JP2005214575A - Refrigerator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a refrigerator provided with a two stage compression refrigerating cycle device capable of improving durability of an opening and closing valve provided in a defrosting circuit by reducing pressure acting on the opening and closing valve and reducing cost. <P>SOLUTION: This refrigerator is provided with the two stage compression refrigerating cycle device constituted by connecting a compressor, a high pressure gas cooler for cooling high pressure side gas refrigerant, a restriction device, and an evaporator for evaporating low pressure liquid refrigerant sequentially. The two stage compression refrigerating cycle device has the defrosting circuit connected between an intermediate pressure gas part in refrigerating cycle and an evaporator inlet side through the opening and closing valve. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a refrigeration apparatus, and more particularly to an evaporator defrost in a refrigeration apparatus including a two-stage compression refrigeration cycle apparatus.

  In recent years, natural refrigerants that are refrigerated in a supercritical refrigeration cycle, such as carbon dioxide, have attracted attention in order to meet the problem of ozone depletion and the need for high temperature hot water supply in hot water supply devices. Further, in a refrigeration apparatus that performs such a supercritical cycle refrigeration operation, a two-stage compression refrigeration cycle apparatus has come to be used because the pressure difference between high and low becomes large.

By the way, the conventional defrost circuit of the evaporator in the two-stage compression refrigeration cycle apparatus is a hot gas defrost circuit in which the discharge side of the two-stage compressor is connected to the inlet side of the evaporator via an on-off valve as disclosed in Patent Document 1, for example. A flow path is provided. When such a hot gas defrost flow path is applied to a refrigeration cycle apparatus in which the high-low pressure difference of the two-stage compressor is increased, the sealing member of the on-off valve that must be installed in the hot gas defrost flow path, the valve Durability such as the strength of the box is a problem. Further, when such durability is to be solved, there arises a problem that the cost is remarkably increased.
JP 11-294906 A

  The present invention has been made to solve the above-described problems of the prior art, and by reducing the pressure acting on the on-off valve provided in the defrost circuit, the durability of the on-off valve is improved and the cost is reduced. An object of the present invention is to provide a refrigeration apparatus provided with a two-stage compression refrigeration cycle apparatus.

  A refrigerating apparatus according to a first solution means according to the present invention is a two-stage compression comprising a compressor, a high-pressure gas cooler that cools a high-pressure side gas refrigerant, a throttling device, and an evaporator that evaporates low-pressure liquid refrigerant. A refrigeration cycle apparatus is provided, and the two-stage compression refrigeration cycle apparatus further includes a defrost circuit connected via an on-off valve between an intermediate pressure gas section in the refrigeration cycle and an evaporator inlet side. And

  Further, the refrigeration apparatus according to the second solving means of the present invention has a low-stage compressor section and a high-stage compressor section, and discharge gas from the low-stage compressor section is discharged into the sealed casing. And a two-stage compressor configured such that the refrigerant in the hermetic casing is sucked into the high-stage compressor section, a high-pressure gas cooler that cools the high-pressure gas refrigerant, the first expansion device, and the refrigeration cycle A two-stage compression refrigeration cycle apparatus configured to sequentially connect an intermediate pressure receiver, a second expansion device, an evaporator, and a gas-liquid separator in order to adjust the refrigerant amount of the refrigerant and to be operated in a supercritical refrigeration cycle The refrigeration cycle apparatus further includes an intermediate pressure refrigerant bypass circuit for bypassing the intermediate pressure gas refrigerant in the intermediate pressure receiver into the casing of the two-stage compressor, the discharge side of the low-stage compressor section, and the evaporator Start the open / close valve Characterized by comprising a defrost circuit.

  Further, the refrigeration apparatus according to the third solution means of the present invention includes a compressor having a gas injection port in an intermediate part of the compression process, a high-pressure gas cooler for cooling the high-pressure side gas refrigerant, a first expansion device, and a refrigeration cycle. A two-stage compression refrigeration cycle apparatus configured to sequentially connect an intermediate pressure receiver, a second expansion device, an evaporator, and a gas-liquid separator in series to adjust the amount of refrigerant in the system and to be operated in a supercritical refrigeration cycle In addition, this two-stage compression refrigeration cycle apparatus opens and closes an intermediate pressure refrigerant bypass circuit that connects a gas portion of the intermediate pressure receiver and a gas injection port, and a gas portion of the intermediate pressure receiver and an inlet side of the evaporator A defrost circuit connected through a valve is provided.

  In each of the above solutions, it is preferable that the intermediate pressure receiver, which is a component device of the refrigeration cycle apparatus, has a volume capable of storing surplus refrigerant due to a change in operating conditions.

  The refrigeration cycle apparatus may be filled with carbon dioxide as a refrigerant.

  The refrigeration cycle apparatus may be configured such that the refrigeration cycle apparatus is configured to heat water with a high-pressure gas cooler.

  The refrigeration apparatus according to the first problem solving means according to the present invention includes a defrost circuit connected via an on-off valve between an intermediate pressure gas section in the refrigeration cycle and the evaporator inlet side in the two-stage compression refrigeration cycle apparatus. Therefore, by opening the on-off valve during the defrosting operation, a high-temperature gas refrigerant having an intermediate pressure is guided to the evaporator, and the defrosting is performed in a short time. Further, during the defrost operation, the discharge gas in the two-stage compression refrigeration cycle does not act on the inlet of the on-off valve, and the intermediate gas pressure acts on the inlet, so that the pressure acting on the on-off valve is lower than in the prior art. For this reason, the pressure resistance performance of the on-off valve can be lowered, and the reliability can be improved and the cost can be reduced.

  Moreover, the refrigeration apparatus according to the third problem solving means of the present invention has a low-stage compressor section and a high-stage compressor section, and the discharge gas of the low-stage compressor section is contained in the sealed casing. In the intermediate pressure receiver between the first throttle device and the second throttle device, including a two-stage compressor configured to be discharged and the refrigerant in the hermetic casing to be sucked into the high-stage compressor section In a two-stage compression refrigeration cycle in which gas-liquid separated intermediate-pressure gas refrigerant is bypassed into the casing of the two-stage compressor, the discharge side of the low-stage compressor section and the inlet side of the evaporator are connected via an on-off valve. Since the defrost circuit to be connected is provided, the open / close valve is opened during the defrost operation, so that the high-temperature gas refrigerant compressed to the intermediate pressure in the compressor is guided to the evaporator and the defrost is performed in a short time. Further, during the defrost operation, the discharge gas in the two-stage compression refrigeration cycle does not act on the inlet of the on-off valve, and the intermediate gas pressure discharged from the low-stage compressor section acts. Therefore, the pressure acting on the on-off valve is lower than that in the prior art, and the pressure resistance performance of the on-off valve can be lowered, thereby improving the reliability and reducing the cost.

  The refrigeration apparatus according to the third problem solving means of the present invention includes a compressor having a gas injection port in an intermediate part of the compression step, and an intermediate pressure receiver between the first expansion device and the second expansion device. In a two-stage compression refrigeration cycle that bypasses the gas-liquid separated intermediate-pressure gas refrigerant to the gas injection port of the compressor, the defroster connects the gas part of the intermediate-pressure receiver and the inlet side of the evaporator via an on-off valve Since the circuit is provided, the defrosting is performed in a short time by opening the on-off valve during the defrosting operation so that the high-temperature gas refrigerant at the intermediate pressure is led from the intermediate pressure receiver to the evaporator. Further, during the defrost operation, the discharge gas in the two-stage compression refrigeration cycle does not act on the inlet of the on-off valve, and the intermediate gas pressure reduced by the first expansion device acts. Therefore, the pressure acting on the on-off valve is lower than that in the prior art, and the pressure resistance performance of the on-off valve can be lowered, thereby improving the reliability and reducing the cost.

  In addition, if the intermediate pressure receiver, which is a component device of the refrigeration cycle apparatus, has a volume capable of storing surplus refrigerant due to changes in operating conditions, sufficient liquid refrigerant for the intermediate pressure receiver during defrost operation where the low pressure is low Therefore, the gas refrigerant having a predetermined intermediate pressure can be stably supplied to the inlet side of the evaporator, and the defrosting operation can be performed efficiently.

  When the refrigeration cycle apparatus is filled with carbon dioxide as a refrigerant, it is provided in the defrost circuit while being able to supply high-temperature hot water or hot water using a high-pressure gas cooler as a heat source with a high-pressure gas cooler. The durability and reliability of the on-off valve can be improved.

  Hereinafter, each embodiment will be described with reference to the drawings.

A first embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a refrigerant circuit diagram of the refrigeration apparatus according to the first embodiment. FIG. 2 is a Mollier diagram of a supercritical refrigeration cycle in the refrigeration apparatus. FIG. 3 is a configuration diagram around the evaporator and the gas-liquid separator of the refrigeration apparatus.

  As shown in FIG. 1, the refrigeration cycle apparatus according to Embodiment 1 is a high-pressure gas that cools a compressor 1, a high-temperature high-pressure gas refrigerant, and heats a heated fluid such as room air, warm water for heating, and hot water. The cooler 2, the first throttle device 3, the intermediate pressure receiver 4 that adjusts the amount of refrigerant in the refrigeration cycle, the second throttle device 5, the evaporator 6 that pumps heat from the outside air, and the gas-liquid separator 7 are sequentially connected in series. Thus, a refrigeration cycle apparatus is formed. In addition, this refrigeration cycle apparatus is configured as an apparatus that is operated in a two-stage compression supercritical refrigeration cycle in which a refrigerant circuit is filled with carbon dioxide as a refrigerant.

  The compressor 1 houses a low-stage compressor section 12, a high-stage compressor section 13, an electric motor and the like in a hermetic casing 11, and discharges a discharge gas from the low-stage compressor section 12 into the hermetic casing 11. The so-called internal intermediate pressure dome type two-stage compressor is formed so that the intermediate-pressure gas refrigerant is sucked into the high-stage compressor section 13. The two-stage compressor 1 is formed by an inverter so that the rotational speed can be varied.

  The high-pressure gas cooler 2 is a heat exchanger that cools the discharge gas discharged from the high-stage compressor unit 13. Since the refrigeration cycle apparatus forms a supercritical refrigeration cycle apparatus, the high-pressure gas cooler 2 does not condense the refrigerant. The high-pressure gas cooler 2 is configured to heat warm water for heating in the case of a hot water heater, to heat indoor air in the case of a hot air heater, and to heat hot water in the case of a hot water heater.

As the first expansion device 3 and the second expansion device 5, electric expansion valves are used, respectively.
The intermediate pressure receiver 4 adjusts the amount of refrigerant in the refrigeration cycle apparatus, and is controlled so that the pressure becomes a critical point or less by opening control of the first expansion device 3 and the second expansion device 5. As a result, surplus refrigerant of the supercritical refrigeration cycle is stored as liquid refrigerant in the intermediate pressure receiver 4.

The evaporator 6 is a heat exchanger that exchanges heat using outside air as a heat source, and the refrigerant itself evaporates by drawing up heat from the outside air as the low-pressure liquid refrigerant evaporates. Further, the evaporator 6 includes a refrigerant temperature sensor 61 that detects the refrigerant temperature in the middle of the evaporator 6 and a refrigerant temperature sensor 62 that detects the refrigerant temperature at the outlet of the evaporator 6. In addition, the superheat degree of the refrigerant | coolant in the evaporator 6 exit is detected by the temperature difference of the refrigerant | coolant temperature which both these refrigerant | coolant temperature sensors 61 and 62 detect. The opening degree of at least one of the first expansion device 3 and the second expansion device 5 is controlled so that the refrigerant at the outlet of the evaporator 6 is overheated.
Further, the evaporator 6 is formed such that the heat exchange pipe 65 meanders from the upper side to the lower side so that the refrigerant flows from the upper side to the lower side (see FIG. 3). 1 and 3, reference numeral 63 denotes a refrigerant inlet, and reference numeral 64 denotes a refrigerant outlet.

Further, the supercritical refrigeration cycle is provided with an intermediate pressure refrigerant bypass circuit 8 that connects the gas portion 41 of the intermediate pressure receiver 4 and the inside of the closed casing 11 of the compressor 1. Thereby, the intermediate-pressure gas refrigerant in the intermediate-pressure receiver 4 is bypassed into the hermetic casing 11 of the compressor 1 which is an intermediate-pressure part in the compression process. The intermediate pressure refrigerant bypass circuit 8 is provided with a capillary tube 81 for adjusting the flow rate and a check valve 82 for blocking the refrigerant flow from the compressor 1 to the intermediate pressure receiver 4.
In addition, the supercritical refrigeration cycle is provided with a defrost circuit 9 that connects the inside of the sealed casing 11 of the compressor 1 and the evaporator inlet side via an on-off valve 91. The on-off valve 91 is closed during normal operation and opened during defrost operation.

  The gas-liquid separator 7 is an airtight container having an appropriate shape such as a cylindrical shape, and includes a refrigerant inlet 71 at a lower part of the container and a refrigerant outlet 72 at an upper part. Further, as shown in FIG. 3, the gas-liquid separator 7 is provided at a position where the refrigerant inlet 71 is higher than the refrigerant outlet 64 of the evaporator 6 by a predetermined head difference H1. Further, the pipe 73 connecting the refrigerant inlet 71 of the gas-liquid separator 7 and the refrigerant outlet 64 of the evaporator 6, that is, the cross-sectional area of the liquid refrigerant return pipe 73 from the gas-liquid separator 7 to the evaporator 6 is large. It is configured to be larger than the cross-sectional area of the compressor suction pipe 14 by using a pipe having a diameter.

  The operation in the normal operation of the supercritical refrigeration cycle configured as described above will be described based on the Mollier diagram of FIG. The symbols for indicating each point on the Mollier diagram are shown corresponding to the state of the refrigerant at the position of each symbol on the circuit attached to the refrigerant circuit of FIG. In the following description, symbols for displaying each point on the Mollier diagram are also shown.

  In the low-stage compressor section 12 of the two-stage compressor 1, the low-pressure gas refrigerant a1 on the outlet side of the gas-liquid separator 7 is sucked and compressed. The intermediate-pressure gas refrigerant b <b> 1 compressed by the low-stage compressor unit 12 is discharged into the sealed casing 11. In the hermetic casing 11, the intermediate pressure gas refrigerant g1 that has been gas-liquid separated in the intermediate pressure receiver 4 and the discharge gas b1 of the low-stage compressor section 12 are mixed to form a gas refrigerant c1. The high-stage compressor section 13 sucks the mixed refrigerant c1 and becomes a high-pressure refrigerant d1 and is discharged from the two-stage compressor 1.

  The high-pressure refrigerant d1 discharged from the two-stage compressor 1 is cooled by heating a heated fluid such as room air, hot water for heating, hot water supply water, etc. in the high-pressure gas cooler 2. The cooled high-pressure gas refrigerant e1 is expanded by the first expansion device 3 and becomes a gas-liquid mixed refrigerant f1 having a pressure equal to or lower than the critical point and flows into the intermediate pressure receiver 4. This gas-liquid mixed refrigerant f1 is gas-liquid separated in the intermediate pressure receiver 4. The intermediate-pressure gas refrigerant g1 that has been gas-liquid separated in the intermediate-pressure receiver 4 flows into the sealed casing 11 of the two-stage compressor 1 through the intermediate-pressure refrigerant bypass circuit 8 as described above.

  On the other hand, the liquid refrigerant h <b> 1 separated by the intermediate pressure receiver 4 is decompressed by the second expansion device 5, becomes a low-pressure gas-liquid mixed refrigerant i <b> 1, and flows into the evaporator 6. The low-pressure gas-liquid mixed refrigerant i1 that has flowed into the evaporator 6 exchanges heat with the outside air (pumps heat from the outside air), evaporates, and flows into the gas-liquid separator 7 as the low-pressure gas refrigerant j1. Further, the low-pressure gas refrigerant j1 that has flowed out of the gas-liquid separator 7, that is, the low-pressure gas refrigerant a1, is sucked into the low-stage compressor section 12 as described above.

  In such a supercritical refrigeration cycle, at least one of the first throttling device 3 and the second throttling device 5 is controlled such that the outlet refrigerant of the evaporator 6 is overheated. At this time, the degree of superheat of the refrigerant is determined by the refrigerant temperature detected by the refrigerant temperature sensor 61 provided in the intermediate portion of the evaporator 6 and the refrigerant temperature detected by the refrigerant temperature sensor 62 provided on the outlet side of the evaporator 6. Is controlled so that the refrigerant on the outlet side of the evaporator 6 has a constant degree of superheat.

  Further, in the refrigeration cycle apparatus, when the operation is stopped for a long time in winter, the refrigerant is condensed and liquefied in the evaporator 6 and the gas-liquid separator 7 that come into contact with the outside air. However, the refrigerant condensed and liquefied by the gas-liquid separator 7 is formed in the evaporator 6 because the refrigerant inlet 71 of the gas-liquid separator 7 is formed higher than the refrigerant outlet 64 of the evaporator 6 by a predetermined height H1. Returned. The liquid refrigerant returned from the gas-liquid separator 7 to the evaporator 6 and the liquid refrigerant liquefied by the evaporator 6 are stored in the evaporator 6. Therefore, when activated in this state, liquid refrigerant flows out of the evaporator 6, but this liquid refrigerant is separated into gas and liquid by the gas-liquid separator 7, so that the liquid refrigerant does not return to the compressor 1.

Since the cooling device according to the first embodiment is configured as described above, the following effects can be obtained during normal operation.
(1) In the refrigeration apparatus according to the first embodiment, the intermediate pressure receiver 4 that adjusts the amount of refrigerant in the refrigeration cycle apparatus is provided between the first expansion device 3 and the second expansion device 5 that are in an intermediate pressure state. Therefore, the amount of refrigerant in the refrigeration cycle apparatus can be adjusted without storing liquid refrigerant in the low-pressure side circuit. Therefore, during normal operation, the outlet of the evaporator 6 does not need to be in a wet state, and is switched to normal operation immediately after start-up or immediately after defrost operation when the refrigerant is stagnant due to a long-term stoppage. Except for a transition period such as time, it is possible to prevent the liquid refrigerant from flowing out of the evaporator 6. Further, since the excess refrigerant is stored in the intermediate pressure receiver 4 under the intermediate pressure, the volume of the intermediate pressure receiver 4 that stores the refrigerant can be reduced.

  (2) Moreover, in Example 1, the intermediate pressure receiver 4 is surplus by controlling at least one of the first expansion device 3 and the second expansion device 5 so that the refrigerant at the outlet of the evaporator 6 is overheated. Refrigerant control that prevents liquid return to the compressor 1 can be performed while storing the refrigerant.

  (3) The refrigerant temperature sensor 61 that detects the refrigerant temperature in the middle of the evaporator 6 and the refrigerant temperature sensor 62 that detects the refrigerant temperature at the evaporator outlet, and the temperatures detected by the refrigerant temperature sensors 61 and 62. Since the superheat degree at the outlet of the evaporator 6 is detected based on the difference, the superheat degree of the refrigerant at the outlet of the evaporator 6 during normal operation can be reliably detected.

  (4) Since the intermediate-pressure refrigerant bypass circuit 8 for bypassing the intermediate-pressure gas refrigerant in the intermediate-pressure receiver 4 into the sealed casing 11 of the compressor 1 is provided, the bypassed intermediate-pressure gas refrigerant is contained in the compressor. Increase the pressure. As a result, the compression work is reduced and the coefficient of performance of the system is improved.

  (5) In this case, the compressor 1 is a so-called internal intermediate pressure dome type compressor that is configured as a two-stage compressor and discharges the discharge gas of the low-stage compressor section 12 into the hermetic casing 11. The intermediate pressure refrigerant bypass circuit 8 can be easily formed.

  (6) In the refrigeration apparatus according to the first embodiment, the gas-liquid separator 7 is provided on the outlet side of the evaporator 6, and in particular, the liquid refrigerant separated by the gas-liquid separator 7 is supplied to the evaporator 6. Since it is formed so as to return, the liquid does not return to the compressor 1 even in a transition period such as the start of operation described above.

  (7) Further, since the gas-liquid separator 7 is provided so that the refrigerant inlet 71 of the gas-liquid separator 7 is higher than the refrigerant outlet 64 of the evaporator 6, the gas-liquid separator 7 is in operation and is not operating. The liquid refrigerant flowing into the gas-liquid separator 7 together with the gas refrigerant or the liquid refrigerant liquefied by the gas-liquid separator 7 is separated into gas and liquid and returned to the evaporator 6 by gravity. Therefore, power for returning the refrigerant from the gas-liquid separator 7 to the evaporator 6 becomes unnecessary, and the configuration is simplified. Further, since the liquid refrigerant in the gas-liquid separator 7 is always returned to the evaporator 6 without performing any operation when the operation is stopped, the liquid return to the compressor 1 in the transition period such as the start-up is surely prevented. be able to. Further, since the gas-liquid separator 7 is restarted from the state where there is no liquid refrigerant, the discharge temperature rises quickly and the rise time is shortened.

  (8) The cross-sectional area of the pipe 73 connecting the refrigerant outlet 64 of the evaporator 6 and the refrigerant inlet 71 of the gas-liquid separator 7, that is, the return pipe 73 of the liquid refrigerant from the gas-liquid separator 7 to the evaporator 6. Is larger than the cross-sectional area of the compressor suction pipe 14, the return pipe 73 can be considered as a part of the gas-liquid separator 7, and the volume of the gas-liquid separator 7 can be reduced accordingly. .

  (9) Moreover, since the volume of the intermediate pressure receiver 4 is set to a size capable of storing surplus refrigerant in the refrigeration cycle apparatus due to a change in operating conditions, the refrigeration cycle apparatus is always operated in an optimal refrigerant amount state. The driving performance coefficient can be improved.

  (10) In addition, since the refrigerant charged in the refrigeration cycle apparatus is carbon dioxide, operation in a supercritical refrigeration cycle in which the gas refrigerant temperature on the high pressure side increases while using a flammable and non-toxic safe refrigerant. It can be carried out.

  (11) Moreover, when it comprises as an apparatus which heats water, such as heating hot water and hot water supply water, by the high pressure gas cooler 2, high temperature hot water for heating and high temperature hot water supply water can be supplied.

Next, the defrost operation in the two-stage compression refrigeration cycle apparatus will be described.
In the above-described two-stage compression refrigeration cycle apparatus, the evaporator 6 starts frosting when normal operation is continued at a low temperature of the outside air. Moreover, when the frost starts, the heat exchange efficiency of the evaporator 6 is lowered, and the low pressure and the high pressure are gradually lowered. As a result, the amount of liquid refrigerant stored in the intermediate pressure receiver 4 increases, and defrosting is performed when the frost reaches a predetermined amount.

  In the defrosting operation, the on-off valve 91 of the defrost circuit 9 is opened, the discharged gas refrigerant of the low-stage compressor section 12 is bypassed to the inlet side of the evaporator 6 through the on-off valve 91 of the defrost circuit 9, and the intermediate pressure gas The evaporator 6 is heated by the latent heat of the refrigerant.

At this time, a part of the refrigerant discharged from the high-stage compressor section 13 includes the high-pressure gas cooler 2, the first throttling device 3, the gas section 41 of the intermediate pressure receiver 4, the capillary tube 81, the check valve 82, The refrigerant flows into the defrost circuit 9 through the intermediate pressure refrigerant bypass circuit 8, but the refrigerant flow rate to the defrost circuit 9 is adjusted through the intermediate pressure refrigerant bypass circuit 8 by adjusting the opening of the first expansion device 3. . Further, by adjusting the opening degree of the second expansion device 5 during the defrost operation, the liquid refrigerant in the intermediate pressure receiver 4 is prevented from flowing to the evaporator 6 side.
Therefore, when the defrosting operation is performed, a high-temperature refrigerant having an intermediate pressure is supplied into the evaporator 6, and the temperature is lowered by the evaporator 6 to a low pressure. Further, during the defrosting operation, when the discharge amount discharged from the low stage compressor unit 12 to the defrost circuit decreases and the discharge pressure from the low stage compressor unit 12 decreases, the liquid in the intermediate pressure receiver 4 is caused by the pressure difference. The refrigerant is released. As a result, the refrigerant flow rate from the intermediate pressure refrigerant bypass circuit 8 to the defrost circuit 9 is increased, and the refrigerant flow rate of the intermediate-pressure gas refrigerant to the evaporator 6 is stabilized. Further, by performing the defrosting operation in this way, the gas refrigerant at the intermediate pressure acts on the on-off valve 91 without flowing in the discharge gas refrigerant of the two-stage compression refrigeration cycle. The performance can be lowered.

  In the refrigeration cycle apparatus, when the evaporator 6 returns to normal operation after the defrost operation, a part of the liquid refrigerant flows out from the evaporator 6, but the gas-liquid separator 7 separates the gas and liquid. There is no worry of the liquid refrigerant returning to the machine 1.

Next, Example 2 will be described with reference to FIGS. FIG. 4 is a refrigerant circuit diagram of the refrigeration apparatus according to the second embodiment. FIG. 5 is a Mollier diagram of a supercritical refrigeration cycle by the refrigeration cycle apparatus.
The second embodiment is the same as the first embodiment except that the compressor 1 is a compressor 300 having a gas injection port, and the high pressure gas refrigerant and the low pressure refrigerant are heat-exchanged between the evaporator 6 and the gas-liquid separator 7. The heat exchanger 303 is provided.

The compressor 300 is a compressor having a gas injection port 302 at an intermediate pressure portion in the compression process, and a high-pressure gas refrigerant is introduced into the sealed casing 301. An intermediate pressure refrigerant bypass circuit 8 is provided between the gas portion 41 of the intermediate pressure receiver 4 and the gas injection port 302. The intermediate pressure gas refrigerant is prevented from flowing out from the gas injection port 302 of the compressor 300 to the intermediate pressure refrigerant bypass circuit 8. Therefore, the intermediate pressure refrigerant bypass circuit 8 is not provided with the check valve 82 as in the first embodiment, and is provided with only the capillary tube 81 for adjusting the refrigerant flow rate. The heat exchanger 303 is configured to exchange heat between the low-pressure refrigerant at the outlet of the evaporator 6 and the high-pressure gas refrigerant at the outlet side of the high-pressure gas cooler 2.
Other configurations are the same as those of the first embodiment.

  Next, Example 2 configured as described above will be described based on the Mollier diagram of FIG. The symbols for indicating each point on the Mollier diagram are shown correspondingly to indicate the state of the refrigerant at a position on the circuit attached to the refrigerant circuit of FIG.

First, the refrigeration cycle during normal operation will be described. In this description, symbols for displaying each point on the Mollier diagram are also shown.
In the compressor 300, the low-pressure gas refrigerant a2 on the outlet side of the gas-liquid separator 7 is sucked and compressed. On the other hand, the intermediate-pressure gas refrigerant h <b> 2 that has been gas-liquid separated in the intermediate-pressure receiver 4 is introduced from the gas injection port 302 of the compressor 300 during the compression process in the compressor 300. Therefore, the gas refrigerant b2 compressed to the intermediate pressure by the compressor 300 is mixed with the intermediate pressure gas refrigerant h2 introduced from the gas injection port 302 to become the mixed refrigerant c2. Further, the mixed refrigerant c <b> 2 is compressed and discharged into the sealed casing 301. The high-pressure gas refrigerant d2 is discharged from the sealed casing 301 into the refrigerant circuit.

  The high-pressure gas refrigerant d2 discharged from the compressor 300 is cooled by heating a heated fluid such as room air, heating hot water, hot water supply water, or the like in the high-pressure gas cooler 2. The high-pressure gas refrigerant e2 cooled by the high-pressure gas cooler 2 is further cooled by the heat exchanger 303. The high-pressure gas refrigerant f2 cooled by the high-pressure gas cooler 2 is expanded by the first throttling device 3 and flows into the intermediate pressure receiver 4 as a gas-liquid mixed refrigerant g2 having a pressure below the critical point. This gas-liquid mixed refrigerant g2 is gas-liquid separated in the intermediate pressure receiver 4. The intermediate-pressure gas refrigerant h2 that has been gas-liquid separated in the intermediate-pressure receiver 4 flows into the sealed casing 301 of the compressor 300 through the intermediate-pressure refrigerant bypass circuit 8 as described above.

  On the other hand, the liquid refrigerant i2 that has been gas-liquid separated by the intermediate pressure receiver 4 is depressurized by the second expansion device 5 and flows into the evaporator 6 as a low-pressure gas-liquid mixed refrigerant j2. The low-pressure gas-liquid mixed refrigerant j2 that has flowed into the evaporator 6 exchanges heat with the outside air, pumps heat from the outside air, evaporates, and flows into the heat exchanger 303 as a wet low-pressure refrigerant k2. The wet low-pressure refrigerant k2 that has flowed into the heat exchanger 303 is heated by exchanging heat with the high-pressure gas refrigerant e2, and becomes superheated low-pressure gas refrigerant l2 and flows into the gas-liquid separator 7. Further, the low-pressure gas refrigerant 12 that has flowed into the gas-liquid separator 7, that is, the low-pressure gas refrigerant a 2, flows out of the gas-liquid separator 7 and is sucked into the compressor 300.

  In such a supercritical refrigeration cycle, at least one of the first throttling device 3 and the second throttling device 5 is controlled so that the outlet refrigerant of the evaporator 6 is overheated, as in the case of the first embodiment. . At this time, the degree of superheat of the refrigerant is such that the temperature difference between the refrigerant temperature detected by the refrigerant temperature sensor 61 in the middle of the evaporator 6 and the refrigerant temperature detected by the refrigerant temperature sensor 62 on the outlet side of the evaporator 6 is constant. Thus, the refrigerant on the outlet side of the evaporator 6 is controlled to have a certain degree of superheat.

  In the refrigeration cycle apparatus, when normal operation is performed after the winter long-time operation is stopped, liquid refrigerant flows out from the evaporator 6, but the gas-liquid separator 7 is the same as in the first embodiment. Therefore, there is no fear that the liquid refrigerant returns to the compressor 1.

  Since the cooling device according to the second embodiment is configured as described above, during the normal operation, as in the case of the first embodiment, the above-described (1) to (4) and (6) to (11). There is an effect.

  In the case of the second embodiment, since the heat exchanger 303 for exchanging heat between the high-pressure refrigerant and the low-pressure refrigerant is provided between the evaporator 6 and the gas-liquid separator 7, the temperature of the outlet refrigerant of the evaporator 6 increases. In addition, liquid return to the compressor 300 can be prevented more reliably.

Next, the defrosting operation of the evaporator 6 in the two-stage compression refrigeration cycle apparatus will be described.
In the above-described two-stage compression refrigeration cycle apparatus, the evaporator 6 starts frosting when normal operation is continued at a low temperature of the outside air. Moreover, when the frost starts, the heat exchange efficiency of the evaporator 6 is lowered, and the low pressure and the high pressure are gradually lowered. As a result, the amount of liquid refrigerant stored in the intermediate pressure receiver 4 increases, and defrosting is performed when the frost reaches a predetermined amount.

  In the defrosting operation, the on-off valve 91 of the defrost circuit 9 is opened, the first throttling device 3 is opened, and the second throttling device 5 is closed, whereby the high-pressure gas refrigerant discharged from the compressor 300 is changed to the high-pressure gas cooler 2, Through the expansion device 3, the gas part 41 of the intermediate pressure receiver 4, the capillary tube 81, the intermediate pressure refrigerant bypass circuit 8, and the defrost circuit 9, the refrigerant becomes an intermediate pressure gas refrigerant and is bypassed to the evaporator 6 inlet side. Thereby, the defrost of the evaporator 6 by the latent heat of the gas refrigerant of intermediate pressure is performed.

  Further, by performing the defrosting operation in this way, the gas refrigerant at the intermediate pressure acts on the on-off valve 91 without flowing in the discharge gas refrigerant of the two-stage compression refrigeration cycle. The performance can be lowered.

  In the refrigeration cycle apparatus, when the evaporator 6 is defrosted and returned to normal operation, liquid refrigerant flows out of the evaporator 6 but is separated into gas and liquid by the gas-liquid separator 7. There is no worry about the return of the liquid refrigerant. Furthermore, since the heat exchanger 303 for exchanging heat between the high-pressure refrigerant and the low-pressure refrigerant is provided between the evaporator 6 and the gas-liquid separator 7, the temperature of the outlet refrigerant of the evaporator 6 increases, Liquid return can be prevented more reliably.

  The refrigeration apparatus detailed above can be widely used for general refrigeration apparatuses. In particular, heat pump home air conditioners that use outside air as a heat source, commercial air conditioners (packaged air conditioners), heat pump hot water devices that use outside air sources, and outdoor air heat sources. It is used for a heat pump hot water supply device.

It is a refrigerant circuit figure of the refrigerating device concerning Example 1 of the present invention. It is a Mollier diagram of the supercritical refrigeration cycle in the same refrigeration apparatus. It is a block diagram around the evaporator and gas-liquid separator of the freezing apparatus. It is a refrigerant circuit figure of the freezing apparatus which concerns on Example 2 of this invention. It is a Mollier diagram of the supercritical refrigeration cycle in the same refrigeration apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Compressor 2 High pressure gas cooler 3 1st expansion device 4 Intermediate pressure receiver 5 2nd expansion device 6 Evaporator 7 Gas-liquid separator 8 Intermediate pressure refrigerant bypass circuit 9 Defrost circuit 11 Sealed casing 12 Low stage compressor section 13 Higher stage compressor section 41 Gas section 91 On-off valve 300 Compressor 302 Gas injection port 303 Heat exchanger

Claims (6)

  A two-stage compression type compressor, a high-pressure gas cooler that cools the high-pressure side gas refrigerant, a throttling device, and a two-stage compression refrigeration cycle apparatus that is connected in sequence to an evaporator that evaporates the low-pressure liquid refrigerant. The stage compression refrigeration cycle apparatus is provided with a defrost circuit that is connected via an on-off valve between an intermediate pressure portion in the refrigeration cycle and an evaporator inlet side.   It has a low-stage compressor section and a high-stage compressor section, and the discharge gas from the low-stage compressor section is discharged into the sealed casing, and the refrigerant in the sealed casing is transferred to the high-stage compressor section. Two-stage compressor configured to be sucked in, high-pressure gas cooler that cools the high-pressure side gas refrigerant, first throttle device, intermediate pressure receiver that adjusts the amount of refrigerant in the refrigeration cycle, second throttle device, and evaporator The gas-liquid separator is sequentially connected in series, and is provided with a two-stage compression refrigeration cycle apparatus configured to be operated in a supercritical refrigeration cycle. The refrigeration cycle apparatus further includes an intermediate pressure in an intermediate pressure receiver. An intermediate pressure refrigerant bypass circuit for bypassing the gas refrigerant in the casing of the two-stage compressor, and a defrost circuit for connecting the discharge side of the low-stage compressor section and the inlet side of the evaporator by opening an on-off valve It is characterized by comprising Freezing equipment.   Compressor having a gas injection port in the middle of the compression process, high-pressure gas cooler that cools the high-pressure side gas refrigerant, first throttle device, intermediate-pressure receiver that adjusts the amount of refrigerant in the refrigeration cycle, second throttle device, evaporation And a gas-liquid separator are sequentially connected in series, and a two-stage compression refrigeration cycle apparatus configured to be operated in a supercritical refrigeration cycle is provided. The two-stage compression refrigeration cycle apparatus further includes an intermediate pressure receiver. An intermediate pressure refrigerant bypass circuit that connects the gas section and the gas injection port, and a defrost circuit that connects the gas section of the intermediate pressure receiver and the inlet side of the evaporator via an on-off valve Refrigeration equipment.   The refrigeration apparatus according to claim 2 or 3, wherein the intermediate pressure receiver, which is a component device of the refrigeration cycle apparatus, has a volume capable of storing surplus refrigerant due to a change in operating conditions.   The refrigeration apparatus according to any one of claims 1 to 4, wherein the refrigeration cycle apparatus is filled with carbon dioxide as a refrigerant.   6. The refrigeration apparatus according to claim 5, wherein the refrigeration cycle apparatus is configured to heat water by a high-pressure gas cooler.

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