side of the electronic expansion valve 3 to the inlet side (before compression) of the compressor 1 through the evaporator 4. As described above, when the compressor 1 includes the first compressor 1a and the second compressor 1b and performs a two-stage compression operation, the high-pressure side of the refrigerant circulation path refers to the second compressor 1b. From the outlet side (after compression) to the inlet side of the electronic expansion valve 3 through the gas cooler 2, the low pressure side of the refrigerant circulation path is the second compression from the outlet side of the electronic expansion valve 3 through the evaporator 4 Up to the inlet side (before compression) of the machine 1b. That is, the low pressure side of the refrigerant circulation path is between the first compressor 1a and the second compressor 1b, and reaches the second compressor 1b from the first compressor 1a via the intermediate heat exchanger 10 to the middle. Including the path that becomes pressure.

  As shown in FIGS. 2 to 5, the internal heat exchanger 14 is provided with a high-pressure side refrigerant pipe 141 between the high-pressure side gas cooler 2 and the electronic expansion valve 3. The internal heat exchanger 14 is provided with a low-pressure side refrigerant pipe 142 between the evaporator 4 on the low-pressure side and the compressor 1 (first compressor 1a). The high-pressure side refrigerant pipe 141 forms a capillary tube as a resistance pipe, and is housed inside the low-pressure side refrigerant pipe 142. In addition, a plurality of (three in this embodiment) high-pressure side refrigerant pipes 141 are provided inside the low-pressure side refrigerant pipe 142. Thus, the internal heat exchanger 14 has a double-pipe structure in which the high-pressure side refrigerant pipe 141 is housed inside the low-pressure side refrigerant pipe 142.

  In addition, the internal heat exchanger 14 is formed in a spiral shape in the vertical direction in a form in which a plurality of high-pressure refrigerant pipes 141 are housed inside the low-pressure refrigerant pipe 142 as described above. Specifically, as shown in FIG. 2 to FIG. 4, the high-pressure side refrigerant pipe 141 is provided with an inlet portion 141 a of the high-pressure side refrigerant pipe 141 at a spiral lower end portion, and a high-pressure side refrigerant at the spiral upper end portion. An outlet 141b of the pipe 141 is provided. The inlet portion 141a and the outlet portion 141b form a single mouth tube that converges a plurality of resistance pipes of the high-pressure side refrigerant pipe 141. On the other hand, as shown in FIGS. 2 to 4, the low-pressure side refrigerant pipe 142 is provided so as to cover the resistance pipe of the high-pressure side refrigerant pipe 141, and the outlet portion from the rear stage of the inlet portion 141 a of the high-pressure side refrigerant pipe 141. It reaches the former stage of 141b and is formed in a spiral shape. This low-pressure side refrigerant pipe 142 is provided with an inlet 142a at a spiral upper end and an outlet 142b at a spiral lower end. As described above, the internal heat exchanger 14 is provided in such a manner that the high-pressure side refrigerant pipe 141 sends the refrigerant from below to above, and the low-pressure side refrigerant pipe 142 is provided in a form that sends the refrigerant from above to below. Thus, a counter flow is generated in the refrigerant on the high pressure side and the low pressure side. Thereby, the carbon dioxide obtained from the gas cooler 2 becomes easy to liquefy. On the other hand, the carbon dioxide vaporized from the evaporator 4 is supplied to the compressor 1. Moreover, the internal heat exchanger 14 is reducing the installation volume by making it spiral. Note that the heat exchange amount can be freely set by changing the lengths of the high-pressure side refrigerant pipe 141 and the low-pressure side refrigerant pipe 142.

  As shown in FIG. 3, the high-pressure side refrigerant pipe 141 is provided in such a manner that the outer peripheral walls of the respective resistance pipes are in a non-contact form, and the outer peripheral wall of each of the resistance pipes forming the high-pressure side refrigerant pipe 141. It is desirable in terms of mutual heat exchange that the low pressure side refrigerant pipe 142 is provided in a form that is not in contact with the inner peripheral wall. Further, a flexible tube-shaped heat insulating material 143 is provided on the outer periphery of the low-pressure side refrigerant pipe 142 so that heat exchange between the low-pressure side and the high-pressure side is not affected by outside air. It is.

  As shown in FIGS. 4 and 5, a first fixing member 144A and a second fixing member 144B are provided at the respective ends of the high-pressure side refrigerant pipe 141 and the low-pressure side refrigerant pipe 142 to prevent leakage of carbon dioxide.

  As shown in FIG. 5, the first fixing member 144 </ b> A has an insertion hole 144 </ b> Aa through which each high-pressure side refrigerant pipe 141 is inserted, and is formed in a columnar shape so as to be inserted into the end of the low-pressure side refrigerant pipe 142. . Here, the end of the low-pressure refrigerant pipe 142 is one open end of the trifurcated branch pipe 142c that forms the inlet 142a (or outlet 142b) of the low-pressure refrigerant pipe 142. The branch pipe 142c has an inlet part 142a (or an outlet part 142b) on the side part of the main pipe that opens in opposite directions. The branch pipe 142c is inserted into the main pipe through the high-pressure refrigerant pipe 141, one open end of the main pipe is connected to the low-pressure refrigerant pipe 142, and the high-pressure refrigerant pipe 141 is extended from the other open end. It is out. The other opening end is the end of the low-pressure side refrigerant pipe 142. 144 A of 1st adhering members are inserted in the edge part of the low voltage | pressure side refrigerant | coolant piping 142 in the form which penetrated several high pressure side refrigerant | coolant piping 141 in insertion hole 144Aa. The first fixing member 144A is brazed from a portion exposed from the end portion of the low-pressure side refrigerant pipe 142, so that the end portion of the low-pressure side refrigerant pipe 142 and the outer peripheral surface of each high-pressure side refrigerant pipe 141 are hermetically sealed. It has a property and is fixed.

  As shown in FIG. 5, the second fixing member 144 </ b> B has an insertion hole 144 </ b> Ba through which each high-pressure side refrigerant pipe 141 is inserted, and is inserted into the mouth pipe 141 c disposed at the end of the high-pressure side refrigerant pipe 141. It is formed in a column shape. Here, the mouth tube 141c is a cylindrical tube that forms the outlet portion 141b (or the inlet portion 142a) of the high-pressure side refrigerant pipe 141, and converges the end ports of the plurality of high-pressure side refrigerant pipes 141 into one mouth. Is. The mouth tube 141c converges the end ports of the plurality of high-pressure refrigerant pipes 141 at one opening end portion, and the other opening end portion forms an outlet portion 141b (or an inlet portion 142a) of the high-pressure side refrigerant piping 141. . The second fixing member 144B is provided separately from the first fixing member 144A, and is inserted into one opening end of the mouth tube 141c in a form in which a plurality of high-pressure refrigerant pipes 141 are inserted into the insertion hole 144Ba. is there. And the 2nd adhering member 144B is brazed from the part exposed from one opening end part of the mouth pipe 141c, and the inside of the mouth pipe arranged at the end of each high-pressure side refrigerant pipe 141 and the end It is fixed to the peripheral surface with airtightness.

  Further, as shown in FIG. 5, the first fixing member 144A and the second fixing member 144B are spaced apart from each other, and the outer peripheral surface of the high-pressure side refrigerant pipe 141 is exposed.

  Hereinafter, the operation of the refrigerant cooling circuit of the present invention using carbon dioxide as the refrigerant will be described. First, the carbon dioxide returned from the evaporators 4a, 4b, and 4c in the refrigerator is sucked into the first compressor 1a through the internal heat exchanger 14 and compressed at a low pressure (compressed to about 6 MPa). The carbon dioxide discharged from the first compressor 1a is cooled through the intermediate heat exchanger 10, and then sucked into the second compressor 1b and compressed at a high pressure (compressed to about 9 MPa). At this time, the refrigerating machine oil discharged together with carbon dioxide from the second compressor 1b is returned to the inlet side of the first compressor 1a by the oil separator 11.

  Next, the carbon dioxide discharged from the second compressor 1 b is pre-cooled by the evaporation means 15 and sent to the gas cooler 2. The carbon dioxide sent to the gas cooler 2 is radiated and liquefied, and reaches the electronic expansion valve 3 via the internal heat exchanger 14.

  Next, in the electronic expansion valve 3, the carbon dioxide is depressurized and the evaporation temperature and flow rate are controlled. Thereafter, carbon dioxide reaches the evaporators 4a, 4b, 4c via the pressure reducing means 13a, 13b, 13c through the electromagnetic valves 12a, 12b, 12c which are selectively opened.

  Finally, the carbon dioxide supplied to the evaporators 4a, 4b, 4c absorbs heat and is vaporized as heated steam. The inside of the refrigerator provided with the evaporators 4a, 4b, 4c is cooled by the absorption of carbon dioxide. The carbon dioxide is sucked into the first compressor 1a from the evaporators 4a, 4b, and 4c via the internal heat exchanger 14 and returned to be circulated.

  In the carbon dioxide circulation operation, the internal heat exchanger 14 performs heat exchange between the high-pressure side refrigerant pipe 141 and the low-pressure side refrigerant pipe 142. As described above, the internal heat exchanger 14 includes the high-pressure refrigerant pipe 141 that forms a resistance pipe inside the low-pressure refrigerant pipe 142. For this reason, since a mutual heat exchange area can be taken large, heat exchange efficiency improves. Further, by installing a plurality of high-pressure refrigerant pipes 141 inside the low-pressure refrigerant pipe 142, the heat exchange area can be further increased, so that the heat exchange efficiency is further improved. In addition, since the low-pressure side refrigerant pipe 142 is covered with the heat insulating material 143, the influence of outside air at the time of heat exchange, that is, heat exchange with the outside is suppressed, so that the heat exchange efficiency is further improved. As described above, since the heat exchange efficiency is improved, carbon dioxide is easily liquefied in the gas cooler 2, so that it is possible to suppress an increase in pressure on the high pressure side. Further, since the heat exchange efficiency is improved, carbon dioxide is vaporized in the evaporator 4, so that it is possible to prevent the carbon dioxide from being supplied to the compressor 1 while being partially liquefied. Furthermore, by improving the heat exchange efficiency, the refrigeration oil discharged from the compressor 1 is easily circulated through the refrigerant circulation path and returned to the compressor 1. In particular, the internal heat exchanger 14 is provided in such a form that the low-pressure side refrigerant pipe 142 sends the refrigerant from above to below, and the high-pressure side refrigerant pipe 141 sends the refrigerant from below to above. For this reason, it becomes possible to improve the return of the refrigeration oil to the compressor 1 on the low pressure side.

  Also, the internal heat exchanger 14 cools the refrigerant temperature at the high-pressure side outlet to a predetermined temperature (for example, 18 ° C.) or less to prevent the high-pressure side pressure from exceeding the specification limit. Specifically, as described above, when the number of the coolers of the heat insulating casing is three, the circulation operation of all three chambers in each refrigerant circulation path can be considered. Here, the high-pressure side pressure of the internal heat exchanger 14 when all three chambers are circulated is 10 MPa (reference pressure), and the high-pressure side pressure of the specification limit in the refrigerant cooling circuit in this embodiment is 12 MPa. To do. In this case, at the time of circulation operation of only one chamber where the high pressure side pressure is the highest, the refrigerant temperature at the high pressure side outlet of the internal heat exchanger 14 for the high pressure side pressure not exceeding the specification limit is 18 ° C. or less. That is, if the refrigerant temperature at the high-pressure side outlet is cooled to 18 ° C. or less by the internal heat exchanger 14, the high-pressure side pressure does not exceed the specification limit. As described above, in the internal heat exchanger 14, in the refrigerant cooling circuit in which a plurality of refrigerant circulation paths are formed using carbon dioxide refrigerant, for example, when the refrigerant is circulated through one evaporator 4a, the refrigerant is circulated. Although surplus occurs, the liquid refrigerant is vaporized and returned to the compressor 1 by heat exchange between the low pressure side and the high pressure side by the low pressure side refrigerant pipe 142 and the high pressure side refrigerant pipe 141. As a result, liquid compression in the compressor 1 can be prevented and damage to the compressor 1 can be prevented. Moreover, since the high pressure side is cooled at the same time, the refrigerant density increases and the high pressure side pressure can be lowered.

  The internal heat exchanger 14 described above has a double-pipe structure in which the high-pressure side refrigerant pipe 141 is housed inside the low-pressure side refrigerant pipe 142, and the end of the low-pressure side refrigerant pipe 142 is inserted through the high-pressure side refrigerant pipe 141. And the first fixing member 144A brazed to the outer peripheral surface of the high-pressure side refrigerant pipe 141 and the first fixing member 144A. The first fixing member 144A is provided separately from the high-pressure side refrigerant pipe 141. A second fixing member 144B brazed with airtightness is provided between the end of the refrigerant pipe 141 and the inner peripheral surface of the mouth tube 141c disposed at the end. For this reason, the first fixing member 144A side and the second fixing member 144B side are separately fixed. As a result, the influence of mutual heating can be prevented in the brazing operation, so that no brazing failure occurs at the respective ends of the high-pressure side refrigerant pipe 141 and the low-pressure side refrigerant pipe 142, and the end of the low-pressure side refrigerant pipe 142. The airtightness between the gas pipe and the outer peripheral surface of the high-pressure side refrigerant pipe 141 and between the end of the high-pressure side refrigerant pipe 141 and the inner peripheral surface of the mouth tube 141c disposed at the end can be reliably maintained. It becomes possible.

  Furthermore, the first fixing member 144A and the second fixing member 144B are arranged separately from each other, and the outer peripheral surface of the high-pressure side refrigerant pipe 141 is exposed. For this reason, the part exposed from the end of the low-pressure refrigerant pipe 142 is brazed for the first fixing member 144A, and the part exposed from one opening end of the mouth pipe 141c is used for the second fixing member 144B. Braze. As a result, in each of the brazing operations, the operation can be performed while visually observing each brazed part, so that the brazing operation can be performed easily and reliably.

  Here, for example, when the first fixing member 144A and the second fixing member 144B are integrally formed as the fixing member 144 as shown in FIG. 6, the parts to be brazed are both ends of the fixing member 144 and the high-pressure side. There are a portion with the refrigerant pipe 141, a portion with the outer peripheral surface of the fixing member 144 and the branch pipe 142c and the mouth pipe 141c. In this case, the both ends of the fixing member 144 and the portion of the high-pressure side refrigerant pipe 141 are brazed, and the outer peripheral surface of the fixing member 144 and the portions of the branch pipe 142c and the mouth pipe 141c are brazed. Thus, if each part is brazed individually, it will receive to the influence of the heating of the part brazed later with respect to the part brazed previously, and there exists a possibility that a brazing defect may arise. In addition, it is difficult to confirm whether or not there is a brazing defect because the portions of both ends of the fixing member 144 and the high-pressure side refrigerant pipe 141 cannot be visually observed after all the brazing is finished. On the other hand, the internal heat exchanger 14 of the present embodiment can prevent the influence of mutual heating in the brazing operation as described above by the above-described configuration, and further perform the operation while visually observing the brazed part. Can do.

It is the schematic which shows one Example of the refrigerant cooling circuit to which the internal heat exchanger which concerns on this invention is applied. It is a perspective view which shows an internal heat exchanger. It is sectional drawing which shows an internal heat exchanger. It is a perspective view which shows the high voltage | pressure side refrigerant | coolant piping of an internal heat exchanger. It is sectional drawing which shows a fixing member. It is sectional drawing which shows the conventional fixing member.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Compressor 1a 1st compressor 1b 2nd compressor 2 Gas cooler (heat radiator)
21 Fan 22 Fan motor 3 Electronic expansion valve (throttle part)
4 (4a, 4b, 4c) Evaporator 41 Fan 42 Fan motor 10 Intermediate heat exchanger 11 Oil separator 12a, 12b, 12c Solenoid valve 13a, 13b, 13c Pressure reducing means 14 Internal heat exchanger 141 High-pressure side refrigerant piping 141a Inlet part 141b outlet part 141c port pipe 142 low-pressure side refrigerant pipe 142a inlet part 142b outlet part 142c branch pipe 143 heat insulating material 144A first fixing member 144Aa insertion hole 144B second fixing member 144Ba insertion hole 15 evaporation means

Claims (4)

A compressor that compresses the refrigerant; a radiator that dissipates the refrigerant supplied from the compressor; a throttle that adjusts a flow rate of the refrigerant supplied from the radiator; and a refrigerant supplied from the throttle In an internal heat exchanger that is provided in a refrigerant cooling circuit that forms a refrigerant circulation path having an evaporator that is fed back to the compressor and performs heat exchange between a high-pressure side and a low-pressure side of the refrigerant circulation path ,
The high-pressure side refrigerant piping is built inside the low-pressure side refrigerant piping,
A first fixing member that is inserted through the high-pressure side refrigerant pipe and has airtightness and fixed to an end portion of the low-pressure side refrigerant pipe and an outer peripheral surface of the high-pressure side refrigerant pipe;
It is provided separately from the first fixing member, and has an airtightness in an end portion of the high-pressure side refrigerant pipe passing through the high-pressure side refrigerant pipe and an inner peripheral surface of the mouth pipe disposed at the end portion. An internal heat exchanger comprising: a fixed second fixing member.   2. The internal heat exchanger according to claim 1, wherein an outer peripheral surface of the high-pressure side refrigerant pipe is exposed by separating the first fixing member and the second fixing member.   A plurality of the high-pressure side refrigerant pipes are built in the low-pressure side refrigerant pipe, and the first fixing member and the second fixing member are related to the high-pressure side refrigerant pipe, the low-pressure side refrigerant pipe, and the mouth pipe. The internal heat exchanger according to claim 1 or 2, wherein the internal heat exchanger is fixed with airtightness.   The internal heat exchanger according to any one of claims 1 to 3, wherein the refrigerant is carbon dioxide.

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