Auto-cascade refrigeration system, its control method, storage device and processor

Abstract

The present invention discloses a self-cascade refrigeration system, its control method, a storage device and a processor. The self-cascade refrigeration system includes a first throttle valve J1, an evaporative condenser EC, a second regenerator R2, a bypass B led out from the return gas outlet pipeline of the evaporative condenser, and a two-position three-way solenoid valve W. The first interface a of the two-position three-way solenoid valve is communicated with the return gas outlet pipeline of the second regenerator, the second interface b is communicated with the return gas inlet pipeline of the evaporative condenser, and the third interface c is communicated with the other end of the bypass. The two-position three-way solenoid valve is used to switch the flow direction of the return gas working medium flowing out of the second regenerator. The present invention reduces the heat exchange loss between high-temperature and low-temperature working media in the evaporative condenser and improves the cooling rate.

Description

Technical Field

[0001] The present invention relates to the technical field of refrigeration, and particularly to a self-cascade refrigeration system, a control method thereof, a storage device and a processor. Background Art

[0002] In the field of ultra-low temperature refrigeration, self-cascade or multi-stage cascade refrigeration systems are currently adopted. The multi-stage cascade refrigeration cycle usually consists of at least two separate refrigeration systems, and its construction cost is relatively high. Therefore, the self-cascade system has a certain cost advantage and is also an implementation scheme selected by some enterprises.

[0003] The self-cascade refrigeration cycle utilizes the characteristic that the gas-liquid phase components of azeotropic multi-component mixed refrigerants are different at phase equilibrium. After one-time compression, the high-boiling refrigerant and the low-boiling refrigerant are automatically separated through a condenser and a gas-liquid separator and enter two refrigeration cycles for cascading, so that the refrigerant with the lowest boiling point enters the evaporator to achieve the purpose of producing low temperature. Since the self-cascade refrigeration system adds a gas-liquid separator and reduces a compressor and an oil separator, it has the advantages of reducing the volume of the refrigeration device, reducing costs, reducing moving parts, and being simple and reliable.

[0004] However, in the self-cascade refrigeration system, the low-boiling refrigerant evaporates and absorbs heat to condense the high-boiling refrigerant into a liquid state, and the heat exchange process between the two mainly takes place through an evaporative condenser. In order to improve the refrigeration coefficient, a regenerator is usually installed on the low-temperature side to subcool the low-temperature refrigerant entering the evaporator, so that the temperature of the low-temperature refrigerant at the exhaust port of the regenerator is usually higher than that of the throttled liquid high-temperature refrigerant. If they are directly mixed and flow into the evaporative condenser, since the high-temperature refrigerant first cools the low-temperature refrigerant coming out of the exhaust port of the regenerator and then they are jointly used to cool the low-temperature refrigerant at the outlet of the gas-liquid separator, it will inevitably lead to a large heat exchange loss in the condensation evaporator. Summary of the Invention

[0005] The present invention provides a self-cascade refrigeration system, a control method thereof, a storage device and a processor to solve the technical problem of large heat exchange loss between high- and low-temperature refrigerants existing in the above-mentioned prior art.

[0006] The self-cascade refrigeration system provided by the present invention includes a first throttle valve J1, an evaporative condenser EC, a second regenerator R2, a bypass B led out from the return air outlet pipe of the evaporative condenser, and a two-position three-way solenoid valve W. The first interface a of the two-position three-way solenoid valve is communicated with the return air outlet pipe of the second regenerator, the second interface b is communicated with the return air inlet pipe of the evaporative condenser, and the third interface c is communicated with the other end of the bypass. The two-position three-way solenoid valve is used to switch the flow direction of the return air refrigerant flowing out of the second regenerator.

[0007] Further, temperature detection elements are respectively arranged on the outlet pipeline of the first throttle valve and the return gas outlet pipeline of the second regenerator.

[0008] In one embodiment, when the temperature of the return gas outlet working medium of the second regenerator is higher than the temperature of the outlet working medium of the first throttle valve, the first interface a of the two-way three-way solenoid valve is disconnected from the second interface b and communicated with the third interface c; when the temperature of the return gas outlet working medium of the second regenerator is not higher than the temperature of the outlet working medium of the first throttle valve, the first interface a of the two-way three-way solenoid valve is communicated with the second interface b and disconnected from the third interface c.

[0009] In another embodiment, when the enthalpy value of the return gas outlet working medium of the second regenerator is higher than the enthalpy value of the outlet working medium of the first throttle valve, the first interface a of the two-way three-way solenoid valve is disconnected from the second interface b and communicated with the third interface c; when the enthalpy value of the return gas outlet working medium of the second regenerator is not higher than the enthalpy value of the outlet of the first throttle valve, the first interface a of the two-way three-way solenoid valve is communicated with the second interface b and disconnected from the third interface c.

[0010] Preferably, the auto-cascade refrigeration system includes a compressor A, a condenser C, a first regenerator R1, an evaporative condenser EC, a second regenerator R2, a second throttle valve J2, and an evaporator E that are sequentially connected by pipelines. The high-pressure medium-temperature working medium discharged from the first regenerator enters the gas-liquid separator S. The gas in the gas-liquid separator is communicated with the inlet of the evaporative condenser through a pipeline, and the liquid in the gas-liquid separator is communicated with the return gas inlet of the evaporative condenser through a pipeline. The outlet of the evaporator is communicated with the second regenerator, the two-way three-way valve, the evaporative condenser, the first regenerator, and the suction port of the compressor through pipelines in sequence.

[0011] Preferably, the controller of the auto-cascade refrigeration system communicates with the temperature detection element and controls the on-off of the two-way three-way solenoid valve according to the comparison result of the temperature / enthalpy value of the return gas outlet working medium of the second regenerator and the temperature / enthalpy value of the outlet working medium of the first throttle valve.

[0012] The present invention also proposes a control method for the above auto-cascade refrigeration system, including:

[0013] Real-time monitoring of the working medium temperatures at the return gas outlet of the second regenerator and the outlet of the first throttle valve;

[0014] When the temperature of the return gas outlet working medium of the second regenerator is higher than the temperature of the outlet working medium of the first throttle valve, control the first interface a of the two-way three-way solenoid valve to be disconnected from the second interface b and communicated with the third interface c;

[0015] When the temperature of the working medium at the gas return outlet of the second recuperator is not higher than the temperature at the outlet of the first throttle valve, control the first interface a and the second interface b of the two-way three-way solenoid valve to be connected and disconnect from the third interface c.

[0016] As an alternative embodiment, according to the corresponding relationship between temperature and enthalpy value, the enthalpy values of the working medium at the gas return outlet of the second recuperator and at the outlet of the first throttle valve can be monitored in real time;

[0017] When the enthalpy value of the working medium at the gas return outlet of the second recuperator is higher than the enthalpy value of the working medium at the outlet of the first throttle valve, control the first interface a and the second interface b of the two-way three-way solenoid valve to be disconnected and connect to the third interface c; when the enthalpy value of the working medium at the gas return outlet of the second recuperator is not higher than the enthalpy value at the outlet of the first throttle valve, control the first interface a and the second interface b of the two-way three-way solenoid valve to be connected and disconnect from the third interface c.

[0018] The present invention also proposes a storage device for storing a computer program, and when the computer program runs, it executes the control method of the above-mentioned self-cascade refrigeration system.

[0019] The present invention also proposes a processor for running a computer program, and when the computer program runs, it executes the control method of the above-mentioned self-cascade refrigeration system.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. Reduce the heat transfer loss between high-temperature and low-temperature working media in the evaporative condenser and improve the cooling rate;

[0022] 2. Reduce the consumption of high-temperature working medium refrigerant;

[0023] 3. Facilitate the better separation of the high-temperature working medium at the outlet of the condenser from the mixed working medium. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The following will describe the present invention in detail with reference to the accompanying drawings and specific embodiments, where:

[0025] Figure 1 is the schematic diagram of a traditional self-cascade refrigeration system;

[0026] Figure 2 is the temperature and component concentration diagram of the self-cascade system;

[0027] Figure 3 is the schematic diagram of the self-cascade refrigeration system proposed by the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the following specific embodiments are only used to explain the present invention and do not constitute a limitation to the present invention.

[0029] Please refer to Figure 1 , the traditional auto-cascade refrigeration system includes: compressor A, condenser C, first recuperator R1, gas-liquid separator S, evaporative condenser EC, second recuperator R2, first throttle valve J1, second throttle valve J2 and evaporator E. The mixed refrigerant is compressed by compressor A, condensed by condenser C, and precooled by first recuperator R1, and then flows into gas-liquid separator S. The gaseous refrigerant in the gas-liquid separator becomes a low-temperature and low-pressure liquid refrigerant after passing through evaporative condenser EC, second recuperator R2, and second throttle valve J2, and then flows into evaporator E to absorb heat for refrigeration. The gaseous refrigerant flowing out of evaporator E returns to the compressor for re-compression and circulation after passing through second recuperator R2, evaporative condenser EC, and first recuperator R1 in sequence. The liquid refrigerant in gas-liquid separator S is depressurized by first throttle valve J1 and then converges with the refrigerant from the gas return outlet of the second recuperator through a three-way valve, and flows into the gas return inlet of evaporative condenser EC to exchange heat with the gaseous refrigerant from the gas-liquid separator.

[0030] Figure 2 is the temperature and component concentration diagram of the auto-cascade system. Since the auto-cascade refrigeration system uses a mixed refrigerant, the temperature line (also known as the bubble point line) from liquid to gas and the temperature line (also known as the dew point line) from gas to liquid are different. The upper part of the elliptical part in the figure is the dew point line, and the lower part is the bubble point line. The difference between the upper and lower lines represents the temperature change at the same component concentration. Figure 1 and Figure 2 show the temperatures corresponding to different state points of the refrigerant in the cycle in numbers. As can be seen from Figure 2 , the temperature of the gaseous refrigerant at state point 81 flowing out of evaporator E is T 81 , and the state point is 91 after passing through second recuperator R2, and the temperature rises to T 91 , and this temperature is higher than the temperature T 52 of the refrigerant at state point 52 flowing out of first throttle valve J1. If the two refrigerants with different temperatures are directly mixed and flow into evaporative condenser EC, since the high-temperature refrigerant from first throttle valve J1 first cools the low-temperature refrigerant from the exhaust port of the second recuperator, and then is jointly used to cool the gaseous refrigerant at the outlet of the gas-liquid separator, it will inevitably lead to an increase in heat transfer loss in the condensation evaporator.

[0031] Based on the traditional auto-cascade refrigeration system, the auto-cascade refrigeration system proposed by the present invention adds a bypass and a two-way three-way solenoid valve. Temperature detection elements are used to detect the exhaust temperature of the evaporator and the temperature of the high-temperature refrigerant after throttling in the gas-liquid separator, and the flow direction of the low-temperature refrigerant returning from the evaporator is switched through the two-way three-way valve according to the detection results.

[0032] As Figure 3 shown, in the auto-cascade refrigeration system proposed by the present invention, temperature detection elements are respectively arranged at the outlet of the first throttle valve J1 and the return air pipe outlet of the second regenerator R2, and a bypass B is led out from the return air outlet pipe of the evaporative condenser EC. The other end of the bypass is connected to the third interface c of the two-way three-way valve W. The return air outlet pipe of the second regenerator R2 is connected to the first interface a of the two-way three-way valve, and the return air inlet pipe of the evaporative condenser EC is connected to the second interface b of the two-way three-way valve. The controller of the auto-cascade refrigeration system communicates with the temperature detection element and the two-way three-way valve. When the temperature of the refrigerant at the return air outlet of the second regenerator is higher than the temperature of the refrigerant at the outlet of the first throttle valve, the first interface a and the third interface c of the two-way three-way valve are controlled to be connected, the first interface a is disconnected from the second interface b, and the refrigerant at the return air outlet of the second regenerator is combined with the refrigerant at the return air outlet of the evaporative condenser through the bypass; when the temperature of the refrigerant at the return air outlet of the second regenerator is not higher than the temperature of the refrigerant at the outlet of the first throttle valve, the first interface a and the second interface b of the two-way three-way valve are connected, the first interface a is disconnected from the third interface c, and the refrigerant at the return air outlet of the second regenerator is combined with the refrigerant at the outlet of the first throttle valve and enters the evaporative condenser to exchange heat with the gaseous refrigerant from the gas-liquid separator.

[0033] When the temperature of the refrigerant at the return air outlet of the second regenerator is higher than the temperature of the refrigerant at the outlet of the first throttle valve, if it directly mixes with the liquid high-temperature refrigerant and flows into the evaporative condenser, the liquid high-temperature refrigerant will first cool the low-temperature refrigerant from the return air, and then jointly cool the gaseous high-temperature refrigerant in the gas-liquid separator. Since the liquid low-temperature refrigerant undergoes two temperature difference heat exchanges, the heat exchange loss is relatively large. In view of this situation, the two-way three-way solenoid valve in the present invention disconnects the channel between the return air and the evaporative condenser, and connects the bypass B between the return air and the return air outlet pipe of the evaporative condenser, so that the exhaust gas in the gas-liquid separator exchanges heat with the refrigerant coming from the first throttle valve, and the return air at the outlet of the second regenerator is combined with the return air at the outlet of the evaporative condenser. In this way, on the one hand, the high-temperature and high-pressure gas can be precooled, and on the other hand, the heat exchange temperature difference in the evaporative condenser is small and the heat exchange efficiency is high.

[0034] When the outlet temperature of the return gas pipe of the second regenerator is not higher than the temperature of the working medium at the outlet of the first throttle valve, the first interface a and the second interface b of the two-way three-way solenoid valve are connected, and the first interface a and the third interface c are disconnected. At this time, the gaseous low-temperature working medium and the liquid working medium are mixed and flow into the evaporative condenser for heat exchange. Since the heat exchange temperature difference in the evaporative condenser is small, the heat exchange efficiency is high. The present invention effectively reduces the heat exchange loss and improves the refrigeration coefficient of the system by reducing the heat exchange temperature difference and the number of heat exchange stages.

[0035] Based on the traditional self-cascade refrigeration system, the present invention adds a bypass B and a two-way three-way solenoid valve W, and monitors the temperature T of the state point 52 at the outlet of the first throttle valve in real time 52 and the temperature T of the return gas state point 91 91 . When the temperature T 91 is higher than the temperature T 52 , the two-way three-way solenoid valve W conducts the bypass B, so that the state point 91 and the state point 110 are conducted, and the channel between the state point 91 and the state point 10 is disconnected. The return gas of the second regenerator R2 directly enters the first regenerator R1 to exchange heat with the working medium coming out of the condenser C, and precools the intake air of the first regenerator R1. When the temperature T of the state point 91 91 is not higher than the temperature T of the state point 52 52 , the two-way three-way solenoid valve W disconnects the bypass between the state point 91 and the state point 110, and the pipeline between the state point 91 and the state point 10 is conducted. The return gas coming out of the second regenerator R2 is mixed with the liquid flowing out of the first throttle valve J1 and then flows into the evaporative condenser EC to cool down the gaseous low-temperature working medium flowing out of the gas-liquid separator S.

[0036] It should be noted that the above embodiments select a two-stage self-cascade refrigeration system and a two-way three-way solenoid valve, which are only used to illustrate the control method for changing the refrigerant flow direction of the present invention, and are not intended to limit the present invention.

[0037] As an alternative embodiment, the above method of controlling the on-off of the three-way solenoid valve by detecting the temperature of a specific state point can be changed to detecting the enthalpy value of a specific state point to control the on-off of the three-way solenoid valve. Because there is a corresponding relationship between temperature and enthalpy value, when the temperature is high, the enthalpy value is usually also high. The temperature T of the state point 91 91 is higher than the temperature T of the state point 52 52 is equivalent to the enthalpy value H of the state point 91 91 being higher than the enthalpy value H of the state point 52 52 . The control method based on enthalpy value is the same as the control method based on temperature, that is, when the enthalpy value H of the state point 91 91 is higher than the enthalpy value H of the state point 52 52 , the two-way three-way solenoid valve W conducts the bypass between the state point 91 and the state point 110, and the pipeline between the state point 91 and the state point 10 is disconnected; when the enthalpy value H of the state point 91 91The enthalpy value H not higher than the state point 52 52 When it is, the two-way three-way solenoid valve W disconnects the bypass between the state point 91 and the state point 110, and opens the passage between the state point 91 and the state point 10.

[0038] The present invention also provides a control method for the above self-cascade refrigeration system, including the following steps:

[0039] Real-time monitor the working medium temperature / enthalpy value at the gas return outlet of the second regenerator and the outlet of the first throttle valve;

[0040] When the working medium temperature / enthalpy value at the gas return outlet of the second regenerator is higher than the working medium temperature / enthalpy value at the outlet of the first throttle valve, control the first interface a and the second interface b of the two-way three-way solenoid valve to disconnect, and the first interface a and the third interface c to communicate;

[0041] When the working medium temperature / enthalpy value at the gas return outlet of the second regenerator is not higher than the temperature / enthalpy value at the outlet of the first throttle valve, control the first interface a and the second interface b of the two-way three-way solenoid valve to communicate, and the first interface a and the third interface c to disconnect.

[0042] The control method of the self-cascade refrigeration system proposed by the present invention can be compiled into a computer program and stored in a storage device. When a processor calls the computer program stored in the storage device, the above control method of the self-cascade refrigeration system can be executed.

[0043] The above is only the specific implementation manner of the present invention. It should be noted that any modifications, equivalent replacements, and changes made within the spirit and framework of the concept of the present invention should be included in the protection scope of the present invention.

Claims

1. A self - cascading refrigeration system, comprising a compressor A, a condenser C, a first regenerator R1, a gas - liquid separator S, an evaporative condenser EC, a second regenerator R2, a second throttle valve J2 and an evaporator E connected in sequence by pipelines. The gas in the gas - liquid separator is communicated with the air inlet of the evaporative condenser through a pipeline, and the liquid in the gas - liquid separator is communicated with the return air inlet of the evaporative condenser after passing through a first throttle valve J1. It is characterized in that, It also includes a bypass B led out from the suction outlet pipe of the evaporative condenser and a two-position three-way solenoid valve W. The first interface a of the two-position three-way solenoid valve is communicated with the suction outlet pipe of the second regenerator, the second interface b is communicated with the suction inlet pipe of the evaporative condenser, and the third interface c is communicated with the other end of the bypass B. The two-position three-way solenoid valve is used to switch the flow direction of the suction working medium flowing out of the second regenerator; temperature detection elements are respectively arranged on the outlet pipe of the first throttle valve and the suction outlet pipe of the second regenerator.

2. The self - cascading refrigeration system according to claim 1, characterized in that, When the temperature of the suction outlet working medium of the second regenerator is higher than the temperature of the outlet working medium of the first throttle valve, the first interface a and the second interface b of the two-position three-way solenoid valve are disconnected and communicated with the third interface c; when the temperature of the suction outlet working medium of the second regenerator is not higher than the temperature of the outlet working medium of the first throttle valve, the first interface a and the second interface b of the two-position three-way solenoid valve are communicated and disconnected from the third interface c.

3. The self - cascading refrigeration system according to claim 1, characterized in that, When the enthalpy value of the suction outlet working medium of the second regenerator is higher than the enthalpy value of the outlet working medium of the first throttle valve, the first interface a and the second interface b of the two-position three-way solenoid valve are disconnected and communicated with the third interface c; when the enthalpy value of the suction outlet working medium of the second regenerator is not higher than the enthalpy value of the outlet of the first throttle valve, the first interface a and the second interface b of the two-position three-way solenoid valve are communicated and disconnected from the third interface c.

4. The self - cascading refrigeration system according to claim 1, characterized in that, The working medium discharged by the compressor enters the gas-liquid separator S after passing through the condenser and the first regenerator. The outlet of the evaporator is communicated with the second regenerator, the two-position three-way solenoid valve, the evaporative condenser, the first regenerator and the suction port of the compressor in sequence through pipes.

5. The self - cascading refrigeration system according to claim 1, characterized in that, The controller of the self-cascade refrigeration system communicates with the temperature detection element and controls the on-off of the two-position three-way solenoid valve according to the comparison result of the temperature / enthalpy value of the suction outlet working medium of the second regenerator and the temperature / enthalpy value of the outlet working medium of the first throttle valve.

6. A control method for the self - cascading refrigeration system according to any one of claims 1 - 5, characterized in that, It includes: Real-time monitoring of the working medium temperatures at the suction outlet of the second regenerator and the outlet of the first throttle valve; When the temperature of the suction outlet working medium of the second regenerator is higher than the temperature of the outlet working medium of the first throttle valve, control the first interface a and the second interface b of the two-position three-way solenoid valve to be disconnected and communicate with the third interface c; When the temperature of the suction outlet working medium of the second regenerator is not higher than the outlet temperature of the first throttle valve, control the first interface a and the second interface b of the two-position three-way solenoid valve to be communicated and disconnected from the third interface c.

7. A control method for the self - cascading refrigeration system according to any one of claims 1 - 5, characterized in that, It includes: Real-time monitoring of the working medium enthalpy values at the suction outlet of the second regenerator and the outlet of the first throttle valve; When the enthalpy value of the suction outlet working medium of the second regenerator is higher than the enthalpy value of the outlet working medium of the first throttle valve, control the first interface a and the second interface b of the two-position three-way solenoid valve to be disconnected and communicate with the third interface c; When the enthalpy value of the suction outlet working medium of the second regenerator is not higher than the enthalpy value of the outlet of the first throttle valve, control the first interface a and the second interface b of the two-position three-way solenoid valve to be communicated and disconnected from the third interface c.

8. A storage device for storing a computer program, characterized in that, When the computer program runs, it executes the control method of the self-cascade refrigeration system according to claim 6 or 7.

9. A processor for running a computer program, characterized in that, When the computer program runs, it executes the control method of the auto-cascade refrigeration system according to claim 6 or 7.

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