Low temperature control system and control method

Abstract

The present invention discloses a low-temperature control system, including a primary circuit, a liquid spray circuit, a pressure relief circuit and a control device; the primary circuit is provided with a primary compressor, a primary oil separator, a primary condenser, a first gas-liquid separator, a primary filter dryer, a first heat exchanger, a first throttling device, a primary evaporator and a second gas-liquid separator in sequence; the exhaust port of the first gas-liquid separator is connected to a pressure relief solenoid valve, a suction capillary, an expansion tank and a spray capillary in sequence to form the pressure relief circuit, and the spray capillary is connected to the inlet end of the second gas-liquid separator. The present invention also provides a control method for a low-temperature control system. The present invention is applied to a low-temperature or ultra-low-temperature refrigeration system, and can achieve refrigeration with greater cooling capacity and lower temperature.

Description

Technical Field

[0001] The present invention relates to the field of low-temperature refrigeration technology, and in particular to a low-temperature control system and a control method. Background Art

[0002] With the development of science and technology, many fields have higher and higher requirements for low-temperature freezing technology. Cryogenic storage boxes are mainly used for research in cryogenic electronics, cryogenic medicine, cryogenic biology, cryogenic test environment and life sciences. Existing cryogenic storage boxes generally use cascade or self-cascade systems, and the refrigerant uses a mixture of one or more refrigerants. For systems with lower target temperatures, the lower the boiling point of the refrigerant required, the greater the exhaust pressure of the system, and the higher the exhaust temperature, which poses a huge challenge to the reliability of the system.

[0003] In this regard, it is necessary to improve the existing technology. Summary of the invention

[0004] The object of the present invention is to provide a low temperature control system to solve the problem of excessively high exhaust pressure or exhaust temperature in low temperature or ultra-low temperature refrigeration systems in the prior art.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is:

[0006] A low temperature control system, comprising a primary circuit, a liquid spray circuit, a pressure relief circuit and a control device;

[0007] The primary loop is provided with a primary compressor, a primary oil separator, a primary condenser, a first gas-liquid separator, a primary drying filter, a first heat exchanger, a first throttling device, a primary evaporator and a second gas-liquid separator in sequence;

[0008] The primary oil separator is used to separate the compressor oil in the primary circuit and send it back to the primary compressor;

[0009] The first heat exchanger is provided with a first branch from the first inlet to the first outlet and a second branch from the second inlet to the second outlet;

[0010] The liquid discharge port of the first gas-liquid separator is connected to the primary drying filter and is divided into two paths, namely a first interface and a second interface. The first interface is connected to the liquid injection valve provided on the primary compressor to form the liquid injection circuit. The liquid injection valve can control the flow rate in the liquid injection circuit. The second interface is connected to the first inlet. The first outlet is connected to the first throttling device, the primary evaporator and the second inlet in sequence. The second outlet is connected to the inlet end of the second gas-liquid separator. The exhaust port of the second gas-liquid separator is connected to the compressor. The second branch is used to cool the first branch.

[0011] The exhaust port of the first gas-liquid separator is connected to the pressure relief solenoid valve, the suction capillary, the expansion tank and the discharge capillary in sequence to form the pressure relief circuit, and the discharge capillary is connected to the inlet end of the second gas-liquid separator;

[0012] The control device includes a controller, a temperature sensor and a pressure sensor. The temperature sensor can detect the exhaust temperature of the first-stage compressor, and the pressure sensor can detect the exhaust pressure of the first-stage compressor. The controller is electrically connected to the temperature sensor, the pressure sensor and the pressure relief solenoid valve, respectively, and can control the opening of the pressure relief solenoid valve according to the exhaust temperature or the exhaust pressure.

[0013] Preferably, the primary circuit is further provided with a second heat exchanger and a second throttling device;

[0014] The second heat exchanger is provided with a third branch from the third inlet to the third outlet, a fourth branch from the fourth inlet to the fourth outlet, and a fifth branch from the fifth inlet to the fourth outlet.

[0015] The exhaust port of the first gas-liquid separator is divided into two routes, namely the third interface and the fourth interface, the third interface is connected to the pressure relief circuit, the fourth interface is connected to the third inlet, the third outlet is connected to the first inlet, and the second outlet is connected to the fifth inlet;

[0016] The second interface is connected to the second throttling device and the fourth inlet in sequence, the fourth outlet is connected to the second gas-liquid separator, and the fourth branch is used to cool the third branch.

[0017] Preferably, it further comprises a secondary loop, wherein the primary loop and the secondary loop are connected via a third heat exchanger;

[0018] The third heat exchanger is provided with a sixth branch from the sixth inlet to the sixth outlet and a seventh branch from the seventh inlet to the seventh outlet;

[0019] The secondary circuit is provided with a secondary compressor, a secondary condenser, a secondary filter dryer, a third throttling device, a seventh branch and a third gas-liquid separator in sequence;

[0020] The second interface is connected to the sixth inlet, the sixth outlet is connected to the second throttling device, and the seventh branch is used to cool the sixth branch.

[0021] Preferably, it further comprises a secondary loop, wherein the primary loop and the secondary loop are connected via a third heat exchanger;

[0022] The third heat exchanger is provided with a sixth branch from a sixth inlet to a sixth outlet and a seventh branch from a seventh inlet to a seventh outlet;

[0023] The secondary circuit is provided with a secondary compressor, a secondary condenser, a secondary filter dryer, a third throttling device, a seventh branch and a third gas-liquid separator in sequence;

[0024] The second interface is connected to the sixth inlet, the sixth outlet is connected to the first inlet, and the seventh branch is used to cool the sixth branch.

[0025] The liquid spray circuit is provided with a liquid spray drying filter.

[0026] The present invention also proposes a control method for a low temperature control system, using the low temperature control system as described above, and the specific technical solution is as follows:

[0027] The control method comprises the following steps:

[0028] Step 1: Start the system, open the pressure relief solenoid valve to release pressure, and then close the pressure relief solenoid valve;

[0029] Step 2: The controller detects whether there is an abnormality in the temperature sensor and / or the pressure sensor. If there is an abnormality, execute step 4; otherwise, execute step 3;

[0030] Step 3: The controller monitors the exhaust pressure and exhaust temperature in real time. When the exhaust pressure is ≥3.5MPa, the pressure relief solenoid valve is opened to relieve the pressure, and the pressure relief is stopped when the exhaust pressure is <2.8MPa, and the solenoid valve is closed to stop the pressure relief. Alternatively, when the exhaust temperature is ≥120℃, the pressure relief solenoid valve is opened to relieve the pressure, and the pressure relief is stopped when the exhaust temperature is <110℃.

[0031] Step 4: The controller monitors the ambient temperature in real time. When the ambient temperature Te≥43℃, the pressure relief solenoid valve is opened for pressure relief, and then the pressure relief solenoid valve is closed, and then the pressure is relieved once at a time interval T1; when the ambient temperature is 38℃≤Te<43℃, the pressure relief solenoid valve is opened for pressure relief, and then the pressure relief solenoid valve is closed, and then the pressure is relieved once at a time interval T2; when the ambient temperature is 32℃≤Te<38℃, the pressure relief solenoid valve is opened for pressure relief, and then the pressure relief solenoid valve is closed, and then the pressure is relieved once at a time interval T3; when the ambient temperature is 20℃≤Te<32℃, the pressure relief solenoid valve is opened for pressure relief, and then the pressure relief solenoid valve is closed, and then the pressure is relieved once at a time interval T4; when the ambient temperature Te<20℃, the pressure relief solenoid valve is closed.

[0032] Preferably, the T1 is not less than 20 min, the T2 is not less than 30 min, the T3 is not less than 50 min, and the T4 is not less than 70 min.

[0033] Preferably, the pressure relief time of the pressure relief solenoid valve in step 1 and step 4 is not less than 2s.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The present invention is applied to low-temperature or ultra-low-temperature refrigeration systems, and can achieve refrigeration with greater cooling capacity and lower temperature. The exhaust temperature and exhaust pressure of the compressor can be reduced through the pressure relief circuit, thereby improving the refrigeration efficiency of the system; the system energy efficiency can be improved through the liquid injection circuit, and the exhaust temperature and exhaust pressure can be reduced; the primary circuit can be cooled through the secondary circuit, thereby improving the efficiency of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solution of the present invention, the drawings required for use in the implementation mode will be briefly introduced below. Obviously, the drawings described below are only some implementation modes of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0037] Figure 1 It is a schematic diagram of the overall structure of the first embodiment of the present invention.

[0038] Figure 2 It is a schematic diagram of the overall structure of the second embodiment of the present invention.

[0039] Figure 3 It is a schematic diagram of the overall structure of embodiment 3 of the present invention.

[0040] Figure 4 It is a schematic diagram of the overall structure of embodiment 4 of the present invention.

[0041] In the figure: 1, primary compressor; 2, primary oil separator; 3, primary condenser; 4, first gas-liquid separator; 5, primary filter drier; 6, first heat exchanger; 7, first throttling device; 8, primary evaporator; 9, second gas-liquid separator; 10, liquid spray valve; 11, pressure relief solenoid valve; 12, suction capillary; 13, expansion tank; 14, discharge capillary; 15, controller; 16, temperature sensor; 17, pressure sensor; 18, second heat exchanger; 19, second throttling device; 20, third heat exchanger; 21, secondary compressor; 22, secondary condenser; 23, secondary filter drier; 24, third throttling device; 2 5. The third gas-liquid separator; a. The inlet end of the first gas-liquid separator; b. The discharge port of the first gas-liquid separator; c. The exhaust port of the first gas-liquid separator; d. The first inlet of the first heat exchanger; e. The first outlet of the first heat exchanger; f. The second inlet of the first heat exchanger; g. The second outlet of the first heat exchanger; h. The third inlet of the second heat exchanger; i. The third outlet of the second heat exchanger; j. The fourth inlet of the second heat exchanger; k. The fourth outlet of the second heat exchanger; m. The fifth inlet of the second heat exchanger; n. The sixth inlet of the third heat exchanger; o. The sixth outlet of the third heat exchanger; p. The seventh inlet of the third heat exchanger; q. The seventh outlet of the third heat exchanger. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0043] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", and "fixed" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be internal communication between two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0044] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0045] Embodiment 1

[0046] like Figure 1 As shown, a preferred embodiment of the present invention provides a low-temperature control system, including: a primary circuit, a liquid injection circuit, a pressure relief circuit and a control device.

[0047] Among them, the primary loop is provided with a primary compressor 1, a primary oil separator 2, a primary condenser 3, a first gas-liquid separator 4, a primary drying filter 5, a first heat exchanger 6, a first throttling device 7, a primary evaporator 8 and a second gas-liquid separator 9 in sequence.

[0048] Specifically, the exhaust port of the primary compressor 1 is connected to the primary oil separator 2 , and the primary oil separator 2 is used to separate the compressor oil in the primary circuit and send it back to the primary compressor 1 .

[0049] The function of the first gas-liquid separator 4 is to separate the refrigerant discharged from the primary condenser 3 into gas and liquid. The first gas-liquid separator 4 is provided with an inlet end a, a discharge port b and an exhaust port c. The primary condenser 3 is connected to the inlet end a, and the discharge port b is connected to the primary drying filter 5. After passing through the primary drying filter 5, the refrigerant is divided into two paths, namely the first interface and the second interface.

[0050] The first heat exchanger 6 is provided with a first branch from the first inlet d to the first outlet e and a second branch from the second inlet f to the second outlet g, the second interface is connected to the first inlet d, the first outlet e is connected to the first throttling device 7, the first throttling device 7 is connected to the first-stage evaporator 8, the first-stage evaporator 8 is connected to the second inlet f, the second outlet g is connected to the inlet end of the second gas-liquid separator 9, and the exhaust port of the second gas-liquid separator 9 is connected to the intake port of the first-stage compressor 1.

[0051] The second branch on the first heat exchanger 6 is used to cool the first branch to improve the refrigeration efficiency.

[0052] Among them, the first interface is connected to the liquid injection valve 10 arranged on the first-stage compressor 1 to form the liquid injection circuit. The liquid injection valve can control the flow in the liquid injection circuit. Specifically, the purpose of setting up the liquid injection circuit is to reduce the exhaust temperature and exhaust pressure of the first-stage compressor 1 and improve the refrigeration efficiency of the system.

[0053] Furthermore, a liquid spray drying filter (not shown in the figure) is provided on the liquid spray circuit.

[0054] The pressure relief circuit is provided with a pressure relief solenoid valve 11, a suction capillary 12, an expansion tank 13 and a discharge capillary 14 in sequence. Specifically, the exhaust port c of the first gas-liquid separator 4 is connected to the pressure relief solenoid valve 11, the suction capillary 12, the expansion tank 13 and the discharge capillary 14 in sequence, and the discharge capillary 14 is connected to the inlet end of the second gas-liquid separator 9.

[0055] When the exhaust pressure and exhaust temperature are too high, the exhaust temperature and exhaust pressure of the first-stage compressor 1 are reduced through the pressure relief circuit, thereby improving the refrigeration efficiency of the system.

[0056] The control device includes a controller 15, a temperature sensor 16 and a pressure sensor 17, and the controller 15 is electrically connected to the temperature sensor 16, the pressure sensor 17 and the pressure relief solenoid valve 11 respectively. Specifically, the controller 15 is a programmable controller, the temperature sensor 16 is arranged on the primary circuit and can detect the exhaust temperature of the primary compressor 1, and the pressure sensor 17 is arranged on the primary circuit and can detect the exhaust pressure of the primary compressor 1. The controller 15 can control the opening of the pressure relief solenoid valve 11 according to the exhaust temperature or the exhaust pressure, thereby achieving pressure relief, reducing the exhaust temperature and the exhaust pressure of the primary compressor 1, and improving the refrigeration efficiency of the system.

[0057] Embodiment 2

[0058] like Figure 2 As shown, a preferred embodiment of the present invention provides a low-temperature control system. Based on the above-mentioned embodiment 1, this embodiment adds a second heat exchanger 18 and a second throttling device 19 to the primary loop.

[0059] Specifically, the second heat exchanger 18 is provided with a third branch from the third inlet h to the third outlet i, a fourth branch from the fourth inlet j to the fourth outlet k, and a fifth branch from the fifth inlet m to the fourth outlet k.

[0060] The exhaust port c of the first gas-liquid separator 4 is divided into two paths, namely the third interface and the fourth interface. The third interface is connected to the pressure relief circuit to form the pressure relief circuit in the first embodiment. The fourth interface is connected to the third inlet h of the second heat exchanger 18, the third outlet i of the second heat exchanger 18 is connected to the first inlet d of the first heat exchanger 6, and the second outlet g of the first heat exchanger 6 is connected to the fifth inlet m of the second heat exchanger 18. The second interface is connected to the second throttling device 19, the second throttling device 19 is connected to the fourth inlet j of the second heat exchanger 18, and the fourth outlet k of the second heat exchanger 18 is connected to the inlet end of the second gas-liquid separator connection 9.

[0061] The fourth branch of the second heat exchanger 18 is used to cool the third branch to improve the refrigeration efficiency.

[0062] Embodiment 3

[0063] like Figure 3 As shown, a preferred embodiment of the present invention provides a low-temperature control system. Based on the above-mentioned embodiment 2, this embodiment adds a secondary loop, and the primary loop and the secondary loop are connected through a third heat exchanger 20.

[0064] Specifically, the third heat exchanger 20 is provided with a sixth branch from a sixth inlet n to a sixth outlet o and a seventh branch from a seventh inlet p to a seventh outlet q.

[0065] The secondary loop is provided with a secondary compressor 21, a secondary condenser 22, a secondary filter dryer 23, a third throttling device 24, a seventh branch of the third heat exchanger 20 and a third gas-liquid separator 25 in sequence.

[0066] The second port is connected to the sixth inlet n of the third heat exchanger 20 , and the sixth outlet o of the third heat exchanger 20 is connected to the second throttling device 19 .

[0067] Among them, the seventh branch of the third heat exchanger 20 is used to cool the sixth branch to improve the refrigeration efficiency.

[0068] Embodiment 4

[0069] like Figure 4 As shown, a preferred embodiment of the present invention provides a low-temperature control system. Based on the above embodiment 1, this embodiment adds a secondary loop, and the primary loop and the secondary loop are connected through a third heat exchanger 20.

[0070] The third heat exchanger 20 is provided with a sixth branch from a sixth inlet n to a sixth outlet o and a seventh branch from a seventh inlet p to a seventh outlet q.

[0071] The secondary loop is provided with a secondary compressor 21, a secondary condenser 22, a secondary filter dryer 23, a third throttling device 24, a seventh branch of the third heat exchanger 20 and a third gas-liquid separator 25 in sequence.

[0072] The second interface is connected to the sixth inlet n of the third heat exchanger 20 , and the sixth outlet o of the third heat exchanger 20 is connected to the first inlet d of the first heat exchanger 6 .

[0073] Among them, the seventh branch of the third heat exchanger 20 is used to cool the sixth branch to improve the refrigeration efficiency.

[0074] Embodiment 4

[0075] A preferred embodiment of the present invention provides a control method for a low temperature control system, using any one of the low temperature control systems of the first to fourth embodiments above, and the control method specifically comprises the following steps:

[0076] Step 1: First start the system and the compressor runs. Then the controller controls the pressure relief solenoid valve to open for pressure relief. The specific pressure relief time is not less than 2s. Finally, the controller controls the pressure relief solenoid valve to close.

[0077] Step 2: The controller detects whether there is an abnormality in the temperature sensor and / or the pressure sensor. If there is an abnormality, that is, it cannot work normally, execute step 4; otherwise, execute step 3.

[0078] Step 3: The temperature sensor transmits the exhaust temperature detected by the temperature sensor and the exhaust pressure detected by the pressure sensor to the controller. The controller takes corresponding actions according to the exhaust pressure and exhaust temperature monitored in real time. Specifically, when the exhaust pressure is ≥3.5MPa, the pressure relief solenoid valve is controlled to open for pressure relief, and the pressure relief is stopped when the exhaust pressure is <2.8MPa, and the solenoid valve is closed. Alternatively, when the exhaust temperature is ≥120℃, the pressure relief solenoid valve is controlled to open for pressure relief, and the pressure relief is stopped when the exhaust temperature is <110℃.

[0079] Step 4: The controller monitors the ambient temperature in real time. When the ambient temperature Te≥43°C, the controller controls the pressure relief solenoid valve to open for pressure relief, and then closes the pressure relief solenoid valve, and then releases pressure every T1, specifically T1 is not less than 20min, and the present invention is preferably 30min. When the ambient temperature is 38°C≤Te<43°C, the controller controls the pressure relief solenoid valve to open for pressure relief, and then closes the pressure relief solenoid valve, and then releases pressure every T2, specifically T2 is not less than 30min, and the present invention is preferably 40min. When the ambient temperature is 32°C≤Te<38°C, the controller controls the pressure relief solenoid valve to open for pressure relief, and then closes the pressure relief solenoid valve, and then releases pressure every T3, specifically T3 is not less than 50min, and the present invention is preferably 60min. When the ambient temperature is 20°C≤Te<32°C, the controller controls the pressure relief solenoid valve to open for pressure relief, and then closes the pressure relief solenoid valve, and then releases pressure every T4, specifically T4 is not less than 70min, and the present invention is preferably 90min. When the ambient temperature Te is less than 20°C, the pressure relief solenoid valve is closed.

[0080] In summary, the present invention is applied to a low-temperature or ultra-low-temperature refrigeration system, and can achieve refrigeration with greater cooling capacity and lower temperature. The exhaust temperature and exhaust pressure of the compressor can be reduced through the pressure relief circuit, thereby improving the refrigeration efficiency of the system; the system energy efficiency can be improved through the liquid injection circuit, and the exhaust temperature and exhaust pressure can be reduced; the primary circuit can be cooled through the secondary circuit, thereby improving the efficiency of the system.

[0081] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A low temperature control system, characterized in that: It includes a primary circuit, a liquid injection circuit, a pressure relief circuit and a control device; The primary loop is provided with a primary compressor, a primary oil separator, a primary condenser, a first gas-liquid separator, a primary drying filter, a first heat exchanger, a first throttling device, a primary evaporator and a second gas-liquid separator in sequence; The primary oil separator is used to separate the compressor oil in the primary circuit and send it back to the primary compressor; The first heat exchanger is provided with a first branch from the first inlet to the first outlet and a second branch from the second inlet to the second outlet; The liquid discharge port of the first gas-liquid separator is connected to the primary drying filter and then divided into two paths, namely a first interface and a second interface. The first interface is connected to a liquid injection valve provided on the primary compressor to form the liquid injection circuit. The liquid injection valve can control the flow rate in the liquid injection circuit. The first outlet is connected to the first throttling device, the primary evaporator and the second inlet in sequence. The second outlet is connected to the inlet end of the second gas-liquid separator. The exhaust port of the second gas-liquid separator is connected to the compressor. The exhaust port of the first gas-liquid separator is connected to the pressure relief solenoid valve, the suction capillary, the expansion tank and the discharge capillary in sequence to form the pressure relief circuit, and the discharge capillary is connected to the inlet end of the second gas-liquid separator; The control device includes a controller, a temperature sensor and a pressure sensor. The temperature sensor can detect the exhaust temperature of the first-stage compressor, and the pressure sensor can detect the exhaust pressure of the first-stage compressor. The controller is electrically connected to the temperature sensor, the pressure sensor and the pressure relief solenoid valve, respectively, and can control the opening of the pressure relief solenoid valve according to the exhaust temperature or the exhaust pressure. Also comprising a secondary loop, wherein the primary loop and the secondary loop are connected via a third heat exchanger; The third heat exchanger is provided with a sixth branch from a sixth inlet to a sixth outlet and a seventh branch from a seventh inlet to a seventh outlet; The secondary circuit is provided with a secondary compressor, a secondary condenser, a secondary filter dryer, a third throttling device, a seventh branch and a third gas-liquid separator in sequence; The second interface is connected to the sixth inlet, the sixth outlet is connected to the first inlet, and the seventh branch is used to cool the sixth branch; The liquid spray circuit is provided with a liquid spray drying filter.

2. A low temperature control system, characterized in that: It includes a primary circuit, a liquid injection circuit, a pressure relief circuit and a control device; The primary loop is provided with a primary compressor, a primary oil separator, a primary condenser, a first gas-liquid separator, a primary drying filter, a first heat exchanger, a first throttling device, a primary evaporator and a second gas-liquid separator in sequence; The primary oil separator is used to separate the compressor oil in the primary circuit and send it back to the primary compressor; The first heat exchanger is provided with a first branch from the first inlet to the first outlet and a second branch from the second inlet to the second outlet; The liquid discharge port of the first gas-liquid separator is connected to the first-stage drying filter and is divided into two paths, namely a first interface and a second interface. The first interface is connected to the liquid injection valve provided on the first-stage compressor to form the liquid injection circuit. The liquid injection valve can control the flow rate in the liquid injection circuit. The primary circuit is also provided with a second heat exchanger and a second throttling device; The second heat exchanger is provided with a third branch from the third inlet to the third outlet, a fourth branch from the fourth inlet to the fourth outlet, and a fifth branch from the fifth inlet to the fourth outlet. The exhaust port of the first gas-liquid separator is divided into two routes, namely the third interface and the fourth interface, the third interface is connected to the pressure relief solenoid valve, the suction capillary, the expansion tank and the discharge capillary in sequence, the fourth interface is connected to the third inlet, the third outlet is connected to the first inlet, and the second outlet is connected to the fifth inlet; The fourth outlet is connected to the second gas-liquid separator; Also comprising a secondary loop, wherein the primary loop and the secondary loop are connected via a third heat exchanger; The third heat exchanger is provided with a sixth branch from the sixth inlet to the sixth outlet and a seventh branch from the seventh inlet to the seventh outlet; The secondary circuit is provided with a secondary compressor, a secondary condenser, a secondary filter dryer, a third throttling device, a seventh branch and a third gas-liquid separator in sequence; The second interface is connected to the sixth inlet, the sixth outlet is connected to the second throttling device and the fourth inlet in sequence, and the seventh branch is used to cool the sixth branch; The liquid spray circuit is provided with a liquid spray drying filter.

3. A control method for a low temperature control system, characterized in that: Using a low temperature control system as claimed in any one of claims 1 to 2; The control method comprises the following steps: Step 1: Start the system, open the pressure relief solenoid valve to release pressure, and then close the pressure relief solenoid valve; Step 2: The controller detects whether there is an abnormality in the temperature sensor and / or the pressure sensor. If there is an abnormality, execute step 4; otherwise, execute step 3; Step 3: The controller monitors the exhaust pressure and exhaust temperature in real time. When the exhaust pressure is ≥3.5MPa, the pressure relief solenoid valve is opened to relieve the pressure, and the pressure relief is stopped when the exhaust pressure is <2.8MPa, and the solenoid valve is closed to stop the pressure relief. Alternatively, when the exhaust temperature is ≥120℃, the pressure relief solenoid valve is opened to relieve the pressure, and the pressure relief is stopped when the exhaust temperature is <110℃. Step 4: The controller monitors the ambient temperature in real time. When the ambient temperature Te≥43℃, the pressure relief solenoid valve is opened for pressure relief, and then the pressure relief solenoid valve is closed, and then the pressure is relieved once at a time interval T1; when the ambient temperature is 38℃≤Te<43℃, the pressure relief solenoid valve is opened for pressure relief, and then the pressure relief solenoid valve is closed, and then the pressure is relieved once at a time interval T2; when the ambient temperature is 32℃≤Te<38℃, the pressure relief solenoid valve is opened for pressure relief, and then the pressure relief solenoid valve is closed, and then the pressure is relieved once at a time interval T3; when the ambient temperature is 20℃≤Te<32℃, the pressure relief solenoid valve is opened for pressure relief, and then the pressure relief solenoid valve is closed, and then the pressure is relieved once at a time interval T4; when the ambient temperature Te<20℃, the pressure relief solenoid valve is closed.

4. A control method for a low temperature control system according to claim 3, characterized in that: The T1 is no less than 20 min, the T2 is no less than 30 min, the T3 is no less than 50 min, and the T4 is no less than 70 min.

5. The control method of a low temperature control system according to claim 3, characterized in that: The pressure relief time of the pressure relief solenoid valve in step 1 and step 4 is not less than 2s.

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