JP2013174402A - Refrigerating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a refrigerating device using a refrigerant, such as carbon dioxide, the refrigerant device being capable of sending a sufficient amount of a liquid refrigerant to an expansion means for expanding the refrigerant flowing into an evaporator.SOLUTION: In a refrigerating device R, a refrigerant circuit 1 is comprised of a compressor 11, a gas cooler 28, a main expansion means 46A and an evaporator 47A, and a high-pressure side has a supercritical pressure. A high-pressure refrigerant issued from a gas cooler is expanded, decreasing its pressure to an intermediate pressure, and is separated into a saturated liquid refrigerant and a gas refrigerant. Then, the gas refrigerant is expanded for exchanging heat with the saturated liquid refrigerant, the saturated liquid refrigerant is supplied to the main expansion means and the gas refrigerant is returned to the compressor.

Description

  The present invention relates to a refrigeration apparatus in which a refrigerant circuit is configured by a compression unit, a gas cooler, an expansion unit, and an evaporator, and a high pressure side is a supercritical pressure.

  Conventionally, in this type of refrigeration system, a refrigeration cycle is constituted by a compression means, a gas cooler, an expansion means (throttle means), etc., and the refrigerant compressed by the compression means radiates heat at the gas cooler and is decompressed and expanded by the expansion means The refrigerant is evaporated by an evaporator, and the ambient air is cooled by evaporation of the refrigerant at this time. In recent years, chlorofluorocarbon refrigerants cannot be used in this type of refrigeration system due to natural environmental problems. For this reason, what uses the carbon dioxide which is a natural refrigerant | coolant is developed as a substitute of a fluorocarbon refrigerant | coolant (for example, refer patent document 1).

  Carbon dioxide refrigerant has a specific physical property that it occurs at a daily temperature of + 31.1 ° C. in addition to the critical point being a high pressure of 7.38 MPa. For this reason, at normal temperatures, the heat radiation operation on the high pressure side of the refrigeration apparatus using carbon dioxide refrigerant is often performed at a supercritical pressure above the critical point. Since the heat release of carbon dioxide in the critical state has no liquefaction state, the pressure is determined by the density and volume depending on the temperature of the refrigerant in the gas cooler.

  When the refrigerant in this state is expanded by an expansion valve or the like, the dryness of the refrigerant at the evaporator inlet increases and the ratio of the liquid refrigerant decreases. Therefore, in order to ensure the cooling capacity, the refrigerant is not supplied to the evaporator. It is necessary to increase the supply amount. Further, when the amount of refrigerant supplied to the evaporator increases, the speed of the refrigerant flowing in the pipe increases, so that the pressure loss increases, a temperature gradient occurs between the evaporator inlet and outlet, and the heat exchange efficiency deteriorates.

  In addition, when the refrigerant in the critical state expands and falls below the critical pressure, it reaches a liquid / gas two-phase equilibrium state, and when it flows into the evaporator, the evaporator pipe is filled with liquid and gas at the same temperature. It becomes a state filled with bubbles. Therefore, although there is heat exchange near the tube wall, heat transfer to the refrigerant becomes difficult at the center of the tube. From these problems, the evaporator has to be enlarged in order to increase the endothermic effect, and the number of pipes has to be increased or complicated in order to suppress the pressure loss.

  Further, when a carbon dioxide refrigerant having a supercritical pressure on the high pressure side is used, when the outside air temperature rises to, for example, + 25 ° C. to 30 ° C. or higher, the refrigerant is not liquefied in the gas cooler, and the high pressure side is supercritical. In this state, the gas cycle operation is performed. Therefore, since the pressure and density of the refrigerant are high on the high pressure side that has become a supercritical gas, providing a so-called liquid receiver having a large diameter to accommodate it increases the space inside the refrigerator, which is realistic. Is impossible. Furthermore, since the state of the refrigerant is not so-called gas (gas), gas-liquid separation cannot be performed in the receiver. For this reason, in this liquid receiver, it is impossible to adjust the amount of circulating refrigerant, and there is a problem that the high-pressure side pressure abnormally increases due to excessive gas refrigerant in the refrigerant circuit.

  Therefore, a part of the critical refrigerant radiated by the gas cooler is separated and expanded, the remaining separated refrigerant is supercooled by the heat exchanger, and the dryness sent to the expansion valve is lowered. In addition, when a refrigerant amount adjustment tank is connected to the high pressure side of the refrigerant circuit via an expansion valve and the pressure on the high pressure side rises abnormally, the refrigerant is collected in this refrigerant amount adjustment tank and the pressure drops. Is considered to be discharged into the refrigerant circuit (for example, see Patent Document 2).

  A refrigerant circuit diagram of a conventional refrigeration apparatus 100 according to FIG. 4 is shown, and a ph diagram thereof is shown in FIG. The conventional refrigeration apparatus 100 includes a refrigerator 103 and a plurality of showcases 105A and 105B. The refrigerator 103 and the showcases 105A and 105B are connected by refrigerant pipes 107 and 109. And a refrigerant circuit uses the carbon dioxide from which the refrigerant | coolant pressure of a high voltage | pressure side becomes more than the critical pressure (supercritical) as a refrigerant | coolant.

  The refrigerator 103 includes a compressor 111 having first and second rotary compression elements 118 and 120. The first rotary compression element 118 compresses the low-pressure refrigerant sucked into the compressor 111 from the low-pressure side of the refrigerant circuit via the refrigerant pipe 109, boosts it to an intermediate pressure, and discharges it. The second rotary compression element 120 The intermediate pressure refrigerant compressed and discharged by the first rotary compression element 118 is further sucked in, compressed to a high pressure, and discharged to the high pressure side of the refrigerant circuit.

  The refrigerant gas of low pressure (LP: about 2.5 MPa in the normal operation state) sucked into the low pressure portion (a in FIG. 5) of the first rotary compression element 118 is subjected to intermediate pressure ( MP: The pressure is increased to about 5 MPa in a normal operation state (b in FIG. 5), and flows into the intercooler 138. The intercooler 138 air-cools the intermediate pressure refrigerant discharged from the first rotary compression element 118, and the refrigerant in the intercooler 138 is sucked into the second rotary compression element 120 (c in FIG. 5). . Then, the intermediate pressure (MP) refrigerant gas sucked into the second rotary compression element 120 is compressed in the second stage by the second rotary compression element 120 and is subjected to high temperature and high pressure (HP: normal operation state). The refrigerant gas has a supercritical pressure of about 8 MPa) (d in FIG. 5).

  The discharge side of the second rotary compression element 120 is connected to the refrigerant pipe 107 via an oil separator 144, a gas cooler 146, a flow divider 182, and a split heat exchanger 180. The gas cooler 146 is provided with a gas cooler blower 147 for air-cooling it. The showcases 105A and 105B are installed in a store or the like and connected in parallel to the refrigerant pipes 107 and 109. Each showcase 105A, 5B is provided with main expansion means 162A, 162B comprising electric expansion valves and evaporators 163A, 163B, respectively. The main expansion means 162A and 162B are connected to the refrigerant pipe 107, and the evaporators 163A and 163B are connected to the refrigerant pipe 109 and finally connected to the first rotary compression element 118 of the compressor 111.

  The flow divider 182 divides the refrigerant (e in FIG. 5) output from the gas cooler 146 into a first refrigerant flow and a second refrigerant flow, and the first refrigerant flow passes through the auxiliary expansion means 183 including an electric expansion valve. Through the first flow path 180A of the split heat exchanger 180, which becomes an auxiliary circuit. In addition, the second refrigerant flow passes through the second flow path 180B of the split heat exchanger 180 and flows into the refrigerant pipe 107, which becomes the main circuit. That is, the refrigerant is conveyed from the refrigerator 103 to the showcases 105A and 105B at a high pressure.

  The split heat exchanger 180 flows the first refrigerant flow (g in FIG. 5) decompressed by the auxiliary expansion means 183 to the first flow path 180A, and the second refrigerant flow divided by the flow divider 182 The two flow paths 180B are used to exchange heat. Thereby, since the second refrigerant flow is cooled by the first refrigerant flow flowing through the first flow path 180A, the second refrigerant flow (f in FIG. 5) toward the main expansion means 162A and 162B is supercooled. Therefore, the specific enthalpy on the inlet side of the evaporators 163A and 163B can be reduced. Then, the second refrigerant flow (h in FIG. 5) decompressed by the main expansion means 162A, 162B flows into the evaporators 163A, 163B and evaporates, and the inside of the showcases 105A, 105B is absorbed by the endothermic action at this time. Cool to refrigeration temperature.

  FIG. 5 is a ph diagram of the refrigeration apparatus 100. In the refrigerant circuit of FIG. 4, locations indicated by reference numerals (a) to (i) correspond to (a) to (i) in FIG. 5. The supercooling in the split heat exchanger 180 is a portion indicated by (e) to (f) in FIG. 5, and the refrigeration effect from (h) to (a) is increased accordingly. Note that the refrigerant (i in FIG. 5) exiting the first flow path 180 </ b> A is merged with the refrigerant exiting the intercooler 138.

  A refrigerant amount adjustment tank 200 is connected to the refrigerant pipe 107 on the downstream side of the split heat exchanger 180 via a first communication circuit 201. The refrigerant amount adjustment tank 200 has a predetermined volume, and an electric expansion valve 202 is interposed in the first communication circuit 201. The refrigerant amount adjustment tank 200 is connected to a second communication circuit 203 that communicates the upper part of the tank 200 and the outlet of the intercooler 138. The second communication circuit 203 is provided with an electromagnetic valve 204. Yes. The refrigerant quantity adjustment tank 200 is connected to a third communication circuit 205 that communicates the lower portion with the outlet of the intercooler 138. The third communication circuit 205 is provided with an electromagnetic valve 206 and a capillary tube 207. ing.

  When the pressure on the high pressure side abnormally increases, the high pressure refrigerant is collected in the refrigerant amount adjustment tank 200 via the electric expansion valve 202 to suppress the increase in high pressure. When the pressure on the high pressure side decreases, the electromagnetic valve 206 is opened and discharged to the suction side of the second rotary compression element 120 of the compressor 111.

Japanese Patent Publication No. 7-18602 JP 2011-133205 A

  However, in the refrigeration apparatus that conveys the refrigerant at a high pressure as described above, since the refrigerant in the supercritical state flows through the refrigerant pipe 107, it is difficult to accurately determine the refrigerant filling amount with a sight glass or the like. In addition, the refrigerant expands in the summer when the outside air temperature becomes high and contracts in the winter. However, this change becomes large in the refrigerant such as carbon dioxide, so that it cannot be adjusted even if it is recovered / released by the refrigerant amount adjustment tank. . For this reason, when a large amount is charged in consideration of securing the refrigerating capacity, the high-pressure side pressure also suddenly rises depending on the operating conditions. When the high-pressure side pressure changes greatly, the differential pressures before and after the main expansion means 162A, 162B on the showcase 105A, 105B side also change greatly, and cannot be completely controlled by the electric expansion valve.

  Further, it has been found that the supercooling effect in the split heat exchanger 180 can hardly be expected in an environment where the outside air temperature is high. That is, since the auxiliary expansion means 183 is controlled by the intermediate pressure, the intermediate pressure is high in a refrigerated showcase or the like, the temperature is not so low, and the subcooling in the split heat exchanger 180 cannot be performed.

  For example, when the outside air temperature is + 20 ° C., the intermediate pressure (MP) reaches 5 MPa, and when it is + 30 ° C., it reaches 6 MPa. The cooling temperature by the first refrigerant flow in the split heat exchanger 180 is an actually measured value + 15 ° C. to + 23 ° C., and the temperature of the second refrigerant flow leaving the split heat exchanger 180 is + 20 ° C. to + 30 ° C. Met. This is almost the same as the outside air temperature, and it has been found by actual measurement that the subcooling effect in the split heat exchanger 180 is small.

  Further, since the discharge temperature of the first rotary compression element 118 is controlled by the first refrigerant flow from the split heat exchanger 180, the amount of the supplied refrigerant fluctuates, and stable subcooling in the split heat exchanger 180 is obtained. I can't.

  Furthermore, the conventional refrigeration apparatus is operated with a shortage of refrigerant for the purpose of protecting the refrigerator 103. Since the refrigerant supplied to the showcases 105A and 105B expands from the critical pressure, if sufficient subcooling cannot be performed by the split heat exchanger 180, the dryness of the refrigerant in the main expansion means 162A and 162B is also high. As a result, the problem arises that a sufficient cooling effect cannot be obtained in the evaporators 163A and 163B.

  The present invention has been made to solve the conventional technical problem, and in a refrigeration apparatus using a refrigerant such as carbon dioxide, a sufficient amount of saturated liquid for expansion means for expanding the refrigerant flowing into the evaporator. A refrigeration apparatus capable of sending a refrigerant is provided.

  In order to solve the above-mentioned problem, the refrigeration apparatus of the invention of claim 1 is a gas cooler in which a refrigerant circuit is composed of a compression means, a gas cooler, an expansion means, and an evaporator, and the high pressure side becomes a supercritical pressure. The high-pressure refrigerant discharged from the refrigerant is expanded to lower the intermediate pressure and separated into the saturated liquid refrigerant and the gas refrigerant, and then the gas refrigerant is expanded to exchange heat with the saturated liquid refrigerant, and the saturated liquid refrigerant is supplied to the expansion means. The gas refrigerant is returned to the compression means.

  In the refrigeration apparatus according to the second aspect of the present invention, the refrigerant circuit is constituted by the compression means, the gas cooler, the main expansion means, and the evaporator, and the high pressure side becomes the supercritical pressure. Between the gas cooler and the main expansion means, A medium pressure control device connected to the medium pressure control device, the high pressure expansion means for expanding the high pressure refrigerant discharged from the gas cooler to lower the intermediate pressure, and the refrigerant expanded by the high pressure expansion means; An intermediate pressure receiver that separates into saturated liquid refrigerant and gas refrigerant, a liquid refrigerant channel into which saturated liquid refrigerant in the intermediate pressure receiver flows, and a gas refrigerant channel into which gas refrigerant in the intermediate receiver flows And a medium-temperature expansion means for expanding the gas refrigerant in the intermediate-pressure receiver and then flowing into the gas refrigerant flow path of the gas-cooled heat recovery device And refrigerant discharged from the liquid refrigerant flow path of the gas cold heat recovery device To flow into the main expansion means, and returning to the compression means of the refrigerant exiting the gas refrigerant flow path.

  A refrigeration apparatus according to a third aspect of the invention is characterized in that, in the above invention, the refrigerant that has exited the gas refrigerant flow path of the gas cold heat recovery device is sucked into the compression means together with the refrigerant that has exited the evaporator.

  According to a fourth aspect of the present invention, there is provided a refrigeration apparatus according to the second or third aspect of the present invention, wherein the intermediate pressure expansion means inlet pressure sensor detects the pressure of the gas refrigerant flowing into the intermediate pressure expansion means, and the intermediate pressure expansion means inlet pressure. And a control means for controlling the medium pressure expansion means based on the output of the sensor.

  A refrigeration apparatus according to a fifth aspect of the present invention is based on the gas cooler outlet temperature sensor and the gas cooler outlet pressure sensor for detecting the temperature and pressure of the refrigerant discharged from the gas cooler in the inventions of the second to fourth aspects, and the output of each sensor. And a control means for controlling the high-pressure expansion means.

  A refrigeration apparatus according to a sixth aspect of the present invention includes the refrigerator unit including the compression means and the gas cooler and the utilization side unit including the main expansion means and the evaporator according to the second to fifth aspects of the invention. The intermediate pressure control device is also included.

  According to a seventh aspect of the present invention, there is provided a refrigeration apparatus comprising: the refrigeration unit including the compression means and the gas cooler according to the second to fifth aspects of the invention; and the utilization side unit including the main expansion means and the evaporator. Includes an intermediate pressure control device.

  The refrigeration apparatus according to the invention of claim 8 is characterized in that carbon dioxide is used as a refrigerant in each of the above inventions.

  When the refrigerant compressed by the compression means and discharged from the gas cooler is expanded to reduce the pressure to an intermediate pressure, a saturated liquid refrigerant and a gas refrigerant are obtained. In the present invention, the refrigerant discharged from the gas cooler is expanded to reduce its pressure to an intermediate pressure, and then separated into a saturated liquid refrigerant and a gas refrigerant, and the saturated liquid refrigerant is supplied to the main expansion means. The gas-liquid separated gas refrigerant is expanded to form a low-temperature liquid refrigerant and a gas refrigerant. Since it is heat-exchanged with the saturated liquid refrigerant toward the main expansion means, the liquid refrigerant toward the main expansion means can be supercooled using the cold heat of the gas refrigerant.

  This makes it possible to supply a sufficient amount of refrigerant to the main expansion means in the supercooled state regardless of the state of the refrigerant that has come out of the gas cooler, and to reduce the dryness of the refrigerant flowing into the evaporator, A large cooling effect can be obtained in the evaporator of the refrigeration apparatus using the carbon dioxide refrigerant as in the invention of claim 8.

  In particular, since the cooling capacity of the separated gas refrigerant can be replaced with the cooling capacity in the evaporator, the cooling effect in the evaporator is improved even when the gas ratio of the refrigerant discharged from the gas cooler is high. It becomes possible.

  Further, the refrigerant discharged from the gas cooler is expanded by the high-pressure expansion means as in the second aspect of the invention, and the pressure is lowered to the intermediate pressure, and then stored in the intermediate pressure receiver and separated into the saturated liquid refrigerant and the gas refrigerant. By doing so, it is possible to obtain an effect of adjusting the amount of refrigerant, and it is also possible to fill a larger amount of refrigerant in the refrigerant circuit. Furthermore, since it becomes possible to absorb the fluctuation of the high pressure side pressure in the intermediate pressure receiver, the saturated liquid refrigerant can be supplied to the main expansion means at a constant intermediate pressure. Stable superheat control can be performed.

  In this case, as in the second aspect of the invention, the high-pressure expansion means, the intermediate pressure receiver, the liquid refrigerant flow path into which the saturated liquid refrigerant separated by the intermediate pressure receiver flows, and the gas refrigerant flow path into which the gas refrigerant flows A gas cold heat recovery device that exchanges heat between the refrigerant flowing through both flow paths and an intermediate pressure that expands the gas refrigerant separated by the intermediate pressure receiver and then flows into the gas refrigerant flow path of the gas cold heat recovery device If an intermediate pressure control device having an expansion means is configured, and this intermediate pressure control device is included in a refrigerator unit including a compression means and a gas cooler as in the invention of claim 6, the main expansion means and the evaporator are provided. The installation space on the use side unit side can be reduced as compared with the case where the intermediate pressure control device is provided on the use side unit side.

  Conversely, if the medium pressure control device is included in the use side unit as in the invention of claim 7, the use including the main expansion means and the evaporator as in the showcase unit and the refrigerator unit installed in the store. When the side unit and the refrigerator unit are installed apart from each other, a long refrigerant pipe connecting the refrigerator unit and the use side unit can be conveyed at high pressure, reducing the amount of refrigerant charged Will be able to.

  If the refrigerant exiting the gas refrigerant flow path of the gas cold heat recovery device is sucked into the compression means together with the refrigerant exiting the evaporator as in the invention of claim 3, the gas refrigerant in the intermediate pressure receiver The pressure can be lowered to a low pressure by the medium pressure expansion means, and a high supercooling effect by the gas refrigerant can be expected.

  Further, the intermediate pressure expansion means inlet pressure sensor for detecting the pressure of the gas refrigerant flowing into the intermediate pressure expansion means as in the fourth aspect of the invention, and the intermediate pressure expansion means based on the output of the intermediate pressure expansion means inlet pressure sensor. The control means for controlling the saturated refrigerant in the gas cold heat recovery unit by controlling the intermediate pressure expansion means so that the pressure of the gas refrigerant flowing into the intermediate pressure expansion means does not drop too much. It becomes possible to maintain the supercooling effect of the refrigerant.

  Furthermore, as in the invention of claim 5, there are provided a gas cooler outlet temperature sensor and a gas cooler outlet pressure sensor for detecting the temperature and pressure of the refrigerant discharged from the gas cooler, and a control means for controlling the high pressure expansion means based on the output of each sensor. Since it is provided, by this control means, for example, by controlling the high-pressure expansion means so that the flow rate of the refrigerant in the gas cooler does not become too fast, it is possible to ensure the heat dissipation capability of the refrigerant in the gas cooler.

It is a refrigerant circuit figure of the refrigerating device of the example to which the present invention is applied. FIG. 2 is a ph diagram of the refrigeration apparatus in FIG. 1. It is a functional block diagram of the electric circuit of the refrigerator unit of FIG. It is a refrigerant circuit figure of the conventional freezing apparatus. FIG. 5 is a ph diagram of the refrigeration apparatus in FIG. 4.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a refrigerant circuit diagram of a refrigeration apparatus R according to an embodiment of the present invention. The refrigeration apparatus R in the present embodiment cools a low temperature showcase installed in a store such as a supermarket or a convenience store, and includes a refrigerator unit 3 installed outside the store and a plurality of units installed in the store. Showcase units (use side units) 5A and 5B, and the refrigerator unit 3 and the showcase units 5A and 5B are connected by refrigerant pipes 7 and 9 to form a predetermined refrigerant circuit 1. It is.

  The refrigerant circuit 1 of the refrigeration apparatus R uses carbon dioxide whose refrigerant pressure (high pressure) on the high pressure side is equal to or higher than its critical pressure (supercritical) as a refrigerant. This carbon dioxide refrigerant is a natural refrigerant that is friendly to the global environment and takes into consideration flammability and toxicity. As the lubricating oil, existing oils such as mineral oil (mineral oil), alkylbenzene oil, ether oil, ester oil, and PAG (polyalkyl glycol) are used.

  The refrigerator unit 3 includes a compressor (compression unit) 11. In this embodiment, the compressor 11 is an internal intermediate pressure type multistage compression rotary compressor, and a cylindrical sealed container 12 made of a steel plate and an electric motor (not shown) disposed and housed above the inner space of the sealed container 12. And a first (low stage side) rotary compression element (first compression element) 18 and a second (high stage side) rotary compression element (second compression element) 20 driven by the electric element. Has been.

  The first rotary compression element 18 compresses the low-pressure refrigerant sucked into the compressor 11 from the low-pressure side of the refrigerant circuit 1 through the refrigerant pipe 9, boosts it to an intermediate pressure, and discharges it. Further sucks in the intermediate pressure refrigerant compressed and discharged by the first rotary compression element 20, compresses it to a high pressure, and discharges it to the high pressure side of the refrigerant circuit 1. The compressor 11 is a variable frequency compressor, and the rotational speed of the first rotary compression element 18 and the second rotary compression element 20 can be controlled by changing the operating frequency of the electric element.

  A refrigerant introduction pipe 21 is connected to the first rotary compression element 18 of the compressor 11, and the refrigerant introduction pipe 21 is connected to the refrigerant pipe 9. The refrigerant gas having a low pressure (LP: about 2.5 MPa in a normal operation state) sucked into the low pressure portion of the first rotary compression element 18 through these pipes is subjected to an intermediate pressure ( MP: The pressure is increased to about 5 MPa in a normal operation state and discharged into the sealed container 12. Thereby, the inside of the airtight container 12 becomes an intermediate pressure (MP).

  The intermediate-pressure refrigerant gas in the sealed container 12 is discharged to an intermediate-pressure discharge pipe 23 connected to one end of the intercooler 22. The intercooler 22 air-cools the intermediate pressure refrigerant discharged from the first rotary compression element 18, and an intermediate pressure suction pipe 24 is connected to the other end of the intercooler 22. The pipe 24 is connected to the suction side of the second rotary compression element 20 of the compressor 11.

  The intermediate pressure (MP) refrigerant gas sucked into the intermediate pressure portion of the second rotary compression element 20 by the intermediate pressure suction pipe 24 is compressed at the second stage by the second rotary compression element 20 and is heated to a high temperature. The refrigerant gas has a high pressure (HP: a supercritical pressure of about 8 MPa in a normal operation state).

  The high pressure discharge pipe 26 connected to the high pressure chamber side of the second rotary compression element 20 of the compressor 11 is connected to an oil separator 27, a gas cooler 28, and a medium pressure control device 29 of the present invention, which will be described in detail later. Connected to the refrigerant pipe 7. In the present embodiment, the intermediate pressure control device 29 is installed in the refrigerator unit 3.

  The gas cooler 28 radiates and cools the high-temperature and high-pressure refrigerant discharged from the compressor 11, and a gas cooler blower 31 for air-cooling the gas cooler 28 is disposed in the vicinity of the gas cooler 28. The inlet pipe 33 of the intermediate pressure control device 29 is connected to the outlet pipe 32 of the gas cooler 28.

  The intermediate pressure control device 29 includes a high pressure expansion means 34 comprising an electric expansion valve, an intermediate pressure liquid receiver 36 comprising a tank of a predetermined capacity, an intermediate pressure expansion means 37 comprising an electric expansion valve, and a heat exchanger. The gas cold / heat recovery unit 38 is formed. The inlet pipe 33 is an inlet pipe of the high-pressure expansion means 34, and an outlet pipe 39 of the high-pressure expansion means 34 is inserted and connected from above into the intermediate pressure receiver 36 and is opened inside.

  A liquid refrigerant pipe 41 is drawn out from the inner bottom of the intermediate pressure receiver 36, and a gas refrigerant pipe 42 is connected to the upper part of the intermediate pressure receiver 36. The gas cold heat recovery unit 38 has a liquid refrigerant flow path 38A and a gas refrigerant flow path 38B, and exchanges heat between the refrigerants flowing in both flow paths 38A and 38B. The outlet of the liquid refrigerant pipe 41 is connected to the inlet of the liquid refrigerant flow path 38 </ b> A of the gas cold heat recovery unit 38. The intermediate pressure expansion means 37 is interposed in the gas refrigerant pipe 42, and the outlet of the gas refrigerant pipe 42 is connected to the inlet of the gas refrigerant flow path 38 </ b> B of the gas cold heat recovery device 38.

  The outlet of the gas refrigerant flow path 38B of the gas cold heat recovery device 38 is connected to the refrigerant return pipe 43, and the refrigerant return pipe 43 is connected to the refrigerant pipe 9 connected to the refrigerant introduction pipe 21 of the compressor 11. . Further, the outlet of the liquid refrigerant flow path 38 </ b> A of the gas cold heat recovery device 38 is connected to the refrigerant pipe 7.

  On the other hand, the showcase units 5A and 5B are installed in a store or the like, and are connected in parallel to the refrigerant pipes 7 and 9, respectively. Each showcase unit 5A, 5B has case-side refrigerant pipes 44A, 44B that connect the refrigerant pipe 7 and the refrigerant pipe 9, and each case-side refrigerant pipe 44A, 44B comprises an electric expansion valve. Main expansion means 46A and 46B as expansion means and evaporators 47A and 47B are sequentially connected. Each of the evaporators 47A and 47B is adjacent to an unillustrated cool air circulation blower that blows air to the evaporator. The refrigerant pipe 9 joins the refrigerant return pipe 43 as described above, and is then connected to the suction side of the first rotary compression element 18 of the compressor 11 via the refrigerant introduction pipe 21. Thereby, the refrigerant circuit 1 of the refrigeration apparatus R in the present embodiment is configured.

  The refrigerator unit 3 of the refrigeration apparatus R includes a control means 50 configured by a general-purpose microcomputer. The electric devices and sensors are provided in the refrigerator unit 3 and the showcase units 5A and 5B, and the control means are also provided in them. Here, the control means 50 of the refrigerator unit 3 is described. explain.

  On the input side of the control means 50, an output of a gas cooler outlet temperature sensor 51 and a gas cooler outlet pressure sensor 52 which are provided in an outlet pipe 32 of the gas cooler 28 and detect the temperature and pressure of the refrigerant exiting the gas cooler 28, and an intermediate pressure expansion. An output of an intermediate pressure expansion means inlet pressure sensor 53 that is provided in the gas refrigerant pipe 42 on the inlet side of the means 37 and detects the pressure of the gas refrigerant flowing into the intermediate pressure expansion means 37 is connected. An output of a low pressure sensor 54 that is provided in the refrigerant introduction pipe 21 and detects the low pressure side pressure of the refrigerant circuit 1 is connected to the input side of the control means 50.

  Further, the compressor 11, the gas cooler blower 31, the high-pressure expansion unit 34, and the intermediate-pressure expansion unit 37 are connected to the output side of the control unit 50. The control means 50 controls the operation of the compressor 11 and the gas cooler blower 31 based on the output of each sensor, and controls the valve openings of the expansion means 34 and 37.

  Next, the operation of the above configuration will be described. When the compressor 11 is operated by the control means 50, as described above, the low pressure (LP: normal operation state) sucked into the low pressure portion of the first rotary compression element 18 of the compressor 11 via the refrigerant introduction pipe 21. The refrigerant gas of about 2.5 MPa is boosted to an intermediate pressure (MP: about 5 MPa in a normal operation state) by the first rotary compression element 18 and is discharged into the sealed container 12. Thereby, the inside of the airtight container 12 becomes an intermediate pressure (MP).

  The intermediate pressure refrigerant gas in the sealed container 12 flows into the intercooler 22 from the intermediate pressure discharge pipe 23 and radiates heat, and is then sucked into the second rotary compression element 20 of the compressor 11 from the intermediate pressure suction pipe 24. . The intermediate pressure (MP) refrigerant gas sucked into the intermediate pressure portion of the second rotary compression element 20 is compressed in the second stage by the second rotary compression element 20 to generate a high temperature and high pressure (HP: normal operation). In this state, the refrigerant gas becomes a supercritical pressure of about 8 MPa, and flows into the gas cooler 28 from the high-pressure discharge pipe 26 through the oil separator 27.

  The refrigerant radiated by the gas cooler 28 exits from the outlet pipe 32 and reaches the high-pressure expansion means 34 from the inlet pipe 33 of the intermediate pressure control device 29. The refrigerant is squeezed by the high-pressure expansion means 34, the first stage expansion is performed, and the pressure is lowered to 4.5 MPa to 5 MPa. By this first stage expansion, the refrigerant becomes a saturated liquid refrigerant and a gas refrigerant and flows into the intermediate pressure receiver 36 from the outlet pipe 39. The saturated liquid refrigerant that has flowed into the intermediate pressure receiver 36 is stored in the inner bottom part thereof, and the gas refrigerant moves to the upper part for gas-liquid separation.

  The saturated liquid refrigerant stored in the intermediate pressure receiver 36 flows into the liquid refrigerant flow path 38A of the gas cold heat recovery device 38 through the liquid refrigerant pipe 41, passes through there, and flows out to the refrigerant pipe 7. On the other hand, the gas refrigerant in the upper part of the intermediate pressure receiver 36 reaches the intermediate pressure expansion means 37 through the gas refrigerant pipe 42. Then, the pressure is lowered to a low pressure by the intermediate pressure expansion means 37 to expand.

  When the gas refrigerant is expanded to a low pressure, it becomes a low-temperature liquid refrigerant and a gas refrigerant. This gas-liquid mixed refrigerant flows from the gas refrigerant pipe 42 into the gas refrigerant flow path 38B of the gas cold heat recovery device 38, and the liquid refrigerant evaporates. The saturated liquid refrigerant passing through the liquid refrigerant flow path 38A is supercooled by the cold heat of the gas refrigerant and the endothermic action accompanying the evaporation of the liquid refrigerant.

  Then, the saturated liquid refrigerant supercooled by the gas cold heat recovery unit 38 is divided to reach the main expansion means 46A and 46B, where final expansion is performed and flows into the evaporators 47A and 47B, where they are evaporated. To do. Cold air is generated by the endothermic action at this time, and the interior of the showcase units 5A and 5B is cooled to the refrigeration temperature by circulating in the warehouse with a blower.

  The refrigerant exiting each of the evaporators 47A and 47B joins and enters the refrigerant pipe 9. On the other hand, the refrigerant that has passed through the gas refrigerant flow path 38 </ b> B of the gas cold heat recovery device 38 reaches the refrigerant pipe 9 through the refrigerant return pipe 43. Therefore, the refrigerant from the evaporators 47 </ b> A and 47 </ b> B merges and is sucked into the first rotary compression element 18 of the compressor 11 from the refrigerant introduction pipe 21.

  The control means 50 controls the valve opening degree of the high-pressure expansion means 34 based on the outputs of the gas cooler outlet temperature sensor 51 and the gas cooler outlet pressure sensor 52 so that the flow rate of the refrigerant in the gas cooler 28 does not become too fast. If the valve opening degree of the high-pressure expansion means 34 is opened too much, the flow rate of the refrigerant in the gas cooler 28 increases, and sufficient heat dissipation cannot be obtained in the gas cooler 28. The control means 50 monitors the gas cooler outlet temperature and pressure, and controls the valve opening degree of the high-pressure expansion means 34 so as to maintain the required heat dissipation capability in the gas cooler 28. Further, the amount of the gas refrigerant in the intermediate pressure receiver 36 is determined by the valve opening degree of the high pressure expansion means 34.

  Further, the control means 50 determines the valve opening degree of the intermediate pressure expansion means 37 based on the output of the intermediate pressure expansion means inlet pressure sensor 53 so that the pressure (intermediate pressure) of the gas refrigerant flowing into the intermediate pressure expansion means 37 does not decrease too much. To control. That is, the control means 50 controls the valve opening degree of the intermediate pressure expansion means 37 so that the pressure of the gas refrigerant flowing into the intermediate pressure expansion means 37 becomes a constant target value.

  Each showcase unit 5A, 5B is also provided with a chamber temperature sensor (not shown) and a control means for detecting the chamber temperature, and the valve opening degree of the main expansion means 46A, 46B based on the chamber temperature by this control means. And the inside temperature is maintained at a predetermined refrigeration temperature. Based on the output of the low pressure sensor 54, the control means 50 of the refrigerator unit 3 operates by controlling the operating frequency of the compressor 11 when the low pressure side pressure is higher than a predetermined value. Then, the main expansion means 46A, 46B are closed, the low pressure side pressure is reduced to a predetermined value, the compressor 11 is stopped, the main expansion means 46A or 46B is opened, and the low pressure side pressure is increased. The compressor 11 is started.

  FIG. 2 is a ph diagram of the refrigeration apparatus R according to the present invention. In the refrigerant circuit of FIG. 2, locations indicated by reference numerals (a) to (m) correspond to (a) to (m) in FIG. 1. The supercooling in the gas cold heat recovery unit 38 is a portion indicated by (g) to (h) in FIG. 2, and the refrigeration effect from (i) to (a) is increased accordingly. Further, as is clear from this figure, the dryness (i) of the refrigerant at the evaporation temperature of −10 ° C. is significantly lower than the dryness (h) in FIG.

  As described above, in the present invention, the refrigerant discharged from the gas cooler 28 is expanded to reduce its pressure to an intermediate pressure, and then separated into a saturated liquid refrigerant and a gas refrigerant, and the saturated liquid refrigerant is supplied to the main expansion means 46A and 46B. To do. The gas-liquid separated gas refrigerant is expanded by the intermediate pressure expansion means 37 to form a low-temperature liquid refrigerant and a gas refrigerant, and the gas cold heat recovery unit 38 exchanges heat with the saturated liquid refrigerant toward the main expansion means 46A and 46B. As a result, the liquid refrigerant directed to the main expansion means 46A and 46B can be supercooled using the cold heat of the gas refrigerant.

  As a result, a sufficient amount of refrigerant is supplied to the main expansion means 46A and 46B in the supercooled state regardless of the state of the refrigerant discharged from the gas cooler 28, and the dryness of the refrigerant flowing into the evaporators 47A and 47B is reduced. It becomes possible to obtain a large cooling effect in the evaporators 47A and 47B of the refrigeration apparatus R using the carbon dioxide refrigerant.

  In particular, since the cooling capacity of the separated gas refrigerant can be replaced with the cooling capacity of the evaporators 47A and 47B, the evaporators 47A and 47B can be used even when the gas ratio of the refrigerant discharged from the gas cooler 28 is high. It is possible to improve the cooling effect.

  Further, the refrigerant discharged from the gas cooler 28 is expanded by the high-pressure expansion means 34 and the pressure thereof is reduced to an intermediate pressure. Thereafter, the refrigerant is stored in the intermediate pressure receiver 36 and separated into the saturated liquid refrigerant and the gas refrigerant. The pressure receiver 36 can also provide an effect of adjusting the amount of refrigerant, and the refrigerant circuit 1 can be filled with a larger amount of refrigerant. Furthermore, since it is possible to absorb the fluctuation of the high pressure side pressure in the intermediate pressure receiver 36, the saturated liquid refrigerant can be supplied to the main expansion means 46A and 46B at a constant intermediate pressure. Thus, stable superheat control in the evaporators 47A and 47B can be performed.

  At this time, an intermediate pressure control device 29 having a high pressure expansion means 34, an intermediate pressure receiver 36, a gas cold heat recovery device 38, and an intermediate pressure expansion means 37 is configured, and this intermediate pressure control device 29 is configured as the refrigerator unit 3. Therefore, the installation space on the showcase unit 5A, 5B side can be reduced.

  Further, since the refrigerant that has exited the gas refrigerant flow path 38A of the gas cold heat recovery device 38 is sucked into the first rotary compression element 18 of the compressor 11 together with the refrigerant that has exited the evaporators 47A and 47B, The pressure of the gas refrigerant in the pressure receiver 36 can be lowered to a low pressure by the intermediate pressure expansion means 37, and a high supercooling effect by the gas refrigerant can be expected.

  Further, an intermediate pressure expansion means inlet pressure sensor 53 for detecting the pressure of the gas refrigerant flowing into the intermediate pressure expansion means 37 is provided, so that the control means 50 does not cause the pressure of the gas refrigerant flowing into the intermediate pressure expansion means 37 to decrease too much. In addition, since the intermediate pressure expansion means 37 is controlled so as to have a constant target value, it is possible to maintain the supercooling effect of the saturated liquid refrigerant in the gas cold heat recovery unit 38.

  Furthermore, a gas cooler outlet temperature sensor 51 and a gas cooler outlet pressure sensor 52 for detecting the temperature and pressure of the refrigerant discharged from the gas cooler 28 are provided, and the control means 50 provides a high pressure so that the flow rate of the refrigerant in the gas cooler 28 does not become too fast. Since the expansion means 34 is controlled, it is possible to ensure the heat dissipation capability of the refrigerant in the gas cooler 28.

  Although the intermediate pressure control device 29 is provided in the refrigerator unit 3 in the embodiment, the present invention is not limited to this, and may be provided on the showcase unit 5A or 5B side if space is allowed. By doing so, the long refrigerant pipe 7 connecting the refrigerator unit 3 and the showcase units 5A and 5B can be conveyed at high pressure, so that the amount of refrigerant charged can be reduced. Become.

  Moreover, each value shown in the Example is not restricted to it, It should be suitably set according to the capacity | capacitance of a freezing apparatus, and the intended purpose. Further, in the embodiments, the present invention has been described by taking a showcase unit as an example of a use side unit, but the present invention is not limited to this, and the present invention is also effective for a household refrigerator, a commercial refrigerator, a prefabricated refrigerator, an air conditioner, and the like. It is. Furthermore, the refrigerant is not limited to carbon dioxide, and the refrigeration apparatus of the present invention is effective for various refrigerants whose high pressure side is operated at a supercritical pressure.

R Refrigeration equipment 1 Refrigerant circuit 3 Refrigerator unit 5A, 5B Showcase unit (use side unit)
7, 9 Refrigerant piping 11 Compressor 28 Gas cooler 29 Medium pressure control device 34 High pressure expansion means 36 Medium pressure receiver 37 Medium pressure expansion means 38 Gas cold heat recovery unit 38A Liquid refrigerant flow path 38B Gas refrigerant flow path 46A, 46B Main expansion means (Expansion means)
47A, 47B Evaporator 50 Control means 51 Gas cooler outlet temperature sensor 52 Gas cooler outlet pressure sensor 53 Medium pressure expansion means inlet pressure sensor

Claims (8)

In the refrigeration apparatus in which the refrigerant circuit is configured by the compression means, the gas cooler, the expansion means, and the evaporator, and the high pressure side is the supercritical pressure,
The high-pressure refrigerant discharged from the gas cooler is expanded and lowered to an intermediate pressure and separated into a saturated liquid refrigerant and a gas refrigerant, and then the gas refrigerant is expanded to exchange heat with the saturated liquid refrigerant, and the saturated liquid refrigerant is A refrigeration apparatus that supplies the expansion means and returns the gas refrigerant to the compression means. In the refrigeration apparatus in which the refrigerant circuit is configured by the compression means, the gas cooler, the main expansion means, and the evaporator, and the high pressure side is the supercritical pressure,
An intermediate pressure control device connected between the gas cooler and the main expansion means;
The intermediate pressure control device
High-pressure expansion means for expanding the high-pressure refrigerant discharged from the gas cooler to lower it to an intermediate pressure;
An intermediate pressure receiver for storing the refrigerant expanded by the high pressure expansion means and separating the refrigerant into a saturated liquid refrigerant and a gas refrigerant;
A gas having a liquid refrigerant flow path into which the saturated liquid refrigerant in the intermediate pressure receiver flows and a gas refrigerant flow path into which the gas refrigerant in the intermediate liquid receiver flows and exchanging heat between the refrigerant flowing through both flow paths. A cold energy recovery device,
Medium pressure expansion means for expanding the gas refrigerant in the intermediate pressure receiver and then flowing it into the gas refrigerant flow path of the gas cold heat recovery device;
A refrigeration apparatus comprising: a refrigerant that has flowed out of a liquid refrigerant flow path of the gas cold heat recovery device is allowed to flow into the main expansion means; and the refrigerant that has come out of the gas refrigerant flow path is returned to the compression means.   The refrigerating apparatus according to claim 2, wherein the refrigerant that has exited the gas refrigerant flow path of the gas cold heat recovery device is sucked into the compression means together with the refrigerant that has exited the evaporator. An intermediate pressure expansion means inlet pressure sensor for detecting the pressure of the gas refrigerant flowing into the intermediate pressure expansion means;
4. The refrigeration apparatus according to claim 2, further comprising a control unit that controls the intermediate pressure expansion unit based on an output of the intermediate pressure expansion unit inlet pressure sensor. A gas cooler outlet temperature sensor and a gas cooler outlet pressure sensor for detecting a temperature and a pressure of the refrigerant discharged from the gas cooler;
5. The refrigeration apparatus according to claim 2, further comprising a control unit that controls the high-pressure expansion unit based on an output of each sensor. A refrigerator unit including the compression means and a gas cooler;
A use side unit including the main expansion means and an evaporator,
The refrigeration apparatus according to any one of claims 2 to 5, wherein the refrigerator unit also includes the intermediate pressure control device. A refrigerator unit including the compression means and a gas cooler;
A use side unit including the main expansion means and an evaporator,
The refrigeration apparatus according to any one of claims 2 to 5, wherein the use side unit also includes the intermediate pressure control device.   The refrigeration apparatus according to any one of claims 1 to 7, wherein carbon dioxide is used as the refrigerant.

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