JP4363997B2 - Refrigeration equipment - Google Patents

Description

  The present invention relates to a refrigeration apparatus, and more particularly to prevention of liquid return in a refrigeration apparatus operated in a supercritical refrigeration cycle.

  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. Moreover, what is described in patent document 1 is known as a freezing apparatus which performs such supercritical cycle freezing operation.

  For example, as shown in FIG. 2 of Patent Document 1, this refrigeration apparatus is a compressor, a heat exchanger (high-pressure gas cooler), and a heat exchanger that exchanges heat between a high-pressure gas refrigerant and a low-pressure refrigerant in a countercurrent type. Supercritical refrigeration by a refrigeration cycle device in which a closed circuit is configured by sequentially connecting a high-pressure side passage of a flow-type heat exchanger, a throttle valve, an evaporator, a low-pressure side passage of the counter-flow heat exchanger, and a liquid receiver in series It is configured to operate in a cycle. The liquid portion of the liquid receiver is connected to the suction pipe of the compressor and the inlet side of the low-pressure side passage of the counterflow heat exchanger. Then, the amount of excess liquid refrigerant at the evaporator outlet is changed by changing the opening of the throttle valve, and the amount of liquid refrigerant stored in the liquid receiver is changed. In other words, this conventional technology is configured to store excess refrigerant in the low-pressure liquid receiver. However, this conventional technique has a drawback that liquid refrigerant is easily returned to the compressor during normal operation because excess refrigerant is stored in liquid form on the low pressure side. In addition, liquid refrigerant easily accumulates in the liquid receiver even during the defrosting operation, so that there is a problem that the liquid easily returns to the compressor. Furthermore, there is a disadvantage that the liquid refrigerant is more likely to return during a transition period such as when the operation is stopped for a long time in winter or when the operation is switched to the normal operation after the defrosting operation.

FIG. 3 in Patent Document 1 shows a high pressure of a compressor, a heat exchanger (high-pressure gas cooler), and a counter-current heat exchanger that exchanges heat between a high-pressure gas refrigerant and a low-pressure refrigerant in a counter-current type. Operate in a supercritical refrigeration cycle with a refrigeration cycle device that configures a closed circuit by sequentially connecting the low-pressure side passages of the side passage, on-off valve, receiver, throttle valve, evaporator, and counter-current heat exchanger in series. It is configured. Then, the opening / closing adjustment of the throttle valve is simultaneously performed while shutting off the opening / closing valve on the receiver inlet side. That is, the refrigerant is stored in the receiver by increasing or decreasing the amount of refrigerant flowing out from the receiver when the receiver inlet is closed.
However, in this prior art, since the receiver outlet is opened and closed, the flow of the refrigerant to the receiver is intermittent, and the pressure fluctuation on the high pressure side becomes large, so it is difficult to control the refrigerant storage amount. Further, there is no description about measures for preventing the return of the liquid refrigerant to the compressor during the transition period.

FIG. 4 in Patent Document 1 shows a high pressure of a compressor, a heat exchanger (high-pressure gas cooler), and a counter-current heat exchanger that exchanges heat between the high-pressure gas refrigerant and the low-pressure refrigerant in a counter-current type. Side circuit, throttle valve, evaporator, low-pressure side passage of counter-current heat exchanger are connected in series to form a closed circuit, and a series circuit of on-off valve, receiver, and on-off valve in parallel with the throttle valve It is configured to operate in a supercritical refrigeration cycle by a connected refrigeration cycle apparatus. Then, the throttle valve opening control and the opening / closing valve at the receiver inlet / outlet are opened / closed to increase / decrease the amount of refrigerant flowing into or out of the receiver, and the excess refrigerant is stored in the receiver.
However, in this prior art, the pressure in the receiver changes abruptly from a high pressure to a low pressure by opening and closing the opening / closing valve of the receiver inlet / outlet, so that it is difficult to control the refrigerant storage amount. Further, there is no description about measures for preventing the return of the liquid refrigerant to the compressor during the transition period.
Japanese Patent Publication No. 7-18602

  As described above, the conventional technology is easy to return the liquid to the compressor during normal operation and defrosting operation, and at the start of operation after a long-term operation stop in winter or when switching to normal operation after defrosting operation. In the transition period, there was a drawback that the liquid was more easily returned to the compressor.

  The present invention has been made in order to solve the above-described problems of the prior art. During normal operation, during defrosting operation, at the start of operation after a long-term operation stop in winter, or after defrosting operation An object of the present invention is to provide a refrigeration apparatus that can adjust the refrigerant amount adjustment in the refrigeration cycle without causing liquid return to the compressor when switching to operation.

A refrigerating apparatus according to the present invention includes a variable speed compressor, a high-pressure side cooling device that cools a high-pressure side gas refrigerant, a first throttling device, an intermediate receiver for adjusting the amount of refrigerant in the refrigeration cycle, and a second throttling device. , Equipped with a refrigeration cycle device in which a closed circuit is formed by serially connecting an evaporator using heat from the outside as a heat source and a gas-liquid separator, and this refrigeration cycle device is operated in a supercritical refrigeration cycle during normal operation. Thus, the compressor and the first throttle device are in a high pressure state, the first throttle device and the second throttle device are in an intermediate pressure state, and the second throttle device and the compressor are in a low pressure state. In addition, at least one of the first expansion device and the second expansion device is controlled so that the refrigerant at the outlet of the evaporator is overheated, and further, the compressor is controlled to operate at a low speed for a predetermined condition at the start of operation. And this prescribed article As between the discharge pressure of the compressor, characterized in adopting until rises to a preset predetermined pressure, as can be detected that the operation of the transient state is complete.

In addition, a variable speed compressor, a high-pressure side cooling device that cools the high-pressure side gas refrigerant, a first expansion device, an intermediate receiver for adjusting the amount of refrigerant in the refrigeration cycle, a second expansion device, and outside air as a heat source A refrigeration cycle apparatus having a closed circuit formed by sequentially connecting an evaporator and a gas-liquid separator in series, which is operated in a supercritical refrigeration cycle during normal operation, The first throttle device is in a high pressure state, the first throttle device and the second throttle device are in an intermediate pressure state, the second throttle device and the compressor are in a low pressure state, and the evaporator outlet At least one of the first throttling device and the second throttling device is controlled so that the refrigerant in the overheated state is further controlled, and the compressor at the start of operation is controlled to operate at a low speed for a predetermined condition. The cycle device As for conditions, the discharge gas temperature of the compressor, characterized in that it employs a until the rise to a predetermined temperature set in advance can be detected that the operation of the transient state is complete.

  In the refrigeration cycle apparatus, the gas-liquid separator is disposed above the refrigerant outlet of the evaporator, and the liquid refrigerant separated by the gas-liquid separator is connected to the evaporator via a pipe connecting the evaporator and the gas-liquid separator. It may be configured to return to gravity.

  The said refrigeration cycle apparatus is good also as what acts as a heat exchanger with which the said gas-liquid separator heat-exchanges with external air.

  The refrigeration cycle apparatus may be configured such that the cross-sectional area of the pipe connecting the evaporator and the gas-liquid separator is larger than the cross-sectional area of the compressor suction pipe.

  The refrigeration cycle apparatus may be controlled to temporarily stop the compressor when the defrosting operation is stopped, and to restart the operation after a predetermined time has elapsed.

  The refrigeration cycle apparatus may include a high-pressure gas cooler, a high-pressure refrigerant between the first throttling device and an evaporator, and a heat exchanger that exchanges heat between the low-pressure refrigerant between the gas-liquid separators.

In the refrigeration apparatus according to the present invention, the intermediate receiver for adjusting the amount of refrigerant in the refrigeration cycle apparatus is provided between the first expansion device and the second expansion device where the intermediate pressure state is established. The amount of refrigerant in the refrigeration cycle apparatus can be adjusted without storing the refrigerant. In addition, the conventional refrigeration apparatus includes a low-pressure receiver on the low-pressure side. However, the refrigeration cycle apparatus of the present invention does not include such a low-pressure receiver so that the refrigerant at the evaporator outlet is overheated during normal operation. In addition, since at least one of the first throttling device and the second throttling device is controlled, the liquid refrigerant does not flow out to the evaporator outlet. Further, in the refrigeration cycle apparatus of the present invention, since there is no liquid refrigerant storage container in the suction circuit of the compressor, the return of the liquid refrigerant to the compressor is prevented.
Furthermore, since the refrigeration cycle apparatus of the present invention operates the compressor at a low speed for a predetermined condition at the start of operation, it can more reliably prevent the return of liquid refrigerant to the compressor at the start of operation. Can do. In particular, it is easy to return the liquid to the compressor at the time of switching the operation mode after the defrosting operation during the long-term operation suspension period in winter etc., but by operating the compressor at a low speed as described above, Risk can be avoided.

In the refrigeration cycle apparatus according to the present invention, the operation time after the start of operation is between the predetermined condition and until a predetermined time elapses set by predicting that the operation in the transient state at the start of operation is completed. Then, it is possible to set between predetermined conditions with a simple device.
Moreover, even if it employ | adopts until the discharge pressure of a compressor rises to the predetermined pressure set in anticipation that the operation | movement of the transient state after an operation is completed is completed as said predetermined conditions. There is an effect. Further, as the interval between the predetermined conditions, a time until the temperature of the discharge gas refrigerant of the compressor rises to a predetermined temperature set in anticipation of completion of the transient operation after the start of operation is adopted. But there are similar effects.

  In the refrigeration cycle apparatus, the gas-liquid separator is disposed above the refrigerant outlet of the evaporator, and the liquid refrigerant separated by the gas-liquid separator is evaporated via a pipe connecting the evaporator and the gas-liquid separator. If it is configured so that it returns to the vessel by gravity, it is possible to more reliably prevent liquid return in the transitional period such as startup, etc., in combination with operating the compressor at a low speed for a predetermined condition at the start of operation. Can do. For this reason, since it starts without liquid compression, the rise of discharge gas temperature is quick and rise time is shortened. Further, the durability and reliability of the compressor are further improved.

  If the gas-liquid separator acts as a heat exchanger that exchanges heat with the outside air, the refrigerant that has flowed into the gas-liquid separator not only returns to the evaporator but also exchanges heat with the outside air and evaporates. Thus, the return of the liquid refrigerant can be prevented more reliably.

  If the cross-sectional area of the pipe connecting the evaporator and the gas-liquid separator is made larger than the cross-sectional area of the compressor suction pipe, this pipe can be considered as a part of the gas-liquid separator. The volume of can be reduced.

  In the refrigeration cycle apparatus, when the defrosting operation is stopped, if the compressor is temporarily stopped and the operation is resumed after a predetermined time has elapsed, the liquid that has flowed into the gas-liquid separator during the defrosting operation Since the refrigerant can be reliably returned to the evaporator, it is possible to more reliably prevent the liquid refrigerant from returning when the operation is resumed after defrosting. In addition, at the start of operation after defrosting, combined with the operation of the compressor at a low speed for a predetermined condition, it is possible to more reliably prevent liquid return in a transitional period such as startup.

  In the refrigeration cycle apparatus, when a heat exchanger for exchanging heat between the high-pressure gas cooler, the high-pressure refrigerant between the first throttling device and the low-pressure refrigerant between the evaporator and the gas-liquid separator is provided, the liquid to the compressor Return can be prevented more reliably. In addition, since the temperature of the outlet refrigerant of the high-pressure gas cooler can be lowered, the specific enthalpy of the outlet refrigerant of the high-pressure gas cooler and the specific enthalpy on the evaporator inlet side can be reduced, and energy efficiency can be improved. Can do.

  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, a refrigeration cycle apparatus according to Embodiment 1 includes a compressor 1, a high-pressure gas cooler 2 that cools a high-pressure side gas refrigerant and heats a heating fluid such as hot water for heating, hot water, indoor air, and the like. The first throttle device 3, the intermediate receiver 4 for adjusting the amount of refrigerant in the refrigeration cycle, the second throttle device 5, the evaporator 6 for pumping heat from the outside air, and the gas-liquid separator 7 are sequentially connected in series to form a closed circuit. Forming. The cooling device is a supercritical refrigeration cycle in which a refrigerant circuit is filled with carbon dioxide as a refrigerant, and heats a fluid to be heated, such as hot water for heating, hot water, indoor air, etc., by the high-pressure gas cooler 2. It is formed as a device.

The compressor 1 is a so-called internal intermediate pressure dome type two-stage compressor, and houses a low-stage compressor section 12, a high-stage compressor section 13, an electric motor and the like in a sealed casing 11, and the inside of the sealed casing 11. The intermediate-pressure gas refrigerant discharged from the low-stage compressor section 12 is filled, and the high-stage compressor section 13 is formed so as to suck and discharge the intermediate-pressure gas refrigerant. In addition, the two-stage compressor 1 is formed by an inverter so that the number of rotations can be varied, and is operated at a low speed for a predetermined condition at the start of operation.
The period between the predetermined conditions means a period until reaching a predetermined operating condition set in advance so that it can be detected that the operation in the transient state is completed at the start of the operation of the refrigeration apparatus. At the start of operation of the refrigeration apparatus, the discharge pressure and the discharge gas temperature of the compressor 1 gradually increase, and transition from the transient operation to the normal operation is performed. In order to detect the operation in the transient state, the operation time from the start of the operation to the completion of the operation in the transient state, the discharge pressure or the discharge gas temperature when the operation in the transient state is completed are set as predetermined conditions. In addition, it is configured that the compressor 1 is switched from the low speed operation to the normal rotation speed, assuming that the operation in the transitional state is completed when the predetermined condition is satisfied.
In addition, after shifting to the normal operation, the compressor 1 is operated at a high speed when the outside air temperature at which the heating load due to the supercritical refrigeration cycle increases, and conversely, the outside temperature at which the heating load decreases increases. Sometimes configured to be driven at low speed.

  The high-pressure gas cooler 2 is a heat exchanger that cools the discharge gas discharged from the high-stage compressor unit 13. Since this 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 receiver 4 adjusts the amount of refrigerant in the refrigeration cycle, and is controlled so that the pressure becomes a critical point or less by the opening control of the first expansion device 3 and the second expansion device 5. Thereby, the surplus refrigerant of the supercritical refrigeration cycle is stored in the intermediate receiver 4 as a liquid refrigerant.
The intermediate receiver 4 has a volume that can store excess refrigerant in the refrigeration cycle apparatus due to changes in operating conditions.

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 meanders the heat exchange pipe 65 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 connected to the gas portion 41 of the intermediate receiver 4 and the inside of the closed casing 11 of the compressor 1, whereby the intermediate-pressure gas refrigerant in the intermediate receiver 4 is compressed in the compressor compression process. An intermediate pressure refrigerant bypass circuit 8 for bypassing to the intermediate pressure portion is formed. 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 receiver 4. The supercritical refrigeration cycle is also provided with a defrost circuit 9 for defrosting the evaporator 6 by bypassing the gas refrigerant having an intermediate pressure in the compression process of the compressor to the evaporator 6. The defrost circuit 9 is provided with an on / off valve 91 for opening and closing the defrost circuit 9. This on-off valve 91 is closed during normal operation and opened during defrosting 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. The cross-sectional area of the compressor suction pipe 14 is made larger by using a pipe having a diameter. The gas-liquid separator 7 has a volume that can prevent liquid back to the compressor during defrosting.

  The 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 correspondingly shown to indicate the state of the refrigerant at the position of each symbol 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 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 separated by gas and liquid in the intermediate receiver 4 and the discharge gas b1 of the low-stage compressor unit 12 are mixed to form a gas refrigerant c1. The high-stage compressor section 13 sucks the mixed refrigerant c1 and discharges it from the two-stage compressor 1 as a high-pressure refrigerant d1.

  The high-pressure refrigerant d1 discharged from the two-stage compressor 1 is cooled by heating a heating fluid such as warm water for heating, hot water, indoor air, 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 receiver 4. This gas-liquid mixed refrigerant f1 is gas-liquid separated in the intermediate receiver 4. The intermediate-pressure gas refrigerant g1 that has been gas-liquid separated in the intermediate 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 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 expansion device 3 and the second expansion device 5 is controlled so that the outlet refrigerant of the evaporator 6 is in a predetermined superheated state. 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. The refrigerant on the outlet side of the evaporator 6 is controlled to a constant degree of superheat by controlling the temperature difference to be constant.

The above is the refrigeration cycle during normal operation. At the start of operation, since the compressor 1 starts from a state where the high and low pressures are balanced, the discharge pressure and the discharge gas temperature of the compressor 1 are low. The suction pressure of the compressor 1 is high. Further, at the start of the operation, in the transient operation until the operation in the normal state, the discharge pressure and the discharge gas temperature of the compressor 1 gradually increase, and the suction pressure gradually decreases. That is, during this time, the liquid refrigerant existing in the low-pressure side circuit such as the evaporator 6 or the gas-liquid separator 7 is in a state in which it is easily sucked into the compressor 1.
Therefore, in the present invention, the compressor 1 is operated at a low speed during a predetermined condition, in other words, during a predetermined operating condition set in advance so that it can be detected that the operation in the transient state is completed. . More specifically, at the start of operation, until a predetermined time that has been set in advance has elapsed, until the discharge pressure rises to a predetermined pressure that has been set in advance, or the discharge gas temperature has been set in advance. The compressor 1 is operated at a low speed until the temperature rises to the predetermined temperature. Thereby, the liquid refrigerant existing in the low-pressure side circuit is hardly sucked into the compressor 1 and the return of the liquid refrigerant to the compressor 1 is suppressed.

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. Note that 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 and the liquid refrigerant liquefied by the evaporator 6 are stored in the evaporator 6. When activated in this state, liquid refrigerant flows out of the evaporator 6, but this liquid refrigerant is gas-liquid separated by the gas-liquid separator 7, so that the liquid refrigerant does not return to the compressor 1.
Therefore, in addition to the above configuration, in combination with the operation of the compressor 1 at a low speed in the transient operation until the normal operation is started when the operation is started as described above. In addition, liquid return in a transitional period such as startup can be prevented more reliably.

  In the refrigeration cycle apparatus, when the evaporator 6 needs to be defrosted, the opening / closing valve 91 of the defrost circuit 9 is opened, and the opening degree of at least one of the first expansion device 3 and the second expansion device 5 is set. By adjusting, the intermediate-pressure gas refrigerant discharged from the low-stage compressor section 12 is sent from the two-stage compressor 1 to the inlet side of the evaporator 6 via the defrost circuit 9. As a result, the evaporator 6 frosted by the latent heat of the intermediate-pressure gas refrigerant is heated and defrosted. The refrigerant discharged from the high-stage compressor unit 13 is the high-pressure gas cooler 2, the first throttling device 3, the gas unit 41 of the intermediate receiver 4, the capillary tube 81, the check valve 82, and the intermediate-pressure refrigerant bypass circuit. 8 flows into the defrost circuit 9, but the amount can be reduced by adjusting the opening degree of the first expansion device 3. Also, the liquid refrigerant in the intermediate receiver 4 can be prevented from flowing into the evaporator 6 by adjusting the opening of the second expansion device 5.

Further, when the evaporator 6 is defrosted and returned to normal operation, the liquid refrigerant flows out of the evaporator 6, but is separated into gas and liquid by the gas-liquid separator 7, so that the liquid refrigerant returns to the compressor 1. There is no worry. Further, in this embodiment, when the defrosting operation is stopped, the compressor 1 is temporarily stopped and the operation is restarted after a predetermined time. In this way, even if liquid refrigerant is temporarily stored in the gas-liquid separator 7 during defrosting, the stored liquid refrigerant returns to the evaporator 6 by gravity while the compressor 1 is stopped.
Therefore, in addition to the above configuration, the compressor 1 is operated at a low speed in the transient operation until the normal operation is started at the start of operation as described above. Thus, the liquid return in the transition period such as at the start-up can be prevented more reliably.

Since the cooling device according to the first embodiment is configured as described above, the following effects can be obtained.
(1) In the refrigeration apparatus according to the first embodiment, the intermediate 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. In the refrigeration apparatus of the present embodiment, at least one of the first expansion device 3 and the second expansion device 5 is not provided with a low pressure receiver on the low pressure side so that the refrigerant at the outlet of the evaporator 6 is overheated during normal operation. Since it is controlled, the liquid refrigerant does not flow out to the outlet of the evaporator 6. Further, since there is no liquid refrigerant storage container in the suction circuit of the compressor 1, the return of the liquid refrigerant to the compressor 1 is prevented.
Furthermore, the refrigeration apparatus according to the first embodiment performs compression during a predetermined condition at the start of operation, that is, until a predetermined operating condition set in advance so that it can be detected that the operation in the transient state is completed. Since the machine 1 is operated at a low speed, the return of the liquid refrigerant to the compressor 1 at the start of operation can be more reliably prevented. In particular, it is easy to return the liquid to the compressor 1 at the time of switching the operation mode after the defrosting operation during the long-term operation suspension period in winter or the like, but by operating the compressor 1 at a low speed as described above. That danger can be avoided.
In addition, by adopting a period until a predetermined time elapses after the operation time after the start of operation is predicted to complete the operation in a transitional state at the start of the operation as the predetermined condition, or By adopting a period until the discharge pressure of the compressor 1 rises to a predetermined pressure set in anticipation of completion of the transient operation after the start of operation, or the discharge of the compressor 1 By adopting the time until the gas refrigerant temperature rises to the predetermined temperature set in anticipation of completion of the operation in the transitional state after the start of operation, the interval between the predetermined conditions is set by a simple device. be able to.

  (2) Moreover, in Example 1, since the volume of the intermediate receiver 4 is set to a size capable of storing surplus refrigerant in the refrigeration cycle apparatus due to changes in operating conditions, the surplus refrigerant is stored in the low-pressure side circuit. Thus, it is possible to more reliably prevent the liquid refrigerant from returning to the compressor 1 during normal operation or when the operation is resumed after the operation is temporarily stopped.

  (3) Moreover, in this refrigeration cycle apparatus, since the gas-liquid separator 7 has a volume capable of preventing liquid back to the compressor during defrosting, the liquid return to the compressor 1 during defrosting operation is further reduced. It can be surely prevented.

  (4) In addition, the gas-liquid separator 7 is disposed above the refrigerant outlet 64 of the evaporator 6, and the liquid refrigerant separated by the gas-liquid separator 7 connects the evaporator 6 and the gas-liquid separator 7. Therefore, the liquid refrigerant is reliably returned from the gas-liquid separator 7 to the evaporator 6 without any operation when the operation is stopped. In addition, when the operation is started, the compressor 1 is operated at a low speed for a predetermined condition, so that the liquid return in the transition period such as at the start-up can be prevented more reliably. For this reason, since the liquid refrigerant is started without returning to the compressor 1, the discharge gas temperature rises quickly and the rise time is shortened. Moreover, the durability and reliability of the compressor 1 are further improved.

  (5) Since the cross-sectional area of the pipe 73 connecting the evaporator 6 and the gas-liquid separator 7 is larger than the cross-sectional area of the suction pipe 14 of the compressor 1, the pipe 73 is connected to the gas-liquid separator 7. The volume of the gas-liquid separator 7 can be reduced accordingly.

  (6) Since the compressor 1 is temporarily stopped when the defrosting operation is stopped and the operation is restarted after a predetermined time has elapsed, the gas-liquid separator is temporarily stopped while the compressor 1 is stopped. The liquid refrigerant stored in 7 returns to the evaporator 6 by gravity. For this reason, the liquid refrigerant does not return to the compressor 1 and the durability and reliability of the compressor 1 can be improved. In addition, when the operation is started after defrosting, the compressor 1 is operated at a low speed for a predetermined condition, so that liquid return in a transitional period such as startup can be more reliably prevented.

  (7) 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.

  (8) In addition, when applied to a device that heats a heated fluid such as hot water for heating, hot water, indoor air, etc., by using the high-pressure gas cooler 2, high-temperature hot water for heating, hot water, hot air, etc. are supplied. be able to.

Next, Example 2 will be described with reference to FIG. FIG. 4 is a configuration diagram around the evaporator and the gas-liquid separator of the refrigeration apparatus according to the second embodiment.
In the second embodiment, the gas-liquid separator 7 in the first embodiment is changed to a gas-liquid separator 100 that exchanges heat with the outside air, and other configurations are the same as those in the first embodiment.
The gas-liquid separator 100 is configured by arranging an upper header 101 at the upper part and a lower header 102 at the lower part, and arranging a heat exchange tube 103 vertically between the upper and lower headers 101, 102. Moreover, the plate fin 104 is attached to the horizontal direction with respect to the heat exchange tube 103 arrange | positioned in this way. The lower header 102 is arranged so as to give a predetermined head difference H2 to the refrigerant outlet 64 of the evaporator 6 as in the case of the first embodiment. Furthermore, the pipe 105 connecting the refrigerant outlet 64 of the evaporator 6 and the lower header 102, that is, the cross-sectional area of the liquid refrigerant return pipe 105 from the gas-liquid separator 100 to the evaporator 6 uses a large diameter pipe or the like. For example, the cross-sectional area of the compressor suction pipe 14 is larger.

  Therefore, when a gas-liquid mixed refrigerant flows into the gas-liquid separator 100, a part of the liquid refrigerant evaporates by exchanging heat with the outside air, and the remaining liquid refrigerant passes through the heat exchange tube 103 in the vertical direction. Gas-liquid separation is performed, and the separated liquid refrigerant flows to the refrigerant inlet 63 side of the evaporator 6 via the lower header 102 and the return pipe (pipe connecting the refrigerant outlet 64 of the evaporator 6 and the lower header 102) 105. Is formed.

Since the gas-liquid separator 100 acts as a heat exchanger that exchanges heat with outside air as described above, the second embodiment can more reliably prevent the liquid refrigerant from returning to the compressor 1 than in the first embodiment. it can.
Similarly to the case of the first embodiment, a pipe (return pipe) 105 connecting the refrigerant outlet 64 of the evaporator 6 and the lower header 102 can be considered as a part of the gas-liquid separator 100. The volume of the separator 100 can be reduced.

Next, Example 3 will be described with reference to FIG. FIG. 5 is a configuration diagram around the evaporator and the gas-liquid separator of the refrigeration apparatus according to the third embodiment.
In the third embodiment, the configuration of the evaporator 6 in the first embodiment is changed, and the position of the gas-liquid separator 7 is changed. The other configurations are the same as those in the first embodiment.
That is, in Example 3, the evaporator 200 arranges the refrigerant inlet 201 downward, the refrigerant outlet 202 upward, and further arranges the heat exchange tube 203 in a meandering manner from below to above. Is configured. Further, plate fins 204 are arranged in the vertical direction with respect to the heat exchange tube 203. On the other hand, the gas-liquid separator 7 is disposed above the evaporator 200, and the refrigerant inlet 71 of the gas-liquid separator 7 and the refrigerant outlet 72 of the evaporator 200 are connected.

Therefore, the evaporator 200 according to the third embodiment has a structure in which the liquid refrigerant is easily stored because the heat exchange tube 203 is arranged in a meandering manner from the lower side to the upper side. The structure is difficult to flow to the gas-liquid separator 100. When the gas-liquid mixed refrigerant flows into the gas-liquid separator 7, the gas-liquid separator 7 gas-liquid separates the liquid refrigerant from the refrigerant inlet 71 of the gas-liquid separator 7. It is configured to return to the evaporator 6 through the refrigerant outlet 202 and accumulate in the evaporator 6.
Thus, in this Example 3, since a liquid refrigerant accumulates in the evaporator 6, the volume of the gas-liquid separator 7 can be made small.

Next, Example 4 will be described with reference to FIG. FIG. 6 is a configuration diagram around the evaporator and the gas-liquid separator of the refrigeration apparatus according to the fourth embodiment.
In the fourth embodiment, the gas-liquid separator 7 in the third embodiment is changed to the gas-liquid separator 100 in the second embodiment. Other configurations are the same as those in the third embodiment.

  Therefore, the refrigeration apparatus according to the fourth embodiment can achieve the same effects as the refrigeration apparatuses according to the second and third embodiments.

Next, Example 5 will be described with reference to FIGS. FIG. 7 is a refrigerant circuit diagram of the refrigeration apparatus according to the fifth embodiment. FIG. 8 is a Mollier diagram of a supercritical refrigeration cycle by the refrigeration cycle apparatus.
The fifth embodiment is the same as the first embodiment except that the compressor 1 is a one-stage compressor 300 having a variable rotation speed, 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 single-stage compressor in which a gas injection port 302 is provided at an intermediate pressure portion in a 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 receiver 4 and the gas injection port 302. As in the case of the first embodiment, the compressor 300 is formed by an inverter so that the number of rotations is variable, and is operated at a low speed for a predetermined condition at the start of operation.
Further, the heat exchanger 303 is configured such that heat exchange is performed 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 5 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 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 separated in the intermediate 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 hot water for heating, hot-water supply water, indoor air, etc., 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 heat exchanger 303 is expanded by the first expansion device 3 and flows into the intermediate receiver 4 as a gas-liquid mixed refrigerant g2 having a pressure equal to or lower than the critical point. The gas-liquid mixed refrigerant g2 is gas-liquid separated in the intermediate receiver 4. The intermediate-pressure gas refrigerant h2 that has been gas-liquid separated in the intermediate 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 receiver 4 is decompressed 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. . Further, at this time, the superheat degree of the refrigerant is controlled so that the difference temperature between the refrigerant temperature detected by the first refrigerant temperature sensor 61 and the refrigerant temperature detected by the second refrigerant temperature sensor 62 is constant. The refrigerant on the 6 outlet side is controlled to have a certain degree of superheat.

  The above is the refrigeration cycle during normal operation, but by operating the compressor 300 at a low speed during a predetermined condition at the start of operation, the liquid refrigerant present in the low-pressure side circuit is made difficult to be sucked into the compressor 1, The return of the liquid refrigerant to the compressor 1 is suppressed.

  In the refrigeration cycle apparatus, when the operation is stopped for a long time in winter or when the normal operation is performed after the defrosting operation, the liquid refrigerant flows out from the evaporator 6. Similarly, gas-liquid separation by the gas-liquid separator 7 and the operation of the compressor 1 at a low speed in the operation in a transient state up to the normal operation at the start of operation, It is possible to more reliably prevent liquid return during a transition period such as startup.

  In the above refrigeration cycle apparatus, when defrosting of the evaporator 6 is necessary, the opening / closing valve 91 of the defrost circuit 9 is opened, the first expansion device 3 is opened, and the opening of the second expansion device 5 is increased. By adjusting, the high-pressure gas refrigerant discharged from the compressor 300 becomes the high-pressure gas cooler 2, the first throttling device 3, the gas part 41 of the intermediate receiver 4, the capillary tube 81, the intermediate-pressure refrigerant bypass circuit 8 and the defrost circuit 9. Then, it is sent to the inlet side of the evaporator 6 as a gas refrigerant having an intermediate pressure. Thereby, the evaporator 6 can be heated and defrosted.

Further, when the evaporator 6 is defrosted and returned to normal operation, the liquid refrigerant flows out of the evaporator 6, but is separated into gas and liquid by the gas-liquid separator 7, so that the liquid refrigerant returns to the compressor 300. There is no worry. Further, in this embodiment, when the defrosting operation is stopped, the compressor 300 is temporarily stopped and the operation is restarted after a predetermined time. In this way, even if liquid refrigerant is temporarily stored in the gas-liquid separator 7 during defrosting, the stored liquid refrigerant returns to the evaporator 6 by gravity while the compressor 300 is stopped.
Therefore, in addition to the configuration described above, the compressor 300 is operated at a low speed in the transient operation until the normal operation is started when the operation is started as described above. Thus, the liquid return in the transition period such as at the start-up can be prevented more reliably.

  Since the cooling device according to the fifth embodiment is configured as described above, the effects (1) to (8) described above are achieved as in the case of the first embodiment. In addition to this effect, the following effect is obtained. Can be played.

  That is, in the case of Example 5, since the heat exchanger 303 for exchanging heat between the high-pressure gas refrigerant and the low-pressure refrigerant is provided between the evaporator 6 and the gas-liquid separator 7, the wet low-pressure refrigerant k2 at the outlet of the evaporator 6 is provided. And the temperature of the outlet refrigerant of the high-pressure gas cooler 2 can be lowered. Thereby, the liquid return to the compressor 300 can be prevented more reliably. Moreover, the specific enthalpy of the outlet refrigerant of the high-pressure gas cooler 2 and the specific enthalpy on the evaporator inlet side can be reduced, and the energy efficiency can be improved.

  The refrigeration apparatus described in detail above can be widely used for general refrigeration apparatuses. In particular, a heat pump type home air conditioner that uses outside air as a heat source, a commercial air conditioner (packaged air conditioner), a heat pump type hot water heating apparatus that uses an outside air source, and an outside air heat source It is used for the heat pump type hot-water supply apparatus of No ..

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. FIG. 6 is a configuration diagram around an evaporator and a gas-liquid separator of a refrigeration apparatus according to Embodiment 2. FIG. 5 is a configuration diagram around an evaporator and a gas-liquid separator of the refrigeration apparatus according to the third embodiment. FIG. 6 is a configuration diagram around an evaporator and a gas-liquid separator of a refrigeration apparatus according to Embodiment 4. It is a refrigerant circuit figure of the freezing apparatus which concerns on Example 5 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 (Rotation speed variable type) Compressor 2 High pressure gas cooler 3 First throttle device 4 Intermediate receiver 5 Second throttle device 6 Evaporator 7 Gas-liquid separator 8 Intermediate pressure refrigerant bypass circuit 14 Compressor suction pipe 41 Gas section 61 Refrigerant temperature sensor 62 Refrigerant temperature sensor 63 Refrigerant inlet 64 Refrigerant outlet 73 Pipe 300 Compressor 302 Gas injection port 303 Heat exchanger H1 Head difference H2 Head difference

Claims (7)

Rotational speed variable compressor, high pressure side cooling device for cooling high pressure side gas refrigerant, first throttle device, intermediate receiver for adjusting refrigerant quantity in refrigeration cycle, second throttle device, evaporator using outside air as heat source And a refrigeration cycle apparatus in which gas-liquid separators are sequentially connected in series to form a closed circuit. The refrigeration cycle apparatus is operated in a supercritical refrigeration cycle during normal operation. Between the throttle device is in a high pressure state, between the first throttle device and the second throttle device is in an intermediate pressure state, between the second throttle device and the compressor is in a low pressure state, and the refrigerant at the outlet of the evaporator At least one of the first throttle device and the second throttle device is controlled so as to be in an overheated state, and is further controlled to operate the compressor at a low speed for a predetermined condition at the start of operation . As the compressor discharges Pressure, refrigeration apparatus characterized by employing a until the rise preset predetermined pressure to allow detect that the operation of the transient state is complete. Rotational speed variable compressor, high pressure side cooling device for cooling high pressure side gas refrigerant, first throttle device, intermediate receiver for adjusting refrigerant quantity in refrigeration cycle, second throttle device, evaporator using outside air as heat source And a refrigeration cycle apparatus in which gas-liquid separators are sequentially connected in series to form a closed circuit. The refrigeration cycle apparatus is operated in a supercritical refrigeration cycle during normal operation. Between the throttle device is in a high pressure state, between the first throttle device and the second throttle device is in an intermediate pressure state, between the second throttle device and the compressor is in a low pressure state, and the refrigerant at the outlet of the evaporator At least one of the first throttle device and the second throttle device is controlled such that the compressor is in an overheated state, and is further controlled to operate the compressor at a low speed for a predetermined condition at the start of operation. Is the prescribed provision As for the discharge gas temperature of the compressor, the refrigeration apparatus characterized by employing a until the rise preset predetermined temperature can be detected that the operation of the transient state is complete.

In the refrigeration cycle apparatus, the gas-liquid separator is disposed above the refrigerant outlet of the evaporator, and the liquid refrigerant separated by the gas-liquid separator is connected to the evaporator via a pipe connecting the evaporator and the gas-liquid separator. The refrigeration apparatus according to claim 1, wherein the refrigeration apparatus is configured to return to gravity by gravity.

4. The refrigeration apparatus according to claim 3 , wherein the refrigeration cycle apparatus acts as a heat exchanger in which the gas-liquid separator exchanges heat with outside air.

The refrigeration cycle apparatus, a refrigeration apparatus of claim 4, wherein the cross-sectional area of the pipe connecting the evaporator and the gas-liquid separator is configured larger than the cross-sectional area of the compressor intake piping.

The refrigeration cycle apparatus, the defrosting operation is stopped temporarily compressor when stopped, any one of claims 3-6, characterized in that it is controlled to resume operation after a predetermined time has elapsed 1 The refrigeration apparatus according to item.

The refrigeration cycle apparatus claims, characterized in that it comprises a high-pressure gas cooler, evaporator and high-pressure refrigerant between the first expansion device, a heat exchanger for exchanging heat between low pressure refrigerant among the gas-liquid separator The refrigeration apparatus according to any one of 1 to 6 .

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