Cascade refrigeration system and refrigeration equipment

Abstract

The utility model discloses a cascade refrigeration system and refrigeration equipment, and belongs to the field of refrigeration. The cascade refrigeration system comprises a high-temperature refrigeration circulation loop and a low-temperature refrigeration circulation loop which share one intermediate heat exchanger. A bypass pipeline is arranged in a low-temperature refrigeration circulation loop, one end of the bypass pipeline is connected with a liquid outlet of an intermediate heat exchanger, the other end of the bypass pipeline is connected with the air return side of a low-temperature-stage compressor, and an expansion tank, an inlet electromagnetic valve and an outlet electromagnetic valve are arranged on the bypass pipeline. When the pressure relief valve is opened, the inlet electromagnetic valve and the outlet electromagnetic valve are opened, due to the fact that pressure difference exists at the two ends of the bypass pipeline, the liquid refrigerant at the liquid outlet can enter the expansion tank under the action of the pressure difference, and rapid pressure relief is achieved. And when the quantity of the refrigerant in the low-temperature refrigeration circulation loop is small, only the outlet electromagnetic valve is opened, and the set temperature is reduced, so that the refrigerant in the expansion tank enters the low-temperature refrigeration circulation loop.

Description

Technical Field

[0001] This application relates to the field of refrigeration technology, and in particular, to a cascade refrigeration system and a refrigeration device. Background Art

[0002] In recent years, with the development of technology and the improvement of people's requirements for the quality of life, cryogenic refrigeration technology has gradually come into the public eye and is more and more widely used in aspects such as medical and health. However, the traditional single-stage compression refrigeration method cannot achieve the required low-temperature environment.

[0003] Therefore, the industry usually adopts a cascade refrigeration system to achieve a better low-temperature environment. The cascade refrigeration system usually starts the high-temperature refrigeration cycle circuit first and then the low-temperature refrigeration cycle circuit. In the initial stage of startup, the exhaust pressure is likely to be too high, which affects the service life of the compressor and the refrigeration effect of the system.

[0004] Currently, the industry controls the pressure by adding a pressure relief valve, but this method often requires manual adjustment and control, which is a cumbersome process and prone to errors. Summary of the Invention

[0005] In order to overcome the deficiencies of the prior art, this application provides a cascade refrigeration system and a refrigeration device to solve the problem that currently in the industry, the pressure of the cascade system in the initial startup stage is controlled by adding a pressure relief valve, but this method often requires manual adjustment and control, which is a cumbersome process and prone to errors.

[0006] The technical solution adopted by this application to solve its technical problems is as follows:

[0007] In a first aspect, a cascade refrigeration system is provided, including: a high-temperature refrigeration cycle circuit and a low-temperature refrigeration cycle circuit, and the high-temperature refrigeration cycle circuit and the low-temperature refrigeration cycle circuit share an intermediate heat exchanger; it also includes: a bypass pipeline;

[0008] The bypass pipeline is arranged in the low-temperature refrigeration cycle circuit. One end of the bypass pipeline is connected to the liquid outlet of the intermediate heat exchanger, and the other end is connected to the suction side of the low-temperature stage compressor;

[0009] An expansion tank, an inlet solenoid valve and an outlet solenoid valve are arranged on the bypass pipeline. The inlet solenoid valve is arranged on the pipeline between the expansion tank and the liquid outlet, and the outlet solenoid valve is arranged on the pipeline between the expansion tank and the suction side of the low-temperature compressor;

[0010] When the exhaust pressure is greater than the first threshold, the inlet solenoid valve and the outlet solenoid valve open, and the liquid refrigerant at the liquid outlet enters the expansion tank.

[0011] Further, the expansion tank includes a housing, an expansion tank inlet, and an expansion tank outlet;

[0012] The expansion tank inlet is connected to the inlet solenoid valve through a pipeline, and the height of the expansion tank inlet is higher than the height of the liquid refrigerant in the expansion tank;

[0013] The expansion tank outlet is connected to the outlet solenoid valve through a pipeline, and the height of the expansion tank outlet is higher than the height of the liquid refrigerant in the expansion tank.

[0014] Further, it also includes:

[0015] When the exhaust pressure is less than or equal to the first threshold and greater than or equal to the second threshold, the inlet solenoid valve and the outlet solenoid valve are closed.

[0016] Further, it also includes:

[0017] When the system cooling capacity is insufficient, the inlet solenoid valve is closed and the outlet solenoid valve is opened.

[0018] Further, the low-temperature refrigeration cycle loop and the high-temperature refrigeration cycle loop also share a condenser and a condensing fan, and heat exchange occurs between the low-temperature refrigeration loop and the high-temperature refrigeration loop in the condenser.

[0019] Further, in the low-temperature refrigeration cycle loop:

[0020] The outlet of the low-temperature stage compressor is sequentially connected to the condenser and the first oil separator. One oil outlet of the first oil separator is directly connected to the compressor; the gas outlet of the first oil separator is connected to the low-temperature stage throttling device through the intermediate heat exchanger; the low-temperature stage throttling device is connected to the evaporator, and the evaporator is connected to the suction side of the low-temperature stage compressor.

[0021] Further, it also includes: a first regenerator;

[0022] The first regenerator includes two heat-exchanging pipelines. One pipeline is the pipeline between the intermediate heat exchanger and the throttling device, and the other pipeline is the pipeline from the evaporator to the suction side of the low-temperature stage compressor.

[0023] Further, it also includes: a thermal insulation layer;

[0024] The expansion tank, the inlet solenoid valve, the intermediate heat exchanger, the low-temperature stage throttling device, the evaporator, and the first regenerator are all arranged in the thermal insulation layer.

[0025] Further, the high-temperature refrigeration cycle loop includes a high-stage compressor, and the outlet side of the high-stage compressor is sequentially connected to the condenser, the dryer filter, the high-stage throttling device, the intermediate heat exchanger, and the suction side of the high-stage compressor.

[0026] In a second aspect, a refrigeration device is provided, which includes the cascade refrigeration system described above.

[0027] Beneficial effects:

[0028] The technical solution of the present application provides a cascade refrigeration system and a refrigeration device. The cascade refrigeration system includes a high-temperature refrigeration cycle loop and a low-temperature refrigeration cycle loop sharing an intermediate heat exchanger; a bypass pipeline is provided in the low-temperature refrigeration cycle loop. One end of the bypass pipeline is connected to the liquid outlet of the intermediate heat exchanger, and the other end is connected to the suction side of the low-stage compressor. An expansion tank, an inlet solenoid valve, and an outlet solenoid valve are provided on the bypass pipeline. When the exhaust pressure is greater than the first threshold, that is, when the exhaust pressure is relatively high, the inlet solenoid valve and the outlet solenoid valve are opened. Due to the pressure difference between the two ends of the bypass pipeline, the liquid refrigerant at the liquid outlet can enter the expansion tank under the action of the pressure difference to achieve rapid pressure relief. Description of the drawings

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0030] Figure 1 is a schematic structural diagram of a cascade refrigeration system in the prior art;

[0031] Figure 2 is a schematic structural diagram of a cascade refrigeration system provided by an embodiment of the present application;

[0032] Figure 3 is another schematic structural diagram of a cascade refrigeration system provided by an embodiment of the present application;

[0033] Figure 4 is a schematic structural diagram of an expansion tank provided by an embodiment of the present application;

[0034] Figure 5 is a flowchart of a control method for a cascade refrigeration system provided by an embodiment of the present application;

[0035] Figure 6 is a specific flowchart of a control method for a cascade refrigeration system provided by an embodiment of the present application.

[0036] Reference numerals:

[0037] 1 - Low - temperature stage compressor, 2 - First oil separator, 3 - High - temperature stage throttling device, 4 - Inlet solenoid valve, 5 - Expansion tank, 6 - Outlet solenoid valve, 7 - Condensing fan, 8 - Condenser, 9 - Dry filter, 10 - High - temperature stage compressor, 11 - Intermediate heat exchanger, 12 - Low - temperature stage throttling device, 13 - Evaporator, 14 - First regenerative heat exchanger, 15 - Thermal insulation layer, 16 - Expansion tank inlet, 17 - Shell, 18 - Expansion tank outlet. Detailed implementation mode

[0038] To make the purpose, technical solutions and advantages of this application clearer, the technical solutions of this application will be described in detail below with reference to the drawings and embodiments. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all of them. Based on the embodiments in this application, all other implementation manners obtained by those of ordinary skill in the art without creative efforts belong to the scope protected by this application.

[0039] As Figure 1 shown, the cascade refrigeration system consists of a high - temperature refrigeration cycle loop and a low - temperature refrigeration cycle loop. The high - temperature refrigeration cycle loop and the low - temperature refrigeration cycle loop share an intermediate heat exchanger. The two parts are connected by an intermediate heat exchanger to form a whole. This intermediate heat exchanger is both the evaporator of the high - temperature refrigeration cycle loop and the condenser of the low - temperature refrigeration cycle loop. Usually, the high - temperature refrigeration cycle loop is started first in the cascade refrigeration system, and then the low - temperature refrigeration cycle loop is started. In the initial stage of startup, the exhaust pressure is likely to be too high, which affects the service life of the compressor and the refrigeration effect of the system.

[0040] Currently, the industry controls the pressure by adding a pressure relief valve, but this method often requires manual adjustment and control, which is a cumbersome process and prone to errors. Therefore, there is an urgent need for a solution method that can adjust the pressure adaptively.

[0041] To solve this problem, as Figure 2 and Figure 3 shown, the embodiment of this application provides a cascade refrigeration system, including: a high - temperature refrigeration cycle loop and a low - temperature refrigeration cycle loop, and the high - temperature refrigeration cycle loop and the low - temperature refrigeration cycle loop share an intermediate heat exchanger 11;

[0042] It further includes: a bypass pipeline;

[0043] The bypass pipeline is arranged in the low - temperature refrigeration cycle loop. One end of the bypass pipeline is connected to the liquid outlet of the intermediate heat exchanger 11, and the other end is connected to the suction side of the low - temperature stage compressor 1; where the liquid outlet refers to the outlet where the refrigerant flows out of the intermediate heat exchanger 11 in the low - temperature refrigeration cycle loop.

[0044] An expansion tank 5, an inlet solenoid valve 4 and an outlet solenoid valve 6 are provided on the bypass pipeline. The inlet solenoid valve 4 is arranged on the pipeline between the expansion tank 5 and the liquid outlet, and the outlet solenoid valve 6 is arranged on the pipeline between the expansion tank 5 and the suction side of the low-temperature compressor.

[0045] Among them, as Figure 4 shown, the expansion tank 5 includes a housing 17, an expansion tank inlet 16 and an expansion tank outlet 18;

[0046] The expansion tank inlet 16 is connected to the inlet solenoid valve 4 through a pipeline, and the height of the expansion tank inlet 16 is higher than the height of the liquid refrigerant in the expansion tank 5;

[0047] The expansion tank outlet 18 is connected to the outlet solenoid valve 6 through a pipeline, and the height of the expansion tank outlet 18 is higher than the height of the liquid refrigerant in the expansion tank 5.

[0048] That is, neither the expansion tank inlet 16 nor the expansion tank outlet 18 extends below the liquid level, so as to ensure that when the inlet solenoid valve 4 and the outlet solenoid valve 6 are opened, the pressures at the expansion tank inlet 16 and the expansion tank outlet 18 are the same as the pressure at the liquid outlet of the intermediate heat exchanger 11 and the suction side of the compressor 1 respectively.

[0049] When the exhaust pressure is greater than the first threshold, the inlet solenoid valve 4 and the outlet solenoid valve 6 are opened, and the liquid refrigerant at the liquid outlet enters the expansion tank 5.

[0050] When the exhaust pressure is greater than the first threshold, that is, when the exhaust pressure is relatively high, the inlet solenoid valve 4 and the outlet solenoid valve 6 are opened. Due to the pressure difference at both ends of the bypass pipeline, under the action of the pressure difference, the liquid refrigerant at the liquid outlet can enter the expansion tank 5. Since the refrigerant at the liquid outlet of the intermediate heat exchanger 11 is in a liquid state, compared with the gaseous refrigerant, the liquid refrigerant can flow into the expansion tank 5 faster, realizing a faster pressure reduction.

[0051] When the exhaust pressure is less than or equal to the first threshold and greater than or equal to the second threshold, the inlet solenoid valve 4 and the outlet solenoid valve 6 are closed. That is, when the exhaust pressure is within the preset range, at this time, the inlet solenoid valve 4 and the outlet solenoid valve 6 are closed, and the whole system is the same as the normal system.

[0052] Since during pressure relief, a part of the refrigerant enters the expansion tank 5 and no longer participates in the refrigeration of the low-temperature refrigeration cycle loop, the refrigeration capacity of the low-temperature refrigeration cycle loop decreases, that is, the system refrigeration capacity decreases, which may cause the indoor temperature to fail to reach the set temperature for a long time. Therefore, at this time, the inlet solenoid valve 4 can be controlled to be closed and the outlet solenoid valve 6 can be opened. In this way, according to the pressure difference between the expansion tank 5 and the suction side of the compressor, a pressure difference is formed, so that the refrigerant in the expansion tank 5 is replenished back into the low-temperature refrigeration cycle loop.

[0053] Even, in order to increase the pressure difference between the expansion tank 5 and the suction side of the compressor, the set temperature of the system can be lowered so that the refrigerant can be replenished into the low-temperature refrigeration cycle loop faster and in a larger amount.

[0054] Of course, when the refrigerant in the low-temperature refrigeration cycle loop is sufficient, the outlet solenoid valve 6 is closed at this time.

[0055] In one embodiment, as Figure 2 shown, the high-temperature refrigeration cycle loop and the low-temperature refrigeration cycle loop respectively use a condenser 8.

[0056] In another embodiment, as Figure 3 shown, the low-temperature refrigeration cycle loop and the high-temperature refrigeration cycle loop also share a condenser 8 and a condensing fan 7. In the condenser 8, the low-temperature refrigeration loop exchanges heat with the high-temperature refrigeration loop to improve the refrigeration efficiency.

[0057] Among them, the high-temperature refrigeration cycle loop includes a high-stage compressor 10. The outlet side of the high-stage compressor 10 is sequentially connected to the condenser 8, the dryer filter 9, the high-stage throttling device 3, the intermediate heat exchanger 11, and the suction side of the high-stage compressor 10.

[0058] In the low-temperature refrigeration cycle loop:

[0059] The outlet of the low-stage compressor 1 is sequentially connected to the condenser 8 and the first oil separator 2. An oil outlet of the first oil separator 2 is directly connected to the compressor; the gas outlet of the first oil separator 2 is connected to the low-stage throttling device 12 after passing through the intermediate heat exchanger 11; the low-stage throttling device 12 is connected to the evaporator 13, and the evaporator 13 is connected to the suction side of the low-stage compressor 1.

[0060] As a preferred implementation manner of the embodiment of the present application, it further includes: a first regenerator 14;

[0061] The first regenerator 14 includes two heat-exchanging pipelines. One pipeline is the pipeline between the intermediate heat exchanger 11 and the throttling device, and the other pipeline is the pipeline between the evaporator 13 and the suction side of the low-stage compressor 1. The first regenerator 14 can improve the energy utilization efficiency.

[0062] As a preferred implementation manner of the embodiment of the present application, it further includes: a heat-insulating layer 15;

[0063] The expansion tank 5, the inlet solenoid valve 4, the intermediate heat exchanger 11, the low-stage throttling device 12, the evaporator 13, and the first regenerator 14 are all arranged in the heat-insulating layer 15.

[0064] The cascade refrigeration system provided by the embodiment of the present application includes a high-temperature refrigeration cycle circuit and a low-temperature refrigeration cycle circuit sharing an intermediate heat exchanger; a bypass pipeline is arranged in the low-temperature refrigeration cycle circuit. One end of the bypass pipeline is connected to the liquid outlet of the intermediate heat exchanger, and the other end is connected to the suction side of the low-temperature stage compressor. An expansion tank, an inlet solenoid valve, and an outlet solenoid valve are arranged on the bypass pipeline. When the exhaust pressure is greater than the first threshold value, that is, when the exhaust pressure is relatively high, the inlet solenoid valve and the outlet solenoid valve are opened. Due to the pressure difference between the two ends of the bypass pipeline, the liquid refrigerant at the liquid outlet can enter the expansion tank under the action of the pressure difference to achieve rapid pressure relief. And when the amount of refrigerant in the low-temperature refrigeration cycle circuit is small, only the outlet solenoid valve can be opened and the set temperature can be reduced to increase the pressure difference between the suction side of the low-temperature stage compressor and the expansion tank, so that the refrigerant in the expansion tank can enter the low-temperature refrigeration cycle circuit.

[0065] The following provides a specific description. After the high-temperature and high-pressure gas discharged from the low-temperature side compressor 1 passes through the condenser 8 and then through the first oil separator 2, a pressure sensor is arranged to monitor the exhaust pressure.

[0066] When the system monitors that the exhaust pressure is greater than the target pressure range (Pc - Δp, Pc + Δp), the system controls the inlet solenoid valve 4 and the outlet solenoid valve 6 to open, sucking part of the refrigerant into the expansion tank 5. The outlet solenoid valve 6 is connected to the suction side of the compressor 1, and the pressure difference will suck part of the refrigerant in the expansion tank 5 into the compressor 1, effectively relieving the pressure in the system and achieving the purpose of pressure relief. The refrigerant in the low-temperature refrigeration cycle circuit passes through the intermediate heat exchanger 11 and exchanges heat with the refrigerant from the high-temperature refrigeration cycle circuit.

[0067] The internal structure of the expansion tank 5 is as Figure 4 shown. Since the inlet solenoid valve 4 and the expansion tank 5 are installed after the intermediate heat exchanger 11, at this time the refrigerant is in a liquid state. Compared with the gaseous refrigerant, the liquid refrigerant can enter the expansion tank 5 faster, so the pressure relief speed of the system is faster.

[0068] The system continuously monitors the exhaust pressure. When it monitors that the exhaust pressure is within the target pressure range (Pc - Δp, Pc + Δp), the inlet solenoid valve 4 and the outlet solenoid valve 6 are closed. At this time, the low-temperature refrigeration cycle circuit is no different from a normal system. It continues to operate to further exchange heat with the refrigerant in the evaporator 13 circuit in the first regenerator 14. After passing through the low-temperature stage throttling device 12 and the evaporator 13, it returns to the low-temperature side compressor 1, and at this time the system completes a cycle.

[0069] To solve the situation that the refrigeration capacity of the system is insufficient after the refrigerant enters the expansion tank 5, the system provided by the embodiment of the present application can also control the opening and closing of the outlet solenoid valve 6 according to the refrigeration effect during the operation of the system.

[0070] When the system detects that the cooling capacity is insufficient to reach the set temperature, the system will automatically lower the set temperature. At this time, the suction side pressure of the compressor 1 decreases, so as to increase the pressure difference between the suction side of the compressor 1 and the expansion tank 5, and the outlet solenoid valve 6 is opened. At this time, the refrigerant stored in the expansion tank 5 will be sucked into the main pipeline due to the pressure difference, so as to supplement the refrigerant in the system.

[0071] The cascade refrigeration system provided by the embodiment of the present application is different from the conventional method of only increasing the pressure relief valve to adjust the pressure. Instead, a solenoid valve and an expansion tank are added on the low-temperature side, and the solenoid valve is controlled by a program, so as to control the internal pressure of the system and supplement the refrigerant. Compared with the conventional scheme of controlling the system pressure by the pressure relief valve, the present scheme has the following beneficial points:

[0072] 1. This control scheme is more intelligent and can automatically adjust the internal pressure of the system without manual intervention;

[0073] 2. It is monitored and adjusted in real time by the system, so the response is faster and more energy-saving and efficient;

[0074] 3. The added expansion tank can adjust the refrigerant inside the system.

[0075] As Figure 5 shown, the control method of the cascade refrigeration system in the above embodiment is as follows:

[0076] S11: Monitor the current real-time exhaust pressure.

[0077] S12: When the current real-time exhaust pressure is greater than the first threshold, control the inlet solenoid valve and the outlet solenoid valve to open simultaneously. At this time, according to the pressure difference, the liquid refrigerant enters the expansion tank, reducing the exhaust pressure and realizing rapid pressure relief.

[0078] When the real-time exhaust pressure is less than or equal to the first threshold and greater than or equal to the second threshold, control the inlet solenoid valve and the outlet solenoid valve to close, and the system resumes normal operation.

[0079] As a preferred implementation manner of the embodiment of the present application, it further includes: obtaining the indoor temperature;

[0080] If the indoor temperature is still higher than the set temperature after the operation duration reaches the preset duration, the set temperature is reduced from the first set temperature to the second set temperature, and the inlet solenoid valve is controlled to close while the outlet solenoid valve is opened;

[0081] After the indoor temperature reaches the first set temperature, control the outlet solenoid valve to close and restore the set temperature to the first set temperature.

[0082] During the above-mentioned rapid pressure relief process, a part of the refrigerant enters the expansion tank and is stored, resulting in a reduction in the refrigerant in the low-temperature refrigeration cycle circuit and a decrease in the system's refrigeration capacity. Therefore, in the embodiments of the present application, it is determined whether the refrigeration capacity is normal by whether the indoor temperature can reach the set temperature within the preset duration. If the indoor temperature is still higher than the set temperature after the operation duration reaches the preset duration, it indicates that the refrigeration capacity is insufficient. Therefore, at this time, the outlet solenoid valve is opened to allow the refrigerant in the expansion tank to enter the compressor. However, the pressure difference between the suction side of the compressor and the pressure in the expansion tank may be small, and insufficient refrigerant can be replenished from the expansion tank back into the low-temperature refrigeration cycle circuit. Therefore, the system set temperature is lowered, the pressure on the suction side of the compressor is further reduced, the pressure difference between the expansion tank and the suction side of the compressor is increased, and more refrigerant can then return to the low-temperature refrigeration cycle circuit.

[0083] In addition, as a preferred implementation of the present application, when the operating load of the system is greater than the threshold and the system receives a shutdown signal, the inlet solenoid valve and the outlet solenoid valve are controlled to open. That is, under high operating conditions, before the system shuts down, the inlet solenoid valve and the outlet solenoid valve are opened to store a part of the refrigerant in the expansion tank. When the system is restarted next time, the problem of being unable to start due to excessive pressure can be avoided.

[0084] To more clearly illustrate the implementation of the present application, in the embodiments of the present application, taking a refrigerator including the cascade refrigeration system provided in any of the above embodiments as an example, a specific control method is provided, as Figure 6 shown:

[0085] After the refrigerator is powered on and running, the current real-time exhaust pressure P1 is monitored. First, it is determined whether the exhaust pressure P1 is within the set target pressure range (Pc - Δp, Pc + Δp). If P1 is greater than this pressure range, the inlet solenoid valve and the outlet solenoid valve are opened simultaneously, and the pressure difference on both sides will suck the refrigerant into the expansion tank, and the system is depressurized until the exhaust pressure P1 is within the set target pressure range, and the inlet solenoid valve and the outlet solenoid valve are closed.

[0086] While the system detects the pressure, it also detects whether the internal temperature T1 of the cabinet reaches the set temperature range (Tc - Δt, Tc + Δt) after running for F1 time. If T1 cannot reach the set temperature range (Tc - Δt, Tc + Δt), the system automatically lowers the set temperature. At this time, the suction side pressure decreases, the outlet solenoid valve opens, and the refrigerant in the expansion tank is sucked into the main pipeline to supplement the refrigerant in the system until the temperature drops to the previous set temperature range, the outlet solenoid valve closes, and the system adjusts the set temperature back.

[0087] The system will monitor the internal operation of the system in real time and repeat the above actions, which can meet the different ambient temperature and storage requirements of the system and achieve an energy-saving and efficient low-temperature storage effect.

[0088] Under high operating conditions, before the system of the embodiment of the present application shuts down, the inlet solenoid valve and the outlet solenoid valve are opened to store a part of the refrigerant in the expansion tank, and the inlet solenoid valve and the outlet solenoid valve are closed before shutdown. When starting up next time, the system can avoid the problem of inability to start up due to excessive pressure.

[0089] The specific control method provided by the embodiment of the present application can automatically adjust the exhaust pressure on the low-temperature side and the total amount of refrigerant inside the system by setting a solenoid valve and an expansion tank on the low-temperature side, meet the different ambient temperature and storage requirements of the system, and achieve an energy-saving and efficient low-temperature storage effect.

[0090] Based on the same inventive concept, the present application provides a refrigeration device, including the cascade refrigeration system provided in the above embodiment.

[0091] The refrigeration device provided by the embodiment of the present application can control the inlet solenoid valve and the outlet solenoid valve to open when the exhaust pressure is greater than the first threshold, that is, when the exhaust pressure is relatively high. Due to the pressure difference at both ends of the bypass pipeline, under the action of the pressure difference, the liquid refrigerant at the liquid outlet can enter the expansion tank to achieve rapid pressure relief. And when the amount of refrigerant in the low-temperature refrigeration cycle circuit is small, only the outlet solenoid valve can be opened and the set temperature can be lowered to increase the pressure difference between the suction side of the low-temperature stage compressor and the expansion tank, so that the refrigerant in the expansion tank can enter the low-temperature refrigeration cycle circuit.

[0092] It should be noted that in the description of the present application, the terms "first", "second", etc. are only used for descriptive purposes and cannot be construed as indicating or implying relative importance. In addition, in the description of the present application, unless otherwise specified, the meaning of "a plurality" refers to at least two.

[0093] It can be understood that the same or similar parts in the above embodiments can be referred to each other, and the content not detailed in some embodiments can be seen in the same or similar content of other embodiments.

Claims

1. A cascade refrigeration system, comprising: A high-temperature refrigeration cycle loop and a low-temperature refrigeration cycle loop, wherein the high-temperature refrigeration cycle loop and the low-temperature refrigeration cycle loop share an intermediate heat exchanger; characterized in that it also includes: a bypass pipeline; The bypass pipeline is arranged in the low-temperature refrigeration cycle loop, one end of the bypass pipeline is connected to the liquid outlet of the intermediate heat exchanger, and the other end is connected to the return air side of the low-temperature compressor; The bypass pipeline is provided with an expansion tank, an inlet solenoid valve and an outlet solenoid valve, the inlet solenoid valve is provided on the pipeline between the expansion tank and the liquid outlet, and the outlet solenoid valve is provided on the pipeline between the expansion tank and the return air side of the low-temperature compressor; When the exhaust pressure is greater than a first threshold, the inlet solenoid valve and the outlet solenoid valve are opened, and the liquid refrigerant at the liquid outlet enters the expansion tank.

2. The system according to claim 1, characterized in that: The expansion tank comprises a shell, an expansion tank inlet and an expansion tank outlet; The inlet of the expansion tank is connected to the inlet solenoid valve through a pipeline, and the height of the inlet of the expansion tank is higher than the height of the liquid refrigerant in the expansion tank; The outlet of the expansion tank is connected to the outlet solenoid valve through a pipeline, and the height of the outlet of the expansion tank is higher than the height of the liquid refrigerant in the expansion tank.

3. The system according to claim 1, characterized in that Also includes: When the exhaust pressure is less than or equal to the first threshold and greater than or equal to a second threshold, the inlet solenoid valve and the outlet solenoid valve are closed.

4. The system according to claim 1, characterized in that Also includes: When the system refrigeration capacity is insufficient, the inlet solenoid valve is closed and the outlet solenoid valve is opened.

5. The system according to claim 1, characterized in that: The low-temperature refrigeration cycle loop and the high-temperature refrigeration cycle loop also share a condenser and a condensing fan, and the low-temperature refrigeration cycle loop and the high-temperature refrigeration cycle loop exchange heat in the condenser.

6. The system according to claim 5, characterized in that: In the low temperature refrigeration cycle: The air outlet of the low-temperature compressor is connected to the condenser and the first oil separator in sequence, and an oil outlet of the first oil separator is directly connected to the compressor; the air outlet of the first oil separator is connected to the low-temperature throttling device after passing through the intermediate heat exchanger; the low-temperature throttling device is connected to the evaporator, and the evaporator is connected to the return air side of the low-temperature compressor.

7. The system according to claim 6, characterized in that Also includes: First regenerator; The first heat regenerator includes two heat exchange pipelines, one of which is the pipeline between the intermediate heat exchanger and the throttling device, and the other is the pipeline between the evaporator and the return air side of the low-temperature stage compressor.

8. The system according to claim 7, characterized in that Also includes: Insulation layer; The expansion tank, the inlet solenoid valve, the intermediate heat exchanger, the low-temperature stage throttling device, the evaporator and the first regenerator are all arranged in the insulation layer.

9. The system according to claim 5, characterized in that: The high-temperature refrigeration cycle loop includes a high-temperature compressor, and the outlet side of the high-temperature compressor is sequentially connected to the condenser, the drying filter, the high-temperature throttling device, the intermediate heat exchanger and the return side of the high-temperature compressor.

10. A refrigeration device, characterized in that: A cascade refrigeration system comprising the cascade refrigeration system according to any one of claims 1 to 9.

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