Oil return control method of refrigerating system, refrigerating system and environmental box

Abstract

The embodiment of the invention discloses an oil return control method of a refrigerating system, the refrigerating system and an environment box. The oil return control method comprises the steps that the working mode of the refrigerating system, the working state of a first compressor in the refrigerating system and the working state of a second compressor in the refrigerating system are obtained; according to the working mode and the working state of the first compressor, the working states of an electromagnetic valve, a throttling valve and an oil return assembly in a pipeline connected with the first compressor are controlled; according to the working mode and the working state of the second compressor, the working states of an electromagnetic valve, a throttling valve and an oil return assembly in a pipeline connected with the second compressor are controlled, so that oil return control is conducted on the refrigerating system; a pipeline connected with the first compressor and a pipeline connected with the second compressor are both connected with a heat exchanger in the refrigerating system. According to the oil return control method of the refrigerating system, the refrigerating system and the environment box, the control reliability can be improved.

Description

[0001] This application is a divisional application of the application with the application date of July 28, 2023, the application number of 202310944781.9, and the invention creation name of "An oil return control method for a refrigeration system, a refrigeration system and an environmental chamber". Technical Field

[0002] Embodiments of the present invention relate to oil return technology, and in particular to an oil return control method for a refrigeration system, a refrigeration system and an environmental chamber. Background Art

[0003] For the refrigeration system of an environmental chamber such as a constant temperature and humidity environmental chamber, while meeting the cooling rate requirement of the environmental chamber, it is also necessary to ensure the long-term constant temperature and humidity of the environmental chamber. This results in a large refrigerant flow rate during the cooling of the chamber and a small refrigerant flow rate during the constant temperature and humidity of the chamber. In the case of a constant small refrigerant flow rate, the refrigerant flow velocity in the refrigeration system is small, and the lubricating oil in the refrigerant will deposit in the pipeline, resulting in a decrease in the oil return of the compressor and affecting the normal operation of the refrigeration system. Therefore, in order to ensure the normal operation of the refrigeration system, it is necessary to control the oil return of the refrigeration system.

[0004] Currently, the existing oil return methods for refrigeration systems usually rely on oil separation at the compressor exhaust port and the oil return bend provided in the return air pipeline for oil return. However, this method has the problem that some oil is carried into the pipeline or the oil return bend, and the compressor will still experience an oil shortage problem after a long-term constant state. Summary of the Invention

[0005] Embodiments of the present invention provide an oil return control method for a refrigeration system, a refrigeration system and an environmental chamber to solve the problem of oil shortage in the compressor.

[0006] In a first aspect, an embodiment of the present invention provides an oil return control method for a refrigeration system. The refrigeration system includes a pipeline connected to a first compressor and a pipeline connected to a second compressor. The connection relationship of each component in the pipeline connected to the second compressor is as follows: the outlet of the second-stage precooler is connected to the second inlet of the plate heat exchanger; the second outlet of the plate heat exchanger is connected to the first end of the cold bypass solenoid valve and the first end of the second-stage main pipeline solenoid valve; the second end of the cold bypass solenoid valve is connected to the first end of the second-stage cold bypass thermostatic expansion valve; the second end of the second-stage main pipeline solenoid valve is connected to the first end of the second-stage main pipeline throttle valve, and the second end of the second-stage main pipeline throttle valve is connected to the first end of the second-stage evaporator; the second end of the second-stage cold bypass thermostatic expansion valve is connected to the second end of the second-stage evaporator and the inlet of the second compressor; the outlet of the compressor is connected to the inlet of the second-stage precooler; the second inlet of the plate heat exchanger is connected to the first end of the second-stage hot gas quick-opening valve of the oil return assembly, the second end of the second-stage hot gas quick-opening valve of the oil return assembly is connected to the first end of the second-stage hot gas capillary tube of the oil return assembly, and the second end of the second-stage hot gas capillary tube of the oil return assembly is connected to the second end of the second-stage main pipeline throttle valve and the first end of the second-stage evaporator. The oil return control method for the refrigeration system includes:

[0007] Obtain the working mode of the refrigeration system, the working state of the first compressor in the refrigeration system, and the working state of the second compressor in the refrigeration system;

[0008] According to the working mode and the working state of the first compressor, control the working states of the solenoid valve, throttle valve, and oil return assembly in the pipeline connected to the first compressor;

[0009] According to the working mode and the working state of the second compressor, control the working states of the solenoid valve, throttle valve, and oil return assembly in the pipeline connected to the second compressor to perform oil return control on the refrigeration system;

[0010] The controlling the working states of the solenoid valve, throttle valve, and oil return assembly in the pipeline connected to the second compressor according to the working mode and the working state of the second compressor includes:

[0011] When the working mode is the cooling mode or the low-temperature constant mode and the second compressor is started, control the second-stage main pipeline solenoid valve in the pipeline connected to the second compressor to open, the second-stage main pipeline throttle valve to open, the second-stage hot gas quick-opening valve of the oil return assembly to close, and the cold bypass solenoid valve to close.

[0012] Optionally, the controlling the working states of the solenoid valve, throttle valve, and oil return assembly in the pipeline connected to the first compressor according to the working mode and the working state of the first compressor includes:

[0013] When the working mode is the cooling mode or the low - temperature constant mode, and the first compressor starts, control the main - path solenoid valve in the pipeline connected to the first compressor to close, the plate - heat - exchanger solenoid valve to open, the hot - gas quick - opening valve of the oil - return assembly to close, the main - path throttle valve to close, and the cold - bypass solenoid valve to close.

[0014] Optionally, when the working mode is the cooling mode or the low - temperature constant mode, if the actual exhaust temperature of the first compressor exceeds the preset exhaust temperature, control the cold - bypass solenoid valve in the pipeline connected to the first compressor to open.

[0015] Optionally, when the working mode is the high - temperature constant mode, control the main - path solenoid valve in the pipeline connected to the first compressor to open, the plate - heat - exchanger solenoid valve to close, the hot - gas quick - opening valve of the oil - return assembly to open, the bypass solenoid valve to open, the cold - bypass solenoid valve to close, and adjust the opening frequency of the oil - return assembly in the pipeline connected to the first compressor, as well as the opening degree of the main - path throttle valve in the pipeline connected to the first compressor;

[0016] When the working mode is the humidity mode, control the main - path solenoid valve in the pipeline connected to the first compressor to open, the plate - heat - exchanger solenoid valve to close, the hot - gas quick - opening valve of the oil - return assembly to open, the bypass solenoid valve to close, the cold - bypass solenoid valve to close, and adjust the opening frequency of the hot - gas quick - opening valve of the oil - return assembly in the pipeline connected to the first compressor, as well as the opening degree of the main - path throttle valve in the pipeline connected to the first compressor.

[0017] Optionally, the adjustment of the opening frequency of the oil - return assembly in the pipeline connected to the first compressor and the opening degree of the main - path throttle valve in the pipeline connected to the first compressor includes:

[0018] Adjust the opening frequency of the oil - return assembly in the pipeline connected to the first compressor to increase first and then decrease, and adjust the opening degree of the main - path throttle valve in the pipeline connected to the first compressor to increase first and then decrease.

[0019] Optionally, when the working mode is the cooling mode or the low - temperature constant mode, if the actual exhaust temperature of the second compressor exceeds the preset exhaust temperature, control the two - stage cold - bypass solenoid valve in the pipeline connected to the second compressor to open.

[0020] In a second aspect, an embodiment of the present invention provides a refrigeration system, including: a first compressor, a second compressor, solenoid valves, throttle valves, and oil - return assemblies respectively corresponding to the first compressor and the second compressor. The solenoid valves, throttle valves, and oil - return assemblies corresponding to each compressor are arranged in the pipelines connected to the corresponding compressors. The solenoid valves, throttle valves, and oil - return assemblies corresponding to each compressor are all electrically connected to a controller, and the controller is used to execute the oil - return control method as described in the first aspect.

[0021] Optionally, the oil return assembly includes a hot gas quick-opening valve or an electronic expansion valve.

[0022] Optionally, the solenoid valves corresponding to each compressor include a main path solenoid valve and a cold bypass solenoid valve.

[0023] In a third aspect, an embodiment of the present invention provides an environmental chamber, and the environmental chamber is refrigerated by the refrigeration system described in the second aspect.

[0024] The oil return control method, refrigeration system, and environmental chamber provided by the embodiments of the present invention obtain the working mode of the refrigeration system, the working state of the first compressor in the refrigeration system, and the working state of the second compressor in the refrigeration system; according to the working mode and the working state of the first compressor, control the working states of the solenoid valve, throttle valve, and oil return assembly in the pipeline connected to the first compressor; according to the working mode and the working state of the second compressor, control the working states of the solenoid valve, throttle valve, and oil return assembly in the pipeline connected to the second compressor to perform oil return control on the refrigeration system; wherein, the pipelines connected to the first compressor and the second compressor are both connected to the heat exchanger in the refrigeration system. The oil return control method, refrigeration system, and environmental chamber provided by the embodiments of the present invention control the working states of the solenoid valve, throttle valve, and oil return assembly in the pipelines connected to each compressor according to the working mode and the working state of each compressor, such as controlling the on / off of various valve parts, so that the oil in the pipeline can fully flow back to the compressor, ensuring reliable oil return of the compressor, and solving the problem that some oil is brought into the pipeline in the prior art, resulting in oil shortage of the compressor. Description of the Drawings

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0026] Figure 1 is a flowchart of an oil return control method for a refrigeration system provided in Embodiment 1 of the present invention;

[0027] Figure 2 is a flowchart of an oil return control method for a refrigeration system provided in Embodiment 2 of the present invention;

[0028] Figure 3 is a schematic structural diagram of a refrigeration system provided in Embodiment 3 of the present invention. Detailed Embodiments

[0029] To enable those skilled in the art to better understand the solution of the present invention, the following will clearly and completely describe the technical solution in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the scope of protection of the present invention.

[0030] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily need to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances, so that the embodiments of the present invention described here can be implemented in an order other than those illustrated or described here. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0031] Embodiment 1

[0032] Figure 1 is a flowchart of an oil return control method for a refrigeration system provided in Embodiment 1 of the present invention. This embodiment is applicable to aspects such as oil return control of the refrigeration system. This method can be executed by a controller in the refrigeration system. The method specifically includes the following steps:

[0033] Step 110: Obtain the working mode of the refrigeration system, the working state of the first compressor in the refrigeration system, and the working state of the second compressor in the refrigeration system.

[0034] Among them, the controller in the refrigeration system can receive an external signal, and the external signal can include information on the working mode of the refrigeration system to determine the working mode of the refrigeration system. The controller is electrically connected to the first compressor and the second compressor in the refrigeration system to obtain the working state of the first compressor and the working state of the second compressor.

[0035] Step 120: Control the working states of the solenoid valve, throttle valve, and oil return assembly in the pipeline connected to the first compressor according to the working mode and the working state of the first compressor.

[0036] Specifically, when the working mode is the cooling mode or the low-temperature constant mode, and the first compressor is started, control the main path solenoid valve in the pipeline connected to the first compressor to close, the plate heat exchanger solenoid valve to open, the oil return assembly to close, the main path throttle valve to close, and the cold bypass solenoid valve to close to achieve oil return of the first compressor.

[0037] Step 130: Control the working states of the solenoid valve, throttle valve, and oil return assembly in the pipeline connected to the second compressor according to the working mode and the working state of the second compressor, so as to control the oil return of the refrigeration system.

[0038] Among them, the pipelines connected to the first compressor and the second compressor are both connected to the heat exchanger in the refrigeration system. Specifically, when the working mode is the cooling mode or the low-temperature constant mode and the second compressor starts, control the main solenoid valve in the pipeline connected to the second compressor to open, the main throttle valve to open, the oil return assembly to close, and the cold bypass solenoid valve to close, so as to realize the oil return of the second compressor.

[0039] The oil return control method of the refrigeration system provided in this embodiment obtains the working mode of the refrigeration system, the working state of the first compressor in the refrigeration system, and the working state of the second compressor in the refrigeration system; controls the working states of the solenoid valve, throttle valve, and oil return assembly in the pipeline connected to the first compressor according to the working mode and the working state of the first compressor; controls the working states of the solenoid valve, throttle valve, and oil return assembly in the pipeline connected to the second compressor according to the working mode and the working state of the second compressor, so as to control the oil return of the refrigeration system; among them, the pipelines connected to the first compressor and the second compressor are both connected to the heat exchanger in the refrigeration system. The oil return control method of the refrigeration system provided in this embodiment controls the working states of the solenoid valve, throttle valve, and oil return assembly in the pipelines connected to each compressor according to the working mode and the working state of each compressor, such as controlling the on-off of various valve parts, so that the oil in the pipeline can fully flow back to the compressor, ensuring reliable oil return of the compressor, and can solve the problem that some oil is carried into the pipeline in the prior art, resulting in oil shortage of the compressor.

[0040] Embodiment 2

[0041] Figure 2 FIG. 15 is a flowchart of an oil return control method for a refrigeration system provided in Embodiment 2 of the present invention. This embodiment can be applied to aspects such as oil return control of the refrigeration system. This method can be executed by a controller in the refrigeration system. The method specifically includes the following steps:

[0042] Step 210: Obtain the working mode of the refrigeration system, the working state of the first compressor in the refrigeration system, and the working state of the second compressor in the refrigeration system.

[0043] Among them, the controller in the refrigeration system can receive an external signal, and the external signal can include information about the working mode of the refrigeration system to determine the working mode of the refrigeration system. The controller is electrically connected to the first compressor and the second compressor in the refrigeration system to obtain the working state of the first compressor and the working state of the second compressor.

[0044] Step 220: When the working mode is the cooling mode or the low-temperature constant mode and the first compressor starts, control the main path solenoid valve in the pipeline connected to the first compressor to close, the plate heat exchanger solenoid valve to open, the oil return assembly to close, the main path throttle valve to close, and the cold bypass solenoid valve to close.

[0045] Specifically, when the working mode is the cooling mode or the low-temperature constant mode, if the actual exhaust temperature of the first compressor exceeds the preset exhaust temperature, control the cold bypass solenoid valve in the pipeline connected to the first compressor to open.

[0046] Step 230: When the working mode is the high-temperature constant mode, control the main path solenoid valve in the pipeline connected to the first compressor to open, the plate heat exchanger solenoid valve to close, the oil return assembly to open, the bypass solenoid valve to open, the cold bypass solenoid valve to close, and adjust the opening frequency of the oil return assembly in the pipeline connected to the first compressor and the opening degree of the main path throttle valve in the pipeline connected to the first compressor.

[0047] Specifically, adjust the opening frequency of the oil return assembly in the pipeline connected to the first compressor to increase first and then decrease, and adjust the opening degree of the main path throttle valve in the pipeline connected to the first compressor to increase first and then decrease. During the adjustment process, both the opening frequency and the opening degree decrease to their respective preset values and no longer change. The specific magnitudes of the preset values can be determined according to the actual oil return control requirements and are not limited herein.

[0048] Step 240: When the working mode is the humidity mode, control the main path solenoid valve in the pipeline connected to the first compressor to open, the plate heat exchanger solenoid valve to close, the oil return assembly to open, the bypass solenoid valve to close, the cold bypass solenoid valve to close, and adjust the opening frequency of the oil return assembly in the pipeline connected to the first compressor and the opening degree of the main path throttle valve in the pipeline connected to the first compressor.

[0049] Among them, the adjustment of the opening frequency and the opening degree can refer to the description in Step 230 and will not be elaborated herein.

[0050] Step 250: When the working mode is the cooling mode or the low-temperature constant mode and the second compressor starts, control the main path solenoid valve in the pipeline connected to the second compressor to open, the main path throttle valve to open, the oil return assembly to close, and the cold bypass solenoid valve to close.

[0051] Specifically, when the working mode is the cooling mode or the low-temperature constant mode, if the actual exhaust temperature of the second compressor exceeds the preset exhaust temperature, control the cold bypass solenoid valve in the pipeline connected to the second compressor to open.

[0052] The oil return control method of the refrigeration system provided in this embodiment controls the working states of the solenoid valves, throttle valves, and oil return components in the pipelines connected to each compressor according to the working mode and the working states of each compressor. For example, by controlling the opening and closing of various valve parts, the oil in the pipeline can fully flow back to the compressor, ensuring reliable oil return of the compressor, and solving the problem of oil shortage in the compressor caused by some oil being carried into the pipeline in the prior art.

[0053] Embodiment III

[0054] Figure 3 It is a schematic structural diagram of a refrigeration system provided in Embodiment III of the present invention. Refer to Figure 3 , the refrigeration system includes: a first compressor, a second compressor, solenoid valves, throttle valves, and oil return components respectively corresponding to the first compressor and the second compressor.

[0055] Among them, the solenoid valves, throttle valves, and oil return components corresponding to each compressor are arranged in the pipelines connected to the corresponding compressor. The solenoid valves, throttle valves, and oil return components corresponding to each compressor are all electrically connected to the controller, and the controller is used to execute the oil return control method described in any embodiment of the present invention.

[0056] Specifically, when the refrigeration system operates in the cooling mode, the first-stage compressor 1, i.e., the first compressor CM1, starts. The controller controls the main path solenoid valve 5 corresponding to the first-stage compressor 1 to close, the plate heat exchanger solenoid valve 7 to open, the oil return assembly 25 to close, the main path throttle valve 6 to close, and the cold bypass solenoid valve 11 to close. The high-temperature and high-pressure refrigerant flows out from the exhaust port of the first compressor CM1, passes through the oil separator, and enters the first condenser 2 for heat exchange and condensation into high-pressure liquid refrigerant. The liquid refrigerant flows out from the first condenser 2 and successively passes through the dryer filter, the sight glass, and the plate heat exchanger solenoid valve 7, and becomes a low-temperature and low-pressure gas-liquid mixed refrigerant after throttling by the throttle valve before the plate heat exchanger, and then enters the plate heat exchanger 14 for heat exchange and becomes gaseous refrigerant and returns to the compressor suction port, completing the cycle of the first-stage refrigerant. When the first compressor CM1 starts for a period of time and the plate heat exchanger 14 is fully cooled, the second-stage compressor 15, i.e., the second compressor CM2, starts. The controller controls the main path solenoid valve 18 corresponding to the second-stage compressor 15 to open, the main path throttle valve 19 to open, the oil return assembly 26 to close, and the cold bypass solenoid valve 21 to close. The second-stage compressor 15 compresses the second-stage refrigerant into high-temperature and high-pressure gas, and then enters the second-stage pre-cooler 24 for heat exchange with the cooling water, cools into medium-temperature and high-pressure gaseous refrigerant, then passes through the oil separator and enters the plate heat exchanger 14 for further heat exchange, condenses into high-pressure liquid refrigerant and flows out from the plate heat exchanger. The high-pressure liquid refrigerant passes through the main path solenoid valve 18, is throttled by the main path throttle valve 19 and becomes a low-temperature and low-pressure gas-liquid mixed refrigerant, and then enters the second-stage evaporator 20 for heat exchange and refrigeration to cool the inside of the box, and finally the low-pressure gaseous refrigerant flowing out from the second-stage evaporator 20 returns to the compressor suction port, completing the cycle of the second-stage refrigerant. In the cooling mode, when the exhaust temperatures of the first-stage compressor 1 and the second-stage compressor 15 exceed the set value, the controller controls the cold bypass solenoid valves 11 and 21 corresponding to each compressor to open, and the cold bypass thermostatic expansion valves 12 and 22 to open, so as to reduce the compressor suction temperature and further reduce the compressor exhaust temperature. In the cooling mode, the refrigerant flow rate is relatively large. Even if the compressor starts to cool directly without preheating, the lubricating oil in the compressor oil sump is all carried into the pipeline by the refrigerant. Due to the relatively large refrigerant flow rate, the lubricating oil can also be brought back to the compressor suction port, thus realizing oil return.

[0057] The high-temperature constant mode and the low-temperature constant mode are divided according to the constant temperature inside the box. Exemplarily, when the temperature inside the box is constant above 0°C, it is the high-temperature constant mode, and when it is constant below 0°C, it is the low-temperature constant mode. In the high-temperature constant mode, the first-stage compressor 1 starts and the second-stage compressor 15 shuts down.

[0058] In the high-temperature constant mode, the controller controls the main path solenoid valve 5 corresponding to a section of the compressor 1 to open, the main path throttle valve 6 to open, the plate heat exchanger solenoid valve 7 to close, the oil return assembly 25 to open, the bypass solenoid valve 10 to open, and the cold bypass solenoid valve 11 to close. At this time, the liquid refrigerant condensed by the first-stage condenser 2 will pass through the main path solenoid valve 5, be throttled by the main path throttle valve 6, and then enter the first-stage evaporator 8 to exchange heat with the interior of the box. The gaseous refrigerant after heat exchange returns to the compressor through the bypass solenoid valve 10. When the temperature is constantly high, the cooling capacity required inside the box is small. At this time, the controller adjusts the opening degree of the main path throttle valve 6 to be small, and the flow rate of the refrigerant in the first-stage evaporator 8 and the return air pipe at the outlet of the evaporator is very slow. The first-stage low-pressure pressure sensor 13 detects that the suction pressure is very low. At this time, the lubricating oil brought into the pipeline by the refrigerant will be deposited in the evaporator 8 and the return air pipe of the evaporator. After a long-term constant state, the lubricating oil deposited in the evaporator and the return air pipe will be more and more, and the compressor will run out of oil. To solve the above problem of difficult oil return, an oil return assembly 25 is provided between the compressor exhaust port and the evaporator inlet. The oil return assembly 25 includes a first-stage hot gas quick-opening valve 3 and a first-stage hot gas capillary tube 4. When entering the high-temperature constant mode, the controller adjusts the opening frequency of the first-stage hot gas quick-opening valve 3 to be large. At this time, the high-temperature gaseous refrigerant passing through the first-stage hot gas capillary tube 4 is large, and then it is mixed with the low-temperature refrigerant throttled by the main path throttle valve 6 and enters the evaporator. Since the refrigeration capacity of the refrigerant after the high and low temperature mixing is less than the refrigeration capacity of only the throttled low-temperature refrigerant before, and the opening degree of the main path throttle valve 6 is large, the refrigerant flow rate entering the evaporator after mixing will be relatively large. The lubricating oil originally deposited on the evaporator and the return air pipe will also be flushed back to the compressor, realizing oil return on the pipeline. At this time, the first-stage low-pressure sensor 13 detects a higher pressure. If it operates at a large flow rate for a long time, the power consumption of the compressor will increase. To solve the problem of large compressor power consumption, the controller controls the opening frequency of the first-stage hot gas quick-opening valve 3 to slowly decrease, so as to slowly reduce the amount of hot gas entering the evaporator 8. At the same time, the opening degree of the main path throttle valve 6 is also controlled to slowly decrease, so as to keep the temperature inside the box stable. The pressure detected by the first-stage low-pressure sensor 13 will slowly decrease. When it drops to the preset pressure, the controller controls the opening frequency of the first-stage hot gas quick-opening valve 3 to stop decreasing, and at the same time controls the opening degree of the main path throttle valve 6 to stop decreasing. The power consumption of the compressor is small, and the lubricating oil in the evaporator and the return air pipe is not easy to deposit, so that long-term high-temperature constancy can be achieved, and at the same time, the function of regular oil return can be realized.When the high temperature is constant for the set time, the controller controls a hot gas quick-opening valve 3 to slowly increase the opening frequency, the main throttle valve 6 gradually increases the opening degree, and the flow rate of the refrigerant entering the first-stage evaporator 8 will increase. In this way, the lubricating oil deposited in the first-stage evaporator 8 and the return gas pipeline can be brought back to the first-stage compressor 1. At this time, the suction pressure detected by the first-stage low-pressure sensor 13 increases. When it increases to the preset pressure, the controller controls the hot gas quick-opening valve 3 to stop increasing the opening frequency, and the main throttle valve 6 stops increasing the opening degree. After a period of time, the lubricating oil in the first-stage evaporator 8 and the return gas pipeline is flushed back to the first-stage compressor 1, and the opening frequency of the hot gas quick-opening valve 3 slowly returns to the original opening state, and the main throttle valve 6 returns to the original opening degree.

[0059] In the low-temperature constant mode, the state is the same as that in the cooling mode. However, when the temperature is constantly low, the refrigeration capacity required inside the cabinet is very small. Therefore, the opening degree of the main throttle valve 19 is very small. Similar to the high-temperature constant mode, the refrigerant flow rate entering the second-stage evaporator 20 is very small, and it is easy for lubricating oil to deposit in the second-stage evaporator 20 and the return gas pipeline, resulting in a lack of oil in the second-stage compressor 15. Therefore, to solve the problem of difficult oil return in the low-temperature constant mode, an oil return assembly 26 is added between the high-pressure side and the inlet of the second-stage evaporator 20. The oil return assembly 26 includes a second-stage hot gas quick-opening valve 16 and a second-stage hot gas capillary tube 17. When entering the low-temperature constant mode, the adjustment logic of the second-stage hot gas quick-opening valve 16 and the main throttle valve 19 is the same as that in the high-temperature constant mode. When the pressure detected by the second-stage low-pressure sensor 23 reaches the set pressure, the opening degrees of the hot gas quick-opening valve 16 and the main throttle valve 19 are determined. Among them, the hot gas quick-opening valve in each oil return assembly can also be replaced by an electronic expansion valve.

[0060] The difference between the humidity mode and the high-temperature constant mode is that the bypass solenoid valve 10 corresponding to the first-stage compressor 1 is closed, and the refrigerant flowing out of the first-stage evaporator 8 returns to the suction port of the first-stage compressor 1 after passing through the evaporation pressure regulating valve 9. Since the humidity inside the cabinet needs to be kept constant for a long time to prevent frosting of the first-stage evaporator 8 from affecting heat exchange, the evaporation pressure regulating valve 9 is required to increase the evaporation pressure in the first-stage evaporator 8, increase the surface temperature of the first-stage evaporator 8, and thus reduce the frosting of the first-stage evaporator 8. The other control processes of the humidity mode are the same as those of the high-temperature constant mode, and will not be elaborated here.

[0061] This embodiment also provides an environmental chamber, and the environmental chamber is refrigerated by the refrigeration system described in any embodiment of the present invention.

[0062] The refrigeration system and the environmental chamber provided in this embodiment and the oil return control method of the refrigeration system provided in any embodiment of the present invention belong to the same inventive concept and have corresponding beneficial effects. For the technical details not elaborated in this embodiment, please refer to the oil return control method of the refrigeration system provided in any embodiment of the present invention.

[0063] It should be understood that the various forms of processes shown above can be used, with steps reordered, added or deleted. For example, the steps described in the present invention can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution of the present invention can be achieved, and no limitation is imposed herein.

[0064] The above specific embodiments do not constitute a limitation on the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub - combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. An oil return control method for a refrigeration system, the refrigeration system comprising a pipeline connected to a first compressor and a pipeline connected to a second compressor. The connection relationships of the components in the pipeline connected to the second compressor are as follows: the outlet of the secondary pre-cooler is connected to the second inlet of the plate heat exchanger, and the second outlet of the plate heat exchanger is connected to the first end of a cold bypass solenoid valve and the first end of a secondary main pipeline solenoid valve; the second end of the cold bypass solenoid valve is connected to the first end of a secondary cold bypass thermostatic expansion valve; the second end of the secondary main pipeline solenoid valve is connected to the first end of a secondary main pipeline throttle valve, and the second end of the secondary main pipeline throttle valve is connected to the first end of a secondary evaporator; the second end of the secondary cold bypass thermostatic expansion valve is connected to the second end of the secondary evaporator and the inlet of the second compressor; the outlet of the compressor is connected to the inlet of the secondary pre-cooler; the second inlet of the plate heat exchanger is connected to the first end of a two-stage hot gas quick-opening valve of an oil return assembly, the second end of the two-stage hot gas quick-opening valve of the oil return assembly is connected to the first end of a two-stage hot gas capillary tube of the oil return assembly, and the second end of the two-stage hot gas capillary tube of the oil return assembly is connected to the second end of the secondary main pipeline throttle valve and the first end of the secondary evaporator. Characterized in that, Comprising: Obtaining the working mode of the refrigeration system, the working state of the first compressor in the refrigeration system, and the working state of the second compressor in the refrigeration system; Controlling the working states of the solenoid valve, throttle valve, and oil return assembly in the pipeline connected to the first compressor according to the working mode and the working state of the first compressor; Controlling the working states of the solenoid valve, throttle valve, and oil return assembly in the pipeline connected to the second compressor according to the working mode and the working state of the second compressor, so as to perform oil return control on the refrigeration system; The controlling the working states of the solenoid valve, throttle valve, and oil return assembly in the pipeline connected to the second compressor according to the working mode and the working state of the second compressor includes: When the working mode is the cooling mode or the low-temperature constant mode, and the second compressor starts, controlling the secondary main pipeline solenoid valve in the pipeline connected to the second compressor to open, the secondary main pipeline throttle valve to open, the two-stage hot gas quick-opening valve of the oil return assembly to close, and the cold bypass solenoid valve to close.

2. The oil return control method according to claim 1, Characterized in that, The controlling the working states of the solenoid valve, throttle valve, and oil return assembly in the pipeline connected to the first compressor according to the working mode and the working state of the first compressor includes: When the working mode is the cooling mode or the low-temperature constant mode, and the first compressor starts, controlling the main pipeline solenoid valve in the pipeline connected to the first compressor to close, the plate heat exchanger solenoid valve to open, the hot gas quick-opening valve of the oil return assembly to close, the main pipeline throttle valve to close, and the cold bypass solenoid valve to close.

3. The oil return control method according to claim 2, Characterized in that, When the working mode is the cooling mode or the low-temperature constant mode, if the actual exhaust temperature of the first compressor exceeds the preset exhaust temperature, controlling the cold bypass solenoid valve in the pipeline connected to the first compressor to open.

4. The oil return control method according to claim 1, characterized in that, when the working mode is the high-temperature constant mode, control the main path solenoid valve in the pipeline connected to the first compressor to open, the plate heat exchanger solenoid valve to close, the hot gas quick-opening valve of the oil return assembly to open, the bypass solenoid valve to open, the cold bypass solenoid valve to close, and adjust the opening frequency of the oil return assembly in the pipeline connected to the first compressor, and the opening degree of the main path throttle valve in the pipeline connected to the first compressor; when the working mode is the humidity mode, control the main path solenoid valve in the pipeline connected to the first compressor to open, the plate heat exchanger solenoid valve to close, the hot gas quick-opening valve of the oil return assembly to open, the bypass solenoid valve to close, the cold bypass solenoid valve to close, and adjust the opening frequency of the hot gas quick-opening valve of the oil return assembly in the pipeline connected to the first compressor, and the opening degree of the main path throttle valve in the pipeline connected to the first compressor.

5. The oil return control method according to claim 4, characterized in that, the adjustment of the opening frequency of the oil return assembly in the pipeline connected to the first compressor and the opening degree of the main path throttle valve in the pipeline connected to the first compressor includes: adjust the opening frequency of the oil return assembly in the pipeline connected to the first compressor to increase first and then decrease, and adjust the opening degree of the main path throttle valve in the pipeline connected to the first compressor to increase first and then decrease.

6. The oil return control method according to claim 1, characterized in that, further comprising: when the working mode is the cooling mode or the low-temperature constant mode, if the actual exhaust temperature of the second compressor exceeds the preset exhaust temperature, control the two-stage cold bypass solenoid valve in the pipeline connected to the second compressor to open.

7. A refrigeration system, characterized in that, comprising: a first compressor, a second compressor, solenoid valves, throttle valves and oil return assemblies corresponding to the first compressor and the second compressor respectively, the solenoid valves, throttle valves and oil return assemblies corresponding to each compressor are arranged in the pipelines connected to the corresponding compressors, the solenoid valves, throttle valves and oil return assemblies corresponding to each compressor are all electrically connected to the controller, and the controller is used to execute the oil return control method according to any one of claims 1-6.

8. The refrigeration system according to claim 7, characterized in that, the oil return assembly includes a hot gas quick-opening valve or an electronic expansion valve.

9. The refrigeration system according to claim 7, characterized in that, the solenoid valves corresponding to each compressor all include a main path solenoid valve and a cold bypass solenoid valve.

10. An environmental chamber, characterized in that, the environmental chamber is refrigerated by the refrigeration system according to any one of claims 7-9.

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