WO2022195727A1

WO2022195727A1 - Heat source machine for refrigeration apparatus and refrigeration apparatus equipped with same

Info

Publication number: WO2022195727A1
Application number: PCT/JP2021/010638
Authority: WO
Inventors: 崇憲八代; 寛也石原; 智隆石川; 拓未西山; 誠江上; 裕弥井内
Original assignee: 三菱電機株式会社
Priority date: 2021-03-16
Filing date: 2021-03-16
Publication date: 2022-09-22
Also published as: JPWO2022195727A1; DE112021007291T5; JP7523667B2

Abstract

A heat source machine (10A) comprises a first compressor (1b), a first heat exchanger (7), a second heat exchanger (5), a liquid receiver (8), a four-way valve (4), and a flow path switching device (6). In a cooling mode, a first refrigerant circulates through the first compressor (1b), the four-way valve (4), the second heat exchanger (5), the flow path switching device (6), the first heat exchanger (7), the liquid receiver (8), the flow path switching device (6), a load device (20A), and the four-way valve (4) in this order and back to the first compressor (1b). In a defrosting mode, the first refrigerant circulates through the first compressor (1b), the four-way valve (4), the load device (20A), the flow path switching device (6), the first heat exchanger (7), the liquid receiver (8), the flow path switching device (6), the second heat exchanger (5), and the four-way valve (4) in this order and back to the first compressor (1b).

Description

Heat source machine for refrigeration equipment and refrigeration equipment provided with the same

The present disclosure relates to a heat source machine of a refrigeration system and a refrigeration system including the same.

Due to various efforts to address global environmental issues, including the Montreal Protocol, there is a demand for the spread of air conditioners and refrigeration equipment that use refrigerants with a low Global Warming Potential (GWP).

Among various refrigerants, carbon dioxide (refrigerant symbol: R744) has a GWP of 1, and compared to the currently popular Freon refrigerants such as R404A and R32, it has a significantly lower impact on global warming when a refrigerant leaks. . R744 is currently used in water heaters and condensing units.

　Compared to the commonly used Freon refrigerants such as R404A and R32, R744 has a very high pressure and is usually designed with a design pressure of about 12 to 14 MPa. Therefore, a refrigerant circuit using R744 needs to have a high pressure resistance and is difficult to construct.

As a solution, a refrigeration system with a binary cycle system is used. In the binary cycle system, when R744 is used for the low temperature side cycle, pressure rise in the low temperature side cycle can be prevented by operating the high temperature side cycle when the pressure in the low temperature side cycle rises. As a result, the design pressure of the low-temperature side cycle can be lowered to a level equivalent to that of a chlorofluorocarbon refrigerant, and the degree of difficulty in circuit construction can be made the same as when chlorofluorocarbon is used.

WO2020/161803

The refrigeration system is equipped with a defrosting mode to melt the frost that adheres to the cooler. As a defrosting method, for example, a reverse hot gas defrosting method is known, in which a four-way valve changes the circulation direction of the refrigerant so as to send high temperature gas from the compressor to a cooler that normally functions as an evaporator.

Since a typical refrigerating device includes a liquid receiver, in order to perform reverse hot gas defrosting operation using a four-way valve, for example, the refrigerating device described in International Publication No. 2020/161803 (Patent Document 1) Therefore, it is necessary to devise a method such as providing a dedicated bypass circuit.

However, when reverse hot gas defrosting operation is performed in the refrigeration apparatus described in International Publication No. 2020/161803 (Patent Document 1), the refrigerant does not pass through the liquid receiver during defrosting operation, so defrosting operation is started. Before defrosting operation, it is necessary to optimize the amount of refrigerant, such as transferring excess refrigerant unnecessary for the defrosting operation to the liquid receiver in advance.

Even if the surplus refrigerant is transferred to the liquid receiver before the defrosting operation starts, as the frost on the evaporator gradually disappears, the evaporator becomes unable to cool and condense the refrigerant. quantity becomes even smaller. Therefore, it is necessary to transfer the refrigerant to the liquid receiver again during the defrosting operation, which complicates the control of the defrosting operation.

Furthermore, at the end of the defrosting operation, the refrigerant cannot be condensed in the evaporator, so the condensation pressure rises. In this case, the protection works before the equipment's design pressure is exceeded, so shutdown occurs and defrost failure may occur.

The present disclosure eliminates the need to adjust the amount of refrigerant during hot gas defrosting operation in a binary refrigerating device that performs hot gas defrosting operation using a four-way valve, and avoids an increase in condensation pressure at the end of defrosting operation. An object of the present invention is to disclose a heat source machine and a refrigeration apparatus capable of

The present disclosure relates to a heat source machine that forms a refrigeration system together with a load device. The refrigeration system has a cooling mode and a defrosting mode as operation modes. The heat source device includes a first compressor, a first heat exchanger, a second heat exchanger, a liquid receiver, a four-way valve, and a channel switching device. The first compressor, the first heat exchanger, the second heat exchanger, and the liquid receiver together with the load device constitute a first refrigeration cycle device in which the first refrigerant circulates. The four-way valve switches connection destinations of the load device and the second heat exchanger between the cooling mode and the defrosting mode. The flow path switching device is connected to an upstream portion of the flow path through which the first refrigerant flows to the liquid receiver through the first heat exchanger, a downstream portion of the flow path, a load device, and the second heat exchanger, Switching the flow of the first refrigerant. In the cooling mode, the first compressor, the four-way valve, the second heat exchanger, the flow switching device, the first heat exchanger, the receiver, the flow switching device, the load device, the four-way valve in this order, and the first compression A first refrigerant is circulated back to the machine. In the defrosting mode, the first compressor, the four-way valve, the load device, the flow switching device, the first heat exchanger, the liquid receiver, the flow switching device, the second heat exchanger, the four-way valve in this order. A first refrigerant is circulated back to the compressor.

According to the heat source device and the refrigeration system of the present disclosure, it is possible to avoid complicating the control during the defrosting operation because it is unnecessary to adjust the amount of refrigerant while avoiding pressure rise.

1 is a diagram showing a configuration of a refrigerating apparatus according to Embodiment 1; FIG. 4 is a flowchart for explaining control of a compressor in a high temperature side circuit; 4 is a flow chart for explaining fan control when the intercooler is an air-cooled type. 5 is a flowchart for explaining control at the end of defrosting mode; FIG. 10 is a diagram showing the configuration of a refrigeration system according to Embodiment 2; FIG. 10 is a diagram showing the configuration of a refrigeration system according to Embodiment 3; 10 is a flow chart for explaining control for liquid return prevention executed in Embodiment 3. FIG. FIG. 10 is a diagram showing the configuration of a refrigeration system according to Embodiment 5; FIG. 12 is a diagram showing the configuration of a refrigeration system according to Embodiment 6; FIG. 12 is a diagram showing the configuration of a refrigeration system according to Embodiment 7; FIG. 10 is a diagram showing another example of the arrangement of expansion valves;

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. A plurality of embodiments will be described below, but appropriate combinations of the configurations described in the respective embodiments have been planned since the filing of the application. The same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated.

Embodiment 1.
FIG. 1 is a diagram showing the configuration of a refrigeration system according to Embodiment 1. FIG.

A refrigeration system 1000A shown in FIG. 1 includes a heat source device 10A and a load device 20A that utilizes heat or cold heat generated by the heat source device 10A. The heat source device 10A includes a high temperature side circuit 101, a low temperature side circuit 102, and a control device 110.

The high temperature side circuit 101 includes a compressor 1a, a heat exchanger 2, an expansion valve 3a, a heat exchanger 7, which is a cascade heat exchanger, and piping connecting them. The high temperature side circuit 101 constitutes a second refrigeration cycle device RC2 in which a second refrigerant circulates.

The expansion valve 3a is connected to the evaporation side inlet of the heat exchanger 7. An evaporation-side outlet of the heat exchanger 7 is connected to the suction port of the compressor 1a.

The low-temperature side circuit 102 includes a compressor 1b, a four-way valve 4, a heat exchanger 5 acting as an intercooler, a flow path switching device 6 in which four check valves are bridge-connected, a heat exchanger 7, It includes a liquid receiver 8 , an expansion valve 9 , a gas-liquid separator 10 , piping connecting these, a pressure sensor 51 , and a temperature sensor 52 . The low temperature side circuit 102 is connected to the load device 20A and constitutes a first refrigeration cycle device RC1 in which the first refrigerant circulates.

For example, the second refrigerant used in the second refrigeration cycle device RC2 is HFC refrigerant, HFO refrigerant, natural refrigerant (CO ₂ , propane), etc., and the first refrigerant used in the first refrigeration cycle device RC1 is CO ₂ ( R744 refrigerant).

The flow path switching device 6 includes check valves 61-64. The check valves 61-64 are arranged in a bridge shape as shown in FIG. The cooling operation outlet of the heat exchanger 5, the condensation side inlet of the heat exchanger 7, the liquid receiver 8 outlet, and the expansion valve 9 outlet are connected as shown in FIG.

The load device 20A includes an expansion valve 3b, a load-side heat exchanger 11, and a fan 11F that are connected in series by piping. Note that the fan 11F is not essential.

The heat source device 10A and the load device 20A are connected by piping.
The control device 110 is a controller that appropriately operates each component of the heat source device 10A and the load device 20A.

The control device 110 includes a CPU (Central Processing Unit) 111, a memory 112, and a communication interface (not shown). The CPU 111 controls each component of the heat source device 10A and the load device 20A according to the data stored in the memory 112 and the information obtained via the communication interface.

The memory 112 includes, for example, ROM (Read Only Memory), RAM (Random Access Memory), and flash memory. The flash memory stores an operating system, application programs, and various data. Control device 110 shown in FIG. 1 is implemented by CPU 111 executing an operating system and application programs stored in memory 112 . Various data stored in the memory 112 are referenced when the application program is executed.

In the high temperature side circuit 101, the second refrigerant is discharged as a compressed refrigerant gas from the compressor 1a, condensed in the heat exchanger 2 on the heat source side, expanded to a low temperature and low pressure state in the expansion valve 3a, and evaporated in the heat exchanger 7. and is sucked into the compressor 1a.

The refrigeration system 1000A has a cooling mode and a defrosting mode as operation modes. In the cooling mode, the first refrigerant flows in the direction indicated by the solid line arrow in FIG. 1, and in the defrosting mode, the first refrigerant flows in the direction indicated by the broken line arrow. In the present embodiment, the high-temperature, high-pressure gas (hot gas) of the first refrigerant discharged from the compressor 1b is introduced into the load-side heat exchanger 11 by the four-way valve 4 in the defrosting mode.

In the cooling operation, the first refrigerant discharged from the compressor 1b of the low temperature side circuit 102 passes through the four-way valve 4 in the cooling operation direction, is primarily cooled by the heat exchanger 5, passes through the flow path switching device 6, and heat exchanges. It is condensed in the vessel 7, passes through the liquid receiver 8, the expansion valve 9, the flow path switching device 6 again, and flows into the load device 20A from the outlet of the heat source device 10A.

The first refrigerant in a high-pressure liquid state that has flowed into the load device 20A from the heat source device 10A is expanded to a low-temperature, low-pressure state by the expansion valve 3b, evaporated in the load-side heat exchanger 11, and returned to the heat source device 10A in a low-pressure gas state. . Then, the first refrigerant returned from the load device 20A passes through the four-way valve 4 in the cooling operation direction and is sucked into the compressor 1b via the gas-liquid separator 10. As shown in FIG.

In the defrosting operation, the first refrigerant in a high-pressure gas state discharged from the compressor 1b of the low-temperature side circuit 102 passes through the four-way valve 4 in the defrosting operation direction, flows out from the heat source device 10A, and flows through the pipe connected to the load device 20A. flow into

The first refrigerant in the high-pressure gas state that has entered the load device 20A is condensed while exchanging heat with frost in the load-side heat exchanger 11, passes through the expansion valve 3b, and returns to the heat source device 10A.

The high-pressure first refrigerant returned from the load device 20A to the heat source device 10A passes through the flow path switching device 6, is further condensed in the heat exchanger 7, passes through the liquid receiver 8, and reaches the expansion valve 9. The first refrigerant is expanded to a low temperature and low pressure state by the expansion valve 9, passes through the flow switching device 6, evaporates in the heat exchanger 5, passes through the four-way valve 4 in the defrosting operation direction, and passes through the gas-liquid separator 10. and is sucked into the compressor 1b.

The operation method of the high temperature side circuit 101 of the heat source device 10A does not change whether the low temperature side circuit 102 is in cooling operation or defrosting operation. However, for example, when the low-temperature side circuit 102 is in low-capacity operation during cooling operation and the refrigerant can be condensed only in the heat exchanger 5, the high-temperature side circuit 101 can be stopped. Further, when the refrigerant can be condensed only by the load device 20A during the defrosting operation, the high temperature side circuit 101 can be stopped.

The heat exchanger 2 on the heat source side of the high temperature side circuit 101 includes types such as an air-cooled fin-coil heat exchanger and a water-cooled shell-and-tube heat exchanger, but is not particularly limited in this embodiment.

A plate heat exchanger is mainly used as the heat exchanger 7 .
As the heat exchanger 5 of the low temperature side circuit 102, an air-cooled fin coil type heat exchanger is mainly used. In this case, heat is exchanged between the refrigerant and the air by the fan motor and fan 5F, and control device 110 controls the rotational speed of the fan motor.

During the cooling operation, the expansion valve 9 of the low-temperature side circuit 102 is controlled so that the degree of opening is fully open so as not to expand the liquid refrigerant flowing out of the liquid receiver 8 as much as possible. If the expansion valve 9 is an electronic expansion valve, the values detected by a pressure sensor and a temperature sensor (not shown) are input to the control device 110, and the control device 110 performs pulse control of the electronic expansion valve. If pressure loss occurs even when the expansion valve 9 is fully opened, a circuit bypassing the expansion valve 9 may be provided to prevent flash gas from being generated in the liquid pipe. In that case, a solenoid valve or the like is installed in the bypass circuit so that the refrigerant does not pass through the bypass circuit during the defrosting operation.

During defrosting operation, the expansion valve 9 of the low-temperature side circuit 102 keeps the degree of superheat of the refrigerant at the outlet of the heat exchanger 5 constant or the compressor suction pressure constant so that the refrigerant can evaporate in the heat exchanger 5. controlled as When the expansion valve 9 is an electronic expansion valve, the detected values of a pressure sensor and a temperature sensor (not shown) are input to the control device 110, and the control device 110 performs pulse control of the electronic expansion valve. Here, the control target value of the expansion valve 9 is not limited to the value described above, and can be changed as appropriate in order to stabilize the refrigeration cycle.

In the flow switching device 6 of the low temperature side circuit 102, by arranging the direction of the check valves 61 to 64 as shown in FIG. can always pass through the liquid receiver 8. Therefore, surplus refrigerant can be retained in the liquid receiver 8 both during the cooling operation and during the defrosting operation.

The expansion valve 3b of the load device 20A expands the first refrigerant in the liquid state during the cooling operation, and is controlled to keep the degree of superheat of the refrigerant at the refrigerant outlet of the load-side heat exchanger 11 constant. When the expansion valve 3b is an electronic expansion valve, the detected values of a pressure sensor and a temperature sensor (not shown) are input to the control device 110, and the control device 110 performs pulse control of the electronic expansion valve.

The expansion valve 3b of the load device 20A is controlled to be fully open during the defrosting operation so that the liquid refrigerant condensed in the load side heat exchanger 11 is not expanded as much as possible. When the expansion valve 3b is an electronic expansion valve, the detected values of a pressure sensor and a temperature sensor (not shown) are input to the control device 110, and the control device 110 performs pulse control of the electronic expansion valve. If pressure loss occurs even when the expansion valve is fully opened, a flow path bypassing the expansion valve 3b may be provided to prevent an increase in the discharge pressure of the compressor 1b. In that case, an electromagnetic valve or the like is installed in the bypass channel so that the first refrigerant does not pass through the bypass channel during the cooling operation.

The load-side heat exchanger 11 of the load device 20A includes types such as an air-cooled fin-coil heat exchanger and a plate-type heat exchanger, but the type is not particularly limited in this embodiment.

An oil separator, a gas-liquid separator, a pressure sensor, a temperature sensor, a shutoff valve, etc. are not shown in the high temperature side circuit 101, but these may be installed as necessary.

Similarly, in the low temperature side circuit 102, an oil separator, pressure sensor, temperature sensor, shutoff valve, etc. are not shown, but these may be installed as necessary. Although the gas-liquid separator 10 is shown in the drawing, the gas-liquid separator 10 may not be provided if it is judged unnecessary by appropriate control of the on-board equipment.

In the configuration of FIG. 1, the control device 110 is provided in the heat source device 10A, but only the equipment control portion of the load device 20A may be separated from the control device 110 and installed near the load device 20A.

The pressure sensor 51 of the low temperature side circuit 102 detects a pressure rise near the liquid receiver 8 . Although the pressure sensor 51 is provided at the inlet of the heat exchanger 7 in FIG. The control device 110 operates the high temperature side circuit 101 when the detected value of the pressure sensor 51 exceeds a certain threshold, and condenses the R744 refrigerant in the heat exchanger 7 to suppress the pressure increase. This threshold is set to a value with a margin for the design pressure.

FIG. 2 is a flow chart for explaining the control of the compressor of the high temperature side circuit. First, in step S1, control device 110 determines whether or not any one of the following three conditions (1) to (3) is satisfied. Note that thermo-ON is established when the temperature of the cooling target space of the refrigerator rises above a thermo-ON threshold determined based on the target temperature.
(1) The value obtained by the pressure sensor 51 of the low temperature side circuit 102 is equal to or greater than the thermo ON threshold value (2) Satisfying the thermo ON determination (3) There is an operation signal from the low temperature side circuit 102 NO in S1), the determination in step S1 is repeatedly executed. On the other hand, if any one of the above three conditions is satisfied (YES in S1), control device 110 starts high temperature side circuit 101 in step S2. Specifically, the control device 110 starts the operation of the compressor 1a.

Then, in step S3, control device 110 determines whether or not one of the following two conditions (1) to (2) is satisfied. Note that thermo-OFF is established when the temperature of the cooling target space of the refrigerator falls below a thermo-OFF threshold that is determined based on the target temperature.
(1) Thermo OFF determination is satisfied (2) There is a stop signal from the low temperature side circuit 102 If neither of the above two conditions is satisfied (NO in S3), the determination in step S3 is repeatedly executed. On the other hand, if either of the above two conditions is satisfied (YES in S3), control device 110 stops high temperature side circuit 101 in step S4. Specifically, the control device 110 stops the operation of the compressor 1a.

In this way, by setting the information of the pressure sensor 51 of the low temperature side circuit 102 as the operation start condition, the frost melts at the end of the defrosting operation and the evaporator (load side heat exchanger 11) If the refrigerant does not condense sufficiently and the high pressure in the cold side circuit 102 rises, the hot side circuit 101 can be started.

FIG. 3 is a flowchart for explaining fan control when the intercooler is air-cooled. First, in step S11, the control device 110 determines whether or not the operation mode is the cooling mode.

If the operation mode is the cooling mode (YES in S11), the processing from step S12 onwards is executed. In step S12, it is determined whether or not the outlet temperature of the heat exchanger 5 is higher than the determination value of "outside air temperature +α". If the outlet temperature is high (YES in S12), the control device 110 rotates the fan 5F in step S13 so as to reduce heat radiation from the first refrigerant in order to prevent the evaporation load of the high-temperature side cycle from becoming too low. Decrease speed. On the other hand, if the outlet temperature is not higher than the determination value (NO in S12), control device 110 increases the rotational speed of fan 5F in step S14.

In this way, by controlling the rotational speed of the fan 5F so that the outlet temperature of the heat exchanger 5 becomes the value of the low temperature side target condensing temperature +α, the refrigerant is condensed in the heat exchanger 5 when the outside air temperature is low. It is possible to prevent the evaporative load of the high-temperature side cycle from becoming small due to excessive increase.

It should be noted that the value of α can be determined by desk design or experimentally so as to reflect the characteristics of the refrigeration system. In addition, it is possible to consider the influence of the temperature difference on the target temperature, which is not described in the flowchart of FIG. 3, and to cooperate with the protection control.

FIG. 4 is a flowchart for explaining the control when the defrosting mode ends. In order to remove the frost generated in the heat exchanger 5 during the hot gas defrosting operation, the control device 110 forcibly operates the refrigerating device at the end of the defrosting mode regardless of whether the thermostat is ON or OFF.

In step S21, the control device 110 determines whether or not the conditions for ending the defrost mode are satisfied. Conditions for terminating the defrost mode are, for example, when a certain period of time has elapsed after shifting to the defrost mode, when the load side heat exchanger 11 is monitored to detect that defrosting has ended, and when the load side This is established when an increase in the temperature of the refrigerant passing through the heat exchanger 11 is detected.

In step S21, if the conditions for ending the defrosting mode are not met (NO in S21), the control device 110 continues the determination in step S21. On the other hand, in step S21, if the condition for ending the defrosting mode is satisfied (YES in S21), control device 110 changes the operation mode to the cooling mode in step S22. In the cooling mode, switching of the four-way valve 4 changes the flow direction of the refrigerant as indicated by the broken line arrow in FIG. 1 and the solid line arrow.

Subsequently, in step S23, control device 110 determines whether or not the following condition (1) or (2) is satisfied.
(1) The refrigerant temperature at the outlet of the heat exchanger 5 is higher than α°C. (2) A certain period of time has elapsed since the start of the cooling operation mode. Here, the judgment value of the outlet refrigerant temperature of the heat exchanger 5 The value of α that can achieve frost removal can be determined by desk study or test. Also, the fixed time corresponding to the forced operation time can be similarly determined by desk study or test.

In step S23, if the conditions (1) and (2) are not satisfied (NO in S23), the control device 110 continues the determination in step S23. On the other hand, if one of the conditions (1) and (2) is satisfied in step S23 (YES in S23), control device 110 determines in step S24 whether the result of thermo ON determination is thermo ON. determine whether or not If the result of the thermo ON determination is that the thermo is ON (YES at S24), the processing of the flowchart of FIG. 4 is terminated as it is. Control the refrigerator to the OFF state.

Note that the flowchart of FIG. 4 shows an example of the forced operation method after the defrosting operation, and conditions not shown or cooperation with protective control can be implemented as appropriate.

Embodiment 2.
FIG. 5 is a diagram showing the configuration of a refrigeration system according to Embodiment 2. FIG. A refrigeration system 1000B shown in FIG. 5 includes a heat source device 10B and a load device 20A. The heat source device 10B includes a high temperature side circuit 101, a low temperature side circuit 102B, and a control device 110.

Refrigeration system 1000B of the second embodiment shown in FIG. 5 differs from refrigeration system 1000A of the first embodiment shown in FIG. It is that the flow path 22 bypassing the expansion valve 9 and the flow path switching device 6 and the check valve 21 provided in the flow path 22 are added in the middle of the connected piping. The direction of the check valve 21 is the direction in which the refrigerant flows from the liquid receiver 8 toward the load device 20A. The configuration of other parts is the same as that of FIG. 1, so description thereof will not be repeated.

The check valve 21 supplies liquid refrigerant from the heat source device 10B without going through the expansion valve 9 when a pressure drop occurs even if the opening of the expansion valve 9 is fully opened while the low temperature side circuit 102B is performing cooling operation. to prevent the generation of flash gas in the liquid piping. When the pressure drop occurs in the expansion valve 9, the flow path resistance of the expansion valve 9 becomes larger than the flow path resistance of the check valve 21, so the refrigerant flows to the check valve 21 side.

During defrosting operation, there is no reverse flow due to the structure of the check valve, so in principle, it is not necessary to prepare a shutoff valve such as an electromagnetic valve before and after the check valve 21.

Embodiment 3.
FIG. 6 is a diagram showing the configuration of a refrigeration system according to Embodiment 3. FIG. A refrigerating device 1000C shown in FIG. 6 includes a heat source device 10C and a load device 20A. The heat source device 10C includes a high temperature side circuit 101C, a low temperature side circuit 102, and a control device 110.

A refrigerating device 1000C according to the third embodiment shown in FIG. 6 differs from the refrigerating device 1000A according to the first embodiment shown in FIG. A bypass flow path 32 that branches from the middle of the pipe connecting the expansion valve 3 a and the heat exchanger 7 and flows the second refrigerant toward the middle of the pipe connecting the expansion valve 3 a and the heat exchanger 7 . The expansion valve 31 is added. The configuration of other parts is the same as that of FIG. 1, so description thereof will not be repeated.

When an electronic expansion valve is used as the expansion valve 31, the detected values of the pressure sensor and temperature sensor (not shown) are input to the control device 110, and the control device 110 performs pulse control of the electronic expansion valve.

By decompressing a part of the gas discharged from the compressor 1a by the expansion valve 31 and bypassing it to the inlet of the heat exchanger 7, the evaporation load on the heat exchanger 7 can be reduced. Therefore, when the condensation load of the low-temperature side circuit 102 is small, the high-temperature side circuit 101C can be operated at an appropriate degree of superheat, and the return (liquid return) of the second refrigerant in the liquid state to the compressor 1a can be prevented. It is possible to prevent excessive starting and stopping repetitions.

In Embodiment 3, when a large amount of refrigerant is allowed to flow through the bypass passage 32, the condensation pressure in the heat exchanger 2 on the heat source side becomes low, so the refrigerant bypass amount to the bypass passage 32 becomes small. Alternatively, even if the expansion valve 31 installed in the bypass flow path 32 is fully opened, if the evaporation capacity increases with respect to the evaporation load, liquid returns to the compressor 1a.

FIG. 7 is a flowchart for explaining control for liquid return prevention executed in the third embodiment. The processing of this flowchart is called and executed at regular time intervals from the main routine for controlling the second refrigeration cycle device RC2.

First, in step S31, the control device 110 determines whether or not the liquid return determination condition is satisfied. If the conditions for liquid return determination are not satisfied (NO in S31), that is, if liquid return to the compressor 1a does not occur, the process returns to the main routine. If the conditions for liquid return determination are satisfied (YES in S31), the control device 110 determines in step S32 whether or not the degree of opening of the expansion valve 3a is minimum.

If the opening of the expansion valve 3a is not the minimum (NO in S32), the controller 110 reduces the opening of the expansion valve 3a in step S33. A predetermined fixed value can be used as the width of decrease in this case. After reducing the degree of opening of the expansion valve 3a in step S33, the control device 110 executes the liquid return determination again in step S31.

On the other hand, if the opening degree of the expansion valve 3a is the minimum (YES in S32), in step S33, the controller 110 determines whether the opening degree of the expansion valve 31 provided in the bypass flow path 32 is maximum. to decide.

If the degree of opening of the expansion valve 31 is not yet maximum (NO in S34), the controller 110 increases the degree of opening of the expansion valve 31 in step S35. A predetermined fixed value can be used as the increase width in this case.

On the other hand, if the degree of opening of expansion valve 31 is already maximum (YES in S34), controller 110 increases the high temperature side target condensing temperature or decreases the high temperature side target evaporating temperature in step S36, or Do them at the same time.

By performing such control, the refrigerating capacity of the second refrigerating cycle device RC2 can be forcibly reduced, the amount of refrigerant passing through the bypass flow path 32 can be optimized, and liquid return to the compressor 1a can be prevented. be able to.

Although an example is shown in the flowchart of FIG. 7, the order of processing in each step may be changed, the target condensing temperature and target evaporating temperature may be changed in separate processes, and cooperation with other protection controls may be considered. It is assumed that it is possible to make changes such as

Also, although the check valve 21 in the second embodiment is not provided in the third embodiment, the second embodiment and the third embodiment can be combined as needed.

Embodiment 4.
When the heat source device 10A shown in FIG. 1 is an air-cooled type, it is common to select heat exchangers having the same structure for the high-temperature side cycle and the low-temperature side cycle. For example, if the condenser on the heat source machine side of the refrigeration system is an air heat exchanger, the condenser described in International Publication No. 2020/161803 (Patent Document 1) can be the same type of heat exchanger. It is common as However, when a defrosting operation is performed using hot gas, frosting occurs in the heat exchanger 5, and clogging or the like occurs when a high-efficiency PFC heat exchanger is used.

In the fourth embodiment, unlike the first embodiment, a plate-fin tube air heat exchanger is adopted as the heat exchanger 5 of the low temperature side circuit 102 in the heat source equipment 10A.

Furthermore, by using a high-efficiency PFC (parallel flow condenser) heat exchanger as the heat exchanger 2 on the high-temperature side and a plate-fin tube heat exchanger as the heat exchanger 5, the efficiency of the high-temperature side is increased and the temperature is reduced. In addition to the realization of cost reduction, it is possible to improve the resistance to frost formation on the intercooler during the reverse hot gas defrosting operation.

Embodiment 5.
FIG. 8 is a diagram showing the configuration of a refrigeration system according to Embodiment 5. In FIG. A refrigerating device 1000D shown in FIG. 8 includes a heat source device 10D and a load device 20A. The heat source device 10D includes a high temperature side circuit 101, a low temperature side circuit 102D, and a control device 110.

The low temperature side circuit 102D of the second embodiment shown in FIG. 8 differs from the low temperature side circuit 102 of the first embodiment shown in FIG. The only difference is that a vessel 12 and a decompression device 13 for injection are added. The injection flow path 14 branches from the flow path connecting the fourth heat exchanger 12 and the expansion valve 3b, and returns the first refrigerant to the compression intermediate portion of the compressor 1b. The decompression device 13 decompresses the first refrigerant flowing through the branched flow path. During the cooling operation, the fourth heat exchanger 12 cools the first refrigerant flowing from the flow path switching device 6 to the expansion valve 3b with the first refrigerant whose temperature has been lowered by the pressure reduction device 13 in the injection flow path 14. do.

The rest of the configuration of the low temperature side circuit 102D is the same as the low temperature side circuit 102 described in FIG. 1, so the description will not be repeated here.

The flow rate of the refrigerant flowing through the injection flow path 14 is designed based on control target values (degree of superheat, compressor discharge temperature, or liquid temperature) obtained theoretically or experimentally. As the expansion valve 31, an electronic expansion valve, a thermal expansion valve, a capillary tube, or the like is selected.

Although the fourth heat exchanger 12 is shown in FIG. 9, only the pressure reducing device 13 for injection may be arranged in the injection flow path 14 without providing the fourth heat exchanger 12 .

Embodiment 6.
FIG. 9 is a diagram showing the configuration of a refrigeration system according to Embodiment 6. FIG. A refrigeration system 1000E shown in FIG. 9 includes a heat source device 10E and a load device 20A. The heat source device 10E includes a high temperature side circuit 101, a low temperature side circuit 102E, and a control device 110.

A low temperature side circuit 102E of Embodiment 2 shown in FIG. 8 differs from a low temperature side circuit 102D of Embodiment 5 shown in FIG. That is the point. In FIG. 8, the injection flow path 14E branches from the flow path connecting the fourth heat exchanger 12 and the expansion valve 3b, and returns the first refrigerant to the suction port of the compressor 1b.

Other parts of the configuration of the low temperature side circuit 102E are the same as those of the low temperature side circuit 102D described with reference to FIG. 8, so description thereof will not be repeated here. Although the fourth heat exchanger 12 is shown in FIG. 9, the pressure reducing device 13 for injection may be arranged in the injection flow path 14E without providing the fourth heat exchanger 12. FIG.

Embodiment 7.
Embodiment 7 shows an example in which the arrangement of the expansion valve 9 is changed. FIG. 10 is a diagram showing the configuration of a refrigeration system according to Embodiment 7. FIG. A refrigeration system 1000F shown in FIG. 10 includes a heat source device 10F and a load device 20A. The heat source equipment 10F includes a high temperature side circuit 101, a low temperature side circuit 102F, and a control device 110.

A refrigeration system 1000F of Embodiment 7 shown in FIG. 10 differs from the refrigeration system 1000A of Embodiment 1 shown in FIG. The expansion valve 9</b>F is arranged between the heat exchanger 5 and the flow switching device 6 . 10 is the same as that of FIG. 1, the description of other parts will not be repeated.

The expansion valve 9 may be anywhere in the flow path from the liquid receiver 8 to the heat exchanger 5 in the flow of refrigerant during defrosting operation. Therefore, the expansion valve 9 of FIG. 1 can be moved and arranged like the expansion valve 9F of FIG.

FIG. 11 is a diagram showing another example of the arrangement of expansion valves. In the modification shown in FIG. 11, the expansion valve 9G is arranged in series with the check valve 62 in the flow path switching device 6. In the modification shown in FIG.

Note that when the expansion valve 9 is located between the liquid receiver 8 and the channel switching device 6 as in the first embodiment, the expansion valve 3b of the load device 20A may not be installed. 10 and 11, the expansion valve 3b must be installed to perform decompression expansion during the cooling operation.

(summary)
The above embodiments will be summarized with reference to the drawings again.

The present disclosure relates to a heat source device 10A that forms a refrigeration system 1000A together with a load device 20A. The refrigeration system 1000A has a cooling mode and a defrosting mode as operation modes. The heat source device 10A includes a first compressor (1b), a first heat exchanger (7), a second heat exchanger (5), and a liquid receiver 8. A first compressor (1b), a first heat exchanger (7), a second heat exchanger (5), and a liquid receiver 8, together with a load device 20A, form a first refrigeration cycle device RC1 in which a first refrigerant circulates. Configure. The heat source device 10A further includes a four-way valve 4 and a channel switching device 6 . The four-way valve 4 switches the connection destinations of the load device 20A and the second heat exchanger (5) between the cooling mode and the defrosting mode. The flow path switching device 6 includes an upstream portion of a flow path through which the first refrigerant flows to the liquid receiver 8 via the first heat exchanger (7), a downstream portion of the flow path, a load device 20A, and a second heat exchanger. It is connected to the exchanger (5) and switches the flow of the first refrigerant. The downstream part is located downstream of the flow path through which the first refrigerant flows to the liquid receiver 8 via the first heat exchanger (7). In the cooling mode, the first compressor (1b), the four-way valve 4, the second heat exchanger (5), the flow switching device 6, the first heat exchanger (7), the liquid receiver 8, the flow switching device 6. The first refrigerant circulates through the load device 20A and the four-way valve 4 in order and returns to the first compressor (1b). In the defrosting mode, the first compressor (1b), the four-way valve 4, the load device 20A, the channel switching device 6, the first heat exchanger (7), the liquid receiver 8, the channel switching device 6, the second The first refrigerant circulates through the heat exchanger (5) and the four-way valve 4 in order and returns to the first compressor (1b).

Preferably, the channel switching device 6 includes first to fourth check valves 61-64. The first check valve 61 is arranged between the load device 20A and the first heat exchanger (7) in a direction in which the first refrigerant flows from the load device 20A to the first heat exchanger (7). The second check valve 62 is positioned between the outlet of the liquid receiver 8 and the second heat exchanger (5) in the direction in which the first refrigerant flows from the outlet of the liquid receiver 8 to the second heat exchanger (5). placed in A third check valve 63 provides a first flow from the second heat exchanger (5) to the first heat exchanger (7) between the second heat exchanger (5) and the first heat exchanger (7). It is arranged in the direction in which the coolant flows. The fourth check valve 64 is arranged between the outlet of the liquid receiver 8 and the load device 20A in the direction in which the first refrigerant flows from the outlet of the liquid receiver 8 to the load device 20A.

Preferably, the heat source device 10A further includes an expansion valve 9 that adjusts the flow rate of the first refrigerant. The expansion valve 9 is provided on a path through which the first refrigerant flows from the outlet of the liquid receiver 8 to the second heat exchanger (5) in the defrosting mode.

More preferably, as shown in FIG. 5, the heat source device 10B is branched from the pipe connecting the liquid receiver 8 and the expansion valve 9, bypasses the expansion valve 9 and the flow path switching device 6, and connects to the load device 20A. Further provided are a bypass flow path 22 through which the first refrigerant flows, and a fifth check valve 21 provided in the bypass flow path 22 and configured to flow the refrigerant from the liquid receiver 8 toward the load device 20A.

Preferably, the heat source device 10A further includes a second compressor (1a), a third heat exchanger (2), and an expansion valve 3a. The second compressor (1a), the third heat exchanger (2), and the expansion valve 3a together with the first heat exchanger (7) constitute a second refrigeration cycle device RC2 in which the second refrigerant sequentially circulates. A first heat exchanger (7) is configured to exchange heat between a first refrigerant and a second refrigerant. Note that the second refrigeration cycle device RC2 may not necessarily be provided. For example, the first heat exchanger (7) may exchange heat between water or brine and the first refrigerant.

More preferably, as shown in FIG. 6, in the second refrigeration cycle device RC2, the heat source device 10C is branched from the middle of the pipe connecting the second compressor (1a) and the third heat exchanger (2). , a bypass passage 32 for flowing the second refrigerant through a pipe connecting the expansion valve 3a and the first heat exchanger (7), and an expansion valve 31 provided in the bypass passage 32 for adjusting the flow rate of the second refrigerant. further provide.

More preferably, the third heat exchanger (2) is a parallel flow condenser heat exchanger, and the second heat exchanger (5) is a plate fin tube air heat exchanger.

More preferably, the heat source device 10C further includes a control device 110 that controls the expansion valve 31. The control device 110 is configured to increase the degree of opening of the expansion valve 31 when it is determined that liquid return occurs in which the first refrigerant in the liquid state is sucked into the second compressor (1a).

More preferably, as shown in FIG. 7, when the liquid return determination is not resolved even when the degree of opening of the expansion valve 31 is increased to the upper limit, the controller 110 sets the target condensation temperature and the target evaporation temperature of the second refrigeration cycle device RC2. Configured to change temperature.

Preferably, the heat source devices 10A to 10F are provided in one of the paths from the flow path switching device 6 to the liquid receiver 8 via the first heat exchanger (7) and detect the pressure of the first refrigerant. A sensor 51 is further provided. The second refrigeration cycle device RC2 is configured to start operation when the pressure sensor 51 detection value exceeds the judgment value.

Preferably, the second heat exchanger (5) is a plate-fin tube heat exchanger that exchanges heat between air and the first refrigerant.

Preferably, the heat source device 10A further includes a control device 110 that controls the first compressor (1b), the four-way valve 4, and the flow path switching device 6 to switch the operation mode. As shown in FIG. 4, after changing the defrosting mode to the cooling mode, the control device 110 forces the first compressor (1b) to operate continuously for a certain period of time.

Preferably, the heat source device 10A further includes a control device 110 that controls the first compressor (1b), the four-way valve 4, and the flow path switching device 6 to switch the operation mode. As shown in FIG. 4, after the defrost mode is changed to the cooling mode, the control device 110 determines whether a certain period of time has elapsed or the refrigerant temperature at the refrigerant outlet of the second heat exchanger (5) has reached the judgment value. The first compressor (1b) is forcibly operated continuously until it reaches.

Preferably, as shown in FIG. 8, the heat source device 10D includes an injection passage 14 for returning part of the second refrigerant discharged from the liquid receiver 8 to the first compressor (1b), and and a decompression device 13 arranged therein.

More preferably, as shown in FIG. 8, the heat source device 10D performs heat exchange between the first refrigerant discharged from the liquid receiver 8 and the first refrigerant that has passed through the pressure reducing device 13 in the defrosting mode. A fourth heat exchanger 12 is further provided.

In another aspect, the present disclosure relates to a refrigeration system 1000A including any one of the heat source devices 10A to 10E described above and a load device 20A.

In the refrigeration system of the present disclosure described above, the return refrigerant from the load-side heat exchanger 11 is switched to the heat exchanger 7 and the A refrigerant circuit passing through the liquid receiver 8 is constructed.

This eliminates the need to adjust the amount of refrigerant while avoiding an increase in pressure during defrosting operation, and operates the refrigeration cycle on the high temperature side without changing from cooling operation while avoiding complication of control. be able to.

The embodiments disclosed this time should be considered illustrative in all respects and not restrictive. The scope of the present invention is indicated by the scope of the claims rather than the description of the above-described embodiments, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

1a, 1b compressor, 2, 5, 7, 12 heat exchanger, 3a, 3b, 9, 9F, 9G, 31 expansion valve, 4 four-way valve, 5F fan, 6 switching device, 8 liquid receiver, 10 gas liquid Separator, 10A to 10F heat source equipment, 11 load side heat exchanger, 13 decompression device, 14, 14E, 22, 32 flow path, 20A load device, 21, 61 to 64 check valve, 51 pressure sensor, 52 temperature sensor , 101, 101C High temperature side circuit, 102, 102B, 102D, 102E, 102F Low temperature side circuit, 110 Control device, 111 CPU, 112 Memory, 1000A to 1000F Refrigerating device, RC1 First refrigerating cycle device, RC2 Second refrigerating cycle device .

Claims

A heat source machine forming a refrigeration device together with a load device,
The refrigeration system has a cooling mode and a defrosting mode as operation modes,
The heat source machine is
a first compressor, a first heat exchanger, a second heat exchanger, and a liquid receiver, which together with the load device constitute a first refrigeration cycle device in which the first refrigerant circulates;
a four-way valve that switches connection destinations of the load device and the second heat exchanger between the cooling mode and the defrosting mode;
connected to an upstream portion of a flow path through which the first refrigerant flows to the liquid receiver through the first heat exchanger, a downstream portion of the flow path, the load device, and the second heat exchanger; and a channel switching device that switches the flow of the first refrigerant,
In the cooling mode, the first compressor, the four-way valve, the second heat exchanger, the channel switching device, the first heat exchanger, the receiver, the channel switching device, and the load device , the first refrigerant circulates through the four-way valve and back to the first compressor;
In the defrosting mode, the first compressor, the four-way valve, the load device, the flow path switching device, the first heat exchanger, the liquid receiver, the flow path switching device, and the second heat exchange heat source equipment, wherein the first refrigerant circulates so as to return to the first compressor through the four-way valve in order.
The channel switching device includes first to fourth check valves,
The first check valve is arranged between the load device and the first heat exchanger in a direction in which the first refrigerant flows from the load device to the first heat exchanger,
The second check valve is arranged between the outlet of the liquid receiver and the second heat exchanger in a direction in which the first refrigerant flows from the outlet of the liquid receiver to the second heat exchanger. ,
The third check valve is arranged between the second heat exchanger and the first heat exchanger in a direction in which the first refrigerant flows from the second heat exchanger to the first heat exchanger. ,
2. The method according to claim 1, wherein the fourth check valve is arranged between the outlet of the liquid receiver and the load device in a direction in which the first refrigerant flows from the outlet of the liquid receiver to the load device. The heat source machine described.
further comprising a first flow rate adjustment valve that adjusts the flow rate of the first refrigerant,
2. The heat source equipment according to claim 1, wherein said first flow control valve is provided in a path through which said first refrigerant flows from an outlet of said receiver to said second heat exchanger in said defrosting mode.
a bypass flow path branching from a pipe connecting the liquid receiver and the first flow rate control valve, bypassing the first flow rate control valve and the flow path switching device, and allowing the first refrigerant to flow to the load device; ,
4. The heat source equipment according to claim 3, further comprising a fifth check valve provided in said bypass flow path and configured to allow refrigerant to flow from said liquid receiver toward said load device.
The heat source machine is
Further comprising a second compressor, a third heat exchanger, an expansion valve and a first heat exchanger, through which a second refrigerant sequentially circulates, and together with the first heat exchanger, constitutes a second refrigeration cycle device;
The heat source equipment according to claim 1, wherein said first heat exchanger is configured to perform heat exchange between said first refrigerant and said second refrigerant.
In the second refrigerating cycle apparatus, the pipe connecting the second compressor and the third heat exchanger is branched from the middle, and the pipe connecting the expansion valve and the first heat exchanger is connected to the second heat exchanger. a bypass channel through which the refrigerant flows;
6. The heat source equipment according to claim 5, further comprising a second flow rate adjustment valve provided in said bypass flow path and adjusting a flow rate of said second refrigerant.
The third heat exchanger is a parallel flow condenser heat exchanger,
The heat source equipment according to claim 6, wherein the second heat exchanger is a plate-fin tube air heat exchanger.
A control device that controls the second flow rate control valve is further provided, and the control device controls the first flow control valve when it is determined that the liquid state of the first refrigerant is sucked into the second compressor. 7. The heat source machine according to claim 6, configured to increase the degree of opening of the two-flow control valve.
The control device is configured to change the target condensing temperature and the target evaporating temperature of the second refrigerating cycle device when the liquid return does not disappear even when the degree of opening of the second flow control valve is increased to an upper limit. 9. The heat source machine according to claim 8.
further comprising a pressure sensor provided in one of the paths from the flow path switching device to the liquid receiver via the first heat exchanger and detecting the pressure of the first refrigerant;
The heat source machine according to claim 5, wherein said second refrigeration cycle device is configured to start operation when the detected value of said pressure sensor exceeds a judgment value.
The heat source equipment according to claim 1, wherein the second heat exchanger is a plate-fin tube heat exchanger that exchanges heat between air and the first refrigerant.
further comprising a control device that controls the first compressor, the four-way valve, and the flow path switching device to switch the operation mode;
The heat source machine according to claim 1, wherein said control device forcibly continuously operates said first compressor for a certain period of time after changing said defrosting mode to said cooling mode.
A control device for controlling the first compressor, the four-way valve, and the flow path switching device to switch the operation mode,
After changing the defrosting mode to the cooling mode, the control device waits until a certain period of time elapses or until the refrigerant temperature at the refrigerant outlet of the second heat exchanger reaches a judgment value, the first The heat source equipment according to claim 1, wherein the compressor is forced to operate continuously.
an injection passage that returns a portion of the first refrigerant discharged from the liquid receiver to the first compressor;
The heat source machine according to claim 1, further comprising a decompression device arranged in said injection channel.
15. The apparatus according to claim 14, further comprising a fifth heat exchanger that exchanges heat between the first refrigerant discharged from the liquid receiver and the first refrigerant that has passed through the pressure reducing device in the defrosting mode. The heat source machine described.
A refrigeration system comprising the heat source device according to any one of claims 1 to 15 and the load device.