Interconnected cascade cooling system

Abstract

This invention provides a cascaded refrigeration system, comprising a secondary refrigeration system A and a primary refrigeration system B. The secondary refrigeration system A includes a secondary compressor, the output of which is configured as a secondary path. A first secondary condenser and a second secondary condenser are sequentially arranged on the secondary path. The secondary path is divided into five secondary branches, which converge into a secondary loop. One of the secondary branches is equipped with a plate heat exchanger. The primary refrigeration system B includes a primary compressor, the output of which is configured as a primary path. The primary path exchanges heat with the plate heat exchanger. The primary path is divided into five primary branches, which converge into a primary loop. One of the primary branches exchanges heat with the first secondary condenser. This application improves the overall efficiency of the cascaded use of the two refrigeration systems by changing the refrigerant interconnection path within the two systems.

Description

Technical Field

[0001] This invention relates to a refrigeration system, and more particularly to an interconnected cascade refrigeration system. Background Technology

[0002] R508B and R404A refrigerants are commonly used in existing high and low temperature chamber refrigeration systems, particularly in large enclosures such as insulated boxes and testing chambers. Most existing technologies use either a single R508B or R404A refrigerant to achieve refrigeration, or combine two systems to improve cooling performance. However, they cannot interconnect these two systems. When the refrigerant follows different paths within the two systems, the overall efficiency of the refrigeration system varies, resulting in some refrigeration effects not being improved, while energy consumption is significant. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides an interconnected cascade refrigeration system. By altering the refrigerant interconnection path between the two systems, it improves the overall efficiency of the cascaded use of the two refrigeration systems and reduces energy consumption. The technical solution adopted by this invention is as follows:

[0004] An interconnected cascade refrigeration system includes a secondary refrigeration system A and a primary refrigeration system B;

[0005] The auxiliary refrigeration system A includes an auxiliary compressor. The output end of the auxiliary compressor is configured as an auxiliary path. A first auxiliary condenser and a second auxiliary condenser are sequentially arranged on the auxiliary path. The auxiliary path is divided into five auxiliary branches, which converge into a auxiliary loop. The end of the auxiliary loop is connected to the input end of the auxiliary compressor. A plate heat exchanger is arranged on one of the auxiliary branches.

[0006] The main refrigeration system B includes a main compressor. The output end of the main compressor is configured as the main path, which exchanges heat with a plate heat exchanger. The main path is divided into five main branches, which converge into a main loop. The end of the main loop is connected to the input end of the main compressor. One of the main branches exchanges heat with a first auxiliary condenser to increase the suction pressure and subcooling of the main compressor.

[0007] Furthermore, the five sub-branches respectively include

[0008] The first branch is used to cool the body temperature of the auxiliary compressor;

[0009] The second auxiliary branch is used to increase the suction temperature of the auxiliary compressor. The second auxiliary branch is connected between the first auxiliary condenser and the second auxiliary condenser.

[0010] The third branch is used to regulate the temperature inside the incubator;

[0011] The fourth branch is used to regulate the humidity inside the incubator;

[0012] The fifth sub-branch is used to increase the subcooling of the refrigerant in the main path;

[0013] The plate heat exchanger is located on the fifth sub-branch.

[0014] Furthermore, the five main branches respectively include

[0015] The first main branch is used to cool the body temperature of the main compressor. The first main branch is connected to the main outgoing line after heat exchange in the main outgoing line.

[0016] The second main branch is used to increase the intake temperature of the main compressor. The second main branch is connected to the main outgoing line before the heat exchange in the main outgoing line.

[0017] The third main branch is used to regulate the temperature inside the chamber. The third main branch is connected to the main outgoing path after the heat exchange in the main outgoing path.

[0018] The fourth main branch is used to increase the return gas temperature of the main compressor. The fourth main branch is connected to the main outgoing line after heat exchange in the main outgoing line.

[0019] The fifth main branch is used to control the pressure of the main refrigeration system. The fifth main branch is connected to the main outgoing line before the main outgoing line heat exchange.

[0020] The fourth main branch exchanges heat with the first auxiliary condenser.

[0021] Furthermore, a first solenoid valve and a first expansion valve are sequentially arranged on the first secondary branch;

[0022] The second branch is sequentially equipped with a second solenoid valve and a second expansion valve;

[0023] The third branch is sequentially equipped with a third solenoid valve, a third expansion valve, and a first evaporator;

[0024] The fourth branch is sequentially equipped with a fourth solenoid valve, a first capillary tube, a second evaporator, and a fourth expansion valve.

[0025] The fifth branch is sequentially equipped with a fifth solenoid valve and a fifth expansion valve, and the plate heat exchanger is located downstream of the fifth expansion valve.

[0026] Furthermore, the third and fourth sub-branches converge into a sixth branch before converging into the sub-circuit, and the sixth branch is equipped with a return gas pressure regulating valve.

[0027] Furthermore, the third sub-branch is provided with an auxiliary sub-branch in parallel. One end of the auxiliary sub-branch is connected to the sub-path, and the other end of the auxiliary sub-branch is connected between the third sub-expansion valve and the first sub-evaporator.

[0028] The auxiliary sub-branch is sequentially equipped with a sixth solenoid valve and a second capillary tube.

[0029] Furthermore, a secondary filter and a secondary main valve are sequentially arranged on the secondary outlet, with the secondary filter located downstream of the second secondary condenser.

[0030] Furthermore, a first main solenoid valve and a first main expansion valve are sequentially arranged on the first main branch;

[0031] The second main branch is sequentially equipped with a second main solenoid valve and a second main expansion valve.

[0032] The third main branch is sequentially equipped with a third main solenoid valve, a third main expansion valve, and a first main evaporator.

[0033] The fourth main branch is sequentially equipped with a fourth main solenoid valve and a fourth main expansion valve. The fourth main branch exchanges heat with the first auxiliary condenser after the fourth main expansion valve.

[0034] The fifth main branch is sequentially equipped with a fifth main expansion valve, an expansion tank, and a first main capillary tube.

[0035] Furthermore, an auxiliary main branch is provided in parallel with the third main branch. One end of the auxiliary main branch is connected to the main path, and the other end of the auxiliary main branch (b31) is connected between the third main expansion valve and the first main evaporator. A fifth main solenoid valve and a second main capillary tube are sequentially arranged on the auxiliary main branch.

[0036] Furthermore, the main flow path is sequentially provided with a first main condenser, a first main oil separator, a main valve, and a first main filter. The first main oil separator is located upstream of the plate heat exchanger, and the first main filter is located downstream of the plate heat exchanger.

[0037] Advantages of this invention:

[0038] The auxiliary refrigeration system compresses and discharges the refrigerant, which then exchanges heat with the fourth branch of the main refrigeration system through the first auxiliary condenser. This reduces the condensation temperature of the auxiliary refrigeration system's secondary outlet, saving cooling water flow and temperature. At the same time, the return gas temperature of the main refrigeration system is also increased due to the heat exchange effect of the first auxiliary condenser, thereby increasing the superheat of the main refrigeration system, preventing severe frost formation in the main circuit, reducing the amount of unevaporated liquid refrigerant, and avoiding liquid slugging in the main compressor.

[0039] One branch of the auxiliary refrigeration system is selected to condense the ultra-low temperature exhaust gas of the main refrigeration system, so that the main refrigeration system can achieve the ultra-low temperature refrigeration effect in one refrigeration, improve the subcooling degree, reduce the cooling flow, and eliminate the need for other equipment. It is highly efficient in refrigeration and has no excess energy loss.

[0040] The main refrigeration system uses the secondary outflow path of the auxiliary refrigeration system to return gas for heating, preventing the presence of liquid refrigerant from causing severe frost formation and resulting in liquid slugging in the compressor. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the structural composition of the present invention.

[0042] Figure 2 for Figure 1 A schematic diagram of the intermediate and auxiliary refrigeration system A.

[0043] Figure 3 for Figure 1 A schematic diagram of the main refrigeration system B. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0045] Please see the appendix Figure 1-3 The present invention provides an interconnected cascade refrigeration system, comprising a secondary refrigeration system A and a primary refrigeration system B;

[0046] The auxiliary refrigeration system A includes an auxiliary compressor 1. The output end of the auxiliary compressor 1 is configured as an auxiliary path A1. A first auxiliary condenser 11 and a second auxiliary condenser 12 are sequentially arranged on the auxiliary path A1. The auxiliary path A1 is divided into five auxiliary branches, and the five auxiliary branches converge into a auxiliary loop A2. The end of the auxiliary loop A2 is connected to the input end of the auxiliary compressor 10. A plate heat exchanger 13 is arranged on one of the auxiliary branches.

[0047] The main refrigeration system B includes a main compressor 2. The output end of the main compressor 2 is configured as a main path B1, which exchanges heat with a plate heat exchanger 13. The main path B1 is divided into five main branches, which converge into a main loop B2. The end of the main loop B2 is connected to the input end of the main compressor 2. One of the main branches exchanges heat with a first auxiliary condenser 11 to increase the suction pressure and subcooling of the main compressor 2.

[0048] In this application, the auxiliary refrigeration system A uses R404A refrigerant. R404A is suitable for lower temperatures and is also used in the high-temperature stage of cascade refrigeration systems. Its evaporation temperature range is -4℃ to -10℃, and its condensation temperature range is -10℃ to 45℃. It has high refrigeration efficiency and can quickly reduce the temperature of the cabinet and maintain it at a low level. In this application, the main refrigeration system B uses R508B refrigerant. R508B is suitable for ultra-low temperature refrigeration and is also commonly used in the low-temperature stage of cascade refrigeration systems.

[0049] The existing technology regarding the cascaded operation of two refrigeration systems can be simplified as follows: Compressed high-pressure R404A refrigerant vapor is discharged from the compressor, passes through an oil separator, and enters the condenser. Cooling water flows in the condenser, carrying away heat, causing the refrigerant vapor to condense into a high-pressure liquid refrigerant. This liquid refrigerant then passes through a dryer filter, a solenoid valve, and an expansion valve, where its pressure is reduced to a low-pressure liquid refrigerant. This low-pressure liquid refrigerant then enters the condenser-evaporator to absorb heat from R508B, evaporating into a low-pressure gaseous refrigerant before returning to the compressor. Similarly, compressed high-pressure R508B refrigerant, after exiting the compressor, passes through an oil separator and a filter before entering the condenser-evaporator. It absorbs the cooling energy from R404A and condenses into a high-pressure liquid refrigerant, which then enters the evaporator to absorb heat and vaporize into a low-pressure gaseous refrigerant before returning to the compressor.

[0050] In this application, two auxiliary condensers are connected in series on the auxiliary circuit A1. The auxiliary refrigeration system A is no longer used solely for ultra-low temperature treatment of R508B. Before branching off, the auxiliary circuit A1 of the auxiliary refrigeration system A first exchanges heat with one of the low-temperature branches of the main refrigeration system B using the first auxiliary condenser 11. The condensation temperature of R404A is reduced in the auxiliary circuit A1. After further condensation by the second auxiliary condenser 12, the cooling water flow and temperature can be saved without increasing energy consumption, and the normal operation of the main refrigeration system B is not affected. The return gas temperature of the main refrigeration system B is increased due to heat exchange, which increases the superheat, prevents severe frost formation, and reduces the amount of liquid refrigerant in the main circuit B2 that has not been fully evaporated, thus avoiding liquid slugging accidents in the main compressor 2.

[0051] Meanwhile, the function of the auxiliary refrigeration system A to perform ultra-low temperature refrigeration for the main refrigeration system B is placed on a branch. After the auxiliary refrigeration system A exchanges heat with one of the low-temperature side branches of the main refrigeration system B, a branch is set off to exchange heat with the main outlet B1 of the main refrigeration system B. The refrigerant after the two-stage condensation has a stable temperature and flow rate, which makes it more stable and efficient when it performs condensation on the high and low temperature exhaust of the main cooling system B.

[0052] In this application, the five sub-branches respectively include a first sub-branch a1, a second sub-branch a2, a third sub-branch a3, a fourth sub-branch a4, and a fifth sub-branch a5; the first sub-branch a1 is used to cool the body temperature of the auxiliary compressor 1; the second sub-branch a2 is used to increase the suction temperature of the auxiliary compressor 1, and the second sub-branch a2 is connected between the first auxiliary condenser 11 and the second auxiliary condenser 12; the third sub-branch a3 is used to regulate the temperature inside the temperature chamber; the fourth sub-branch a4 is used to regulate the humidity inside the temperature chamber; and the fifth sub-branch a5 is used to increase the subcooling of the refrigerant in the main outlet B1; wherein, the plate heat exchanger 13 is disposed on the fifth sub-branch a5. By arranging five sub-branches in the auxiliary cooling system A, various auxiliary functions are realized, energy consumption is saved, and refrigeration efficiency is improved.

[0053] The first sub-branch a1 serves as a self-cooling circuit. A first sub-solenoid valve 14 and a first sub-expansion valve 15 are sequentially installed on the first sub-branch a1. Specifically, the first sub-solenoid valve 14 is a cold bypass solenoid valve, and the first sub-expansion valve 15 is a thermal expansion valve. A temperature sensor is installed on the sub-circuit A2. By using the temperature monitoring point on the sub-compressor 1 of the PLC, when the body temperature of the sub-compressor 1 is higher than a certain temperature (such as 80°C), the first sub-solenoid valve 14 and the first sub-expansion valve 15 on the first sub-branch a1 are controlled to throttle the refrigerant and adjust the flow rate of refrigerant into the sub-circuit A2, thereby controlling the body temperature of the sub-compressor 1 and achieving the purpose of self-cooling.

[0054] The second auxiliary branch a2 serves as a hot gas bypass. A second auxiliary solenoid valve 16 and a second auxiliary expansion valve 17 are sequentially installed on the second auxiliary branch a2. Specifically, the second auxiliary solenoid valve 16 is a hot bypass solenoid valve, and the second auxiliary expansion valve 17 is a thermostatic expansion valve. Similarly, by using the temperature monitoring point on the auxiliary compressor 1 of the PLC, when the body temperature of the auxiliary compressor 1 is lower than a certain temperature (such as -30℃), the second auxiliary solenoid valve 16 and the second auxiliary expansion valve 17 are controlled to work, adjusting the flow rate of refrigerant into the auxiliary circuit A2, thereby controlling the body temperature of the auxiliary compressor 1 to increase the suction temperature of the compressor.

[0055] It should be noted that the second sub-branch a2 is connected to the sub-path A1 between the two sub-condensers. The refrigerant temperature after pre-condensation in the first sub-condenser 11 is higher than the refrigerant temperature after condensation in the second sub-condenser 12. Since two-stage condensation is set up, the refrigerant after pre-cooling is used as the heat source for the second sub-branch a2, which can reduce energy consumption.

[0056] The third sub-branch a3 serves as a cooling circuit. The third sub-branch a3 is sequentially equipped with a third sub-solenoid valve 18, a third sub-expansion valve 19, and a first sub-evaporator 20. Specifically, the third sub-expansion valve 19 is a thermostatic expansion valve. The third sub-solenoid valve 18 and the third sub-expansion valve 19 are controlled by a PLC to throttle the refrigerant. The refrigerant then evaporates and absorbs heat through the first sub-evaporator 20 to reduce the temperature inside the chamber.

[0057] Furthermore, the third sub-branch a3 is provided with an auxiliary sub-branch a31 in parallel. One end of the auxiliary sub-branch a31 is connected to the sub-path A1, and the other end of the auxiliary sub-branch a31 is connected between the third sub-expansion valve 19 and the first sub-evaporator 20. A sixth sub-solenoid valve 28 and a second sub-capillary tube 29 are sequentially arranged on the auxiliary sub-branch a31.

[0058] Specifically, when the refrigerant flow rate of the third branch a3 is insufficient to meet the demand and the cooling demand is greater, the sixth branch solenoid valve 28 is controlled so that part of the refrigerant is throttled through the second branch capillary tube 29 and then merged with the refrigerant throttled by the third branch expansion valve 19 before entering the first branch evaporator 20 to evaporate and absorb heat, thereby improving the cooling effect.

[0059] Furthermore, a sixth expansion valve 32 is provided downstream of the first evaporator 20 to regulate the flow rate of the refrigerant after it has absorbed heat from the evaporator 20, thereby making the refrigeration system more stable.

[0060] The fourth sub-branch a4 serves as a dehumidification circuit. The fourth sub-branch a4 is sequentially equipped with a fourth sub-solenoid valve 21, a first sub-capillary tube 22, a second sub-evaporator 23, and a fourth sub-expansion valve 24. The refrigerant after evaporation and heat absorption by the second sub-evaporator 23 enters the fourth sub-expansion valve 24 for throttling and dehumidification of the interior of the temperature chamber.

[0061] In order to automatically adjust the cooling capacity of the third sub-branch a3 and the fourth sub-branch a4, the third sub-branch a3 and the fourth sub-branch a4 are first combined into a sixth branch a6 before converging into the sub-circuit A2. The sixth branch a6 is equipped with a return gas pressure regulating valve 27. The return gas pressure of the sub-circuit A2 is automatically adjusted by the return gas pressure regulating valve 27, thereby automatically adjusting the cooling capacity and achieving temperature and humidity balance regulation.

[0062] The fifth sub-branch a5 provides condensation for the ultra-low temperature exhaust gas of the main refrigeration system B. The fifth sub-branch a5 is sequentially equipped with a fifth sub-solenoid valve 25 and a fifth sub-expansion valve 26. The plate heat exchanger 13 is located downstream of the fifth sub-expansion valve 26. The fifth sub-expansion valve 26 is an internally balanced thermostatic expansion valve. Using PLC control, the fifth sub-solenoid valve 25 passes through the fifth expansion valve 26 for throttling before entering the plate heat exchanger 13 to exchange heat with the main refrigeration system B. This helps the main refrigeration system B reach the required cooling temperature upon startup. Using just one branch can increase the subcooling of the main refrigeration system B, allowing the refrigerant to condense fully, reducing the refrigerant cooling flow rate, and eliminating the need for additional refrigeration methods, thus achieving efficient refrigeration and reducing energy consumption.

[0063] In this application, a secondary filter 30 and a secondary main valve 31 are sequentially arranged on the secondary outlet A1. The secondary filter 30 is located downstream of the second secondary condenser 12. The refrigerant in the secondary outlet A1 is filtered to remove impurities by the secondary filter 30, and the secondary main valve 31 can control the overall operating conditions of the first secondary branch a1, the third secondary branch a3, the fourth secondary branch a4, and the fifth secondary branch a5.

[0064] It can be concluded that the second sub-branch a2, as a hot gas bypass, is not controlled by the sub-main valve 31. The refrigerant coming out of the first sub-condenser 11 during pre-condensation can achieve the regulation of the return gas temperature of the main refrigeration system A when the sub-main valve 31 is closed, that is, when the main refrigeration system A does not need to be subcooled, thus ensuring the normal operation of the main refrigeration system A.

[0065] Additionally, a manual valve can be installed on the secondary outflow line A1, upstream and downstream of the second secondary condenser 12, respectively, to restrict the refrigerant path when the second secondary condenser 12 needs maintenance or repair.

[0066] In this application, the five main branches respectively include a first main branch b1, a second main branch b2, a third main branch b3, a fourth main branch b4, and a fifth main branch b5; the first main branch b1 is used to cool the body temperature of the main compressor 2, and the first main branch b1 is connected to the main destination B1 after heat exchange; the second main branch b2 is used to increase the suction temperature of the main compressor 2, and the second main branch b2 is connected to the main destination B1 before heat exchange; the third main branch b3 is used to regulate the temperature inside the chamber, and the third main branch b3 is... The main refrigeration system is connected to the main refrigeration system B1 after heat exchange; the fourth main branch b4 is used to increase the return gas temperature of the main compressor 2, and the fourth main branch b4 is connected to the main refrigeration system B1 after heat exchange; the fifth main branch b5 is used to control the pressure of the main refrigeration system, and the fifth main branch b5 is connected to the main refrigeration system B1 before heat exchange; wherein, the fourth main branch b4 exchanges heat with the first auxiliary condenser 11; by branching into five branches on the main refrigeration system B1, various functions of the main refrigeration system B are realized, improving refrigeration efficiency and saving energy consumption.

[0067] The first main branch b1 serves as a self-cooling branch. A first main solenoid valve 41 and a first main expansion valve 42 are sequentially installed on the first main branch b1. The first main expansion valve 42 is a thermostatic expansion valve. A temperature sensor is installed on the main circuit B2. Using the temperature monitoring point on the main compressor 2 of the PLC, when the body temperature of the main compressor 2 is higher than a certain temperature (such as 80°C), the first main solenoid valve 41 and the first main expansion valve 42 on the first main branch b1 are controlled to throttle the refrigerant after it has passed through the ultra-low temperature condensation of the plate heat exchanger 13, and adjust the flow rate of the refrigerant into the main circuit B2, thereby controlling the body temperature of the main compressor 2 and achieving the purpose of self-cooling of the body.

[0068] The second main branch b2 serves as a hot gas bypass for the main compressor 2. The second main branch b2 is sequentially equipped with a second main solenoid valve 43 and a second main expansion valve 44. The return gas temperature of the main compressor 2 is monitored by the temperature monitoring point on the main compressor 2 using a PLC. When the return gas temperature is lower than a certain temperature (such as -30℃), the second main solenoid valve 43 and the second main expansion valve 44 are controlled to throttle the R508B refrigerant before it passes through the plate heat exchanger 13 for ultra-low temperature refrigeration, so that it flows back to the inlet of the main compressor 2 to increase the suction temperature of the main compressor 2.

[0069] The third main branch b3 serves as a cooling branch. The third main branch b3 is sequentially equipped with a third main solenoid valve 45, a third main expansion valve 46, and a first main evaporator 47. The third main expansion valve 46 is an internally balanced thermostatic expansion valve. By selecting one branch and using the third main solenoid valve 45, the refrigerant expands through the third main expansion valve 46 and then evaporates and absorbs heat through the first main evaporator 47, thereby achieving the cooling function inside the temperature chamber.

[0070] Furthermore, an auxiliary main branch b31 is connected in parallel to the third main branch b3. One end of the auxiliary main branch b31 is connected to the main outlet B1, and the other end of the auxiliary main branch b31 is connected between the third main expansion valve 46 and the first main evaporator 47. A fifth main solenoid valve 53 and a second main capillary tube 54 are sequentially arranged on the auxiliary main branch b31. When the third main branch b3 cannot meet the cooling demand, the refrigerant in the auxiliary branch b31 enters the second main capillary tube 54 through the fifth main solenoid valve 53 for throttling, and then merges with the refrigerant in the third main branch b3 before entering the first main evaporator 47 together for evaporation and heat absorption, thereby increasing the refrigerant flow rate and meeting the suddenly increased cooling demand.

[0071] The fourth main branch b4 serves as a return gas temperature boosting branch. The fourth main branch b4 is sequentially equipped with a fourth main solenoid valve 48 and a fourth main expansion valve 49. The fourth main branch b4 exchanges heat with the first auxiliary condenser 11 after the fourth main expansion valve 49. By controlling the fourth main solenoid valve 48, the refrigerant is throttled from the fourth main expansion valve 49 and then enters the first auxiliary condenser 11 for heat exchange, resulting in a temperature increase. The refrigerant with the increased temperature returns to the main compressor 2, increasing the suction side pressure and subcooling of the main compressor 2, and preventing liquid slugging damage to the main compressor 2.

[0072] The fifth main branch b5 serves as a pressure relief bypass. The fifth main branch b5 is sequentially equipped with a fifth main expansion valve 50, an expansion tank 51, and a first main capillary tube 52. When the system pressure of the main refrigeration system A is higher than a certain value (e.g., 18.6 kg), the pressure relief is quickly initiated. The refrigerant passes through the fifth expansion valve 50 and enters the expansion tank 51 for storage. After pressure relief, the refrigerant is throttled through the first main capillary tube 52 and returns to the auxiliary circuit A2, eventually returning to the main compressor 2 for recirculation, preventing the main compressor 2 from being damaged due to excessive system pressure.

[0073] Furthermore, to facilitate the maintenance and disassembly of the expansion tank 51, manual valves are installed in the fifth main branch b5, upstream and downstream of the expansion tank 51, respectively, to prevent refrigerant leakage during disassembly and maintenance of the expansion tank 51, while ensuring the normal operation of the main refrigeration system B.

[0074] In this application, the main outgoing path B1 is sequentially provided with a first main condenser 55, a first main oil separator 56, a main valve 57 and a first main filter 58. The first main oil separator 56 is located upstream of the plate heat exchanger 13 and the first main filter 58 is located downstream of the plate heat exchanger 13.

[0075] Specifically, the cooling water of the first main condenser 55 is connected to a branch line, the other end of which is connected to the inlet of the oil separator 56. A pressure regulating valve and a throttling pipe are sequentially installed on this branch line. The oil return port of the first main oil separator 56 is connected to the lubricating oil port of the main compressor 2 through the oil return pipeline. The exhaust of the main refrigeration system B preferentially passes through the first main condenser 55. The first main condenser 55, in conjunction with the pressure regulating valve, automatically adjusts the cooling water flow of the first main condenser 55 according to the exhaust pressure of the refrigerant, making full use of the cooling water supply. Then, the lubricating oil of the main compressor 2 contained in the refrigerant is quickly separated by the oil separator 56 and returned to the compressor oil chamber. A high-density oil filter can also be added to the oil return pipeline to filter the lubricating oil and prevent aged oil containing foreign matter from affecting the compressor life.

[0076] The position setting of the main valve 57 indicates that the opening and closing of the main valve 57 does not affect the working status of the second main branch b2 and the fifth main branch b5. That is, the second main branch b2 and the fifth main branch b5 can work independently. This also means that the hot gas bypass used to increase the return gas temperature of the main compressor 2 and the pressure relief bypass used to control the pressure of the refrigeration system are always working. These two bypasses always maintain the safety of the working environment of the main compressor 2.

[0077] As a preferred embodiment of this application, pressure gauges, shock absorbers, needle valves, and other components may also be installed at the inlet and outlet of the auxiliary compressor 1 and the main compressor 2 to monitor the operating status of the compressors.

[0078] It is obvious that, except for the manual valve, all valves and other electrical components in this application are controlled by PLC intelligent control. The working principle and connection method of each electrical component will not be described in detail here.

[0079] In summary, this application utilizes the interconnection and superposition of two refrigeration systems, and achieves efficient refrigeration by arranging the pipelines sequentially and using valves in coordination, thereby saving coolant flow and forming a highly efficient, energy-saving and stable refrigeration system.

[0080] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. An interconnected cascade cooling system, characterized in that: It includes a secondary refrigeration system A and a main refrigeration system B. The secondary refrigeration system A uses R404A refrigerant, and the main refrigeration system B uses R508B refrigerant. The main refrigeration system B can achieve ultra-low temperature refrigeration effect with a single start-up. The auxiliary refrigeration system A includes an auxiliary compressor (1), the output end of which is configured as an auxiliary path (A1). A first auxiliary condenser (11) and a second auxiliary condenser (12) are sequentially arranged on the auxiliary path (A1). The auxiliary path (A1) is divided into five auxiliary branches, which converge into a auxiliary loop (A2). The end of the auxiliary loop (A2) is connected to the input end of the auxiliary compressor (10). A plate heat exchanger (13) is arranged on one of the auxiliary branches. The main refrigeration system B includes a main compressor (2), the output end of the main compressor (2) is configured as a main outlet (B1), the main outlet (B1) exchanges heat with a plate heat exchanger (13), the main outlet (B1) is divided into five main branches, the five main branches converge into a main loop (B2), the end of the main loop (B2) is connected to the input end of the main compressor (2), one of the main branches exchanges heat with a first auxiliary condenser (11) to improve the suction pressure and subcooling of the main compressor (2); The five sub-branches include: The first sub-branch (a1) is used to cool the body temperature of the sub-compressor (1); The second sub-branch (a2) is used to increase the suction temperature of the sub-compressor (1). The second sub-branch (a2) is connected between the first sub-condenser (11) and the second sub-condenser (12). The third sub-branch (a3) ​​is used to regulate the temperature inside the incubator; The fourth sub-branch (a4) is used to regulate the humidity inside the incubator; The fifth sub-branch (a5) is used to increase the subcooling of the refrigerant in the main path (B1); The plate heat exchanger (13) is installed on the fifth sub-branch (a5); The five main branches include: The first main branch (b1) is used to cool the body temperature of the main compressor (2). The first main branch (b1) is connected to the main outlet (B1) after heat exchange with the main outlet (B1). The second main branch (b2) is used to increase the suction temperature of the main compressor (2). The second main branch (b2) is connected to the main outgoing line (B1) before the heat exchange of the main outgoing line (B1). The third main branch (b3) is used to regulate the temperature inside the chamber. The third main branch (b3) is connected to the main outgoing line (B1) after heat exchange. The fourth main branch (b4) is used to increase the return gas temperature of the main compressor (2). The fourth main branch (b4) is connected to the main outgoing line (B1) after heat exchange. The fifth main branch (b5) is used to control the pressure of the main refrigeration system. The fifth main branch (b5) is connected to the main outgoing line (B1) before the heat exchange of the main outgoing line (B1). The fourth main branch (b4) exchanges heat with the first auxiliary condenser (11).

2. The interconnected cascade cooling system according to claim 1, characterized in that: The first sub-branch (a1) is sequentially provided with a first sub-solenoid valve (14) and a first sub-expansion valve (15). The second sub-branch (a2) is sequentially provided with a second sub-solenoid valve (16) and a second sub-expansion valve (17). The third sub-branch (a3) ​​is sequentially provided with a third sub-solenoid valve (18), a third sub-expansion valve (19) and a first sub-evaporator (20). The fourth sub-branch (a4) is sequentially provided with a fourth sub-solenoid valve (21), a first sub-capillary tube (22), a second sub-evaporator (23) and a fourth sub-expansion valve (24). The fifth branch (a5) is sequentially provided with a fifth solenoid valve (25) and a fifth expansion valve (26), and the plate heat exchanger (13) is located downstream of the fifth expansion valve (26).

3. The interconnected cascade cooling system according to claim 2, characterized in that: The third sub-branch (a3) ​​and the fourth sub-branch (a4) converge into a sixth branch (a6) before converging into the sub-circuit (A2), and the sixth branch (a6) is equipped with a return gas pressure regulating valve (27).

4. The interconnected cascade cooling system according to claim 3, characterized in that: The third sub-branch (a3) ​​is provided with an auxiliary sub-branch (a31) in parallel. One end of the auxiliary sub-branch (a31) is connected to the auxiliary outlet (A1), and the other end of the auxiliary sub-branch (a31) is connected between the third sub-expansion valve (19) and the first sub-evaporator (20). The auxiliary sub-branch (a31) is sequentially provided with a sixth solenoid valve (28) and a second capillary tube (29).

5. The interconnected cascade cooling system according to any one of claims 2-4, characterized in that: A secondary filter (30) and a secondary main valve (31) are sequentially arranged on the secondary outgoing line (A1), and the secondary filter (30) is located downstream of the second secondary condenser (12).

6. The interconnected cascade cooling system according to claim 1, characterized in that: The first main branch (b1) is sequentially provided with a first main solenoid valve (41) and a first main expansion valve (42). The second main branch (b2) is sequentially provided with a second main solenoid valve (43) and a second main expansion valve (44); The third main branch (b3) is sequentially provided with a third main solenoid valve (45), a third main expansion valve (46), and a first main evaporator (47). The fourth main branch (b4) is sequentially provided with a fourth main solenoid valve (48) and a fourth main expansion valve (49). The fourth main branch (b4) exchanges heat with the first auxiliary condenser (11) after the fourth main expansion valve (49). The fifth main branch (b5) is sequentially provided with a fifth main expansion valve (50), an expansion tank (51), and a first main capillary tube (52).

7. The interconnected cascade cooling system according to claim 6, characterized in that: The third main branch (b3) is connected in parallel with an auxiliary main branch (b31). One end of the auxiliary main branch (b31) is connected to the main path (B1), and the other end of the auxiliary main branch (b31) is connected between the third main expansion valve (46) and the first main evaporator (47). The auxiliary main branch (b31) is sequentially equipped with a fifth main solenoid valve (53) and a second main capillary tube (54).

8. The interconnected cascade cooling system according to claim 6 or 7, characterized in that: The main outlet (B1) is sequentially provided with a first main condenser (55), a first main oil separator (56), a main valve (57) and a first main filter (58). The first main oil separator (56) is located upstream of the plate heat exchanger (13), and the first main filter (58) is located downstream of the plate heat exchanger (13).

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