Dual-purpose cooler system of cryogenic refrigerator and control method

Abstract

The invention discloses a dual-purpose cooler system of a cryogenic refrigerator and a control method, relates to the field of cryogenic refrigerator defrosting, and aims to solve the problems of poor defrosting effect and poor precision in the control method in the prior art. According to the technical scheme, an auxiliary cooler is introduced, a three-way switching valve is used for pipeline switching, and when a main cooler needs to be defrosted, the auxiliary cooler is connected with the three-way switching valve, and the auxiliary cooler is connected with the three-way switching valve; the three-way switching valve is used for switching pipeline connection, the main cooler is used for condensing high-temperature gas generated by compression, meanwhile, the main cooler is defrosted, and the auxiliary cooler supplies cold. According to the control method, the external environment temperature or the air outlet temperature of the air cooler serves as the cold source switching standard. And after defrosting of the main cooler is finished, evaporation operation continues to be carried out, and meanwhile, high-temperature gas generated by the aftercooler is used for defrosting and drying the auxiliary cooler. According to the air conditioner, the defrosting purpose can be achieved under the condition that a heating device is not introduced, meanwhile, the energy-saving effect is achieved, cold source switching is more accurate, and the stability of the temperature in the cold using space can be better maintained.

Description

Technical Field

[0001] The present invention relates to the technical field of defrosting of cryogenic refrigerators, and in particular to a dual-purpose refrigerator system and a control method for a cryogenic refrigerator. Background Art

[0002] Currently, cryogenic refrigerators are primarily used in the medical industry to preserve living cells, embryos, and blood. Existing cryogenic refrigerators come in two types: direct cooling and air cooling. Direct cooling has disadvantages including poor temperature uniformity in the cooling compartment, easy frost formation, and the inability to clean the compartment during operation. Air cooling also has disadvantages including difficulty defrosting the refrigerator, poor cooling performance if defrosting is delayed, increased room temperature during defrosting, high power consumption, and the inability to maintain continuous cooling during defrosting.

[0003] Existing air-cooled cryogenic refrigerators use electric heating as the main defrosting method. Taking Xinfei's own reverse Brayton refrigeration cycle system cryogenic refrigerator as an example, the temperature of the cryogenic chamber can reach -120℃. The frost layer of the refrigerator is thick during the refrigeration process and a dense ice layer will form on the refrigerator. Electric heating is used for defrosting, but there is a problem of long defrosting time. When the electric heating is turned on, the temperature can reach more than 300℃, and the surface temperature of the frost layer on the refrigerator is as high as 80-90℃, which causes a large temperature rise in the refrigerator room and poor storage effect of samples. In addition, water vapor is easily formed when the refrigerator is defrosted. When the defrost is completed and refrigeration begins, the water vapor is easily condensed into a dense ice layer attached to the surface of the refrigerator.

[0004] The existing dual-evaporator defrost control system uses the two evaporators as backup for each other. Although the control process takes into account the residual cooling capacity of the evaporator in use and the pre-cooling process of the backup evaporator to be activated when switching the cold source, and sets the delayed opening and delayed closing of the cooling fan, the delay of the existing control system is based on time. Since there is no unique correspondence between time and evaporator temperature, although using time as the delay basis is simple, its accuracy in energy saving and maintaining a constant temperature in the cooling room is poor. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the existing defects and provide a dual-purpose refrigerator system and control method for a deep-freeze refrigerator, which can effectively solve the problems in the background technology.

[0006] In order to achieve the above-mentioned object, the present invention first discloses a dual-purpose refrigerator system for a deep-freeze refrigerator, which adopts a technical solution comprising a reverse Brayton compression-expansion integrated machine, wherein the compression end of the reverse Brayton compression-expansion integrated machine is connected to an aftercooler, the aftercooler is connected to a first flow channel of a heat exchanger and then to the turbine end of the reverse Brayton compression-expansion integrated machine, the turbine end is connected to the refrigerator and then to the second flow channel of the heat exchanger, the second flow channel is connected to the compression end of the reverse Brayton compression-expansion integrated machine, the refrigerator is provided with a cooling fan and a cooling air duct, the cooling fan is connected to the cooling air duct and corresponds to the position of the refrigerator, the cooling air duct is connected to the cooling compartment, and the The cooler includes a main cooler and an auxiliary cooler. The front end of the main cooler is connected to the compression end of the reverse Brayton compression and expansion machine through a first branch, and the rear end of the main cooler is connected to the rear end of the aftercooler through a second branch. The turbine end of the reverse Brayton compression and expansion machine is connected to the auxiliary cooler through a third branch, and the rear end of the auxiliary cooler is connected to the second flow channel inlet of the heat exchanger; the first branch, the second branch and the third branch are all connected to a three-way switching valve; the inlet and outlet of the aftercooler, the main cooler and the auxiliary cooler are all equipped with control valves; and it also includes a heating air duct, and the heating air duct corresponds to the position of the aftercooler and the auxiliary cooler. When the main cooler needs to be defrosted, the connection state of the pipeline can be switched through the three-way switching valve to change the flow direction of the coolant. The main cooler that needs to be defrosted is used to condense the high-temperature gas at the compression end, and the auxiliary cooler is connected to the circulation system to supply cooling to the cooling room through the auxiliary cooler. In this device, the main cooler and the auxiliary cooler are no longer backup for each other.

[0007] As a preferred technical solution of the present invention, the compression end working fluid outlet of the reverse Brayton compression and expansion machine is connected to the first port of the third three-way switching valve, the second port thereof is connected to the inlet of the aftercooler, and the third port is connected to the front end of the main cooler. The pipeline from the third port to the front end of the main cooler is the first branch. When the main cooler needs to be defrosted, by switching the third three-way valve, the connection between the working fluid outlet of the reverse Brayton compression and expansion machine and the inlet of the aftercooler can be switched to the connection between the working fluid outlet of the reverse Brayton compression and expansion machine and the inlet of the main cooler.

[0008] As a preferred technical solution of the present invention, the working fluid outlet at the turbine end of the reverse Brayton compressor is connected to the first port of a second three-way switching valve. The second port of the second three-way switching valve is connected to the inlet of the main chiller and the first branch. The third port of the second three-way switching valve is connected to the inlet of the auxiliary chiller. The pipeline connected to the third port is the third branch. By switching the connecting pipeline of the second three-way switching valve, it is possible to switch between cooling supply by the main chiller and cooling supply by the auxiliary chiller.

[0009] As a preferred technical solution of the present invention, the first flow channel and the second flow channel of the heat exchanger have opposite flow directions, and the outlet of the first flow channel is connected to the turbine end working fluid inlet of the reverse Brayton compression and expansion machine; the outlet of the second flow channel is connected to the compression end working fluid inlet of the reverse Brayton compression and expansion machine, which can exchange heat between the fluid to be compressed and the fluid to be turbined, thereby achieving the effect of heat energy recovery.

[0010] As a preferred technical solution of the present invention, the outlet rear end of the main cooler is connected to the first port of a first three-way switching valve, the second port of the first three-way switching valve is connected to the inlet of the second flow channel of the heat exchanger, and the third port is connected to the inlet of the first flow channel of the heat exchanger. The pipeline connected to the third port constitutes the second branch. When the main cooler is providing cooling, the first three-way switching valve sends the refrigerant after cooling into the second flow channel of the heat exchanger for initial heating before entering the compressor end working medium inlet. When the main cooler is defrosting, the first three-way switching valve sends the condensed refrigerant into the heat exchanger for further cooling before entering the turbine end working medium inlet.

[0011] As a preferred technical solution of the present invention, the cooling air duct includes a first cooling air duct and a second cooling air duct, wherein the inlet of the first cooling air duct is equipped with a main cooling air blower and corresponds to the position of the main cooling device, and the first cooling air duct is equipped with a main cooling air valve; the inlet of the second cooling air duct is equipped with an auxiliary cooling air blower and corresponds to the position of the auxiliary cooling device, and the second cooling air duct is equipped with an auxiliary cooling air valve, and the second cooling air duct is also connected to a hot air outlet pipeline via a three-way pipe fitting, and the auxiliary cooling air valve controls the opening and closing of the second cooling air duct and the hot air outlet pipeline; the first cooling air duct and the second cooling air duct are connected to the cooling room after being combined. The connection state between the cooling air duct and the cooling room can be changed by controlling the opening and closing state of the cooling air valve.

[0012] As a preferred technical solution of the present invention, a heating fan is installed at the inlet of the heating air duct. It can blow the heat generated by the aftercooler into the heating air duct and then discharge it to the outside. During this process, the hot air in the heating air duct defrosts and dries the auxiliary cooler, preventing the water vapor on the auxiliary cooler surface from condensing into ice again after defrosting.

[0013] The present invention also discloses a control method for a dual-purpose refrigerator system based on the above-mentioned deep freezer, the technical solution adopted is to include the following steps: Step 1, determining the current operating status of the deep freezer, determining that the main refrigerator is used as the refrigerator, and the auxiliary refrigerator is on standby, and then proceeding to step 2; Step 2: Check whether the main cooler has reached the defrost condition. If not, continue to check. If it has reached the defrost condition, proceed to step 3. Step 3: The main cooler starts to defrost with hot air, the heating fan stops, and the main cooling fan continues to run to cool, and its outlet air temperature T1 is monitored; the auxiliary cooler starts pre-cooling and monitors the external ambient temperature T2 of the auxiliary cooler; the heating air valve closes, the auxiliary cooling air valve closes the hot air outlet pipe, and the second cooling air duct is opened; In step 4, the outlet air temperature T1 of the main cooling fan corresponding to the main cooler and the external ambient temperature T2 of the auxiliary cooler are used as the judgment basis for the delayed switching of the cold source. When the set conditions are met, the cold source is switched, otherwise, return to step 3; the delay basis for the cold source switching is set to temperature, which can be accurately controlled based on the difference between the outlet air temperature or the external ambient temperature of the cooler and the set temperature or actual temperature difference of the cooling space. Compared with time-based control, temperature control is more in line with the core reason for delaying the switching of the cold source and is more conducive to ensuring the stability of the temperature of the cooling space; Step 5: Monitor whether the external ambient temperature T6 of the main cooler reaches the defrost stop temperature T5. If not, continue to defrost the main cooler with hot gas. If it reaches, proceed to step 6. Step 6: The main cooler stops defrosting and starts pre-cooling, and monitors its external ambient temperature T6. The external ambient temperature T6 of the main cooler is used as the judgment basis for delaying the switching of the cold source until the set condition is reached, and the main cooling fan and the main cooling air valve are turned on. When the main cooler starts pre-cooling, the heating fan is turned on, the auxiliary cooling fan is stopped, and the auxiliary cooling air valve opens the hot air outlet pipe. Step 7: After a defrost cycle of the main cooler is completed, the auxiliary cooler begins to defrost and dry.

[0014] As a preferred technical solution of the present invention, in step 4, when the outlet air temperature T1 of the main cooling fan corresponding to the main cooler is ≥ the set temperature T3+3K of the cooling room, or the outlet air temperature T1 of the main cooling fan corresponding to the main cooler is ≥ the room temperature T4 of the cooling room, the main cooling fan is stopped and the main cooling air valve is closed; when the external ambient temperature T2 of the auxiliary cooler is ≤ the set temperature T3+3K of the cooling room, or the external ambient temperature T2 of the auxiliary cooler is ≤ the room temperature T4 of the cooling room, the auxiliary cooling fan is turned on.

[0015] As a preferred technical solution of the present invention, in step 6, when the external ambient temperature T6 of the main cooler is ≤ the set temperature T3+3K of the cooling room, or the external ambient temperature T6 of the main cooler is ≤ the room temperature T4 of the cooling room, the main cooling fan and the main cooling air valve are turned on.

[0016] Compared with the prior art, the present invention has the following advantages: by controlling the three-way switching valve to switch the connection of the pipeline, the present invention can directly use the main cooler as an aftercooler when it is needed to defrost the main cooler. While condensing the high-temperature airflow at the compression end, the main cooler is defrosted while the auxiliary cooler is used to provide cooling. This system can defrost the main cooler without introducing external heat sources such as electric heating. After the auxiliary cooler finishes providing cooling, the auxiliary cooler is defrosted and dried by dissipating heat from the aftercooler, achieving the purpose of defrosting while achieving energy saving, and preventing the water vapor on the outer wall of the auxiliary cooler from condensing into ice again. In the control method of this system, the outlet air temperature of the main cooler is used as the delay standard for the delayed switching of the cold source. This is more accurate than the time delay and is more conducive to maintaining the temperature stability in the cooling space. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the system of the present invention; Figure 2 This is a flow chart of the control method of the present invention.

[0018] In the figure: 1. Reverse Brayton compression and expansion unit; 2. Aftercooler; 3. Heat exchanger; 4. Main cooler; 5. Auxiliary cooler; 6. Cooling room; 7. First three-way switching valve; 8. Second three-way switching valve; 9. Third three-way switching valve; 10. Main cooling air valve; 11. Auxiliary cooling air valve; 12. Heating air valve; 13. Heating fan; 14. Main cooling air fan; 15. Auxiliary cooling air fan; 16. First cooling air duct; 17. Second cooling air duct; 18. Heating air duct; 19. Hot air outlet pipe. DETAILED DESCRIPTION

[0019] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention. Example 1

[0020] like Figure 1As shown, the present invention first discloses a dual-use refrigerator system for a cryogenic refrigerator. The technical solution adopted is as follows: it includes a reverse Brayton compressor / expander 1, the compression-end working medium outlet of the reverse Brayton compressor / expander 1 is connected to the first port of a third three-way switching valve 9, the second port of the third three-way switching valve 9 is connected to the inlet of an aftercooler 2, the outlet of the aftercooler 2 is connected to the first flow channel inlet of a heat exchanger 3, the first flow channel outlet is connected to the turbine-end working medium inlet of the reverse Brayton compressor / expander 1, the turbine-end working medium outlet is connected to the first port of a second three-way switching valve 8, the second port of the second three-way switching valve 8 is connected to the inlet of a main refrigerator 4, the outlet of the main refrigerator 4 is connected to the first port of a first three-way switching valve 7, the second port of the main refrigerator 4 is connected to the second flow channel inlet of the heat exchanger 3, and the second flow channel outlet is connected to the compression-end working medium inlet of the reverse Brayton compressor / expander 1. The pipeline connection order is the flow path of the refrigerant when the main refrigerator 4 is used as a refrigerator. In order to deliver the cold energy generated by the main cooler 4 into the cooling room 6, a first cooling air duct 16 is also provided. The first cooling air duct 16 is connected to the cooling room 6, and a main cooling air fan 14 is provided at its entrance. A main cooling air valve 10 is provided in the first cooling air duct 16 to control the opening and closing of the first cooling air duct 16.

[0021] In order to maintain continuous cooling for the cooling compartment 6 when the main cooler 4 needs to be defrosted, an auxiliary cooler 5 is also introduced, and the third port of the third three-way switching valve 9 is connected between the second port of the second three-way switching valve 8 and the inlet of the main cooler 4 through the first branch. The high-temperature gas at the outlet of the compression end of the reverse Brayton compression and expansion machine 1 can be directly passed into the main cooler 4 through the switching of the third three-way switching valve 9. While the high-temperature gas is condensed by the main cooler 4, the main cooler 4 is defrosted by the high-temperature gas. In order to pass the condensed refrigerant into the heat exchanger 3, the third port of the first three-way switching valve 7 is connected to the first flow channel of the heat exchanger 3 through the second branch. At the inlet, since the main cooler 4 is in the defrost stage, the third port of the second three-way switching valve 8 is connected to the inlet of the auxiliary cooler 5 through the third branch, and the refrigerant is evaporated through the auxiliary cooler 5. The outlet of the auxiliary cooler 5 is connected to the inlet of the second flow channel of the heat exchanger 3. In order to deliver the cold energy generated by the auxiliary cooler 5 into the cooling room 6, a second cooling air duct 17 is also provided. The inlet of the second cooling air duct 17 corresponds to the position of the auxiliary cooler 5, and an auxiliary cooling fan 15 is installed at the inlet. After the second cooling air duct 17 is connected with the first cooling air duct 16, they are both passed into the cooling room 6. The connection between the second cooling air duct 17 and the first cooling air duct 16 is located at the rear end of the main cooling air valve 10.

[0022] In order to be able to defrost the auxiliary cooler 5 when the low-temperature fluid is evaporated in the main cooler 4, a heating air duct 18 is also provided. The inlet of the heating air duct 18 corresponds to the position of the aftercooler 2, and the outlet corresponds to the position of the auxiliary cooler 5. A heating fan 13 is provided at the inlet, and a heating air valve 12 is installed in the heating air duct 18. In order to be able to discharge the hot air blown to the auxiliary cooler 5, a hot air outlet pipe 19 is also connected to the auxiliary cooling air valve 11 of the second cooling air duct 17. The auxiliary cooling air valve 11 can control the opening and closing of the second cooling air duct 17 and the opening and closing of the hot air outlet pipe 19.

[0023] like Figure 2 As shown, the present invention also discloses a control method for the dual-use cooler system, which adopts a technical solution comprising the following steps: Step 1, the deep freezer starts running, the main cooling air valve 10 in the first cooling air duct 16 and the heating air valve 12 in the heating air duct 18 are opened, the auxiliary cooling air valve 11 in the second cooling air duct 17 opens the hot air outlet pipe 19, the second cooling air duct 17 is closed, and the main cooling fan 14 and the heating fan 13 are turned on; the third three-way switching valve 9 connects the compression end working medium outlet of the reverse Brayton compression and expansion machine 1 with the inlet of the aftercooler 2, the second three-way switching valve 8 connects the turbine end working medium outlet of the reverse Brayton compression and expansion machine 1 with the inlet of the main cooler 4, and the first three-way switching valve 7 connects the outlet of the main cooler 4 with the second flow channel inlet of the heat exchanger 3; at this time, the compression end of the reverse Brayton compression and expansion machine 1 compresses the refrigerant and sends it to the aftercooler 2 from the working medium outlet for cooling, and the cooled fluid enters the heat exchanger 3 from the first flow channel inlet The first flow channel enters the turbine end working medium inlet of the reverse Brayton compression and expansion machine 1 after passing through the first flow channel, and enters the main cooler 4 after being evaporating in the main cooler 4. The low-temperature gas generated enters the second flow channel of the heat exchanger 3, exchanges heat with the fluid in the first flow channel in countercurrent flow, and then enters the compression end working medium inlet of the reverse Brayton compression and expansion machine 1 to form a cycle; the main cooling fan 14 sends the cooling energy generated by the main cooler 4 into the cooling room 6 through the first cooling air duct 16. During this process, a dense ice layer gradually adheres to the outer surface of the main cooler 4; in order to quickly discharge the heat generated by the aftercooler 2, the heating fan 13 blows the heat generated by the aftercooler 2 to the auxiliary cooler 5 through the heating air duct 18 to dry the surface of the auxiliary cooler 5, and then enters the second cooling air duct 17 and is transferred to the hot air outlet pipe 19 at the auxiliary cooling air valve 11 for discharge; Step 2: monitor the frost condition of the main cooler 4, and proceed to step 3 after it reaches the defrosting condition; Step 3, control the three-way switching valve to change the pipeline connection state, the third three-way switching valve 9 connects the compression end working medium outlet of the reverse Brayton compression and expansion machine 1 with the first branch, the first three-way switching valve 7 connects the outlet of the main cooler 4 with the second branch, and the second three-way switching valve 8 connects the turbine end working medium outlet of the reverse Brayton compression and expansion machine 1 with the third branch; at this time, the flow path of the refrigerant is from the compression end working medium outlet of the reverse Brayton compression and expansion machine 1 through the first branch into the main cooler 4. Since the main cooler 4 has a dense ice layer attached to the surface, the temperature of the main cooler 4 is relatively low. While the high-temperature gas generated by the reverse Brayton compression and expansion machine 1 is condensed by the main cooler 4, the main cooler 4 begins to defrost. After the refrigerant passes through the main cooler 4 and is condensed, it enters the first flow channel of the heat exchanger 3 through the second branch, and then enters the reverse Brayton compression and expansion machine 1 through the first flow channel. The hot air is blown away by the heat from the exhaust pipe 11 and then blown away by the exhaust pipe 12. The hot air is then blown away by the exhaust pipe 13 and then blown away by the exhaust pipe 14. Step 4: Detect and determine whether the outlet air temperature T1 of the main cooling fan 14 rises to the set temperature T3+3K of the cooling room 6 or to the room temperature T4 of the cooling room 6. If it has not risen to that level, the main cooling fan 14 maintains its current state. If it has risen to the set temperature T3+3K of the cooling room 6 or to the room temperature T4 of the cooling room 6, proceed to step 5. At the same time, determine whether the external ambient temperature T2 of the auxiliary cooling device 5 drops to the set temperature T3+3K of the cooling room 6 or to the room temperature T4 of the cooling room 6. If it has not dropped to that level, the auxiliary cooling fan 15 maintains its current state. If it has reached that level, turn on the auxiliary cooling fan 15 and proceed to step 7. Step 5: The main cooler 4 continues to defrost with hot gas and continuously monitors the external ambient temperature T6 of the main cooler 4. The main cooling fan 14 is shut down and the main cooling air valve 10 is closed. Step 6, determining whether the external ambient temperature T6 of the main cooler 4 has risen to the defrost stop temperature T5, if not, proceed to step 5, if so, proceed to step 7; Step 7: Switch the first three-way switching valve 7, the second three-way switching valve 8, and the third three-way switching valve 9 back to the state of step 1. The main cooler 4 stops defrosting and performs pre-cooling. The external ambient temperature T6 of the main cooler 4 is monitored. At this time, the temperature of the main cooler 4 begins to drop, but still does not meet the cooling requirement. Therefore, the main cooling fan 14 is delayed to start; the aftercooler 2 starts to run, the heating fan 13 is turned on, and the auxiliary cooling fan 15 is stopped at the same time. The auxiliary cooling air valve 11 closes the second cooling air duct 17 and opens the hot air outlet pipe 19. The auxiliary cooler 5 starts to defrost and dry. Step 8, determine whether the external ambient temperature T6 of the main cooler 4 drops to the set temperature T3+3K of the cooling room 6, or the room temperature T4 of the cooling room 6. If not, maintain the current state. If it has been reached, turn on the main cooling fan 14 and the main cooling air valve 10; complete a defrost cycle of the main cooler 4.

[0024] The circuits and mechanical connections involved in the present invention are conventional means used by those skilled in the art, and technical inspiration can be obtained through limited experiments, and they are common knowledge.

[0025] Components not described in detail herein are prior art.

[0026] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A dual-use refrigerator system for a deep freeze refrigerator, comprising a reverse Brayton compression and expansion integrated machine (1), the compression end of the reverse Brayton compression and expansion integrated machine (1) is connected to an aftercooler (2), the aftercooler (2) is connected to the first flow channel of a heat exchanger (3) and then to the turbine end of the reverse Brayton compression and expansion integrated machine (1), the turbine end is connected to the aftercooler and then to the second flow channel of the heat exchanger (3), the second flow channel is connected to the compression end of the reverse Brayton compression and expansion integrated machine (1), the aftercooler is provided with a cooling fan and a cooling air duct, the cooling fan is connected to the cooling air duct and corresponds to the position of the aftercooler, and the cooling air duct is connected to the cooling compartment (6), characterized in that: The cooler includes a main cooler (4) and an auxiliary cooler (5), the compression end of the reverse Brayton compression and expansion integrated machine (1) is connected to the front end of the main cooler (4) through a first branch, the rear end of the main cooler (4) is connected to the rear end of the aftercooler (2) through a second branch, the turbine end of the reverse Brayton compression and expansion integrated machine (1) is connected to the auxiliary cooler (5) through a third branch, and the rear end of the auxiliary cooler (5) is connected to the second flow channel inlet of the heat exchanger (3); the first branch, the second branch and the third branch are all connected to a three-way switching valve; the inlet and outlet of the aftercooler (2), the main cooler (4) and the auxiliary cooler (5) are all equipped with control valves; and the heat supply air duct (18) is also included, and the heat supply air duct (18) corresponds to the position of the aftercooler (2) and the auxiliary cooler (5).

2. The dual-purpose refrigerator system of claim 1, wherein: The working fluid outlet of the compression end of the reverse Brayton compression and expansion machine (1) is connected to the first port of the third three-way switching valve (9), the second port thereof is connected to the inlet of the aftercooler (2), and the third port is connected to the front end of the main cooler (4), and the pipeline connected to the third port is the first branch.

3. The dual-purpose refrigerator system of claim 2, wherein: The working fluid outlet of the turbine end of the reverse Brayton compression and expansion machine (1) is connected to the first port of the second three-way switching valve (8), the second port of the second three-way switching valve (8) is connected to the inlet of the main cooler (4) and the first branch, the third port of the second three-way switching valve (8) is connected to the inlet of the auxiliary cooler (5), and the pipeline connected to the third port is the third branch.

4. The dual-purpose refrigerator system of claim 3, wherein: The first flow channel and the second flow channel of the heat exchanger (3) flow in opposite directions. The outlet of the first flow channel is connected to the turbine-end working medium inlet of the reverse Brayton compression and expansion machine (1); and the outlet of the second flow channel is connected to the compression-end working medium inlet of the reverse Brayton compression and expansion machine (1).

5. The dual-purpose refrigerator system of claim 4, wherein: The outlet rear end of the main cooler (4) is connected to the first port of the first three-way switching valve (7), the second port of the first three-way switching valve (7) is connected to the second flow channel inlet of the heat exchanger (3), and the third port is connected to the first flow channel inlet of the heat exchanger (3), and the pipeline connected to the third port is the second branch.

6. The dual-purpose refrigerator system of claim 5, wherein: The cooling air duct includes a first cooling air duct (16) and a second cooling air duct (17). The inlet of the first cooling air duct (16) is equipped with a main cooling air blower (14), which corresponds to the position of the main cold storage device (4). The first cooling air duct (16) is equipped with a main cooling air valve (10). The inlet of the second cooling air duct (17) is equipped with an auxiliary cooling air blower (15), which corresponds to the position of the auxiliary cold storage device (5). The second cooling air duct (17) is equipped with an auxiliary cooling air valve (11). The second cooling air duct (17) is also connected to a hot air outlet pipe (19) through a three-way pipe fitting. The auxiliary cooling air valve (11) controls the opening and closing of the second cooling air duct (17) and the hot air outlet pipe (19). The first cooling air duct (16) and the second cooling air duct (17) are connected to the cold storage room (6) after being combined.

7. The dual-purpose refrigerator system of claim 6, wherein: A heating fan (13) is installed at the inlet of the heating air duct (18).

8. A control method for a dual-purpose refrigerator system of a cryogenic refrigerator according to claim 7, characterized in that: The following steps are involved: Step 1, determining the current operating state of the deep freezer, determining that the main refrigerator (4) is used as the refrigerator and the auxiliary refrigerator (5) is on standby, and then proceeding to step 2; Step 2, detecting whether the main cooler (4) has reached the defrosting condition. If the defrosting condition has not been reached, maintaining the current state and continuing the detection. If the defrosting condition has been reached, proceeding to step 3; Step 3: The main cooler (4) starts to defrost with hot air, the heating fan (13) stops, the main cooling fan (14) continues to operate to cool, and monitors its outlet air temperature T1; the auxiliary cooler (5) starts pre-cooling and monitors the external ambient temperature T2 of the auxiliary cooler (5); the heating air valve (12) is closed, the auxiliary cooling air valve (11) closes the hot air outlet pipe (19), and the second cooling air duct (17) is opened; Step 4, using the air outlet temperature T1 of the main cooling fan (14) corresponding to the main cooler (4) and the external ambient temperature T2 of the auxiliary cooler (5) as the judgment basis for delayed switching of the cooling source, when the set conditions are met, switching the cooling source, otherwise returning to step 3; Step 5, monitoring whether the external ambient temperature T6 of the main cooler (4) reaches the defrost stop temperature T5, if not, continuing the hot gas defrosting of the main cooler (4), if it reaches, proceeding to step 6; Step 6: The main cooler (4) stops defrosting and starts pre-cooling, and monitors its external ambient temperature T6. The external ambient temperature T6 of the main cooler (4) is used as a judgment basis for delayed switching of the cold source until the set condition is reached, and the main cooling fan (14) and the main cooling air valve (10) are turned on. When the main cooler (4) starts pre-cooling, the heating fan (13) is turned on, the auxiliary cooling fan (15) is stopped, and the auxiliary cooling air valve (11) opens the hot air outlet pipe (19). Step 7, a defrosting cycle of the main cooler (4) is completed, and the auxiliary cooler (5) starts to defrost and dry.

9. The control method of the dual-purpose refrigerator system of the deep freezer according to claim 8, characterized in that: In the step 4, when the outlet air temperature T1 of the main cooling fan (14) corresponding to the main cooler (4) is greater than or equal to the set temperature T3+3K of the cooling room (6), or when the outlet air temperature T1 of the main cooling fan (14) corresponding to the main cooler (4) is greater than or equal to the room temperature T4 of the cooling room (6), the main cooling fan (14) is stopped and the main cooling air valve (10) is closed; when the external ambient temperature T2 of the auxiliary cooler (5) is less than or equal to the set temperature T3+3K of the cooling room (6), or when the external ambient temperature T2 of the auxiliary cooler (5) is less than or equal to the room temperature T4 of the cooling room (6), the auxiliary cooling fan (15) is turned on.

10. The control method of the dual-purpose refrigerator system of a cryogenic refrigerator according to claim 8, characterized in that: In step 6, when the external ambient temperature T6 of the main cooler (4) is less than or equal to the set temperature T3+3K of the cooling room (6), or the external ambient temperature T6 of the main cooler (4) is less than or equal to the room temperature T4 of the cooling room (6), the main cooling fan (14) and the main cooling air valve (10) are turned on.

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