Refrigeration cycle system bypass valve control method and cascade refrigeration cycle system

Abstract

The invention relates to a refrigeration cycle system bypass valve control method and a cascade refrigeration cycle system, the exhaust temperature of a compressor in the refrigeration cycle system is obtained, and when the exhaust temperature is larger than or equal to a set opening temperature threshold value, a first bypass valve is opened to a preset initial opening degree; wherein the first bypass valve is connected with the condenser and the load evaporator, and when the first bypass valve is switched on, a refrigerant output by the condenser and a refrigerant output by the load evaporator are mixed, so that the return air temperature is reduced. If the production temperature of the refrigeration cycle system is smaller than the set production temperature threshold value, the opening degree of a first bypass valve is subjected to step control according to the exhaust temperature of a compressor; and if the production temperature of the refrigeration cycle system is larger than or equal to the production temperature threshold value, the opening degree of the first bypass valve is controlled according to the exhaust temperature of the compressor or the temperature of the load evaporator. The refrigerant flow of the bypass branch is adjustable, and the temperature control stability of the system and the operation reliability of the compressor are improved.

Description

Technical Field

[0001] This application relates to the field of refrigeration equipment technology, and in particular to a bypass valve control method for a refrigeration cycle system and a cascade refrigeration cycle system. Background Technology

[0002] The testing equipment uses a refrigeration system as the cold source and a heating system as the heat source. It provides a stable temperature supply to the load through a thermo-cold confrontation method, thereby controlling the temperature of electronic components at the load end and performing low-temperature, room-temperature, and high-temperature tests on the electronic components. In traditional refrigeration systems, a bypass branch is drawn from the condenser, mixing a portion of the refrigerant output from the condenser with the refrigerant returning to the compressor suction end from the external load. This lowers the return gas temperature and prevents excessively high exhaust temperatures that could trigger alarms. However, this method cannot adjust the refrigerant flow rate of the bypass branch according to actual conditions, resulting in poor temperature control stability. Summary of the Invention

[0003] Therefore, it is necessary to provide a bypass valve control method for a refrigeration cycle system and a cascade refrigeration cycle system that can improve temperature control stability in order to address the above problems.

[0004] The first aspect of this application provides a method for controlling a bypass valve in a refrigeration cycle system, comprising:

[0005] Obtain the discharge temperature of the compressor in the refrigeration cycle system;

[0006] When the exhaust temperature is greater than or equal to the set opening temperature threshold, the first bypass valve is opened to a preset initial opening degree; wherein, the first bypass valve is connected to the condenser and the load evaporator, and when the first bypass valve is open, it mixes the refrigerant output by the condenser with the refrigerant output by the load evaporator to reduce the return gas temperature.

[0007] If the production temperature of the refrigeration cycle system is lower than the set production temperature threshold, the opening degree of the first bypass valve is controlled in stages according to the discharge temperature of the compressor.

[0008] If the production temperature of the refrigeration cycle system is greater than or equal to the production temperature threshold, the opening degree of the first bypass valve is controlled according to the discharge temperature of the compressor or the temperature of the load evaporator.

[0009] In one embodiment, after obtaining the exhaust temperature of the compressor in the refrigeration cycle system, the method further includes: when the exhaust temperature is less than a set opening temperature threshold, controlling the first bypass valve to remain closed.

[0010] In one embodiment, the opening degree of the first bypass valve is controlled in stages according to the exhaust temperature of the compressor, including:

[0011] Based on the preset relationship between exhaust temperature and opening degree, the target opening degree corresponding to the current exhaust temperature of the compressor is determined;

[0012] The first bypass valve is adjusted to the target opening degree until the compressor's exhaust temperature is lower than the set closing temperature threshold, at which point the first bypass valve is controlled to close; the closing temperature threshold is lower than the opening temperature threshold.

[0013] In one embodiment, controlling the opening degree of the first bypass valve based on the compressor's exhaust temperature or the temperature of the loaded evaporator includes:

[0014] Obtain the actual temperature of the load evaporator;

[0015] If the actual temperature of the load evaporator does not reach the set temperature, the opening degree of the first bypass valve is controlled according to the set temperature and the actual temperature of the load evaporator.

[0016] If the actual temperature of the load evaporator reaches the set temperature, the opening degree of the first bypass valve is controlled according to the actual exhaust temperature of the compressor and the target exhaust temperature.

[0017] In one embodiment, the opening degree of the first bypass valve is controlled based on the set temperature and the actual temperature of the loaded evaporator, including:

[0018]

[0019] in, The target opening degree of the first bypass valve. This represents the current actual opening degree of the first bypass valve.

[0020] In one embodiment, the opening degree of the first bypass valve is controlled based on the actual discharge temperature and the target discharge temperature of the compressor, including:

[0021]

[0022] in, The target opening degree of the first bypass valve. This represents the current actual opening degree of the first bypass valve.

[0023] In one embodiment, after controlling the opening degree of the first bypass valve based on the actual exhaust temperature and the target exhaust temperature of the compressor, the method further includes:

[0024] If the difference between the average value of the continuously collected exhaust temperatures (a set number) and the latest collected exhaust temperature is less than or equal to the set temperature difference threshold, the refrigeration cycle system enters the temperature control stabilization stage.

[0025] A second aspect of this application provides a cascade refrigeration cycle system, including a high-temperature stage circulation loop, a low-temperature stage circulation loop, and a controller. A first bypass valve in the low-temperature stage circulation loop is connected to a condenser-evaporator and a load evaporator. When the first bypass valve is open, it mixes the refrigerant output from the condenser-evaporator with the refrigerant output from the load evaporator to reduce the return gas temperature. The controller is connected to the first bypass valve and controls the bypass valve according to the above method.

[0026] In one embodiment, the low-temperature stage circulation loop includes a main circulation path and a bypass branch, the bypass branch connecting the condenser evaporator and the load evaporator in the main circulation path, and the first bypass valve is disposed in the bypass branch.

[0027] In one embodiment, the main circulation path includes a condenser-evaporator, a cryogenic compressor, an oil separator, a second bypass valve, an electronic expansion valve, a regenerator, a first shut-off valve, a second shut-off valve, and an expansion tank. The oil separator is connected to the cryogenic compressor, the condenser-evaporator, and the expansion tank. The electronic expansion valve is connected to the condenser-evaporator and the regenerator. The regenerator is connected to the second bypass valve and the first shut-off valve. The second bypass valve is connected to the condenser-evaporator and the oil separator. The first shut-off valve is connected to one end of the load evaporator. The second shut-off valve is connected to the other end of the load evaporator and the regenerator. The regenerator is also connected to the expansion tank and the cryogenic compressor.

[0028] The aforementioned bypass valve control method and cascade refrigeration cycle system for the refrigeration cycle system obtain the compressor's discharge temperature in the refrigeration cycle system. When the discharge temperature is greater than or equal to a set opening temperature threshold, the first bypass valve opens to a preset initial opening degree. The first bypass valve connects the condenser and the load evaporator. When the first bypass valve is open, it mixes the refrigerant output from the condenser with the refrigerant output from the load evaporator to reduce the return gas temperature. If the production temperature of the refrigeration cycle system is lower than the set production temperature threshold, the opening degree of the first bypass valve is controlled in stages according to the compressor's discharge temperature; if the production temperature of the refrigeration cycle system is greater than or equal to the production temperature threshold, the opening degree of the first bypass valve is controlled according to the compressor's discharge temperature or the temperature of the load evaporator. By combining the compressor's discharge temperature and the temperature of the load evaporator in the refrigeration cycle system to control the opening degree of the first bypass valve, the refrigerant flow rate of the bypass branch can be adjusted, improving the system's temperature control stability and the compressor's operational reliability. Attached Figure Description

[0029] Figure 1 This is a flowchart of a bypass valve control method for a refrigeration cycle system in one embodiment;

[0030] Figure 2This is a schematic diagram of the control flow of a refrigeration cycle system in one embodiment;

[0031] Figure 3 This is a schematic diagram of the structure of a cascade refrigeration cycle system in one embodiment.

[0032] Explanation of reference numerals in the attached diagram: 1. High-temperature stage compressor; 2. Water-cooled condenser; 3. Thermal expansion valve; 4. Condenser-evaporator; 5. Low-temperature stage compressor; 6. Oil separator; 7. Second bypass valve; 8. Electronic expansion valve; 9. Regenerator; 10. First shut-off valve; 11. Second shut-off valve; 12. First bypass valve; 13. Expansion tank; 14. First angle valve; 15. Second angle valve. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0035] When used herein, the singular forms of “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising / including” or “having,” etc., specify the presence of the stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. Meanwhile, the term “and / or” as used in this specification includes any and all combinations of the associated listed items.

[0036] In one embodiment, such as Figure 1 As shown, a bypass valve control method for a refrigeration cycle system is provided, including:

[0037] Step S110: Obtain the discharge temperature of the compressor in the refrigeration cycle system. Specifically, an discharge temperature sensor can be installed at the discharge port of the compressor in the refrigeration cycle system, and the discharge temperature sensor can be connected to the controller to collect the compressor's discharge temperature and send it to the controller.

[0038] Step S120: When the exhaust temperature is greater than or equal to the set opening temperature threshold, open the first bypass valve to the preset initial opening degree.

[0039] The first bypass valve is located in the bypass branch and connects the condenser and the load evaporator. Specifically, the first bypass valve can be an electronic expansion valve. When the first bypass valve is open, it mixes the refrigerant output from the condenser with the refrigerant output from the load evaporator to lower the return gas temperature. The specific values ​​of the opening temperature threshold A and the initial opening degree Ø are not unique and can be set according to actual needs. For example, the opening temperature threshold A can be set to 100℃, and the initial opening degree Ø can be set to 40%. After the refrigeration cycle system starts up, the controller obtains the compressor's discharge temperature for judgment. If the discharge temperature is ≥ the opening temperature threshold A, it is considered that the bypass branch needs to be used to lower the return gas temperature, and the controller opens the first bypass valve to the initial opening degree Ø. It can be understood that if the discharge temperature is less than the set opening temperature threshold A, the controller keeps the first bypass valve closed and can obtain the compressor's discharge temperature again to continuously monitor whether the discharge temperature is greater than or equal to the set opening temperature threshold.

[0040] Step S130: If the production temperature of the refrigeration cycle system is lower than the set production temperature threshold, the opening degree of the first bypass valve is controlled in stages according to the discharge temperature of the compressor.

[0041] The production temperature refers to the target temperature required for product testing, which can be set and saved in the controller according to actual needs. The production temperature threshold C is not unique and can be set according to actual requirements. The production temperature threshold C can be set to a value lower than the opening temperature threshold A, for example, 25℃. If the production temperature of the refrigeration cycle system is lower than the production temperature threshold C, it is defined as a low-temperature production temperature. At this time, the heat generated at the load end is small, and for the refrigeration cycle system, the return gas temperature is not high, and the exhaust temperature is also relatively low. In this case, the controller controls the opening degree of the first bypass valve in stages according to the compressor's exhaust temperature, so that there is a smoother transition stage when the temperature fluctuates, avoiding repeated fluctuations in exhaust temperature between opening and closing the first bypass valve.

[0042] In one embodiment, step S130 includes: determining the target opening degree corresponding to the current exhaust temperature of the compressor according to a preset correspondence between exhaust temperature and opening degree; adjusting the first bypass valve to the target opening degree until the exhaust temperature of the compressor is less than the set closing temperature threshold, and then controlling the first bypass valve to close.

[0043] In this design, the closing temperature threshold B is less than the opening temperature threshold A, for example, it can be set to 60℃. The production temperature threshold C can also be set to be less than the closing temperature threshold B. A correspondence between exhaust temperature and opening degree can be established and stored in the controller according to actual production needs. The controller determines the corresponding target opening degree based on the current exhaust temperature of the compressor, and then adjusts the opening degree of the first bypass valve. For example, four levels of opening degree for the first bypass valve can be set according to the compressor's exhaust temperature: 5% for exhaust temperature above 90℃; 10% for exhaust temperature above 95℃; 15% for exhaust temperature above 100℃; and 20% for exhaust temperature above 110℃. After adjusting the first bypass valve to the target opening degree of the corresponding level, it remains unchanged until the compressor's exhaust temperature is ≤ closing temperature threshold B. At this point, it can be considered that there is no need to further reduce the return gas temperature, and the controller closes the first bypass valve. It is understood that in other embodiments, other numbers of levels can also be set to adjust the opening degree of the first bypass valve according to the compressor's exhaust temperature.

[0044] Step S140: If the production temperature of the refrigeration cycle system is greater than or equal to the production temperature threshold, the opening degree of the first bypass valve is controlled according to the discharge temperature of the compressor or the temperature of the load evaporator.

[0045] If the production temperature of the refrigeration cycle system is greater than or equal to the production temperature threshold C, it is defined as a high-temperature production temperature. At this time, the load heat generation is very large, and the return gas temperature will be relatively high for the refrigeration cycle system, which will further lead to an increase in the exhaust temperature. Therefore, the controller controls the opening degree of the first bypass valve according to the exhaust temperature of the compressor or the temperature of the load evaporator, so that the first bypass valve is in the continuous open stage to avoid the exhaust temperature from exceeding the alarm value.

[0046] In one embodiment, step S140 includes: obtaining the actual temperature of the load evaporator; if the actual temperature of the load evaporator does not reach the set temperature, controlling the opening of the first bypass valve according to the set temperature and the actual temperature of the load evaporator; if the actual temperature of the load evaporator reaches the set temperature, controlling the opening of the first bypass valve according to the actual discharge temperature of the compressor and the target discharge temperature.

[0047] Similarly, a temperature sensor can be installed on the load evaporator and connected to the controller to detect the actual temperature of the load evaporator and send it to the controller. The controller analyzes the detected actual temperature to determine whether the actual temperature control of the refrigeration cycle system during product testing has reached the set temperature. If the set temperature is very low, the opening of the electronic expansion valve in the main circuit is very small, and the opening of the first bypass valve is too large, resulting in excessive bypass flow. The actual temperature of the load evaporator will not reach the set temperature. In this case, the opening of the first bypass valve is controlled according to the set temperature, specifically including:

[0048]

[0049] in, The target opening degree of the first bypass valve. This represents the current actual opening degree of the first bypass valve. After controlling the opening degree of the first bypass valve according to the set temperature, the actual temperature of the load evaporator is checked again to see if it has reached the set temperature.

[0050] If the actual temperature of the evaporator under load reaches the set temperature, the opening degree of the first bypass valve needs to be controlled according to the actual discharge temperature of the compressor, specifically including:

[0051]

[0052] in, The target opening degree of the first bypass valve. This represents the current actual opening degree of the first bypass valve. When the coefficient is positive, the opening degree of the first bypass valve is decreased; when the coefficient is negative, the opening degree of the first bypass valve is increased.

[0053] Furthermore, after controlling the opening degree of the first bypass valve based on the actual exhaust temperature and the target exhaust temperature of the compressor, the method further includes: if the difference between the average value of the continuously collected set number of exhaust temperatures and the latest collected exhaust temperature is less than or equal to the set temperature difference threshold, then the refrigeration cycle system enters the temperature control stabilization stage.

[0054] The specific values ​​for the number of sensors and the temperature difference threshold M can also be set according to actual needs. During the adjustment of the first bypass valve, the controller reads and records the exhaust temperature collected by the exhaust temperature sensor every N seconds (e.g., 10 seconds). The average value is calculated using the exhaust temperatures of a continuously set number (e.g., 10). The difference between the average value and the last value among the set number of temperature values ​​is calculated. If the difference is ≤ the temperature difference threshold M (e.g., 2℃), it can be considered that the temperature control has entered a stable stage.

[0055] Specifically, such as Figure 2As shown, after the refrigeration cycle system starts up, the compressor's discharge temperature is checked. If the discharge temperature is less than the opening temperature threshold A (e.g., 100℃), the first bypass valve remains closed. If the discharge temperature is greater than or equal to the opening temperature threshold A, the first bypass valve is opened to an initial opening degree Ø (e.g., 40%). At this time, the system's operating production temperature is used to determine the temperature (here, production temperature refers to the target temperature required for product testing). If the production temperature is less than the production temperature threshold C (e.g., 25℃), it is defined as a low-temperature production temperature because the heat generated at the load end is relatively small, and for the refrigeration cycle system, the return gas temperature is not high, and the discharge temperature is also relatively low. In this case, control is performed according to the discharge temperature range to ensure a smoother transition period during temperature fluctuations, avoiding repeated fluctuations in discharge temperature between opening and closing the first bypass valve. For example, the opening degree of the first bypass valve can be set to 4 levels based on the exhaust temperature: 5% for exhaust temperature above 90℃; 10% for exhaust temperature above 95℃; 15% for exhaust temperature above 100℃; and 20% for exhaust temperature above 110℃. After reaching the set temperature level, the first bypass valve will close when the exhaust temperature is ≤ the closing temperature threshold B (e.g., 60℃).

[0056] If the production temperature is greater than or equal to the production temperature threshold C (e.g., 25℃), it is defined as a high-temperature production temperature. At this temperature, the load heat generation is very large, resulting in a relatively high return gas temperature for the refrigeration cycle system, further leading to an increase in the exhaust temperature. Therefore, the first bypass valve remains continuously open to prevent the exhaust temperature from exceeding the alarm value. At this point, it is necessary to further determine whether the refrigeration cycle system temperature control has reached the set temperature based on the actual temperature of the load evaporator. If the set temperature is very low, the main circuit electronic expansion valve opening is small, and the first bypass valve opening is too large, resulting in excessive bypass flow and the actual temperature of the load evaporator failing to reach the set temperature. In this case, the opening of the first bypass valve is controlled according to the set temperature, and the actual temperature of the load evaporator is checked again to see if it reaches the set temperature. If it does, the opening of the first bypass valve needs to be controlled according to the exhaust temperature. During the adjustment process, the exhaust temperature collected by the exhaust temperature sensor is read and recorded every N seconds (e.g., 10 seconds). The temperature control stability phase is considered to have been entered when the difference between the average of 10 consecutive exhaust temperatures and the last of these 10 temperature values ​​is less than or equal to the temperature difference threshold M (e.g., 2℃).

[0057] The above-mentioned bypass valve control method for the refrigeration cycle system controls the action of the first bypass valve in the bypass branch according to the actual temperature of the load end and the actual discharge temperature of the compressor. It can achieve accurate temperature control at all set temperature points, avoiding the problem of not being able to reach the target temperature when the extreme low temperature is set. At the same time, it enables the compressor to operate under a suitable discharge temperature, avoiding liquid carryover during compressor operation, which can cause liquid slugging and compressor frosting, thus improving the reliability of compressor operation.

[0058] It should be understood that although the steps in the flowcharts of the embodiments described above are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the embodiments described above may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages of other steps.

[0059] Based on the same inventive concept, this application also provides a refrigeration cycle system bypass valve control device for implementing the above-described refrigeration cycle system bypass valve control method. The solution provided by this device is similar to the solution described in the above method; therefore, the specific limitations of one or more embodiments of the refrigeration cycle system bypass valve control device provided below can be found in the limitations of the refrigeration cycle system bypass valve control method described above, and will not be repeated here.

[0060] In one embodiment, a bypass valve control device for a refrigeration cycle system is provided, comprising: a data acquisition module and an opening control module, wherein:

[0061] The data acquisition module is used to acquire the discharge temperature of the compressor in the refrigeration cycle system.

[0062] The opening control module is used to open the first bypass valve to a preset initial opening degree when the exhaust temperature is greater than or equal to a set opening temperature threshold. The first bypass valve connects the condenser and the load evaporator. When the first bypass valve is open, it mixes the refrigerant output from the condenser with the refrigerant output from the load evaporator to reduce the return gas temperature. If the production temperature of the refrigeration cycle system is less than the set production temperature threshold, the opening degree of the first bypass valve is controlled in stages according to the compressor's exhaust temperature. If the production temperature of the refrigeration cycle system is greater than or equal to the production temperature threshold, the opening degree of the first bypass valve is controlled according to the compressor's exhaust temperature or the temperature of the load evaporator.

[0063] In one embodiment, the opening control module is further configured to control the first bypass valve to remain closed when the exhaust temperature is less than a set opening temperature threshold.

[0064] In one embodiment, the opening control module is further configured to determine the target opening corresponding to the current exhaust temperature of the compressor based on a preset correspondence between exhaust temperature and opening; adjust the first bypass valve to the target opening until the exhaust temperature of the compressor is less than a set closing temperature threshold, and then control the first bypass valve to close; the closing temperature threshold is less than the opening temperature threshold.

[0065] In one embodiment, the opening control module is further configured to obtain the actual temperature of the load evaporator; if the actual temperature of the load evaporator does not reach the set temperature, the opening of the first bypass valve is controlled according to the set temperature and the actual temperature of the load evaporator; if the actual temperature of the load evaporator reaches the set temperature, the opening of the first bypass valve is controlled according to the actual discharge temperature of the compressor and the target discharge temperature.

[0066] In one embodiment, the opening control module is further configured to, if the difference between the average value of a set number of continuously collected exhaust temperatures and the latest collected exhaust temperature is less than or equal to a set temperature difference threshold, then the refrigeration cycle system enters the temperature control stabilization stage.

[0067] Each module in the bypass valve control device of the aforementioned refrigeration cycle system can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in the processor of a computer device in hardware form or independent of it, or stored in the memory of a computer device in software form, so that the processor can call and execute the operations corresponding to each module.

[0068] In one embodiment, a cascade refrigeration cycle system is also provided, including a high-temperature stage circulation loop, a low-temperature stage circulation loop, and a controller. A first bypass valve in the low-temperature stage circulation loop connects a condenser-evaporator and a load evaporator. When the first bypass valve is open, it mixes the refrigerant output from the condenser-evaporator with the refrigerant output from the load evaporator to reduce the return gas temperature. The controller is connected to the first bypass valve and controls the bypass valve according to the method described above. The controller can be, but is not limited to, various personal computers, laptops, smartphones, tablets, and portable wearable devices. Portable wearable devices can be smartwatches, smart bracelets, head-mounted devices, etc.

[0069] Specifically, such as Figure 3 As shown, in the high-temperature stage circulation loop, the high-temperature stage compressor 1, water-cooled condenser 2, thermostatic expansion valve 3, and condenser-evaporator 4 (i.e., the condenser mentioned above) are connected in sequence, with condenser-evaporator 4 connected to the high-temperature stage compressor 1. The water-cooled condenser 2 exchanges heat with an external chiller, and the condenser-evaporator 4 exchanges heat with the low-temperature stage circulation loop.

[0070] Furthermore, the low-temperature stage circulation loop includes a main circulation path and a bypass branch. The main circulation path includes a condenser-evaporator 4 (i.e., the condenser mentioned above), a low-temperature stage compressor 5, an oil separator 6, a second bypass valve 7, an electronic expansion valve 8, a regenerator 9, a first shut-off valve 10, a second shut-off valve 11, and an expansion tank 13. The oil separator 6 is connected to the low-temperature stage compressor 5, the condenser-evaporator 4, and the expansion tank 13 (specifically connected to the output port of the expansion tank 13). The electronic expansion valve 8 is connected to the condenser-evaporator 4 and the regenerator 9. The regenerator 9 is connected to the second bypass valve 7 and the first shut-off valve 10. The second bypass valve 7 is connected to the condenser-evaporator 4 and the oil separator 6. The first shut-off valve 10 is connected to one end of the load evaporator, and the second shut-off valve 11 is connected to the other end of the load evaporator and the regenerator 9. The regenerator 9 is also connected to the expansion tank 13 (specifically connected to the input port of the expansion tank 13) and the low-temperature stage compressor 5.

[0071] The second bypass valve 7 can also be an electronic expansion valve. The main circulation path may also include a first angle valve 14 and a second angle valve 15. The first angle valve 14 is located at the inlet of the expansion tank 13, and the second angle valve 15 is located at the outlet of the expansion tank 13. The main function of the expansion tank 13 is to stabilize the system pressure when the unit is not running, preventing damage to system piping components. The operation of the expansion tank 13 can be adjusted by controlling the opening and closing of the first angle valve 14 and the second angle valve 15. The first shut-off valve 10 and the second shut-off valve 11 are connected to the load evaporator to control the flow path. The bypass branch connects the condenser evaporator 4 and the load evaporator in the main circulation path. The first bypass valve 12 is located in the bypass branch and is specifically connected to the second shut-off valve 11. Furthermore, the controller can also be connected to the thermal expansion valve 3, the second bypass valve 7, the electronic expansion valve 8, the first shut-off valve 10, the second shut-off valve 11, the first angle valve 14, and the second angle valve 15 for on / off / opening control.

[0072] In the low-temperature stage circulation loop, the refrigerant in the condenser-evaporator 4, after heat exchange with the high-temperature stage circulation loop, is transported to the regenerator 9 via the electronic expansion valve 8 for further heat exchange. Then, it is transported to the load evaporator via the first shut-off valve 10. The refrigerant output from the load evaporator is transported to the regenerator 9 via the second shut-off valve 11, where it exchanges heat with the refrigerant output from the electronic expansion valve 8 before being transported to the low-temperature stage compressor 5. The refrigerant output from the low-temperature stage compressor 5 is returned to the condenser-evaporator 4 via the oil separator 6 for heat exchange with the high-temperature stage circulation loop. When the first bypass valve 12 is open, the refrigerant output from the condenser-evaporator 4 is transported to both the electronic expansion valve 8 and the first bypass valve 12. The refrigerant output from the first bypass valve 12 mixes with the refrigerant output from the second shut-off valve 11 to lower the return gas temperature. The mixed refrigerant is then sent to the regenerator 9 for heat exchange with the refrigerant output from the electronic expansion valve 8. In addition, when the second bypass valve 7 is open, part of the refrigerant output from the oil separator 6 is also mixed with the refrigerant output from the regenerator 9 through the second bypass valve 7, and then transported to the load evaporator through the first shut-off valve 10.

[0073] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0074] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for controlling a bypass valve in a refrigeration cycle system, characterized in that, include: Obtain the discharge temperature of the compressor in the refrigeration cycle system; When the exhaust temperature is greater than or equal to the set opening temperature threshold, the first bypass valve is opened to a preset initial opening degree; wherein, the first bypass valve is connected to the condenser and the load evaporator, and when the first bypass valve is open, it mixes the refrigerant output by the condenser with the refrigerant output by the load evaporator to reduce the return gas temperature. If the production temperature of the refrigeration cycle system is lower than the set production temperature threshold, the opening degree of the first bypass valve is controlled in stages according to the discharge temperature of the compressor. If the production temperature of the refrigeration cycle system is greater than or equal to the production temperature threshold, the opening degree of the first bypass valve is controlled according to the discharge temperature of the compressor or the temperature of the load evaporator.

2. The method according to claim 1, characterized in that, After obtaining the discharge temperature of the compressor in the refrigeration cycle system, the method further includes: when the discharge temperature is less than a set opening temperature threshold, controlling the first bypass valve to remain closed.

3. The method according to claim 1, characterized in that, The opening degree of the first bypass valve is controlled in stages according to the exhaust temperature of the compressor, including: Based on the preset relationship between exhaust temperature and opening degree, the target opening degree corresponding to the current exhaust temperature of the compressor is determined; The first bypass valve is adjusted to the target opening degree until the compressor's exhaust temperature is lower than the set closing temperature threshold, at which point the first bypass valve is controlled to close; the closing temperature threshold is lower than the opening temperature threshold.

4. The method according to claim 1, characterized in that, The opening degree of the first bypass valve is controlled according to the discharge temperature of the compressor or the temperature of the loaded evaporator, including: Obtain the actual temperature of the load evaporator; If the actual temperature of the load evaporator does not reach the set temperature, the opening degree of the first bypass valve is controlled according to the set temperature and the actual temperature of the load evaporator. If the actual temperature of the load evaporator reaches the set temperature, the opening degree of the first bypass valve is controlled according to the actual exhaust temperature of the compressor and the target exhaust temperature.

5. The method according to claim 4, characterized in that, Based on the set temperature and the actual temperature of the loaded evaporator, the opening degree of the first bypass valve is controlled, including: ； in, The target opening degree of the first bypass valve. This represents the current actual opening degree of the first bypass valve.

6. The method according to claim 4, characterized in that, Based on the actual discharge temperature and target discharge temperature of the compressor, the opening degree of the first bypass valve is controlled, including: ； in, The target opening degree of the first bypass valve. This represents the current actual opening degree of the first bypass valve.

7. The method according to claim 4, characterized in that, After controlling the opening degree of the first bypass valve based on the actual discharge temperature and the target discharge temperature of the compressor, the method further includes: If the difference between the average value of the continuously collected exhaust temperatures (a set number) and the latest collected exhaust temperature is less than or equal to the set temperature difference threshold, the refrigeration cycle system enters the temperature control stabilization stage.

8. A cascade refrigeration cycle system, characterized in that, The system includes a high-temperature stage circulation loop, a low-temperature stage circulation loop, and a controller. A first bypass valve in the low-temperature stage circulation loop is connected to a condenser-evaporator and a load evaporator. When the first bypass valve is open, it mixes the refrigerant output from the condenser-evaporator with the refrigerant output from the load evaporator to reduce the return gas temperature. The controller is connected to the first bypass valve, and the bypass valve is controlled according to any one of claims 1 to 7.

9. The cascade refrigeration cycle system according to claim 8, characterized in that, The low-temperature stage circulation loop includes a main circulation path and a bypass branch. The bypass branch connects the condenser evaporator and the load evaporator in the main circulation path, and the first bypass valve is located in the bypass branch.

10. The cascade refrigeration cycle system according to claim 9, characterized in that, The main circulation path includes a condenser-evaporator, a cryogenic compressor, an oil separator, a second bypass valve, an electronic expansion valve, a regenerator, a first shut-off valve, a second shut-off valve, and an expansion tank. The oil separator connects the cryogenic compressor, the condenser-evaporator, and the expansion tank. The electronic expansion valve connects the condenser-evaporator and the regenerator. The regenerator connects the second bypass valve and the first shut-off valve. The second bypass valve connects the condenser-evaporator and the oil separator. The first shut-off valve connects to one end of the load evaporator. The second shut-off valve connects to the other end of the load evaporator and the regenerator. The regenerator also connects to the expansion tank and the cryogenic compressor.

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