JP2015148407A - Refrigeration device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem in supercooling a refrigerant flowed out of a gas cooler by a refrigerant flowed out of an evaporator in a refrigeration device in which a high pressure side becomes supercritical pressure.SOLUTION: A refrigeration device includes: a heat exchanger 29 provided on a downstream side of a gas cooler 28 and an upstream side of an electric expansion valve 33; a bypass circuit 60 connected in parallel with respect to a series circuit of an electric expansion valve 39 and an evaporator 41; an electric expansion valve 65 provided in the bypass circuit; and a control device 57. The refrigeration device flows a refrigerant flowing out of the evaporator and sucked into a compressor 11 into a first flow passage 29A of the heat exchanger 29, and flows a refrigerant flowing out of the gas cooler and flowing into the electric expansion valve 33 into a second flow passage 29B of the heat exchanger 29. Thereby, the refrigerant flowing in the second flow passage 29B of the heat exchanger 29 is supercooled by the refrigerant flowing in th first flow passage 29A of the heat exchanger 29.

Description

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

  Conventionally, this type of refrigeration apparatus has a refrigeration cycle composed of a compression means, a gas cooler, a throttle means, etc., and the refrigerant compressed by the compression means dissipates heat in the gas cooler and is depressurized by the throttle means, and then in an evaporator. The refrigerant was evaporated, and ambient air was 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, the thing using the carbon dioxide which is a natural refrigerant | coolant is developed as a substitute of a fluorocarbon refrigerant | coolant. The carbon dioxide refrigerant is a refrigerant having a high and low pressure difference, and has a low critical pressure. It is known that the high pressure side of the refrigerant cycle is brought into a supercritical state by compression (see, for example, Patent Document 1).

  Moreover, in the heat pump device constituting the water heater, a carbon dioxide refrigerant capable of obtaining an excellent heating action in the gas cooler has been used. In that case, the refrigerant discharged from the gas cooler is expanded in two stages, There has also been developed an apparatus in which a gas-liquid separator is interposed between expansion devices to enable gas injection into a compressor (see, for example, Patent Document 2).

  On the other hand, for example, in an refrigeration system that uses an endothermic action in an evaporator installed in a showcase or the like to cool the interior, the refrigerant temperature at the outlet of the gas cooler is high due to factors such as high outside air temperature (heat source temperature on the gas cooler side). Under higher conditions, the specific enthalpy at the inlet of the evaporator increases, which causes a problem that the refrigerating capacity is remarkably reduced. In such a case, if the discharge pressure (high-pressure side pressure) of the compression means is increased in order to ensure the refrigeration capacity, the compression power increases and the coefficient of performance decreases.

  Therefore, the refrigerant cooled by the gas cooler is divided into two refrigerant streams, one of the divided refrigerant streams is throttled by the auxiliary throttle means, and then flows into one passage of the split heat exchanger to be compressed (compressor means) A so-called split-cycle refrigeration system is proposed in which the refrigerant flow is returned to the intermediate pressure portion of the other, and the other refrigerant flow is passed through the other flow path of the split heat exchanger to exchange heat, and then flows into the evaporator via the main throttle means. ing. According to such a refrigeration apparatus, the second refrigerant flow can be cooled by the first refrigerant flow expanded under reduced pressure, and the refrigeration capacity can be improved by reducing the specific enthalpy at the inlet of the evaporator. (For example, refer to Patent Document 3).

Japanese Patent Publication No. 7-18602 JP 2007-178042 A JP 2011-133207 A

  As another method for reducing the specific enthalpy at the inlet of the evaporator as described above, a heat exchanger is provided at the outlet of the gas cooler, and the refrigerant and evaporator on the high-pressure side that has discharged the gas cooler to the two flow paths of the heat exchanger are discharged. It is conceivable to flow the low-pressure side refrigerant and cool the high-pressure side refrigerant with the low-pressure side refrigerant.

  Although the refrigerant flowing into the main throttle means can be supercooled also by such a method, the temperature of the low-pressure side refrigerant that comes out of the heat exchanger and is sucked into the compressor rises. Along with this, the temperature inside the compressor rises (the temperature of the refrigerant in the intermediate pressure section and the temperature of the discharged refrigerant rises), which lowers the operating efficiency of the compressor and causes the risk of causing damage. .

  The present invention has been made to solve the conventional technical problem, and in a refrigeration system having a supercritical pressure on the high pressure side, the refrigerant that has exited the gas cooler is supercooled with the refrigerant that has exited the evaporator. The purpose is to solve the problem.

  The present invention relates to a refrigeration apparatus in which a refrigerant circuit is configured by a compression unit, a gas cooler, a main throttle unit, and an evaporator, and the high pressure side is at a supercritical pressure, and is downstream of the gas cooler and upstream of the main throttle unit. Pressure adjusting throttle means connected to the refrigerant circuit on the side, a receiver downstream of the pressure adjusting throttle means, connected to the refrigerant circuit upstream of the main throttle means, and downstream of the gas cooler A heat exchanger provided in the refrigerant circuit upstream of the pressure adjusting throttle means and a gas cooler to the liquid receiver through the heat exchanger and the pressure adjusting throttle means, and from the lower part of the liquid receiver to the refrigerant To the main throttle means, the auxiliary circuit for returning the refrigerant in the receiver to the intermediate pressure part of the compression means via the auxiliary throttle means, and the series circuit of the main throttle means and the evaporator A bypass circuit connected in parallel to the A bypass throttling means provided in the bypass circuit, a pressure regulating throttling means, an auxiliary throttling means, and a control means for controlling the bypass throttling means, and the refrigerant drawn from the evaporator and sucked into the compression means By flowing the refrigerant flowing out of the gas cooler and flowing into the pressure adjusting throttle means into the second flow path of the heat exchanger, the first flow path of the heat exchanger is made to flow through the first flow path of the heat exchanger. The refrigerant flowing through the second flow path of the heat exchanger is supercooled by the flowing refrigerant.

  The refrigeration apparatus according to a second aspect of the invention is characterized in that in the above invention, the control means controls the suction temperature of the low-pressure side refrigerant sucked into the compression means by the bypass throttling means to a predetermined target value.

  According to a third aspect of the present invention, there is provided a refrigeration apparatus comprising an internal heat exchanger provided in a refrigerant circuit downstream of the liquid receiver and upstream of the main throttling means in each of the above-mentioned inventions. By flowing the refrigerant going to the exchanger through the first flow path of the internal heat exchanger and flowing the refrigerant going out of the lower part of the receiver and going to the main throttle means into the second flow path of the internal heat exchanger, The refrigerant flowing through the second flow path of the internal heat exchanger is supercooled by the refrigerant flowing through the first flow path of the exchanger.

  In the refrigeration apparatus according to a fourth aspect of the present invention, in each of the above inventions, the control means controls the high-pressure side pressure of the refrigerant circuit upstream of the pressure adjustment throttle means to a predetermined target value by the pressure adjustment throttle means. It is characterized by.

  According to a fifth aspect of the present invention, in the refrigeration apparatus of the present invention, the auxiliary throttle means has a first auxiliary circuit throttle means in each of the above inventions, and the auxiliary circuit causes the refrigerant to flow out from the upper part of the liquid receiver. The control means controls the pressure of the refrigerant in the liquid receiver to a predetermined target value by the first auxiliary circuit throttle means.

  In the refrigeration apparatus according to a sixth aspect of the present invention, in each of the above inventions, the auxiliary throttle means has a second auxiliary circuit throttle means, and the auxiliary circuit causes the refrigerant to flow out from the lower part of the liquid receiver, and the second auxiliary circuit. The control means controls the discharge temperature of the refrigerant discharged from the compression means to the gas cooler to a predetermined target value by the second auxiliary circuit restriction means. To do.

  According to a seventh aspect of the present invention, there is provided a refrigeration apparatus comprising a blower for air-cooling the gas cooler in each of the above-mentioned inventions, and the control means is such that the temperature of the refrigerant exiting the gas cooler becomes a predetermined target value determined with respect to the outside air temperature. And controlling the operation of the blower.

  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.

  According to the present invention, in the refrigerating apparatus in which the refrigerant circuit is configured by the compression means, the gas cooler, the main throttle means, and the evaporator, and the high pressure side becomes the supercritical pressure, the downstream side of the gas cooler, the main throttle means A pressure adjusting throttle means connected to the upstream refrigerant circuit, a receiver downstream of the pressure adjusting throttle means upstream of the main throttle means, and a gas cooler A heat exchanger provided in the refrigerant circuit downstream and upstream of the pressure adjusting throttle means, and from the gas cooler to the liquid receiver via the heat exchanger and the pressure adjusting throttle means, the lower part of the receiver A main circuit for causing the refrigerant to flow out from the main throttle means, an auxiliary circuit for returning the refrigerant in the receiver to the intermediate pressure portion of the compression means via the auxiliary throttle means, and a series of the main throttle means and the evaporator Bypass circuit connected in parallel to the circuit And a bypass throttling means provided in the bypass circuit, a pressure adjusting throttling means, an auxiliary throttling means, and a control means for controlling the bypass throttling means. The refrigerant flows through the first flow path of the heat exchanger, and the refrigerant flowing out of the gas cooler and flowing into the pressure adjusting throttle means flows through the second flow path of the heat exchanger. The refrigerant flowing in the second flow path of the heat exchanger is supercooled by the low-pressure side refrigerant flowing in the first flow path, and the dryness of the refrigerant at the outlet of the pressure adjusting throttle means can be reduced.

  The refrigerant flowing through the second flow path of the heat exchanger enters the receiver through the pressure adjusting throttle means, flows out from the lower part of the receiver, is throttled by the main throttle means, and then flows into the evaporator. Therefore, the specific enthalpy at the inlet of the evaporator can be reduced by supercooling in the heat exchanger, and the refrigerating capacity can be effectively improved.

  Also, a part of the refrigerant liquefied by expansion by the pressure adjusting throttle means evaporates in the receiver and becomes a gas refrigerant whose temperature is lowered, and the rest becomes a liquid refrigerant once in the lower part of the receiver. It will be stored. Then, since the liquid refrigerant in the lower part in the liquid receiver flows into the main throttle means, it is possible to allow the refrigerant to flow into the main throttle means in a full liquid state, particularly in refrigeration conditions where the evaporation temperature in the evaporator is high. The refrigeration capacity can be improved.

  Furthermore, since the liquid receiver also has the effect of absorbing fluctuations in the amount of circulating refrigerant in the refrigerant circuit, it also has the effect of absorbing errors in the refrigerant charge amount.

  In particular, a bypass circuit connected in parallel to the series circuit of the main throttle means and the evaporator and a bypass throttle means provided in the bypass circuit are provided. Means bypasses the main throttle means and the evaporator by the bypass throttle means and causes the refrigerant to flow through the first flow path of the heat exchanger, where the refrigerant is evaporated and sucked into the compression means by the suction temperature of the low-pressure side refrigerant By controlling to this target value, it is possible to prevent an increase in the refrigerant suction temperature of the compression means, and to avoid a decrease in operating efficiency and damage of the compression means.

  Further, as in the third aspect of the present invention, an internal heat exchanger provided in a refrigerant circuit downstream of the liquid receiver and upstream of the main throttle means is provided, and the refrigerant exits from the evaporator and travels toward the heat exchanger Is allowed to flow through the first flow path of the internal heat exchanger, and the refrigerant that exits from the lower part of the receiver and flows toward the main throttle means flows into the second flow path of the internal heat exchanger. With the low-pressure side refrigerant flowing in the first flow path, the refrigerant flowing out of the liquid receiver and flowing in the second flow path of the internal heat exchanger can be supercooled. It is possible to further improve the refrigerating capacity by suppressing re-expansion of the refrigerant.

  According to the invention of claim 4, in addition to each of the above inventions, the control means causes the pressure adjustment throttle means to set the high-pressure side pressure of the refrigerant circuit upstream of the pressure adjustment throttle means to a predetermined target value. Since the control is performed, the high pressure side pressure at which the refrigerant is discharged from the compression means is increased, so that the operation efficiency of the compression means is reduced, or the inconvenience of damaging the compression means can be avoided.

  According to the invention of claim 5, in addition to the above inventions, the auxiliary throttle means has a first auxiliary circuit throttle means, and the auxiliary circuit causes the refrigerant to flow out from the upper part of the receiver, The control circuit controls the pressure of the refrigerant in the liquid receiver to a predetermined target value by the first auxiliary circuit throttle means. With this auxiliary circuit throttling means, it is possible to control the pressure of the refrigerant conveyed from the lower part of the receiver to the main throttling means while suppressing the influence of fluctuations in the high pressure side pressure.

  Further, by lowering the pressure of the refrigerant flowing into the main throttle means by the first auxiliary circuit throttle means, it is possible to use a pipe having a low pressure resistance as a pipe leading to the main throttle means. Thereby, it becomes possible to improve workability and construction cost.

  In particular, when the low temperature gas is extracted from the upper part of the liquid receiver through the first auxiliary circuit throttle means, the pressure in the liquid receiver decreases. As a result, the temperature is lowered in the liquid receiver, so that the refrigerant condenses, and the liquid refrigerant can be effectively stored in the liquid receiver.

  According to the invention of claim 6, in addition to the above inventions, the auxiliary throttle means has the second auxiliary circuit throttle means, and the auxiliary circuit causes the refrigerant to flow out from the lower part of the receiver, and the second And the control means controls the discharge temperature of the refrigerant discharged from the compression means to the gas cooler to a predetermined target value by the second auxiliary circuit throttle means. In addition, so-called injection is performed on the intermediate pressure portion of the compression means to cool the compression means, and it is possible to avoid the disadvantage that the discharge temperature of the refrigerant from the compression means becomes too high.

  Further, according to the invention of claim 7, in addition to the above inventions, a blower for air-cooling the gas cooler is provided, and the control means has a predetermined target value at which the temperature of the refrigerant that has exited the gas cooler is determined with respect to the outside air temperature. Therefore, the temperature of the refrigerant at the outlet of the gas cooler can be maintained at an appropriate value while suppressing excessive operation of the blower that air-cools the gas cooler. On the other hand, the high-pressure side pressure may be controlled by the pressure adjusting throttle means as in the fourth aspect, and by these, the compression means can be protected and stable operation can be maintained.

  In particular, when carbon dioxide is used as the refrigerant as in the invention of claim 8, the above-described inventions can effectively improve the refrigerating capacity and improve the performance.

It is a refrigerant circuit figure of the freezing apparatus of one Example to which this invention is applied (Example 1). FIG. 2 is a Ph diagram of a refrigerant circuit of the refrigeration apparatus in FIG. 1. It is a refrigerant circuit figure of the freezing apparatus of the other Example to which this invention is applied (Example 2). FIG. 4 is a Ph diagram of a refrigerant circuit of the refrigeration apparatus in FIG. 3.

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

(1) Configuration of Refrigeration Apparatus R FIG. 1 is a refrigerant circuit diagram of a refrigeration apparatus R according to an embodiment to which the present invention is applied. The refrigeration apparatus R in this embodiment is a show of a refrigerator unit 3 installed in a machine room or the like of a store such as a supermarket, and one or a plurality of units (only one is shown in the drawing) installed in the store sales area. The refrigerator unit 3 and the showcase 4 are connected by a refrigerant pipe (liquid pipe) 8 and a refrigerant pipe 9 via a unit outlet 6 and a unit inlet 7 so that a predetermined refrigerant circuit 1 is provided. It is composed.

  The refrigerant circuit 1 according to the embodiment uses carbon dioxide (R744) whose refrigerant pressure on the high pressure side is equal to or higher than the critical pressure (supercritical) as the 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 11 as compression means. In the present embodiment, the compressor 11 is an internal intermediate pressure type two-stage compression rotary compressor, and includes a hermetic container 12, an electric element (drive element) 13 disposed and housed in the hermetic container 12, and the electric element 13. Rotational compression comprising a first (low-stage side) rotary compression element (first compression element) 14 and a second (high-stage side) rotary compression element (second compression element) 16 driven by the rotary shaft It consists of a mechanism part.

  The first rotary compression element 14 of the compressor 11 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, increases the pressure to an intermediate pressure, and discharges it into the sealed container 12. The second rotary compression element 16 further sucks in the intermediate pressure refrigerant compressed by the first rotary compression element 14, 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 frequency of the first rotary compression element 14 and the second rotary compression element 16 can be controlled by changing the operating frequency of the electric element 13.

  On the side surface of the sealed container 12 of the compressor 11, a low-stage suction port 17 communicating with the first rotary compression element 14, a low-stage discharge port 18 communicating with the inside of the sealed container 12, and a second rotational compression A high-stage suction port 19 and a high-stage discharge port 21 communicating with the element 16 are formed. One end of the refrigerant introduction pipe 22 is connected to the lower stage side suction port 17 of the compressor 11, and the other end is connected to the refrigerant pipe 9 at the unit inlet 7. A low-stage suction port 17 to which the refrigerant introduction pipe 22 is connected communicates with the suction side of the first rotary compression element 14 that is a low-pressure portion of the compressor 11.

  The refrigerant gas having a low pressure (LP: about 2.6 MPa in a normal operation state) sucked into the suction side (low pressure portion of the compressor 11) of the first rotary compression element 14 from the low stage side suction port 17 The pressure is increased to an intermediate pressure (MP: about 5.5 MPa in a normal operation state) by one rotary compression element 14 and discharged into the sealed container 12. As a result, the inside of the sealed container 12 becomes an intermediate pressure (MP), which becomes an intermediate pressure portion of the compressor 11.

  One end of the intermediate pressure discharge pipe 23 is connected to the low-stage discharge port 18 of the compressor 11 from which the intermediate pressure refrigerant gas in the sealed container 12 is discharged, and the other end is connected to the inlet of the intercooler 24. Has been. The intercooler 24 air-cools the intermediate pressure refrigerant discharged from the first rotary compression element 14, and one end of an intermediate pressure suction pipe 26 is connected to the outlet of the intercooler 24. The other end of the pressure suction pipe 26 is connected to the higher stage suction port 19 of the compressor 11.

  The intermediate pressure (MP) refrigerant gas sucked into the second rotary compression element 16 from the high-stage side suction port 19 is compressed in the second stage by the second rotary compression element 16 to generate a high temperature and high pressure (HP). : Supercritical pressure of about 9 MPa in a normal operation state).

  One end of a high-pressure discharge pipe 27 is connected to the high-stage discharge port 21 communicating with the high-pressure chamber side of the second rotary compression element 16 of the compressor 11, and the other end is an inlet of a gas cooler (heat radiator) 28. It is connected to the. An oil separator 20 is provided in the high-pressure discharge pipe 27. The oil separator 20 separates the oil in the refrigerant discharged from the compressor 11 and returns it to the sealed container 12 of the compressor 11 through the oil passage 25A and the electric valve 25B. Reference numeral 55 denotes a check valve interposed in the high-pressure discharge pipe 27 before the oil separator 20, and the oil separator 20 direction is the forward direction.

  The gas cooler 28 cools the high-pressure discharged 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. In the present embodiment, the gas cooler 28 is juxtaposed with the intercooler 24 described above, and these are disposed in the same air passage.

  One end of a gas cooler outlet pipe 32 is connected to the outlet of the gas cooler 28, and the other end of the gas cooler outlet pipe 32 is connected to an inlet of an electric expansion valve 33 as a pressure adjusting throttle means. The electric expansion valve 33 squeezes and expands the refrigerant discharged from the gas cooler 28, and adjusts the high-pressure side pressure of the refrigerant circuit 1 upstream from the electric expansion valve 33. The outlet of the electric expansion valve 33 is the receiver inlet. It is connected to the upper part of the liquid receiver 36 through a pipe 34.

  The liquid receiver 36 is a volume body (tank) having a space of a predetermined volume inside, and one end of a liquid receiver outlet pipe 37 is connected to the lower part thereof, and the other end of the liquid receiver outlet pipe 37 is a unit. The outlet 6 is connected to the refrigerant pipe 8. In addition, a second flow path 29B of the heat exchanger 29 is interposed in the gas cooler outlet pipe 32. The gas cooler outlet pipe 32, the second flow path 29B of the heat exchanger 29, the electric expansion valve 33, the liquid receiver The receiver inlet pipe 34, the receiver 36 and the receiver outlet pipe 37 constitute the main circuit 38 in the present invention.

  On the other hand, the showcase 4 installed in the store is connected to the refrigerant pipes 8 and 9. The showcase 4 is provided with an electric expansion valve 39 and an evaporator 41 as main throttle means, which are sequentially connected between the refrigerant pipe 8 and the refrigerant pipe 9 to constitute a series circuit (electric expansion). The valve 39 is on the refrigerant pipe 8 side, and the evaporator 41 is on the refrigerant pipe 9 side). Further, the evaporator 41 is provided with a cool air circulation blower (not shown) that blows air to the evaporator 41.

  The refrigerant pipe 9 is connected to the low-stage suction port 17 that communicates with the first rotary compression element 14 of the compressor 11 via the refrigerant introduction pipe 22 as described above. A first flow path 29 </ b> A of the heat exchanger 29 is interposed in the refrigerant introduction pipe 22. Furthermore, a bypass circuit 60 is connected from the receiver outlet pipe 37 to the refrigerant introduction pipe 22 upstream of the first flow path 29A of the heat exchanger 29. The bypass circuit 60 is connected in parallel to the series circuit of the electric expansion valve 39 and the evaporator 41, and an electric expansion valve 65 is provided in the bypass circuit 60 as bypass throttling means.

  On the other hand, one end of a gas pipe 42 is connected to the upper portion of the liquid receiver 36, and the other end of the gas pipe 42 is connected to an inlet of an electric expansion valve 43 as a first auxiliary circuit throttle means. . The gas pipe 42 causes the gas refrigerant to flow out from the upper part of the liquid receiver 36 and flow into the electric expansion valve 43. One end of a return pipe 44 is connected to the outlet of the electric expansion valve 43.

  In addition, one end of a liquid pipe 46 communicating with the lower part of the liquid receiver 36 is connected to the liquid receiver outlet pipe 37 via the liquid receiver outlet pipe 37, and the other end of the liquid pipe 46 is electrically expanded. It communicates with a return pipe 44 on the downstream side of the valve 43. Further, an electric expansion valve 47 as a second auxiliary circuit throttle means is interposed in the liquid pipe 46. The electric expansion valve 43 (first auxiliary circuit throttle means) and the electric expansion valve 47 (second auxiliary circuit throttle means) constitute auxiliary throttle means in the present application. Further, the liquid pipe 46 causes liquid refrigerant to flow out from the lower part of the liquid receiver 36 and flow into the electric expansion valve 47.

  Further, the other end of the return pipe 44 communicates with the intermediate pressure suction pipe 26 as an example of an intermediate pressure region connected to the intermediate pressure portion of the compressor 11. And these return piping 44, the electric expansion valve 43, the electric expansion valve 47, the gas piping 42, and the liquid piping 46 comprise the auxiliary circuit 48 in this invention. Reference numeral 70 denotes a communication pipe that connects the intermediate pressure suction pipe 26 and the refrigerant introduction pipe 22. Reference numeral 75 denotes an electromagnetic valve that is opened when the compressor is started to reduce the starting load.

  With such a configuration, the electric expansion valve 33 is located downstream of the gas cooler 28 and upstream of the electric expansion valve 39. The liquid receiver 36 is located downstream of the electric expansion valve 33 and upstream of the electric expansion valve 39. Furthermore, the heat exchanger 29 is positioned downstream of the gas cooler 28 and upstream of the electric expansion valve 33, and the refrigerant circuit 1 of the refrigeration apparatus R in this embodiment is configured as described above.

  Various sensors are attached to various portions of the refrigerant circuit 1. That is, a high-pressure sensor 49 is attached to the gas cooler outlet pipe 32 downstream of the second flow path 29B of the heat exchanger 29 and upstream of the electric expansion valve 33, and the high-pressure side pressure HP (compressor 11) of the refrigerant circuit 1 is attached. The pressure between the high-stage discharge port 21 and the inlet of the electric expansion valve 33 is detected. Further, a low pressure sensor 51 is attached to a communication pipe 70 (the refrigerant introduction pipe 22 side of the electromagnetic valve 75) communicating with the refrigerant introduction pipe 22 so that the low pressure side pressure LP of the refrigerant circuit 1 (the outlet of the electric expansion valve 39 and the low stage). The pressure between the side suction ports 17) is detected. Further, an intermediate pressure sensor 52 is attached to a communication pipe 70 (on the intermediate pressure suction pipe 26 side of the solenoid valve 75) communicating with the intermediate pressure suction pipe 26, and an intermediate pressure MP that is a pressure in an intermediate pressure region of the refrigerant circuit 1 is provided. (The pressure in the sealed container 12, the intercooler 24, the intermediate pressure suction pipe 26, and the high-stage suction port 19) is detected.

  In addition, a receiver pressure sensor 53 is attached to the gas pipe 42, and the receiver pressure sensor 53 detects the pressure TP in the receiver 36. That is, the pressure in the liquid receiver 36 becomes the pressure of the refrigerant that leaves the refrigerator unit 3 and flows into the electric expansion valve 39 via the refrigerant pipe 8. A gas cooler outlet temperature sensor 54 is attached to the gas cooler outlet pipe 32 downstream of the gas cooler 28 and upstream of the second flow path 29B of the heat exchanger 29. The temperature IT of the refrigerant flowing into the flow path 29B is detected.

  An electric expansion valve inlet temperature sensor 56 is attached to the gas cooler outlet pipe 32 downstream of the second flow path 29B of the heat exchanger 29 and upstream of the electric expansion valve 33, so that the second The temperature OT of the refrigerant exiting the flow path 29B is detected. An outside air temperature sensor 61 is attached to the air inlet side of the gas cooler 28 to detect the outside air temperature AT. In addition, a refrigerator inlet temperature sensor 62 is attached to the refrigerant introduction pipe 22 downstream of the first flow path 29A of the heat exchanger 29 and before the low-stage suction port 17, so that the first The suction temperature ST of the low-pressure side refrigerant sucked into the rotary compression element 14 is detected. Furthermore, a discharge temperature sensor 67 is attached to the high pressure discharge pipe 27 to detect the discharge temperature DT of the refrigerant discharged from the compressor 11 to the gas cooler 28.

  Reference numeral 63 denotes an intermediate pressure suction temperature sensor attached to the intermediate pressure suction pipe 26, which detects the temperature of the intermediate pressure refrigerant sucked into the high-stage suction port 19. Reference numeral 64 denotes a receiver outlet temperature sensor connected to the receiver outlet pipe 37, which detects the temperature of the liquid refrigerant flowing out from the lower part of the receiver 36. Reference numeral 66 denotes a refrigerator outlet temperature sensor attached to the receiver outlet pipe 37 in front of the unit outlet 6, and detects the temperature of the refrigerant flowing from the refrigerator unit 3 to the refrigerant pipe 8.

  These sensors 49, 51, 52, 53, 54, 56, 61, 62, 63, 64, 66, and 67 are input to the control device 57 constituting the control means of the refrigerator unit 3 composed of a microcomputer. It is connected. The output of the control device 57 includes an electric element 13 of the compressor 11, a blower 31, an electric expansion valve (pressure adjusting throttle means) 33, an electric expansion valve (first auxiliary circuit throttle means) 43, and an electric expansion valve. (Second auxiliary circuit throttling means) 47, electric expansion valve 65 (bypass throttling means), electric valve 25B, electric expansion valve (main throttling means) 39 are connected, and the controller 57 sets and outputs each sensor. These are controlled based on data and the like.

  In the following description, it is assumed that the control device 57 controls the electric expansion valve (main throttle means) 39 on the showcase 4 side and the above-mentioned cool air circulation blower. Through a control device (not shown) on the side of the showcase 4 that operates in cooperation with the control device 57. Therefore, the control means in the present invention has a concept including the control device 57, the control device on the showcase 4 side, the main control device described above, and the like.

(2) Operation of Refrigeration Apparatus R Next, the operation of the refrigeration apparatus R with the above configuration will be described. When the electric element 13 of the compressor 11 is driven by the control device 57, the first rotary compression element 14 and the second rotary compression element 16 rotate and the first rotary compression element 14 is rotated from the low-stage suction port 17. The refrigerant gas at a low pressure (LP mentioned above: about 2.6 MPa in the normal operation state) is sucked into the suction side (low pressure portion). Then, the pressure is increased to an intermediate pressure (MP described above: about 5.5 MPa in the normal operation state) by the first rotary compression element 14 and discharged into the sealed container 12. Thereby, the inside of the airtight container 12 becomes an intermediate pressure (MP) (intermediate pressure part).

  Then, the intermediate-pressure refrigerant gas in the sealed container 12 enters the intercooler 24 from the low-stage discharge port 18 through the intermediate-pressure discharge pipe 23, and is then air-cooled there, and then through the intermediate-pressure suction pipe 26 to the high-stage suction. Return to mouth 19. The intermediate pressure (MP) refrigerant gas that has returned to the high-stage suction port 19 is sucked into the second rotary compression element 16, and the second stage compression is performed by the second rotary compression element 16, resulting in a high temperature. The refrigerant gas becomes high-pressure (HP: supercritical pressure of about 9 MPa in the above-described normal operation state) and is discharged from the high-stage discharge port 21 to the high-pressure discharge pipe 27.

(2-1) Control of the electric expansion valve 33 The refrigerant gas discharged to the high-pressure discharge pipe 27 flows into the gas cooler 28 through the check valve 55 and the oil separator 20, and after being cooled in the air, flows out from the gas cooler outlet pipe 32. To do. The refrigerant gas that has entered the gas cooler outlet pipe 32 is supercooled in the second flow path 29B of the heat exchanger 29 as will be described later, and then reaches the electric expansion valve (pressure adjusting throttle means) 33. The electric expansion valve 33 is provided to control the high pressure side pressure HP of the refrigerant circuit 1 upstream of the electric expansion valve 33 to a predetermined target value THP (for example, 9 MPa described above). Is controlled by the controller 57 so that the high pressure side pressure HP becomes the target value THP (PID control).

  This target value THP is determined based on the temperature of the refrigerant flowing into the electric expansion valve 33 detected by the electric expansion valve inlet temperature sensor 56. The target value THP is an appropriate value of the high-pressure side pressure HP corresponding to the temperature of the refrigerant flowing into the electric expansion valve 33. The higher the refrigerant temperature, the higher the target value THP. Thus, by controlling the high-pressure side pressure HP upstream from the electric expansion valve 33 to the target value THP, the high-pressure side pressure HP at which the refrigerant is discharged from the compressor 11 is increased, and the operation of the compressor 11 is performed. It is possible to avoid inconvenience that the efficiency is reduced or the compressor 11 is damaged.

  The supercritical refrigerant gas emitted from the gas cooler 28 was cooled (supercooled) by the low-pressure side refrigerant flowing in the first flow path 29A in the second flow path 29B of the heat exchanger 29 as will be described later. Thereafter, the liquid is liquefied by being throttled and expanded by the electric expansion valve 33, flows into the liquid receiver 36 from the upper part via the liquid receiver inlet pipe 34, and partly evaporates. The liquid receiver 36 temporarily stores and separates the liquid / gas refrigerant exiting the electric expansion valve 33 and absorbs fluctuations in pressure and refrigerant circulation due to the operation of the electric expansion valve 39. .

  The liquid refrigerant accumulated in the lower part of the liquid receiver 36 flows out from the liquid receiver outlet pipe 37 (main circuit 38), exits the refrigerator unit 3, and passes from the refrigerant pipe 8 to the electric expansion valve (main throttle means) 39. Inflow. The refrigerant that has flowed into the electric expansion valve 39 is squeezed there and expanded to further increase the liquid content, and flow into the evaporator 41 to evaporate. The cooling effect is exhibited by the endothermic action. The control device 57 controls the valve opening degree of the electric expansion valve 39 based on the output of a temperature sensor (not shown) that detects the temperatures of the inlet side and the outlet side of the evaporator 41 and sets the superheat degree of the refrigerant in the evaporator 41 to an appropriate value. Adjust to.

  The low-temperature gas refrigerant discharged from the evaporator 41 returns from the refrigerant pipe 9 to the refrigerator unit 3 and flows into the first flow path 29A of the heat exchanger 29 in the refrigerant introduction pipe 22. Therefore, after cooling (supercooling) the high-pressure side refrigerant flowing through the second flow path 29B, the low-stage side suction port 17 that further communicates with the first rotary compression element 14 of the compressor 11 through the refrigerant introduction pipe 22. Sucked into. The above is the flow of the main circuit 38.

(2-2) Control of Electric Expansion Valve 43 Next, the flow of the auxiliary circuit 48 will be described. As described above, an electric expansion valve 43 (first auxiliary circuit throttle means) is connected to the gas pipe 42 connected to the upper portion of the liquid receiver 36, and the liquid receiver 36 is connected via the electric expansion valve 43. The gas refrigerant flows out from the upper part and returns to the intermediate pressure part of the compressor 11 through the return pipe 44 as described above.

  The temperature of the gas refrigerant accumulated in the upper part of the liquid receiver 36 is lowered due to evaporation in the liquid receiver 36. In addition to the function of restricting the refrigerant flowing out from the upper part of the liquid receiver 36, the electric expansion valve 43 has the pressure in the liquid receiver 36 (the pressure of the refrigerant flowing into the electric expansion valve 39) at a predetermined target value SP. Play a role to coordinate. The control device 57 controls the valve opening degree of the electric expansion valve 43 based on the output of the receiver pressure sensor 53. This is because if the valve opening degree of the electric expansion valve 43 increases, the amount of gas refrigerant flowing out from the liquid receiver 36 increases and the pressure in the liquid receiver 36 decreases.

  In the embodiment, the target value SP is set to be lower than the high pressure side pressure HP and higher than the intermediate pressure MP, for example, 6 MPa. Then, the control device 57 determines, for example, that of the electric expansion valve 39 from the difference between the pressure TIP (pressure of the refrigerant flowing into the electric expansion valve 39) in the liquid receiver 36 detected by the liquid receiver internal pressure sensor 53 and the target value SP. An adjustment value (number of steps) of the valve opening is calculated and added to the valve opening at the time of starting to control the pressure TIP (pressure of the refrigerant flowing into the electric expansion valve 39) in the liquid receiver 36 to the target value SP. To do. That is, when the pressure TIP in the liquid receiver 36 rises above the target value SP, the valve opening degree of the electric expansion valve 43 is increased and the gas refrigerant flows out of the liquid receiver 36 into the gas pipe 42. When it falls below the target value SP, the valve opening is reduced and controlled to close.

  By controlling the pressure TIP of the refrigerant in the liquid receiver 36 to the target value SP by the electric expansion valve 43, the influence of fluctuations in the high pressure side pressure HP is suppressed, and the electric expansion valve 39 is provided from the lower part of the liquid receiver 36. It is possible to control the pressure of the refrigerant conveyed to the tank. Further, by reducing the pressure of the refrigerant flowing into the electric expansion valve 39 by the electric expansion valve 43, it is possible to use the refrigerant pipe 8 having a low pressure resistance. Further, by extracting the low-temperature gas from the upper part of the liquid receiver 36 via the electric expansion valve 43, the pressure in the liquid receiver 36 is lowered and the temperature is lowered, so that the refrigerant condenses and the liquid receiver is received. The liquid refrigerant can be effectively stored in 36.

(2-3) Control of the electric expansion valve 47 Further, as described above, the electric expansion valve 47 (second auxiliary circuit throttle) is connected to the liquid pipe 46 connected to the liquid receiver outlet pipe 37 below the liquid receiver 36. And a part of the liquid refrigerant flowing out from the lower portion of the liquid receiver 36 through the electric expansion valve 47 is joined to the gas refrigerant from the gas pipe 42 through the return pipe 44 as described above. It returns to the intermediate pressure part of the compressor 11 via the return pipe 44.

  That is, the liquid refrigerant accumulated in the lower part of the liquid receiver 36 is separated from the liquid receiver outlet pipe 37 connected to the lower part, flows into the liquid pipe 46 constituting the auxiliary circuit 48, and is throttled through the electric expansion valve 47. , Flows into the second rotary compression element 16 of the compressor 11 and evaporates there (injection). The second rotary compression element 16 of the compressor 11 is cooled by the endothermic action at this time.

  Thus, the electric expansion valve 47 throttles the liquid refrigerant flowing out from the lower part of the liquid receiver 36, returns it to the compressor 11 to evaporate it, and cools the compressor 11. However, the control device 57 is an electric expansion valve. By controlling the valve opening of 47, the amount of refrigerant injected into the compressor 11 is adjusted.

  If the amount of refrigerant injected into the compressor 11 increases, the temperature of the compressor 11 decreases and the discharge temperature of the refrigerant discharged from the compressor 11 to the gas cooler 28 also decreases. In this case, the control device 57 controls the valve opening degree of the electric expansion valve 47 based on the refrigerant discharge temperature DT detected by the discharge temperature sensor 67 so that the discharge temperature DT becomes a predetermined target value. The amount of the injection refrigerant to the compressor 11 is adjusted. Thereby, the problem that the temperature of the discharged refrigerant discharged from the second rotary compression element 16 of the compressor 11 becomes abnormally high is prevented.

(2-4) Control of Electric Expansion Valve 65 Next, control of the electric expansion valve 65 by the control device 57 will be described with reference to the Ph diagram of FIG. As described above, the bypass circuit 60 is connected from the receiver outlet pipe 37 to the refrigerant introduction pipe 22 upstream of the first flow path 29A of the heat exchanger 29, and a series circuit of the electric expansion valve 39 and the evaporator 41. In parallel.

  Therefore, when the electric expansion valve 65 is opened, a part of the liquid refrigerant flowing out from the lower part of the liquid receiver 36 to the liquid receiver outlet pipe 37 bypasses and bypasses the electric expansion valve 39 and the evaporator 41. After flowing through the circuit 60 and being throttled by the electric expansion valve 65, it flows directly into the first flow path 29 </ b> A of the heat exchanger 29 through the refrigerant introduction pipe 22. Since the refrigerant flowing into the first flow path 29A evaporates there, the temperature decreases. Thereby, the suction temperature ST of the refrigerant | coolant suck | inhaled by the compressor 11 falls.

  Here, by supercooling the high-pressure side refrigerant with the low-pressure side refrigerant exiting the evaporator 41, the suction temperature of the refrigerant sucked into the compressor 11 is increased. When this temperature rise becomes excessively large, the temperature of the refrigerant sucked into the first rotary compression element 14 of the compressor 11 becomes high, so that the temperature of the intermediate-pressure refrigerant discharged from the first rotary compression element 14 is increased. Will become abnormally high.

  Therefore, the control device 57 is electrically driven so that the suction temperature ST is controlled to a predetermined target value (for example, + 18 ° C.) based on the refrigerant suction temperature ST into the compressor 11 detected by the refrigerator inlet temperature sensor 62. The valve opening degree of the expansion valve 65 is adjusted. Such control prevents the refrigerant discharge temperature of the first rotary compression element 14 of the compressor 11 from becoming abnormally high, thereby protecting the compressor 11.

  The portion indicated by X1 in the Ph diagram of FIG. 2 is the effect of the electric expansion valve 65, and the refrigerant discharge temperature of the first rotary compression element 14 is lowered from the state indicated by the broken line to the state indicated by the solid line. Note that X2 in FIG. 2 is an effect of supercooling in the heat exchanger 29, and the refrigerant flowing into the electric expansion valve 33 is supercooled from the state indicated by the solid line to the state indicated by the broken line.

(2-5) Control of Gas Cooler Blower 31 Next, control of the gas cooler blower 31 by the control device 57 will be described. The control device 57 of the embodiment is based on the temperature of the refrigerant detected by the gas cooler outlet temperature sensor 54 (the temperature of the refrigerant that has exited the gas cooler 28), so that the temperature of the refrigerant reaches a predetermined target value. Control the number of revolutions. In this case, the control device 57 sets a target value for the temperature of the refrigerant that has exited the gas cooler 28 based on the outside air temperature AT detected by the outside air temperature sensor 61. This target value is an appropriate value of the temperature of the refrigerant (the refrigerant that has exited the gas cooler 28) that is predetermined for each outside air temperature.

  In this way, the control device 57 controls the operation (rotation speed) of the gas cooler blower 31 so that the temperature of the refrigerant that has exited the gas cooler 28 becomes a predetermined target value determined with respect to the outside air temperature AT. Thus, the temperature of the refrigerant at the outlet of the gas cooler 28 can be maintained at an appropriate value while suppressing excessive operation of the gas cooler blower 31 that air-cools the gas cooler 28.

  On the other hand, the control device 57 controls the high pressure side pressure HP to the target value by the electric expansion valve 33 upstream of the liquid receiver 36 as described above. The compressor 11 is protected by controlling the refrigerant temperature (the temperature of the refrigerant that has exited the gas cooler 28) by the blower 31, and a stable operation is maintained.

  As described in detail above, in the present invention, in the refrigerating apparatus R in which the refrigerant circuit 1 is configured by the compressor 11, the gas cooler 28, the electric expansion valve 39, and the evaporator 41, and the high pressure side is at the supercritical pressure, the gas cooler 28, the electric expansion valve 33 connected to the refrigerant circuit 1 upstream of the electric expansion valve 39, and the refrigerant downstream of the electric expansion valve 33 and upstream of the electric expansion valve 39. A liquid receiver 36 connected to the circuit 1, a heat exchanger 29 provided in the refrigerant circuit 1 downstream of the gas cooler 28 and upstream of the electric expansion valve 33, a heat exchanger 29 and a heat exchanger 29 A main circuit 38 that reaches the liquid receiver 36 through the electric expansion valve 33, causes the refrigerant to flow out from the lower portion of the liquid receiver 36 and flows into the electric expansion valve 39, and the refrigerant in the liquid receiver 36 is supplied to the electric expansion valve 43. And the compressor 1 through the electric expansion valve 47 An auxiliary circuit 48 for returning to the intermediate pressure portion, a bypass circuit 60 connected in parallel to the series circuit of the electric expansion valve 39 and the evaporator 41, an electric expansion valve 65 provided in the bypass circuit 60, The expansion valve 33, the electric expansion valves 43 and 47, and the control device 57 that controls the electric expansion valve 65. The refrigerant flowing out of the evaporator 41 and sucked into the compressor 11 is supplied to the first flow of the heat exchanger 29. Since the refrigerant flowing into the passage 29A and flowing out of the gas cooler 28 and flowing into the electric expansion valve 33 flows into the second flow path 29B of the heat exchanger 29, it flows through the first flow path 29A of the heat exchanger 29. The high-pressure side refrigerant flowing through the second flow path 29B of the heat exchanger 29 can be supercooled by the low-pressure side refrigerant, and the dryness of the refrigerant at the outlet of the electric expansion valve 33 can be reduced.

  The refrigerant flowing through the second flow path 29B of the heat exchanger 29 enters the liquid receiver 36 through the electric expansion valve 33, flows out from the lower part of the liquid receiver 36, and is throttled by the electric expansion valve 39. Since the refrigerant flows into the evaporator 41, the degree of dryness of the refrigerant at the outlet of the electric expansion valve 33 is reduced by the supercooling in the heat exchanger 29, and the liquid phase ratio of the refrigerant conveyed to the electric expansion valve 39 is increased. You will be able to improve your abilities effectively.

  In addition, a part of the refrigerant liquefied by being expanded by the electric expansion valve 33 is evaporated in the liquid receiver 36 to become a gas refrigerant having a lowered temperature, and the rest becomes a liquid refrigerant in the lower part of the liquid receiver 36. Once it is stored. Then, since the liquid refrigerant in the lower part of the liquid receiver 36 flows into the electric expansion valve 39, the refrigerant can flow into the electric expansion valve 39 in a full liquid state, and in particular, the evaporation temperature in the evaporator 41. However, it is possible to improve the refrigeration capacity under high refrigeration conditions. Further, since the liquid receiver 36 has an effect of absorbing the fluctuation of the circulating refrigerant amount in the refrigerant circuit 1, there is also an effect of absorbing the refrigerant filling amount error.

  In particular, a bypass circuit 60 connected in parallel to the series circuit of the electric expansion valve 39 and the evaporator 41 and an electric expansion valve 65 provided in the bypass circuit 60 are provided. The refrigerant flows through the first flow path 29A of the heat exchanger 29 by bypassing the electric expansion valve 39 and the evaporator 41 by the valve 65, evaporates there, and sets the suction temperature of the low-pressure side refrigerant sucked into the compressor 11 to a predetermined value. Therefore, it is possible to prevent an increase in the refrigerant suction temperature of the compressor 11 and to avoid a reduction in operating efficiency and damage to the compressor 11 in advance.

  Further, since the control device 57 controls the high pressure side pressure of the refrigerant circuit 1 upstream of the electric expansion valve 33 to a predetermined target value by the electric expansion valve 33, the high pressure side pressure at which the refrigerant is discharged from the compressor 11. As a result, the operating efficiency of the compressor 11 decreases, or the inconvenience of damaging the compressor 11 can be avoided.

  The auxiliary circuit 48 has an electric expansion valve 43 and a gas pipe 42 for allowing the refrigerant to flow out from the upper portion of the liquid receiver 36 and into the electric expansion valve 43. Since the pressure of the refrigerant in 36 is controlled to a predetermined target value, the electric expansion valve 43 suppresses the influence of fluctuations in the high-pressure side pressure and is conveyed from the lower part of the liquid receiver 36 to the electric expansion valve 39. It will be possible to control the pressure.

  Further, by lowering the pressure of the refrigerant flowing into the electric expansion valve 39 by the electric expansion valve 43, it is possible to use a refrigerant pipe 8 having a low pressure resistance strength that reaches the electric expansion valve 39. Thereby, it becomes possible to improve workability and construction cost. In particular, when the low-temperature gas is extracted from the upper part of the liquid receiver 36 via the electric expansion valve 43, the pressure in the liquid receiver 36 decreases. As a result, the temperature is lowered in the liquid receiver 36, so that the refrigerant condenses, and the liquid refrigerant can be effectively stored in the liquid receiver 36.

  Further, the auxiliary circuit 48 has an electric expansion valve 47 and a liquid pipe 46 through which refrigerant flows out from the lower part of the liquid receiver 36 and flows into the electric expansion valve 47, and the control device 57 is driven by the electric expansion valve 47. Since the discharge temperature of the refrigerant discharged to the gas cooler 28 is controlled to a predetermined target value, the compressor 11 is cooled by injecting the intermediate pressure portion of the compressor 11, and the refrigerant from the compressor 11 and the compressor 11. It is possible to avoid inconvenience that the discharge temperature becomes too high.

  Furthermore, the gas cooler blower 31 for air-cooling the gas cooler 28 is provided, and the control device 57 of the gas cooler blower 31 is set so that the temperature of the refrigerant exiting the gas cooler 28 becomes a predetermined target value determined with respect to the outside air temperature. Since the operation is controlled, it is possible to maintain the temperature of the refrigerant at the outlet of the gas cooler 28 at an appropriate value while suppressing excessive operation of the gas cooler blower 31 that air-cools the gas cooler 28. On the other hand, the high-pressure side pressure only needs to be controlled by the electric expansion valve 33, thereby protecting the compressor 11 and maintaining stable operation.

  In particular, when carbon dioxide is used as in the embodiment, the refrigerating capacity can be effectively improved and the performance can be improved.

  Next, another embodiment of the present invention will be described with reference to FIGS. 3 and 4, the same reference numerals as those in FIGS. 1 and 2 denote the same or similar functions. In the case of this embodiment, an internal heat exchanger 68 is added to the refrigerant circuit 1 of FIG. The internal heat exchanger 68 is provided in the refrigerant circuit 1 downstream of the liquid receiver 36 and upstream of the electric expansion valve 39 (main throttle means).

  The internal heat exchanger 68 has a first flow path 68A and a second flow path 68B, and the first flow path 68A is a connection point between the bypass circuit 60 and the first flow path of the heat exchanger 29. The second flow path 68 </ b> B is interposed in the liquid receiver outlet pipe 37 before branching from the liquid pipe 46. With this configuration, the liquid refrigerant that flows out from the liquid receiver 36 to the liquid receiver outlet pipe 37 and flows through the second flow path 68 </ b> B is a low-temperature low-pressure refrigerant that has passed through the evaporator 41 and the bypass circuit 60. Is cooled by the first flow path 68A. The refrigerant that has passed through the bypass circuit 60 is throttled by the electric expansion valve 65 and then evaporated in the first flow path 68A to exhibit a cooling action.

  The portion indicated by X3 in the Ph diagram of FIG. 4 is the effect of the internal heat exchanger 68, and the temperature of the refrigerant flowing into the electric expansion valve 39 can be lowered from the state indicated by the solid line to the state indicated by the broken line. . In this way, the internal heat exchanger 68 is further provided in the refrigerant circuit 1 downstream of the liquid receiver 36 and upstream of the electric expansion valve 39, and the refrigerant that leaves the evaporator 41 and goes to the heat exchanger 29 is supplied. By flowing the refrigerant that flows from the lower part of the receiver 36 toward the electric expansion valve 39 to the second flow path 68B of the internal heat exchanger 68, the internal heat is passed through the first flow path 68A of the internal heat exchanger 68. With the low-pressure side refrigerant flowing through the first flow path 68A of the exchanger 68, the refrigerant flowing out of the liquid receiver 41 and flowing through the second flow path 68B of the internal heat exchanger 68 can be supercooled. Further, it is possible to further improve the refrigerating capacity by suppressing the re-expansion of the liquid refrigerant from the liquid receiver 36 toward the electric expansion valves 39, 47, and 65.

R Refrigeration apparatus 1 Refrigerant circuit 3 Refrigerator unit 4 Showcase 8, 9 Refrigerant pipe 11 Compressor 22 Refrigerant introduction pipe 26 Intermediate pressure suction pipe 28 Gas cooler 29 Heat exchanger 29A First flow path 29B Second flow path 32 Gas cooler Outlet piping 33 Electric expansion valve (throttle means for pressure adjustment)
36 Liquid receiver 37 Gas cooler outlet piping 38 Main circuit 39 Electric expansion valve (main throttle means)
41 Evaporator 42 Gas piping 43 Electric expansion valve (first auxiliary circuit throttle means)
44 Return piping 46 Liquid piping 47 Electric expansion valve (second auxiliary circuit throttle means)
48 Auxiliary circuit 57 Control device (control means)
60 Bypass circuit 65 Electric expansion valve (throttle means for bypass)
68 Internal heat exchanger 68A First flow path 68B Second flow path

Claims (8)

In the refrigerating apparatus in which the refrigerant circuit is configured by the compression means, the gas cooler, the main throttle means, and the evaporator, and the high pressure side is the supercritical pressure,
A pressure adjusting throttle means connected to the refrigerant circuit downstream of the gas cooler and upstream of the main throttle means;
A liquid receiver connected to the refrigerant circuit downstream of the pressure adjusting throttle means and upstream of the main throttle means;
A heat exchanger provided in the refrigerant circuit downstream of the gas cooler and upstream of the pressure adjusting throttle means;
A main circuit that leads from the gas cooler to the liquid receiver through the heat exchanger and the pressure adjusting throttle means, and causes the refrigerant to flow out from the lower part of the liquid receiver and flow into the main throttle means;
An auxiliary circuit for returning the refrigerant in the receiver to the intermediate pressure part of the compression means via auxiliary throttle means;
A bypass circuit connected in parallel to a series circuit of the main throttle means and the evaporator;
Bypass throttle means provided in the bypass circuit;
The pressure adjusting throttle means, the auxiliary throttle means, and a control means for controlling the bypass throttle means,
The refrigerant that comes out of the evaporator and is sucked into the compression means flows into the first flow path of the heat exchanger, and the refrigerant that comes out of the gas cooler and flows into the pressure adjusting throttle means becomes the second of the heat exchanger. The refrigerant flowing through the first flow path is supercooled by the refrigerant flowing through the first flow path of the heat exchanger, and the refrigerant flowing through the second flow path of the heat exchanger.   2. The refrigeration apparatus according to claim 1, wherein the control unit controls the suction temperature of the low-pressure side refrigerant sucked into the compression unit by the bypass throttling unit to a predetermined target value. An internal heat exchanger provided in the refrigerant circuit downstream of the liquid receiver and upstream of the main throttle means;
The refrigerant exiting from the evaporator and flowing toward the heat exchanger is caused to flow through the first flow path of the internal heat exchanger, and the refrigerant exiting from the lower part of the receiver and toward the main throttle means is transferred to the internal heat exchanger. The refrigerant flowing through the second flow path of the internal heat exchanger is supercooled by flowing through the second flow path by the refrigerant flowing through the first flow path of the internal heat exchanger. The refrigeration apparatus according to claim 1 or 2.   The said control means controls the high pressure side pressure of the said refrigerant circuit upstream from the said pressure adjustment throttle means to the predetermined target value by the said pressure adjustment throttle means. The refrigeration apparatus according to any one of the above. The auxiliary throttle means has a first auxiliary circuit throttle means,
The auxiliary circuit has a gas pipe that causes the refrigerant to flow out from the upper part of the receiver and to flow into the first auxiliary circuit throttle means,
5. The control device according to claim 1, wherein the control means controls the pressure of the refrigerant in the liquid receiver to a predetermined target value by the first auxiliary circuit throttle means. The refrigeration apparatus described in 1. The auxiliary throttle means has second auxiliary circuit throttle means,
The auxiliary circuit has a liquid pipe that causes the refrigerant to flow out from the lower part of the receiver and to flow into the second auxiliary circuit throttle means,
The control means controls the discharge temperature of the refrigerant discharged from the compression means to the gas cooler to a predetermined target value by the second auxiliary circuit throttle means. The refrigeration apparatus according to any one of the above. A blower for air-cooling the gas cooler;
The said control means controls the operation | movement of the said air blower so that the temperature of the refrigerant | coolant which came out of the said gas cooler may become the predetermined target value determined with respect to external temperature. The refrigeration apparatus according to any one of the above.   The refrigeration apparatus according to any one of claims 1 to 7, wherein carbon dioxide is used as the refrigerant.

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