A throttling refrigeration system with a mixed working fluid capable of rapid cooling and its control method

Abstract

The present invention discloses a mixed working fluid throttling refrigeration system capable of rapid cooling and a control method, the system comprising an intermediate air supply compressor, a condenser, two regenerators, two capillaries, an evaporator, a two-position three-way solenoid valve with one inlet and two outlets, two check valves and a control module; the control module changes the flow direction of the fluid by monitoring the inlet state of the solenoid valve; at the initial start-up, the evaporator flow path is disconnected, and the refrigerant at the outlet of the solenoid valve flows through the large-flow capillary, and then enters the two regenerators in turn to cool and condense the high-pressure side refrigerant, thereby reducing the condensation pressure and improving the safety of the system; after the working fluid at the inlet of the solenoid valve is condensed into a pure liquid phase, the evaporator flow path flows, and after cooling in the start-up phase, the high-pressure side liquid phase refrigerant is easier to pass through the capillary in front of the evaporator, the refrigerant flow is large, and the cooling rate is fast; in addition, the intermediate air supply compressor has a two-stage compression effect, the compressor efficiency is improved, and the compressor exhaust temperature and system energy efficiency can be effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of refrigeration and cryogenics, and particularly relates to a non-azeotropic mixture throttling refrigeration system capable of rapidly cooling and a control method thereof, which are applied to a low-temperature refrigerator or freezer. Background Art

[0002] With the increasing progress of science and technology, the demand for low-temperature refrigerators or freezers for the preservation of medical supplies and biological products, low-temperature experiments on special materials such as electronic components and chemical materials, and other scientific research and production activities is increasing. The mixture throttling refrigeration system has a simple structure, low cost, and a wide refrigeration temperature range, and has been widely used in low-temperature refrigerators or freezers. At the initial stage of starting the refrigeration system, the whole system is at a relatively high temperature level. In order to obtain a lower refrigeration temperature, a large amount of low-boiling component refrigerants are contained in the mixture refrigerant. Therefore, at this time, most of the refrigerants in the system are in the gas phase, and the ability of the gas-phase refrigerant to pass through the throttling element is poor. This results in that at the initial stage of starting the mixture throttling refrigeration system, on the one hand, the system condensation pressure is high, which is easy to damage the compressor, and on the other hand, the circulating refrigerant flow rate is small, the refrigeration capacity is small, and the cooling rate is slow. As the system temperature decreases and the high-boiling components cool and condense, the content of the liquid-phase refrigerant passing through the throttling element will gradually increase, the condensation pressure will gradually decrease, and the refrigerant flow rate will increase, and the cooling rate will increase accordingly. Aiming at the problems of high starting pressure and slow cooling rate caused by a large amount of gas-phase refrigerant at the initial stage of starting the conventional mixture throttling refrigeration system, the present invention improves the configuration of the regenerator of the mixture throttling refrigeration system, and provides a novel mixture throttling refrigeration system with intermediate gas replenishment. This system can improve the starting performance on the one hand and enhance the system performance in the stable operation stage on the other hand. Summary of the Invention

[0003] In view of the defects and deficiencies existing in the above-mentioned mixed refrigerant throttling refrigeration system, the present invention provides a novel mixed refrigerant throttling refrigeration system with intermediate gas injection for a low-temperature refrigerator or freezer, which can improve the starting and stable operation performance, and a starting stage control method. One regenerator in the conventional mixed refrigerant throttling refrigeration system is divided into two, the compressor adopts an intermediate gas injection compressor, and an additional refrigerant flow path leading to the gas injection port of the compressor is added. In addition, a two-position three-way solenoid valve with one inlet and two outlets is added between the second regenerator and the capillary tube before the evaporator. The outlet Ⅰ of the two-position three-way solenoid valve is connected to a large-flow capillary tube, and the outlet Ⅱ of the two-position three-way solenoid valve is connected to the evaporator flow path. The on-off of the solenoid valve is controlled by the condenser outlet pressure, so as to change the fluid flow direction. At the initial stage of system startup, the outlet Ⅰ is opened and the evaporator flow path is disconnected. The refrigerant provides cooling capacity for the regenerator through the large-flow capillary tube, which can quickly increase the liquid-phase content of the refrigerant on the high-pressure side of the system, and then quickly reduce the condensation pressure. When the refrigerant on the high-pressure side is completely condensed, the outlet Ⅰ is closed and the evaporator flow path is opened. At this time, compared with the conventional system, on the one hand, after the startup stage, the refrigerant on the high-pressure side in the novel system has been quickly cooled and condensed, the refrigerant flow rate through the capillary tube is large, and the temperature reduction rate is fast. On the other hand, the adoption of the intermediate gas injection compressor reduces the compression ratio of each stage of compression, and the stable operation performance of the system is improved.

[0004] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0005] A throttling refrigeration system with a mixed refrigerant that can rapidly cool down, comprising a compressor 101, a condenser 102, a first regenerator 103, a first capillary tube 104, a second regenerator 105, a two-way three-way solenoid valve 106, a second capillary tube 107, a first check valve 108, a third capillary tube 109, an evaporator 110, a second check valve 111 and a control module 112; the outlet of the compressor 101 is connected to the inlet of the condenser 102; the outlet of the condenser 102 is connected to the inlet I of the first regenerator 103; the outlet I of the first regenerator 103 is divided into two paths, one path is connected to the inlet II of the first regenerator 103 after passing through the first capillary tube 104, and the outlet II of the first regenerator 103 is connected to the gas replenishing port of the compressor 101; the other path is connected to the inlet I of the second regenerator 105, the outlet I of the second regenerator 105 is connected to the inlet of the two-way three-way solenoid valve 106, the outlet I of the two-way three-way solenoid valve 106 is connected to the inlet of the second capillary tube 107, the outlet of the second capillary tube 107 is connected to the inlet of the first check valve 108, the outlet II of the two-way three-way solenoid valve 106 is connected to the inlet of the third capillary tube 109, the outlet of the third capillary tube 109 is connected to the inlet of the evaporator 110, the outlet of the evaporator 110 is connected to the inlet of the second check valve 111, the outlet of the second check valve 111 and the outlet of the first check valve 108 converge and then are connected to the inlet II of the second regenerator 105, the outlet II of the second regenerator 105 is connected to the inlet III of the first regenerator 103, and the outlet III of the first regenerator 103 is connected to the suction port of the compressor 101; a pressure sensor and a temperature sensor are provided between the outlet I of the second regenerator 105 and the inlet of the two-way three-way solenoid valve 106, and the pressure sensor and the temperature sensor are connected to the input end of the control module 112; the output end of the control module 112 is connected to the two-way three-way solenoid valve 106.

[0006] The two-way three-way solenoid valve 106 has one inlet and two outlets. The outlet I is sequentially connected to the second capillary tube 107 and the first check valve 108, and the outlet II is sequentially connected to the third capillary tube 109, the evaporator 110 and the second check valve 111; the control module 112 controls the energization and de-energization of the coil of the two-way three-way solenoid valve 106 according to the received pressure and temperature signals at the inlet of the two-way three-way solenoid valve 106, and further controls the movement of the valve core to change the fluid flow direction, so as to achieve the purpose of accelerating the cooling rate.

[0007] In the initial startup stage of the mixed refrigerant throttling refrigeration system, outlet I of the two-way three-way solenoid valve 106 is opened, and outlet II is closed. At this time, the evaporator flow path is disconnected, the evaporator 110 does not refrigerate, and the refrigerant enters the second capillary 107 for throttling, and then enters the two regenerators in sequence to provide cooling capacity for the high-pressure side refrigerant. In addition, the second capillary 107 connected to outlet I of the two-way three-way solenoid valve 106 has a larger flow rate than the third capillary 109 connected to outlet II of the two-way three-way solenoid valve 106, and has stronger ability through the working medium. Therefore, the refrigerant on the high-pressure side of the system can be quickly cooled and condensed, especially the high-boiling components in the mixed refrigerant, and the condensation pressure can be quickly reduced, greatly improving the system safety.

[0008] In the refrigeration stage of the mixed refrigerant throttling refrigeration system, outlet I of the two-way three-way solenoid valve 106 is closed, and outlet II is opened, and the evaporator flow path is unblocked. After the startup stage, the refrigerant on the high-pressure side of the system has been condensed. Compared with directly opening the evaporator flow path at the startup of the system, the ability of the working medium to pass through the third capillary 109 is enhanced, and the refrigerant flow rate is large. Therefore, the cooling rate is accelerated.

[0009] For the control method of the mixed refrigerant throttling refrigeration system, before the system starts to run, outlet I of the two-way three-way solenoid valve 106 is opened, and outlet II is closed, and the evaporator flow path is disconnected. After the system starts, the control module 112 real-time monitors the real-time temperature t i and pressure P i at the inlet of the two-way three-way solenoid valve 106, and calculates and determines the saturation liquid temperature t i corresponding to the real-time pressure P sat,i through the refrigerant physical property query and calculation software Refprop, and compares the real-time temperature t i at the inlet of the two-way three-way solenoid valve 106 with the saturation liquid temperature t sat,i ; if t i >t sat,i , it indicates that the working medium at the inlet of the two-way three-way solenoid valve 106 contains gaseous working medium, then keep outlet I open and outlet II closed unchanged. At this time, the system is in the startup stage, and the evaporator flow path is disconnected, aiming to accelerate the cooling and condensation of the high-pressure side refrigerant; until t i <t sat,i , that is, the working medium at the inlet of the two-way three-way solenoid valve 106 is pure liquid phase, then outlet I of the two-way three-way solenoid valve 106 is closed, and outlet II is opened, and the evaporator flow path is unblocked. At this time, the system enters the refrigeration stage until the system runs stably.

[0010] Compared with the conventional throttling refrigeration system with a mixed refrigerant, the novel throttling refrigeration system with a mixed refrigerant proposed by the present invention is configured with two regenerators, a compressor with intermediate gas injection, and a two-way three-way solenoid valve for changing the fluid flow direction. On the one hand, it can quickly cool and condense the high-pressure side refrigerant by changing the fluid flow direction, reduce the condensation pressure, and accelerate the cooling rate. On the other hand, the intermediate gas injection compressor has the effect of two-stage compression, which can reduce the compression ratio of each stage of compression and effectively improve the system performance. The present invention will effectively promote the development of low-temperature refrigerator or freezer technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a schematic diagram of the refrigeration system of the present invention.

[0012] Figure 2 is a flowchart of the control method of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0013] In order to make the technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.

[0014] As Figure 1As shown in the figure, a hybrid refrigerant throttling refrigeration system with intermediate gas injection for rapid cooling, comprising a compressor 101, a condenser 102, a first recuperator 103, a first capillary tube 104, a second recuperator 105, a two-way three-way solenoid valve 106, a second capillary tube 107, a first check valve 108, a third capillary tube 109, an evaporator 110, a second check valve 111 and a control module 112; the outlet of the compressor 101 is connected to the inlet of the condenser 102; the outlet of the condenser 102 is connected to the inlet I of the first recuperator 103; the outlet I of the first recuperator 103 is divided into two paths, one path is connected to the inlet II of the first recuperator 103 after passing through the first capillary tube 104, and the outlet II of the first recuperator 103 is connected to the gas injection port of the compressor 101; the other path is connected to the inlet I of the second recuperator 105, the outlet I of the second recuperator 105 is connected to the inlet of the two-way three-way solenoid valve 106, the outlet I of the two-way three-way solenoid valve 106 is connected to the inlet of the second capillary tube 107, the outlet of the second capillary tube 107 is connected to the inlet of the first check valve 108, the outlet II of the two-way three-way solenoid valve 106 is connected to the inlet of the third capillary tube 109, the outlet of the third capillary tube 109 is connected to the inlet of the evaporator 110, the outlet of the evaporator 110 is connected to the inlet of the second check valve 111, the outlet of the second check valve 111 and the outlet of the first check valve 108 converge and then are connected to the inlet II of the second recuperator 105, the outlet II of the second recuperator 105 is connected to the inlet III of the first recuperator 103, and the outlet III of the first recuperator 103 is connected to the suction port of the compressor 101; a pressure sensor and a temperature sensor are provided between the outlet I of the second recuperator 105 and the inlet of the two-way three-way solenoid valve 106, and the pressure sensor and the temperature sensor are connected to the input end of the control module 112; the output end of the control module 112 is connected to the two-way three-way solenoid valve 106.

[0015] Two recuperators are configured in the novel hybrid refrigerant throttling refrigeration system. The first recuperator 103 has three fluid channels, and the second recuperator 105 has two fluid channels; the two series-connected recuperators cool and condense the high-pressure side refrigerant, reducing the throttling loss when the refrigerant flows through the capillary tube. At the same time, the low-pressure side refrigerant absorbs heat in the two recuperators to prevent liquid slugging of the compressor 101; in addition, the first recuperator 103 simultaneously provides heat for the medium-pressure refrigerant flowing to the gas injection port of the compressor 101.

[0016] The compressor 101 in the novel hybrid refrigerant throttling refrigeration system is an intermediate gas injection compressor, which has the effect of two-stage compression. The compression ratio of each stage is reduced, the compressor efficiency is improved, the compressor exhaust temperature can be reduced, and the system energy efficiency can be effectively improved.

[0017] The two-position three-way solenoid valve 106 has one inlet and two outlets. Outlet I is successively connected to the second capillary 107 and the first check valve 108, and outlet II is successively connected to the third capillary 109, the evaporator 110, and the second check valve 111. The control module 112 controls the energization and de-energization of the coil of the two-position three-way solenoid valve 106 according to the received inlet pressure and temperature signals of the two-position three-way solenoid valve 106, and then controls the movement of the valve core to change the fluid flow direction, so as to achieve the purpose of accelerating the cooling rate.

[0018] In the initial stage of starting of the mixed refrigerant throttling refrigeration system, outlet I of the two-position three-way solenoid valve 106 is opened and outlet II is closed. At this time, the evaporator flow path is disconnected, the evaporator 110 does not refrigerate, and the refrigerant enters the second capillary 107 for throttling, and then successively enters two regenerators to provide cooling capacity for the high-pressure side refrigerant. In addition, the second capillary 107 connected to outlet I of the two-position three-way solenoid valve 106 has a larger flow rate than the third capillary 109 connected to outlet II of the two-position three-way solenoid valve 106 and has stronger ability to pass the working medium. Therefore, the high-pressure side refrigerant of the system can be quickly cooled and condensed, especially the high-boiling component in the mixed refrigerant, and the condensation pressure can be quickly reduced, greatly improving the system safety.

[0019] In the refrigeration stage of the mixed refrigerant throttling refrigeration system, outlet I of the two-position three-way solenoid valve 106 is closed and outlet II is opened, and the evaporator flow path is in circulation. After the start-up stage, the high-pressure side refrigerant of the system has been condensed. Compared with directly opening the evaporator flow path at the start of the system, the ability of the working medium to pass through the third capillary 109 is enhanced and the refrigerant flow rate is large. Therefore, the cooling rate is accelerated.

[0020] Figure 2 As shown in the flowchart of the control method in the start-up stage of the present invention, the system control method is as follows: Before the system starts to run, outlet I of the two-position three-way solenoid valve 106 is opened and outlet II is closed, and the evaporator flow path is disconnected. After the system starts, the control module 112 monitors the real-time temperature t i and pressure P i at the inlet of the two-position three-way solenoid valve 106 in real time, calculates and determines the saturation liquid temperature t i corresponding to the real-time pressure P sat,i through the refrigerant physical property query and calculation software Refprop, and compares the real-time temperature t i at the inlet of the two-position three-way solenoid valve 106 with the saturation liquid temperature t sat,i ; if t i >t sat,i , it indicates that there is gaseous working medium in the working medium at the inlet of the two-position three-way solenoid valve 106, then keep outlet I open and outlet II closed unchanged. At this time, the system is in the start-up stage and the evaporator flow path is disconnected, aiming to accelerate the cooling and condensation of the high-pressure side refrigerant; until t i <t sat,i, that is, if the working medium at the inlet of the two-position three-way solenoid valve 106 is pure liquid phase, the outlet I of the two-position three-way solenoid valve 106 is closed and the outlet II is opened, and the evaporator flow path is in circulation. At this time, the system enters the refrigeration stage until the system runs stably.

[0021] After the system runs stably, the specific working process of the refrigeration cycle is as follows: The high-temperature and high-pressure superheated steam at the outlet of the compressor 101 is cooled to a two-phase flow through the condenser 102, and then cooled to a liquid-phase fluid through the first recuperator 103 and then divided into two fluid streams; one stream is throttled to the intermediate pressure through the first capillary tube 104 to become a two-phase flow, and then heated to become a gas-phase fluid through the first recuperator 103 and then enters the gas replenishing port of the compressor 101; the other stream is cooled to a subcooled liquid in the second recuperator 105, and then throttled to become a two-phase fluid through the third capillary tube 109, and then absorbs heat in the evaporator 110 and the dryness increases; the fluid at the outlet of the evaporator 110 is heated successively through the second recuperator 105 and the first recuperator 103 to become superheated steam; the superheated steam is compressed to the intermediate pressure in the compressor 101 through the first-stage compression, and then mixed with the gas-phase fluid at the gas replenishing port of the compressor 101 and then compressed to become high-temperature and high-pressure superheated steam through the second-stage compression, completing the entire cycle process.

Claims

1. A throttling refrigeration system with a mixed refrigerant capable of rapid cooling, characterized in that: It includes a compressor (101), a condenser (102), a first regenerator (103), a first capillary tube (104), a second regenerator (105), a two-position three-way solenoid valve (106), a second capillary tube (107), a first check valve (108), a third capillary tube (109), an evaporator (110), a second check valve (111) and a control module (112); the outlet of the compressor (101) is connected to the inlet of the condenser (102); the outlet of the condenser (102) is connected to the inlet I of the first regenerator (103); the outlet I of the first regenerator (103) is divided into two paths, one path is connected to the inlet II of the first regenerator (103) after passing through the first capillary tube (104), and the outlet II of the first regenerator (103) is connected to the gas supplement port of the compressor (101); the other path is connected to the inlet I of the second regenerator (105), the outlet I of the second regenerator (105) is connected to the inlet of the two-position three-way solenoid valve (106), the outlet I of the two-position three-way solenoid valve (106) is connected to the inlet of the second capillary tube (107), the outlet of the second capillary tube (107) is connected to the inlet of the first check valve (108), the outlet II of the two-position three-way solenoid valve (106) is connected to the inlet of the third capillary tube (109), the outlet of the third capillary tube (109) is connected to the inlet of the evaporator (110), the outlet of the evaporator (110) is connected to the inlet of the second check valve (111), the outlet of the second check valve (111) and the outlet of the first check valve (108) converge and then are connected to the inlet II of the second regenerator (105), the outlet II of the second regenerator (105) is connected to the inlet III of the first regenerator (103), and the outlet III of the first regenerator (103) is connected to the suction port of the compressor (101); a pressure sensor and a temperature sensor are arranged between the outlet I of the second regenerator (105) and the inlet of the two-position three-way solenoid valve (106), and the pressure sensor and the temperature sensor are connected to the input end of the control module (112); the output end of the control module (112) is connected to the two-position three-way solenoid valve (106).

2. The throttling refrigeration system with a mixed refrigerant capable of rapid cooling according to claim 1, wherein Two regenerators are configured in the system. The first regenerator (103) has three fluid channels, and the second regenerator (105) has two fluid channels; the two regenerators connected in series cool and condense the refrigerant on the high-pressure side, reducing the throttling loss when the refrigerant flows through the capillary tube. At the same time, the refrigerant on the low-pressure side absorbs heat in the two regenerators to prevent liquid slugging of the compressor (101); in addition, the first regenerator (103) provides heat for the medium-pressure refrigerant flowing to the gas supplement port of the compressor (101).

3. The throttling refrigeration system with a mixed refrigerant capable of rapid cooling according to claim 1, characterized in that, The compressor (101) is an intermediate gas-supplement compressor, which has the effect of two-stage compression. The compression ratio of each stage of compression is reduced, the compressor efficiency is improved, the exhaust temperature of the compressor is reduced, and the energy efficiency of the system is improved.

4. The throttling refrigeration system with a mixed refrigerant capable of rapid cooling according to claim 1, characterized in that, The two-position three-way solenoid valve (106) has one inlet and two outlets. Outlet I is successively connected to the second capillary tube (107) and the first check valve (108), and outlet II is successively connected to the third capillary tube (109), the evaporator (110), and the second check valve (111); the control module (112) controls the energization and de-energization of the coil of the two-position three-way solenoid valve (106) according to the received inlet pressure and temperature signals of the two-position three-way solenoid valve (106), and then controls the movement of the valve core to change the fluid flow direction, so as to achieve the purpose of accelerating the cooling rate; in the initial stage of startup, outlet I of the two-position three-way solenoid valve (106) is opened and outlet II is closed. At this time, the evaporator flow path is disconnected, the evaporator (110) does not refrigerate, and the refrigerant enters the second capillary tube (107) for throttling, and then successively enters two regenerators to provide cooling capacity for the high-pressure side refrigerant; in addition, the second capillary tube (107) connected to outlet I of the two-position three-way solenoid valve (106) has a larger flow rate than the third capillary tube (109) connected to outlet II of the two-position three-way solenoid valve (106), and has stronger ability to pass the working medium; Therefore, the refrigerant on the high-pressure side of the system can be quickly cooled and condensed, especially the high-boiling components in the mixed refrigerant, the condensation pressure is quickly reduced, and the system safety is improved; In the refrigeration stage, outlet I of the two-position three-way solenoid valve (106) is closed and outlet II is opened, and the evaporator flow path is unblocked; After the startup stage, the refrigerant on the high-pressure side of the system has been condensed. Compared with directly opening the evaporator flow path at the start of the system, the ability of the working medium to pass through the third capillary tube (109) is enhanced, the refrigerant flow rate is large, and therefore the cooling rate is accelerated.

5. The control method of the throttling refrigeration system with a mixed working medium capable of rapid cooling according to any one of claims 1 to 4, characterized in that: Before the system starts running, the outlet I of the two-position three-way solenoid valve (106) is open, the outlet II is closed, and the evaporator flow path is disconnected; after the system starts, the control module (112) monitors the real-time temperature t at the inlet of the two-position three-way solenoid valve (106) in real time i and the pressure P i , and calculates and determines the real-time pressure P through the refrigerant physical property query and calculation software Refprop i corresponding to the saturation liquid temperature t sat,i , compares the real-time temperature t at the inlet of the two-position three-way solenoid valve (106) i with the saturation liquid temperature t sat,i ; if t i >t sat,i , it indicates that the working fluid at the inlet of the two-position three-way solenoid valve (106) contains gaseous working fluid, then keep the outlet I open and the outlet II closed unchanged. At this time, the system is in the startup stage and the evaporator flow path is disconnected. The purpose is to accelerate the cooling and condensation of the refrigerant on the high-pressure side; until t i <t sat,i , that is, the working fluid at the inlet of the two-position three-way solenoid valve (106) is pure liquid phase, then the outlet I of the two-position three-way solenoid valve (106) is closed and the outlet II is opened, and the evaporator flow path is in circulation. At this time, the system enters the refrigeration stage until the system runs stably.

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