JP2005337700A - Refrigerant cooling circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve heat exchanging efficiency in an internal heat exchanger, to inhibit pressure rise on a high pressure side, to promote liquefaction of a refrigerant passing through an evaporator, and to improve the returning of refrigerant oil to a compressor. <P>SOLUTION: A plurality of high pressure-side refrigerant pipes 14A constituting a resisting pipe conduit are mounted inside of a low pressure-side refrigerant pipe 14B, and the low pressure-side refrigerant pipe 14B is covered by a heat insulating material 14C. Thus a heat exchanging area of the high pressure-side refrigerant pipes 14A and the low pressure-side refrigerant pipe 14B can be largely taken, and further the heat exchanging efficiency can be improved as it is hardly affected by the outside air. The refrigerant can be easily liquefied by a gas cooler by improving the heat exchanging efficiency, thus the pressure rise at high pressure side can be inhibited, and the refrigerant oil can be easily returned to the compressor. Further as the high pressure-side refrigerant pipes 14A and the low pressure-side refrigerant pipe 14B are spirally formed in the vertical direction, the refrigerant is delivered from an upper part to a lower part by the low pressure-side refrigerant pipe 14B, and the refrigerant is delivered from the lower part to the upper part by the high pressure-side refrigerant pipe 14A, and the delivery of the refrigerant oil to the compressor can be improved. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a refrigerant cooling circuit that forms a refrigerant circulation path for cooling, for example, an interior of a heat insulating housing.

  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.

  Moreover, if the heat exchange efficiency of the internal heat exchanger is poor, 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.

  In addition, when there are a plurality of coolers in the heat insulating housing and each of the coolers is cooled independently, specifically, for example, in a vending machine, the plurality of product storages are cooled independently. There is a case. In this case, an evaporator is arranged in each cooler (commodity storage), the outlet side path of the throttle is branched and connected to each evaporator, and the outlet side path of each evaporator is assembled. By connecting to the compressor, a plurality of refrigerant circulation paths having a common compressor, radiator, and throttle are formed. In addition, an electromagnetic valve is provided in each of the paths from the throttle unit to the evaporator. Then, by selectively opening each solenoid valve, the refrigerant is circulated through an evaporator connected to a path with the opened solenoid valve. Thereby, each refrigerator (product storage) is cooled independently. However, in a refrigerant cooling circuit in which a plurality of evaporators are connected to form a plurality of refrigerant circulation paths, the amount of refrigerant circulation is set based on the state in which the refrigerant is circulated through all the evaporators. For this reason, for example, when the refrigerant is circulated through one evaporator, surplus is generated in the circulating refrigerant. As a result, the liquid refrigerant may return to the compressor and the compressor may be damaged. Further, in the supercritical state where the refrigerant is not vaporized, the excess refrigerant increases, the liquid / gas state is mixed, the high-pressure side pressure is increased, and the pressure becomes abnormal and exceeds the specification limit of the refrigerant cooling circuit. This problem becomes prominent when carbon dioxide having a supercritical temperature of about 31 ° C. is used as the refrigerant in the refrigerant cooling circuit. To solve this problem, the liquid refrigerant is prevented from returning to the compressor by separating the gas and liquid using an accumulator, or the refrigerant is temporarily retained in the accumulator to prevent the refrigerant from flowing into the high pressure side. It is conceivable to prevent an increase in pressure. However, it is not preferable because an accumulator having a volume for retaining the refrigerant is required and the cooling efficiency is reduced due to discarding the amount of heat generated by cooling.

  In view of the above circumstances, the present invention can improve the heat exchange efficiency in the internal heat exchanger, suppress an increase in pressure on the high pressure side, promote the liquefaction of the refrigerant in the radiator, and further compress An object of the present invention is to provide a refrigerant cooling circuit that can improve the return of refrigeration oil to the machine and that can prevent inconvenience due to excess refrigerant when a plurality of refrigerant circulation paths are formed.

  In order to achieve the above object, a refrigerant cooling circuit according to claim 1 of the present invention includes a compressor that compresses a refrigerant, a radiator that dissipates heat supplied from the compressor, and is supplied from the radiator. Forming a refrigerant circulation path having a throttle part for adjusting the flow rate of the refrigerant to be cooled and an evaporator for evaporating the refrigerant supplied from the throttle part and returning it to the compressor, In the refrigerant cooling circuit provided with an internal heat exchanger for exchanging heat between the low pressure side and the low pressure side, the internal heat exchanger includes a high pressure side refrigerant pipe forming a resistance line inside the low pressure side refrigerant pipe. A counter flow is formed between the low-pressure side refrigerant pipe and the high-pressure side refrigerant pipe.

  A refrigerant cooling circuit according to a second aspect of the present invention is the refrigerant cooling circuit according to the first aspect, wherein the internal heat exchanger includes a plurality of the high-pressure side refrigerant pipes forming a resistance pipe in the low-pressure side refrigerant pipe. It is characterized by that.

  A refrigerant cooling circuit according to a third aspect of the present invention is characterized in that, in the first or second aspect, the low-pressure side refrigerant pipe is covered with a heat insulating material.

  In order to achieve the above object, a refrigerant cooling circuit according to a fourth aspect of the present invention includes a compressor that compresses the refrigerant, a radiator that dissipates the refrigerant supplied from the compressor, and is supplied from the radiator. Forming a refrigerant circulation path having a throttle part for adjusting the flow rate of the refrigerant to be cooled and an evaporator for evaporating the refrigerant supplied from the throttle part and returning it to the compressor, In the refrigerant cooling circuit provided with the internal heat exchanger for exchanging heat between the low-pressure side and the low-pressure side, the internal heat exchanger includes a flat low-pressure refrigerant pipe and a plurality of resistance pipes inside the flat shape A high pressure side refrigerant pipe having a passage is arranged in parallel with each other, and a counter flow is formed between the low pressure side refrigerant pipe and the high pressure side refrigerant pipe.

  The refrigerant cooling circuit according to a fifth aspect of the present invention is characterized in that, in the fourth aspect, the low-pressure side refrigerant pipe and the high-pressure side refrigerant pipe are both covered with a heat insulating material.

  A refrigerant cooling circuit according to a sixth aspect of the present invention is the refrigerant cooling circuit according to any one of the first to fifth aspects, wherein the internal heat exchanger is configured to send the refrigerant from above to the low pressure side refrigerant pipe, The side refrigerant pipe is provided in such a form that the refrigerant is sent from below to above.

  A refrigerant cooling circuit according to a seventh aspect of the present invention is the refrigerant cooling circuit according to any one of the first to sixth aspects, wherein the internal heat exchanger has a length of the low-pressure side refrigerant pipe and the high-pressure side refrigerant pipe set to 1. It is characterized by being 3 m or more.

  The refrigerant cooling circuit according to an eighth aspect of the present invention is the refrigerant cooling circuit according to any one of the first to seventh aspects, wherein the internal heat exchanger has the low-pressure side refrigerant pipe and the high-pressure side refrigerant pipe arranged in a spiral shape. It is characterized by being.

  A refrigerant cooling circuit according to a ninth aspect of the present invention is the refrigerant cooling circuit according to any one of the first to eighth aspects, wherein the refrigerant is carbon dioxide.

  A refrigerant cooling circuit according to claim 10 of the present invention includes a compressor that compresses carbon dioxide refrigerant, a radiator that dissipates heat of carbon dioxide refrigerant supplied from the compressor, and a carbon dioxide refrigerant supplied from the radiator. A throttle unit that adjusts the flow rate of the refrigerant, and an evaporator that evaporates the carbon dioxide refrigerant supplied from the throttle unit and returns the refrigerant to the compressor. A plurality of the evaporators are provided, and the compressor, the radiator And a refrigerant cooling circuit in which a plurality of refrigerant circulation paths having the same throttle portion are formed, and an internal heat exchanger that performs heat exchange between the high-pressure side and the low-pressure side of the refrigerant circulation path is provided. To do.

  The refrigerant cooling circuit according to an eleventh aspect of the present invention is the refrigerant cooling circuit according to the tenth aspect, wherein the internal heat exchanger includes a high-pressure side refrigerant pipe forming a resistance pipe inside the low-pressure side refrigerant pipe, Heat exchange is performed between the refrigerant pipe and the high-pressure side refrigerant pipe.

  A refrigerant cooling circuit according to a twelfth aspect of the present invention is the refrigerant cooling circuit according to the tenth or eleventh aspect, wherein when the carbon dioxide refrigerant returning from the evaporator to the compressor is accompanied by surplus, the internal heat exchanger is The refrigerant temperature at the outlet of the refrigerant pipe is set to an amount of heat exchange so that the high-pressure side pressure is lower than the specification limit of the compressor.

  The refrigerant cooling circuit according to the present invention includes an internal heat exchanger in which a high-pressure side refrigerant pipe forming a resistance pipe is provided inside a low-pressure side refrigerant pipe, and is opposed between the low-pressure side refrigerant pipe and the high-pressure side refrigerant pipe. Make a flow. Thereby, since a mutual heat exchange area can be taken large, heat exchange efficiency can be improved. In addition, by installing a plurality of high-pressure refrigerant pipes that form resistance pipes inside the low-pressure refrigerant pipe, the heat exchange area can be further increased, so that the heat exchange efficiency can be further improved. Furthermore, by covering the low-pressure refrigerant pipe with a heat insulating material, the heat exchange efficiency can be further improved because the influence of outside air during heat exchange, that is, heat exchange with the outside is suppressed.

  The refrigerant cooling circuit according to the present invention is a state in which the flat low-pressure side refrigerant pipe and the high-pressure side refrigerant pipe having a plurality of resistance pipes in the flat shape are in contact with each other for the internal heat exchanger. Are arranged in parallel to form a counter flow between the low-pressure side refrigerant pipe and the high-pressure side refrigerant pipe. Thereby, since a mutual heat exchange area can be taken large, heat exchange efficiency can be improved. Furthermore, by covering both the low-pressure side refrigerant pipe and the high-pressure side refrigerant pipe with a heat insulating material, the influence of outside air during heat exchange, that is, heat exchange with the outside can be suppressed, so that the heat exchange efficiency can be further improved.

  And since heat-exchange efficiency improves and a refrigerant | coolant becomes easy to liquefy in a heat radiator, the pressure rise on a high voltage | pressure side can be suppressed. Further, since the heat exchange efficiency is improved, carbon dioxide is vaporized in the evaporator, so that it is possible to eliminate the situation where carbon dioxide is supplied to the compressor while being partially liquefied. Furthermore, by improving the heat exchange efficiency, the refrigeration oil discharged from the compressor can be easily circulated through the refrigerant circulation path and returned to the compressor.

  In addition, the low pressure side refrigerant pipe sends the refrigerant from above to below, and the high pressure side refrigerant pipe sends the refrigerant from below to above, so that the refrigeration oil can be returned to the compressor on the low pressure side. can do.

  If the length of the low-pressure side refrigerant pipe and the high-pressure side refrigerant pipe is set to 1.3 m or more, the refrigerant temperature at the high-pressure side outlet of the internal heat exchanger is cooled to a predetermined temperature or lower, and the high-pressure side pressure exceeds the specification limit. The situation can be prevented. Furthermore, if the low-pressure side refrigerant pipe and the high-pressure side refrigerant pipe are arranged in a spiral shape, the installation volume can be reduced even if the low-pressure side refrigerant pipe and the high-pressure side refrigerant pipe are formed long.

  In particular, the internal heat exchanger of the present invention is useful for a refrigerant cooling circuit in which carbon dioxide is used as a refrigerant and the refrigerant circulation path is in a relatively high pressure state.

  Also, internal heat is provided in which a plurality of evaporators are provided to form a plurality of refrigerant circulation paths that share a compressor, a radiator, and a throttle, and heat is exchanged between the high-pressure side and the low-pressure side of the refrigerant circulation path. An exchange was provided. The internal heat exchanger includes a high-pressure side refrigerant pipe forming a resistance line inside the low-pressure side refrigerant pipe, and performs heat exchange between the low-pressure side refrigerant pipe and the high-pressure side refrigerant pipe. As a result, in a 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, surplus is generated in the circulating refrigerant. The liquid refrigerant can be vaporized and returned to the compressor by exchanging heat between the low pressure side and the high pressure side through the low pressure side refrigerant pipe and the high pressure side refrigerant pipe. As a result, liquid compression in the compressor can be prevented and damage to the compressor 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. In particular, when the surplus refrigerant amount is large, the high-pressure side pressure increases, but the cooling heat capacity (heat exchange amount) also increases, so the high-pressure side pressure can be reduced.

  Exemplary embodiments of a refrigerant cooling circuit 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 according to the present invention. As shown in FIG. 1, the refrigerant cooling circuit in this embodiment mainly includes a compressor 1, a gas cooler (heat radiator) 2, an electronic expansion valve (throttle portion) 3, and an evaporator 4 to connect refrigerant. A circulating refrigerant circulation path is 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 the present embodiment, the compressor 1 uses the intermediate heat exchanger 10 to perform a two-stage compression operation. Specifically, in the two-stage compression operation, the compressor 1 has an intermediate heat between the first compressor 1a that performs the first-stage compression operation and the second compressor 1b that performs the second-stage compression operation. An exchanger 10 is provided. Then, 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.

  Note that the temperature at the periphery of the evaporator 4 decreases as the evaporator 4 absorbs the heat at the periphery. As the refrigeration cycle, it is necessary to throw away the heat of evaporation absorbed by the evaporator 4, but the inside of the heat-insulating housing provided with the evaporator 4 is considerably lower than the outside temperature, and is taken away from the low temperature part. Heat cannot be thrown away directly to the hot outside. Therefore, the compressor 1 plays the role of converting carbon dioxide supplied from the evaporator 4 into high-temperature and high-pressure steam in order to discard the evaporation heat of the evaporator 4 at a temperature higher than the outside air temperature.

  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 related to 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 heated by the evaporating pipe through which high-temperature and high-pressure carbon dioxide passes, and is absorbed by the evaporating sheet and evaporates. 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 plan view showing the internal heat exchanger, FIG. 3 is a front view showing the internal heat exchanger, FIG. 4 is a side view showing the internal heat exchanger, FIG. 5 is a perspective view showing the internal heat exchanger, and FIG. FIG. 3 is a cross-sectional view of an internal heat exchanger.

  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 of the compressor 1 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 from the outlet side of the electronic expansion valve 3 to the inlet side of the compressor 1 through the evaporator 4.

  As shown in FIGS. 2 to 6, the internal heat exchanger 14 is provided with a high-pressure side refrigerant pipe 14 </ b> A between the gas cooler 2 on the high-pressure side and the electronic expansion valve 3. The internal heat exchanger 14 is provided with a low-pressure side refrigerant pipe 14B between the evaporator 4 on the low-pressure side and the compressor 1 (first compressor 1a). The high-pressure side refrigerant pipe 14A is a capillary tube as a resistance pipe, and is built inside the low-pressure side refrigerant pipe 14B. In addition, a plurality of (three in this embodiment) high-pressure side refrigerant pipes 14A are provided inside the low-pressure side refrigerant pipe 14B. Thus, the internal heat exchanger 14 has a double-pipe structure in which the high-pressure side refrigerant pipe 14A is housed inside the low-pressure side refrigerant pipe 14B.

  As described above, 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 side refrigerant pipes 14A are housed inside the low-pressure side refrigerant pipe 14B. Specifically, as shown in FIGS. 2 to 5, the high-pressure side refrigerant pipe 14 </ b> A is provided with an inlet portion 14 </ b> Aa of the high-pressure side refrigerant pipe 14 </ b> A at the spiral lower end, and the high-pressure side refrigerant pipe 14 </ b> A at the spiral upper end. 14Ab is provided. The inlet portion 14Aa and the outlet portion 14Ab are formed as a single pipe that converges a plurality of resistance pipes of the high-pressure side refrigerant pipe 14A. And the high-pressure side refrigerant | coolant piping 14A is formed in the spiral form with the form which bundled the some resistance pipe line, as shown in FIG. On the other hand, the low-pressure side refrigerant pipe 14B is provided so as to cover all the resistance lines of the high-pressure side refrigerant pipe 14A as shown in FIG. 6, and the high-pressure side refrigerant pipe 14A as shown in FIGS. From the rear stage of the inlet part 14Aa to the front stage of the outlet part 14Ab, a spiral shape is formed. This low-pressure side refrigerant pipe 14B is provided with an inlet portion 14Ba on the upper end side that is spiraled and an outlet portion 14Bb on the lower end side that is spiraled. Thus, the internal heat exchanger 14 is provided in such a mode that the high-pressure side refrigerant pipe 14A sends the refrigerant from below to above, and the low-pressure side refrigerant pipe 14B 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.

  As shown in FIG. 6, the high-pressure side refrigerant pipe 14 </ b> A is provided in such a manner that the outer peripheral walls of the respective resistance pipes are in a non-contact manner, and the outer peripheral walls of the respective resistance pipes constituting the high-pressure side refrigerant pipe 14 </ b> A It is preferable in terms of mutual heat exchange that the low pressure side refrigerant pipe 14B is provided in a form that is not in contact with the inner peripheral wall. Further, a flexible tube-shaped heat insulating material 14C is provided on the outer periphery of the low-pressure side refrigerant pipe 14B so that heat exchange between the low-pressure side and the high-pressure side is not affected by outside air. It is.

  In the present embodiment, the high-pressure refrigerant pipe 14A has an outer diameter of the resistance pipe of φ3.0 mm, a thickness of 0.5 mm, and a length of 2060 mm. The low-pressure side refrigerant pipe 14B has an outer diameter of φ9.52 mm, a wall thickness of 0.8 mm, and a length of 1957 mm. Further, the heat insulating material 14C has an outer diameter of φ19.0 mm, a wall thickness of 3.0 mm, and a length of 1800 mm. As described above, the internal heat exchanger 14 is long but has a spiral shape to reduce the installation volume.

  The length of the internal heat exchanger 14 is preferably 1.3 m or more. If this length is explained in full detail, when the cooler of a heat insulation housing is made into three rooms as mentioned above, circulation operation of all the three rooms of each refrigerant circulation path may be considered. As shown in FIG. 7, 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 of the specification limit in the refrigerant cooling circuit in this embodiment. It is assumed that the pressure was 12 MPa. 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. Further, as shown in FIG. 8, the exchange heat amount of the internal heat exchanger 14 for setting the refrigerant temperature on the high pressure side to at least 18 ° C. is 160 W. And as shown in FIG. 9, the length of the said internal heat exchanger 14 for setting the exchange heat amount of the internal heat exchanger 14 to 160 W or more will be 1.3 m or more. Thus, if the length of the internal heat exchanger 14 is 1.3 m or more, the refrigerant temperature at the high-pressure side outlet of the internal heat exchanger 14 is set to 18 ° C. or less, and the high-pressure side pressure is within the specification value (12 MPa). Can be.

  FIG. 10 is a diagram showing the heat exchange amount of the internal heat exchanger. As shown in FIG. 10, the heat exchange amount of the internal heat exchanger 14 is such that when the carbon dioxide refrigerant returning to the compressor 1 (1a) from the evaporator 4 (4a, 4b, 4c) is accompanied by surplus, the high-pressure side refrigerant pipe The refrigerant temperature at the outlet of 14A (exit part 14Ab) is set to a heat exchange amount that makes the high-pressure side pressure lower than the specification limit of the compressor 1. For example, in FIG. 1, the heat exchange amount ratio of the evaporator 4 is set to “1: 2: 3” in the evaporator 4a: evaporator 4b: evaporator 4c. Further, the surplus refrigerant amount when all (three) evaporators 4 are operated with the refrigerant circulation amount “a” is set to “0”. In this case, when only one evaporator 4a is operated, the surplus refrigerant amount is 5a / 6, and the internal heat is reduced when the volume of the first compressor 1a as the first stage is 2 cc as shown in FIG. The heat exchange amount min of the exchanger 14 is 160 W according to the equation y = 80x (y: internal heat exchanger heat exchange amount, x = compressor capacity, 80: coefficient). Furthermore, the heat exchange amount max of the internal heat exchanger 14 is 1000 W according to the equation y = 500x (y: internal heat exchanger heat exchange amount, x = compressor capacity, 500: coefficient). That is, according to the above example, the heat exchange amount of the internal heat exchanger 14 is changed from the evaporator 4 (4a, 4b, 4c) to the compressor 1 (1a) as shown in FIGS. When the returned carbon dioxide refrigerant is accompanied by surplus, the refrigerant temperature at the outlet of the high-pressure side refrigerant pipe 14A (exit portion 14Ab) is set to a temperature at which the high-pressure side pressure falls below the specification limit (12 MPa) of the compressor 1 (18 ° C or less ) Is set to the heat exchange amount (160W to 1000W). In the above example, the temperature at which the high-pressure side pressure falls below the specification limit of the compressor 1 is set to 18 ° C. or lower, but may be 20 ° C. or lower.

  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 14B and the high pressure side refrigerant pipe 14A. 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.

  Hereinafter, the operation of the refrigerant cooling circuit of the present invention using carbon dioxide as the refrigerant will be described. In the following operation of the refrigerant cooling circuit, only the electromagnetic valve 12a is open, and the other electromagnetic valves 12b and 12c are closed.

  The carbon dioxide returned from the evaporator 4a in the refrigerator is sucked into the first compressor 1a via 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, the carbon dioxide passes through the electromagnetic valve 12a in the open state and reaches the evaporator 4a through the decompression means 13a.

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

  In the carbon dioxide circulation operation, the evaporators 4b and 4c provided in the path having the solenoid valves 12b and 12c in the closed state are connected to the evaporator 4a and the outlet side of the refrigerant circulation path in which the circulation operation is performed. It is gathered. For this reason, conventionally, when only the solenoid valve 12a is in an open state, the pressure difference between the inlet side and the outlet side of the solenoid valves 12b and 12c in the closed state becomes substantially equal. However, in this embodiment, decompression means 13a, 13b, and 13c are provided in the paths between the electromagnetic valves 12a, 12b, and 12c and the evaporators 4a, 4b, and 4c, respectively. For this reason, in the path having the closed solenoid valves 12b and 12c, the decompression means 13b and 13c act as a throttle for applying pressure resistance in the path, so that the outlet side of the closed solenoid valves 12b and 12c has a low pressure. 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.

  In the carbon dioxide circulation operation, the internal heat exchanger 14 exchanges heat between the high-pressure side refrigerant pipe 14A and the low-pressure side refrigerant pipe 14B. Here, the internal heat exchanger 14 has a high-pressure side refrigerant pipe 14 </ b> A that forms a resistance line inside the low-pressure side refrigerant pipe 14 </ b> B. 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 side refrigerant pipes 14A inside the low-pressure side refrigerant pipes 14B, the mutual heat exchange area can be further increased, thereby further improving the heat exchange efficiency. Further, since the low-pressure side refrigerant pipe 14B is covered with the heat insulating material 14C, 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 an increase in pressure on the high pressure side can be suppressed. Further, since the heat exchange efficiency is improved, carbon dioxide is vaporized in the evaporator 4, so that it is possible to eliminate a situation where carbon dioxide is 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 14B sends the refrigerant from above to below, and the high-pressure side refrigerant pipe 14A 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.

  Further, in the internal heat exchanger 14, the length of the high-pressure side refrigerant pipe 14A and the low-pressure side refrigerant pipe 14B is set to 1.3 m or more. Thereby, the refrigerant | coolant temperature of the high voltage | pressure side exit of the internal heat exchanger 14 is cooled to 18 degrees C or less, and the situation where a high voltage | pressure side pressure exceeds a specification limit is prevented. Furthermore, since the high pressure side refrigerant pipe 14A is spirally formed in the vertical direction with the low pressure side refrigerant pipe 14B built in, it is possible to reduce the installation volume. Note that the heat exchange amount can be freely set by changing the lengths of the high-pressure side refrigerant pipe 14A and the low-pressure side refrigerant pipe 14B.

  Hereinafter, another embodiment of the internal heat exchanger will be described. FIG. 11 is a sectional view showing another embodiment of the internal heat exchanger.

  As shown in FIG. 11, the internal heat exchanger 14 ′ is configured such that the high-pressure side refrigerant pipe 14 </ b> A ′ has a plurality of resistance pipes in a flat shape. Further, in the internal heat exchanger 14 ', the low-pressure side refrigerant pipe 14B' has a flat shape. The flat outer peripheral surfaces of the high-pressure side refrigerant pipe 14A ′ and the low-pressure side refrigerant pipe 14B ′ are arranged in contact with each other. Thereby, since a mutual heat exchange area can be taken large, heat exchange efficiency improves.

  In addition, the internal heat exchanger 14 'has a high pressure side refrigerant pipe 14A' and a low pressure side refrigerant pipe 14B 'both covered with a heat insulating material 14C'. This suppresses the influence of outside air during heat exchange, that is, heat exchange with the outside, so that the heat exchange efficiency is further improved. 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 addition, since the heat exchange efficiency is improved, carbon dioxide is easily liquefied in the gas cooler 2, so that an increase in pressure on the high pressure side can be suppressed. Further, since the heat exchange efficiency is improved, carbon dioxide is vaporized in the evaporator 4, so that it is possible to eliminate a situation where carbon dioxide is supplied to the compressor 1 while being partially liquefied.

  Although not clearly shown in the figure, the internal heat exchanger 14 'is formed in a form in which a high-pressure side refrigerant pipe 14A' and a low-pressure side refrigerant pipe 14B 'are arranged side by side in a spiral form, In the pipe 14A ′, the refrigerant is sent from below to above, and in the low-pressure side refrigerant pipe 14B ′, the refrigerant is sent from above to below. Thereby, it becomes possible to improve the return of the refrigeration oil to the compressor 1 on the low pressure side.

  In the internal heat exchanger 14 ', the length of the high-pressure side refrigerant pipe 14A' and the low-pressure side refrigerant pipe 14B 'is 1.3 m or more. Thereby, the refrigerant | coolant temperature of the high voltage | pressure side exit of the internal heat exchanger 14 is cooled to 18 degrees C or less, and the situation where a high voltage | pressure side pressure exceeds a specification limit is prevented. Further, since the high-pressure side refrigerant pipe 14A 'and the low-pressure side refrigerant pipe 14B' are formed in a spiral shape in the vertical direction, the installation volume can be reduced. The heat exchange amount can be freely set by changing the lengths of the high-pressure side refrigerant pipe 14A ′ and the low-pressure side refrigerant pipe 14B ′.

It is the schematic which shows one Example of the refrigerant cooling circuit which concerns on this invention. It is a top view which shows an internal heat exchanger. It is a front view which shows an internal heat exchanger. It is a side view which shows an internal heat exchanger. It is a perspective view which shows an internal heat exchanger. It is sectional drawing of an internal heat exchanger. It is a figure which shows the relationship between a high voltage | pressure side pressure and the refrigerant | coolant temperature of the high voltage | pressure side exit of an internal heat exchanger. It is a figure which shows the relationship between the amount of exchange heat of an internal heat exchanger, and the refrigerant | coolant temperature of the high voltage | pressure side exit of an internal heat exchanger. It is a figure which shows the relationship between the length of an internal heat exchanger, and the amount of exchange heat of an internal heat exchanger. It is a figure which shows the heat exchange amount of an internal heat exchanger. It is sectional drawing which shows another Example of an internal heat exchanger.

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 14A High-pressure side refrigerant piping 14Aa Inlet part 14Ab Outlet part 14B Low pressure side refrigerant pipe 14Ba Inlet part 14Bb Outlet part 14C Heat insulating material 14 'Internal heat exchanger 14A' High pressure side refrigerant pipe 14B 'Low pressure side refrigerant pipe 14C' Heat insulating material 15 Evaporating means

Claims (12)

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 A refrigerant cooling circuit provided with an internal heat exchanger that forms a refrigerant circulation path having an evaporator to be returned to the compressor and performs heat exchange between a high pressure side and a low pressure side of the refrigerant circulation path. ,
The internal heat exchanger includes a high-pressure side refrigerant pipe forming a resistance line inside the low-pressure side refrigerant pipe, and forms a counter flow between the low-pressure side refrigerant pipe and the high-pressure side refrigerant pipe. Refrigerant cooling circuit.   2. The refrigerant cooling circuit according to claim 1, wherein the internal heat exchanger includes a plurality of the high-pressure side refrigerant pipes forming a resistance pipe inside the low-pressure side refrigerant pipe.   The refrigerant cooling circuit according to claim 1 or 2, wherein the low-pressure refrigerant pipe is covered with a heat insulating material. 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 A refrigerant cooling circuit provided with an internal heat exchanger that forms a refrigerant circulation path having an evaporator to be returned to the compressor and performs heat exchange between a high pressure side and a low pressure side of the refrigerant circulation path. ,
The internal heat exchanger includes a low-pressure refrigerant pipe arranged in parallel with a flat low-pressure side refrigerant pipe and a high-pressure refrigerant pipe having a plurality of resistance pipes in contact with each other. A refrigerant cooling circuit, wherein a counter flow is formed between a pipe and the high-pressure side refrigerant pipe.   The refrigerant cooling circuit according to claim 4, wherein both the low-pressure side refrigerant pipe and the high-pressure side refrigerant pipe are covered with a heat insulating material.   The internal heat exchanger is provided in such a form that the low-pressure refrigerant pipe sends refrigerant from above to below, and the high-pressure refrigerant pipe sends refrigerant from below to above. The refrigerant cooling circuit as described in any one of -5.   The refrigerant cooling circuit according to any one of claims 1 to 6, wherein the internal heat exchanger has a length of the low-pressure side refrigerant pipe and the high-pressure side refrigerant pipe set to 1.3 m or more.   The refrigerant cooling circuit according to any one of claims 1 to 7, wherein the internal heat exchanger has the low-pressure side refrigerant pipe and the high-pressure side refrigerant pipe arranged in a spiral shape.   The refrigerant cooling circuit according to claim 1, wherein the refrigerant is carbon dioxide. A compressor that compresses the carbon dioxide refrigerant, a radiator that dissipates the carbon dioxide refrigerant supplied from the compressor, a throttle unit that adjusts a flow rate of the carbon dioxide refrigerant supplied from the radiator, and the throttle unit A plurality of refrigerant circulation paths having an evaporator for evaporating supplied carbon dioxide refrigerant and returning it to the compressor, wherein a plurality of the evaporators are provided, and the compressor, the radiator and the throttle unit are shared In the refrigerant cooling circuit that forms
An internal heat exchanger for exchanging heat between a high pressure side and a low pressure side of the refrigerant circulation path is provided.   The internal heat exchanger includes a high-pressure side refrigerant pipe that forms a resistance pipe inside the low-pressure side refrigerant pipe, and performs heat exchange between the low-pressure side refrigerant pipe and the high-pressure side refrigerant pipe. The refrigerant cooling circuit according to claim 10.   When the carbon dioxide refrigerant returning from the evaporator to the compressor is accompanied by surplus, the internal heat exchanger reduces the refrigerant temperature at the outlet of the high-pressure side refrigerant pipe, and the high-pressure side pressure is below the specification limit of the compressor. The refrigerant cooling circuit according to claim 10 or 11, wherein the heat exchange amount is set to such a temperature.

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