Two-stage compression refrigeration system applied to refrigeration house and control method

Abstract

The refrigerating system comprises a compressor, an evaporative condenser, a gas-liquid separator, a heat regenerator, an evaporator, a heat recoverer, an energy storage device, a terrace heat exchanger, an oil separator, an oil cooler, a water pump, a temperature control valve, an electronic expansion valve, a three-way valve, a control device, a temperature sensor and a pressure sensor. The control device collects signals of compressor outlet and inlet pressure sensors and temperature sensors, evaporator outlet pressure sensors and temperature sensors, an oil return temperature sensor and a floor heat exchanger temperature sensor. Condensing pressure is adjusted by controlling starting and stopping of a condenser side fan and a water pump, and the opening degree of the three-way valve is controlled to enable the oil return temperature to be within a safe range. The evaporation temperature is maintained by adjusting the opening degree of an evaporator inlet electronic expansion valve. By monitoring the terrace temperature in the refrigeration house, the electromagnetic valve is controlled to adjust the refrigerant flow in the terrace heat exchanger to maintain the outlet temperature, and the energy storage device is intermittently put into the refrigeration house to improve the system energy efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cold storage refrigeration, in particular to a two-stage compression refrigeration system applied to a cold storage and a control method. BACKGROUND

[0002] The performance of a refrigeration system is crucial for many application scenarios, and with the increasing demand for refrigeration in various industries, the refrigeration system is facing more stringent challenges. In recent years, China's cold chain logistics has developed rapidly, and the cold storage inventory has increased year by year. The existing single-stage compression refrigeration cycle is limited by the compression ratio of the compressor, and it is difficult to effectively play a role in systems where the ambient temperature and the refrigeration temperature differ greatly. When the refrigeration temperature difference is large, the industry usually uses a two-stage compression refrigeration system. However, the energy efficiency of the current two-stage compression refrigeration system still needs to be improved to meet the energy-saving needs.

[0003] During the process of the refrigeration system from the ambient temperature zone to the refrigeration temperature zone, in addition to the temperature change in the pressure reduction process and the pressure increase process, there is an optimal matching of heat exchange between the hot-side refrigerant and the cold-side refrigerant. At the same time, the flash separation process separates part of the throttling gas-phase refrigerant, and the separated liquid-phase refrigerant can increase the refrigerating capacity of the evaporator after throttling. The current technology still does not fully achieve optimal matching of internal heat exchange and application of flash separation technology. Therefore, in the face of the current low energy efficiency of the refrigeration system, it is still necessary to reduce the heat loss of internal heat exchange and increase the refrigerating capacity, so as to improve the performance of the refrigeration system. SUMMARY

[0004] In view of the defects and deficiencies in the prior art, the purpose of the present application is to provide a two-stage compression refrigeration system applied to a cold storage and a control method. The refrigeration system uses two-stage compression throttling separation technology to increase the refrigerating capacity in the evaporator, optimizes the heat exchange matching of the internal heat exchange pipeline of the system, and reduces the heat loss in the heat exchange process. The system is configured with a compressor oil return control logic to ensure the safe and stable operation of the compressor, and is configured with an energy storage device to meet the temperature of the floor heat exchanger in the cold storage. The new refrigeration system and its control method improve the energy efficiency of the refrigeration system and the stable operation of the system.

[0005] To achieve the above technical purpose, the present application adopts the following technical scheme: A two-stage compression refrigeration system applied to a cold storage includes a high-pressure stage compressor, an outlet of the high-pressure stage compressor being connected with an inlet of a first oil separator, a first outlet of the first oil separator being connected with an inlet of a refrigerant side of an evaporative condenser, a first pipeline of a refrigerant outlet of the evaporative condenser being connected with an inlet of a first electronic expansion valve, the first electronic expansion valve being connected with an inlet of a cold side of a first heat regenerator, an outlet of the cold side of the first heat regenerator being connected with an inlet of a gas-liquid separator, a liquid outlet of the gas-liquid separator being connected with an inlet of a hot side of a second heat regenerator, an outlet of the hot side of the second heat regenerator being connected with an inlet of a second electronic expansion valve, an outlet of the second electronic expansion valve being connected with an inlet of an evaporator, an outlet of the evaporator being connected with an inlet of a cold side of the second heat regenerator, an outlet of the cold side of the second heat regenerator being connected with an inlet of a low-pressure stage compressor, an outlet of the low-pressure stage compressor being connected with an inlet of a second oil separator, a first outlet of the second oil separator being connected with an inlet of a hot side of a heat recovery device, an outlet of the hot side of the heat recovery device being connected with an inlet of a first three-way valve, an outlet of the first three-way valve being connected with an internal heat exchange pipeline of the gas-liquid separator and an inlet of a hot side of the first heat regenerator, an outlet of the hot side of the first heat regenerator being connected with an outlet of a gas phase of the gas-liquid separator and an inlet of the high-pressure stage compressor, a second outlet of the first oil separator being connected with an inlet of a hot side of a first oil cooler and an inlet of a second three-way valve, an outlet of the hot side of the first oil cooler being connected with an inlet of the second three-way valve, an outlet of the second three-way valve being connected with an inlet of the high-pressure stage compressor, a second pipeline of the refrigerant outlet of the evaporative condenser being connected with an inlet of a first temperature control valve, an outlet of the first temperature control valve being connected with an inlet of a cold side of the first oil cooler, an outlet of the cold side of the first oil cooler being connected with an outlet of the first oil separator and an inlet of the evaporative condenser, a second outlet of the second oil separator being connected with an inlet of a hot side of a second oil cooler and an inlet of a third three-way valve, an outlet of the hot side of the second oil cooler being connected with an inlet of the third three-way valve, an outlet of the third three-way valve being connected with an inlet of the low-pressure stage compressor, an outlet of the first temperature control valve being connected with an inlet of a second temperature control valve, an outlet of the second temperature control valve being connected with an inlet of a cold side of the second oil cooler, an outlet of the cold side of the second oil cooler being connected with an outlet of the second oil separator and an inlet of the hot side of the heat recovery device, an outlet of a cold side of the heat recovery device being connected with an inlet of a first water pump, an outlet of the first water pump being connected with inlets of a third temperature control valve and an energy storage device, outlets of the third temperature control valve and the energy storage device being connected with an inlet of a floor heat exchanger, an outlet of the floor heat exchanger being connected with an inlet of a cold side of the heat recovery device, an outlet of a water side of the evaporative condenser being connected with an inlet of a second water pump, water being connected with an inlet of a water side of the evaporative condenser.The inlet of the control device is connected with a first pressure sensor for measuring the outlet pressure of the high-pressure stage compressor, a second pressure sensor for measuring the suction port pressure of the high-pressure stage compressor, a third pressure sensor for measuring the outlet pressure of the evaporator, a first temperature sensor for measuring the suction port temperature of the high-pressure stage compressor, a second temperature sensor for measuring the oil return temperature at the inlet of the high-pressure stage compressor, a third temperature sensor for measuring the oil return temperature at the inlet of the low-pressure stage compressor, a fourth temperature sensor for measuring the outlet water return temperature of the floor heat exchanger, and a fifth temperature sensor for measuring the outlet temperature of the evaporator; the outlet of the control device is connected with a second water pump, a first three-way valve, a second three-way valve, a third three-way valve, a first temperature control valve, a second temperature control valve, a third temperature control valve, a second electronic expansion valve, and a regulating mechanism of a fan arranged near the evaporative condenser.

[0006] The high-temperature and high-pressure exhaust gas of the high-pressure stage compressor in the two-stage compression refrigeration system enters the evaporative condenser after passing through the first oil separator; after cooling, it is used as refrigerant and throttled by the first electronic expansion valve; after throttling, it enters the gas-liquid separator after absorbing heat in the first heat exchanger; the gas phase of the gas-liquid separator and the gas phase of the hot side outlet of the first heat exchanger are mixed and then enter the high-pressure stage compressor; the liquid phase in the gas-liquid separator is cooled by the second heat exchanger and then throttled by the second electronic expansion valve; the throttled refrigerant enters the evaporator to absorb heat and evaporate, and then enters the second heat exchanger to absorb heat; the heat-absorbed refrigerant enters the low-pressure stage compressor to increase pressure and temperature; the exhaust gas of the low-pressure stage compressor enters the heat recovery device after passing through the second oil separator; after cooling in the heat recovery device, it enters the first heat exchanger to release heat and then enters the high-temperature stage compressor to complete the refrigeration cycle; in order to protect the lubrication characteristics of the compressor operation, the lubricating oil of the first oil separator is cooled by the first oil cooler, and after mixing with part of the oil return to meet the oil return temperature setting, it enters the suction port of the high-pressure stage compressor; the cold source of the first oil cooler comes from part of the refrigerant condensed by the evaporative condenser, which absorbs heat in the first oil cooler and then enters the inlet of the evaporative condenser to cool again; the lubricating oil of the second oil separator is cooled by the second oil cooler, and after mixing with part of the oil return to meet the oil return temperature setting, it enters the suction port of the low-pressure stage compressor; the cold source of the second oil cooler comes from part of the refrigerant condensed by the evaporative condenser, which absorbs heat in the second oil cooler and then enters the inlet of the heat recovery device to cool again; the cold side water supply of the heat recovery device enters the floor heat exchanger through the first water pump and is intermittently fed into the energy storage device, and then enters the heat recovery device to absorb heat after cooling in the floor heat exchanger; the outlet of the heat recovery device is connected with the heat exchange pipeline inside the gas-liquid separator to prevent gas-liquid entrainment during gas-liquid separation.

[0007] The gas-liquid separator is a cyclone type gas-liquid separator, which includes a main body pipe, a refrigerant inlet, a gas phase outlet and a liquid phase outlet arranged on the main body pipe, a filamentous isolation net and a refrigerant heat exchange pipeline arranged in the upper space of the main body pipe, and a spiral flow channel and a conical structure arranged in the lower space of the main body pipe, which are beneficial to the formation of liquid seal.

[0008] The control method of the dual-stage compression refrigeration system applied to the cold storage comprises: the control device collects the outlet pressure of the high-pressure stage compressor, controls the start and stop of the fan and the second water pump; the control device collects the suction port pressure and temperature of the high-pressure stage compressor, and controls the opening degree of the first three-way valve; the control device collects the temperature and pressure of the evaporator outlet, and controls the opening degree of the second electronic expansion valve; the control device collects the oil return temperature of the high-pressure stage compressor and the low-pressure stage compressor, and controls the opening degrees of the second three-way valve, the third three-way valve, the first temperature control valve and the second temperature control valve; the control device collects the outlet temperature of the floor heat exchanger, and controls the opening degree of the third temperature control valve, so as to ensure the stable operation of the refrigeration system; the outlet set pressure of the high-temperature stage compressor is P10, and the deviation value is Δ10; the suction set pressure and set temperature of the high-temperature stage compressor are P20 and T20 respectively, and the deviation values are Δ21 and Δ22; the set pressure and set temperature of the evaporator outlet are P30 and T30 respectively, and the deviation values are Δ31 and Δ32; the oil return temperature of the high-pressure stage compressor and the low-pressure stage compressor is T40, and the deviation value is Δ40; the outlet set temperature of the floor heat exchanger is T50, and the deviation value is Δ50; and the control method is as follows: 1) The control device collects the signal P1 of the first pressure sensor arranged at the outlet of the high-pressure stage compressor, when P1>P10+Δ10, the control device controls the fan and the second water pump to start; when P1 2) The control device collects the signal P2 of the second pressure sensor arranged at the suction port of the high-pressure stage compressor and the signal T1 of the first temperature sensor, when P2>P20+Δ21 and T1>T20+Δ22, the control device controls the first three-way valve to reduce the flow rate into the gas-liquid separator; when P2 3) The control device collects the signal P3 of the third pressure sensor arranged at the outlet of the evaporator and the signal T5 of the fifth temperature sensor, when P3>P30+Δ31, T5>T30+Δ32, the control device controls the second electronic expansion valve to reduce the refrigerant flow into the evaporator, to reduce the temperature in the evaporator; when P3 4) The control device collects the signal T2 of the second temperature sensor arranged at the inlet of the high-pressure stage compressor and the signal T3 of the third temperature sensor arranged at the inlet of the low-pressure stage compressor, when T2>T40+Δ40, the control device controls the opening of the second three-way valve and the first temperature control valve, to adjust the oil return flow distribution and increase the refrigerant flow on the cold side of the first oil cooler; when T2 5) The control device collects the signal T4 of the fourth temperature sensor arranged at the outlet of the floor heat exchanger; when T4>T50+Δ50, the control device controls the opening of the third temperature control valve to increase the circulating water flow in the floor heat exchanger, and the energy storage device is put into operation; when T4

[0009] Compared with the prior art, the present application has the following advantages: 1. Considering the problem of large heat loss in the heat exchange of high-temperature refrigerant and low-temperature refrigerant in the refrigeration system, the present application optimizes the heat exchange pipeline in the system by configuring a multi-stage internal heat exchanger, improves the heat exchange process of the internal refrigerant, and thus improves the system performance; 2. Increase the refrigerating capacity of the refrigeration system by using efficient gas-liquid separator components and throttling separation process, and configure the corresponding control method, change the flow distribution of refrigerant through valve control, ensure the safe operation of the system, auxiliary energy storage device to reduce the energy consumption of the system, realize efficient operation in different scenes. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 A two-stage compression refrigeration system composition applied to a cold storage is described.

[0011] Figure 2 The structure diagram of the gas-liquid separator used in the system.

[0012] 1. High-pressure compressor; 2. Evaporative condenser; 3. First electronic expansion valve; 4. First regenerator; 5. Gas-liquid separator; 6. Second regenerator; 7. Second electronic expansion valve; 8. Evaporator; 9. Low-pressure compressor; 10. Heat recovery device; 11. First oil separator; 12. Second oil separator; 13. Energy storage device; 14. Floor heat exchanger; 15. First three-way valve; 16. Control device; 111. First oil cooler; 112. First temperature control valve; 113. Second three-way valve; 121. Second oil cooler; 122. Second temperature control valve; 123. Third three-way valve; 101. First water pump; 141. Third temperature control valve; 202. Second water pump; 161. First temperature sensor; 162. Second pressure sensor; 163. First pressure sensor; 164. Second temperature sensor; 165. Third temperature sensor; 166. Fourth temperature sensor; 167. Third pressure sensor; 168. Fifth temperature sensor; 201. Fan; 202. Second water pump; 501. Refrigerant inlet; 502. Gas phase outlet; 503. Liquid phase outlet; 504. Main body pipe; 505. Refrigerant heat exchange pipe; 506. Filament isolation net; 507. Spiral flow channel. DETAILED DESCRIPTION

[0013] The specific embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0014] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and an embodiment, it should be understood that the embodiment described herein is only used to explain the present application, and does not limit the present application.

[0015] Embodiment As Figure 1As shown, the application is a two-stage compression refrigeration system applied to cold storage, which comprises a high-pressure stage compressor 1, an outlet of the high-pressure stage compressor 1 being connected with an inlet of a first oil separator 11, a first outlet of the first oil separator 11 being connected with a refrigerant side inlet of an evaporative condenser 2, a first pipeline of a refrigerant side outlet of the evaporative condenser 2 being connected with an inlet of a first electronic expansion valve 3, the first electronic expansion valve 3 being connected with a cold side inlet of a first regenerator 4, a cold side outlet of the first regenerator 4 being connected with an inlet of a gas-liquid separator 5, a liquid phase outlet of the gas-liquid separator 5 being connected with a hot side inlet of a second regenerator 6, a hot side outlet of the second regenerator 6 being connected with an inlet of a second electronic expansion valve 7, an outlet of the second electronic expansion valve 7 being connected with an inlet of an evaporator 8, an outlet of the evaporator 8 being connected with a cold side inlet of the second regenerator 6, a cold side outlet of the second regenerator 6 being connected with an inlet of a low-pressure stage compressor 9, an outlet of the low-pressure stage compressor 9 being connected with an inlet of a second oil separator 12, a first outlet of the second oil separator 12 being connected with a hot side inlet of a heat recovery device 10, a hot side outlet of the heat recovery device 10 being connected with an inlet of a first three-way valve 15, an outlet of the first three-way valve 15 being connected with an internal heat exchange pipeline of the gas-liquid separator 5 and a hot side inlet of the first regenerator 4, a hot side outlet of the first regenerator 4 being connected with a gas phase outlet of the gas-liquid separator 5, and the mixed gas phase outlet and the gas phase outlet being connected with an inlet of the high-pressure stage compressor 1, a second outlet of the first oil separator 11 being connected with a hot side inlet of a first oil cooler 111 and an inlet of a second three-way valve 113, a hot side outlet of the first oil cooler 111 being connected with an inlet of the second three-way valve 113, an outlet of the second three-way valve 113 being connected with an inlet of the high-pressure stage compressor 1, a second pipeline of the refrigerant side outlet of the evaporative condenser 2 being connected with an inlet of a first temperature control valve 112, an outlet of the first temperature control valve 112 being connected with a cold side inlet of the first oil cooler 111, a cold side outlet of the first oil cooler 111 being connected with an outlet of the first oil separator 11, and the mixed outlet being connected with an inlet of the evaporative condenser 2, a second outlet of the second oil separator 12 being connected with a hot side inlet of a second oil cooler 121 and an inlet of a third three-way valve 123, a hot side outlet of the second oil cooler 121 being connected with an inlet of the third three-way valve 123, an outlet of the third three-way valve 123 being connected with an inlet of the low-pressure stage compressor 9, an outlet of the first temperature control valve 112 being connected with an inlet of a second temperature control valve 122, an outlet of the second temperature control valve 122 being connected with a cold side inlet of the second oil cooler 121, a cold side outlet of the second oil cooler 121 being connected with an outlet of the second oil separator 12, and the mixed outlet being connected with a hot side inlet of the heat recovery device 10, a cold side outlet of the heat recovery device 10 being connected with an inlet of a first water pump 101, an outlet of the first water pump 101 being connected with an inlet of a third temperature control valve 141 and an energy storage device 13, outlets of the third temperature control valve 141 and the energy storage device 13 being connected with an inlet of a floor heat exchanger 14, an outlet of the floor heat exchanger 14 being connected with a cold side inlet of the heat recovery device 10, a water side outlet of the evaporative condenser 2 being connected with an inlet of a second water pump 202, and water being connected with a water side inlet of the evaporative condenser 2.The inlet of the control device 16 is connected with the first pressure sensor 163 arranged at the outlet of the high-pressure stage compressor 1, the second pressure sensor 162 arranged at the suction port of the high-pressure stage compressor 1, the third pressure sensor 167 arranged at the outlet of the third pressure measuring evaporator 8, the first temperature sensor 161 arranged at the suction port of the high-pressure stage compressor 1, the second temperature sensor 164 arranged at the inlet of the high-pressure stage compressor 1, the third temperature sensor 165 arranged at the inlet of the low-pressure stage compressor 9, the fourth temperature sensor 166 arranged at the outlet of the floor heat exchanger 14, and the fifth temperature sensor 168 arranged at the outlet of the measuring evaporator 8; the outlet of the control device 16 is connected with the second water pump 202, the first three-way valve 15, the second three-way valve 113, the third three-way valve 123, the first temperature control valve 112, the second temperature control valve 122, the third temperature control valve 141, the second electronic expansion valve 7, and the adjusting mechanism of the fan 201 arranged near the evaporative condenser 2.

[0016] The working process of the two-stage compression refrigeration system applied to the cold storage according to the application is as follows: Figure 1As shown, the high-temperature and high-pressure exhaust gas of the high-pressure stage compressor 1 enters the evaporative condenser 2 after passing through the first oil separator 11; after cooling, it is throttled by the first electronic expansion valve 3 and then enters the gas-liquid separator 5 after absorbing heat in the first heat exchanger 4; the gas phase of the gas-liquid separator 5 mixes with the gas phase of the hot side outlet of the first heat exchanger 4 and then enters the high-pressure stage compressor 1; the liquid phase in the gas-liquid separator 5 is throttled by the second electronic expansion valve 7 after being cooled by the second heat exchanger 6; the throttled refrigerant enters the evaporator 8 to absorb heat and evaporate, and then enters the second heat exchanger 6 to absorb heat; the heat-absorbed refrigerant enters the low-pressure stage compressor 9 to increase pressure and temperature; the exhaust gas of the low-pressure stage compressor 9 enters the heat recovery device 10 after passing through the second oil separator 12; after being cooled by the heat recovery device 10, it enters the first heat exchanger 4 to release heat and then enters the high-temperature stage compressor 1 to complete the refrigeration cycle process; in order to protect the lubrication characteristics of the compressor operation, the lubricating oil of the first oil separator 11 is cooled by the first oil cooler 111, mixed with part of the oil return, and then enters the suction port of the high-pressure stage compressor 1 after meeting the oil return temperature setting; the cold source of the first oil cooler 111 comes from part of the refrigerant condensed by the evaporative condenser 2, which is cooled again by entering the inlet of the evaporative condenser 2 after absorbing heat by the first oil cooler 111; the lubricating oil of the second oil separator 12 is cooled by the second oil cooler 121, mixed with part of the oil return, and then enters the suction port of the low-pressure stage compressor 9 after meeting the oil return temperature setting; the cold source of the second oil cooler 121 comes from part of the refrigerant condensed by the evaporative condenser 2, which is cooled again by entering the inlet of the heat recovery device 10 after absorbing heat by the second oil cooler 121; the cold side water supply of the heat recovery device 10 enters the floor heat exchanger 14 through the first water pump 101 and is intermittently put into the energy storage device 13, and then enters the heat recovery device 10 to absorb heat after being cooled by the floor heat exchanger 14; part of the refrigerant at the outlet of the heat recovery device 10 is connected to the heat exchange pipeline inside the gas-liquid separator 5 to prevent gas-liquid entrainment during the gas-liquid separation process.

[0017] The application discloses a control method of a two-stage compression refrigerating system applied to a cold storage, wherein a control device 16 collects the outlet pressure of a high-pressure stage compressor 1, and controls the start and stop of a fan 201 and a second water pump 202; the control device 16 collects the suction port pressure and temperature of the high-pressure stage compressor 1, and controls the opening degree of a first three-way valve 15; the control device 16 collects the temperature and pressure of the outlet of an evaporator 8, and controls the opening degree of a second electronic expansion valve 7; the control device 16 collects the oil return temperature of the inlets of the high-pressure stage compressor 1 and a low-pressure stage compressor 9, and controls the opening degrees of a second three-way valve 113, a third three-way valve 123, a first temperature control valve 112 and a second temperature control valve 122; the control device 16 collects the outlet temperature of a floor heat exchanger 14, and controls the opening degree of a third temperature control valve 141, so as to ensure the stable operation of the refrigerating system; the set pressure P10 of the outlet of the high-temperature stage compressor 1 is 1.8 MPa, and the deviation value Delta10 is 0.05 MPa; the set pressure and set temperature of the suction of the high-temperature stage compressor 1 are 0.5 MPa and 5 DEG C respectively, the deviation values Delta21 and Delta22 are 0.05 MPa and 2 DEG C respectively; the set pressure and set temperature of the outlet of the evaporator 8 are 0.45 MPa and -10 DEG C respectively, the deviation values Delta31 and Delta32 are 0.05 MPa and 2.5 DEG C respectively; the oil return temperature T40 of the high-pressure stage compressor 1 and the low-pressure stage compressor 9 is 45 DEG C, and the deviation value Delta40 is 2.5 DEG C; the set temperature T50 of the outlet of the floor heat exchanger 14 is 5 DEG C, and the deviation value Delta50 is 2.0 DEG C; and the control method is as follows: 1) The control device 16 collects the signal P1 of the exhaust pressure sensor, i.e. the first pressure sensor 163, of the high-pressure stage compressor 1, when P1>1.85 MPa, the control device 16 controls the fan 201 and the second water pump 202 to start; when P1<1.75 MPa, the control device 16 controls the fan 201 and the second water pump 202 to stop; when 1.75 MPa≤P1≤1.85 MPa, the control device 16 controls the fan 201 and the second water pump 202 to stop, so as to ensure that the exhaust pressure of the high-pressure stage compressor 1 is in the safe operation range; 2) The control device 16 collects the signal P2 of the second pressure sensor 162 arranged at the suction port of the high-pressure stage compressor 1 and the signal T1 of the first temperature sensor 161, when P2>0.55 MPa and T1>7 DEG C, the control device 16 controls the first three-way valve 15 to reduce the flow rate into the gas-liquid separator 5; when P2<0.45 MPa and T1<3 DEG C, the control device 16 controls the first three-way valve 15 to increase the flow rate into the gas-liquid separator 5, so as to ensure that the state of the refrigerant at the inlet of the high-pressure stage compressor 1 is above the saturated temperature; when 0.45 MPa≤P2≤0.55 MPa and 3 DEG C≤T1≤7 DEG C, the control device 16 controls the opening degree of the first three-way valve 15 to be unchanged; 3) Control device 16 collects the signal P3 of the third pressure sensor 167 and the signal T5 of the fifth temperature sensor 168 set at the outlet of the evaporator 8, when P3> 0.50 MPa, T5> -7.5℃, the control device (16) controls the second electronic expansion valve 7 to reduce the refrigerant flow into the evaporator 8, to reduce the temperature in the evaporator; when P3<0.40 MPa, T5<-12.5℃, the control device 16 controls the second electronic expansion valve 7 to increase the refrigerant flow in the evaporator 8, to increase the temperature in the evaporator; when 0.40 MPa≤P3≤0.50 MPa, -12.5℃≤T5≤-7.5℃, the control device 16 controls the opening of the second electronic expansion valve 7 unchanged; 4) Control device 16 collects the signal T2 of the second temperature sensor 164, which is the oil return temperature sensor of the high-pressure stage compressor 1, and the signal T3 of the third temperature sensor 165 at the inlet of the low-pressure stage compressor 9, when T2> 47.5℃, the control device 16 controls the opening of the second three-way valve 113 and the first temperature control valve 112 to adjust the oil return flow distribution and increase the refrigerant flow on the cold side of the first oil cooler 111; when T2<42.5℃, the control device 16 controls the opening of the second three-way valve 113 and the first temperature control valve 112 to adjust the oil return flow distribution and reduce the refrigerant flow on the cold side of the first oil cooler 111; when 42.5℃≤T2≤47.5℃, the control device 16 controls the opening of the second three-way valve 113 and the first temperature control valve 112 unchanged; when T3> 47.5℃, the control device 16 controls the opening of the third three-way valve 123 and the second temperature control valve 122 to adjust the oil return flow distribution and increase the refrigerant flow on the cold side of the second oil cooler 121; when T3<42.5℃, the control device 16 controls the opening of the third three-way valve 123 and the second temperature control valve 122 to adjust the oil return flow distribution and reduce the refrigerant flow on the cold side of the second oil cooler 121; when 42.5℃≤T3≤47.5℃, the control device 16 controls the opening of the third three-way valve 123 and the second temperature control valve 122 unchanged; 5) Control device 16 collects the signal T4 of the fourth temperature sensor 166, which is the return water temperature sensor of the floor heat exchanger 14; when T4> 7℃, the control device 16 controls the opening of the third temperature control valve 141 to reduce the circulating water flow in the floor heat exchanger 14, and stops the operation of the energy storage device 13; when T4<3℃, the control device 16 controls the opening of the third temperature control valve 141 to increase the circulating water flow in the floor heat exchanger 14, and stops the operation of the energy storage device 13; when 3℃≤T4≤7℃, the control device 16 maintains the opening of the third temperature control valve 141 unchanged, and operates the energy storage device 13.

[0018] As Figure 2As shown, the gas-liquid separator 5 in the refrigeration system of the present application is a cyclone gas-liquid separator, comprising a main pipe 504, a refrigerant inlet 501, a gas phase outlet 502 and a liquid phase outlet 503 arranged on the main pipe 504, a filament isolation net 506 and a refrigerant heat exchange pipe 505 arranged in the upper space of the main pipe 504, and a spiral flow channel 507 and a conical structure arranged in the lower space of the main pipe 504, which are beneficial to form a liquid seal.

Claims

1. A two-stage compression refrigeration system applied to a cold storage, characterized in that, The application relates to a refrigeration system, which comprises a high-pressure stage compressor (1), a first oil separator (11), a first outlet of the first oil separator (11), an evaporative condenser (2), a first pipeline of a refrigerant outlet of the evaporative condenser (2), a first electronic expansion valve (3), a cold side inlet of a first heat regenerator (4), a gas-liquid separator (5), a hot side inlet of a second heat regenerator (6), a second electronic expansion valve (7), an evaporator (8), a cold side inlet of the second heat regenerator (6), a low-pressure stage compressor (9), a second oil separator (12), a hot side inlet of a heat recovery device (10), a first three-way valve (15), a gas phase outlet of the gas-liquid separator (5), a second outlet of the first oil separator (11), a hot side inlet of a first oil cooler (111), a second three-way valve (113), a second pipeline of the refrigerant outlet of the evaporative condenser (2), a first temperature control valve (112), a cold side inlet of the first oil cooler (111), a second outlet of the second oil separator (12), a hot side inlet of a second oil cooler (121), a third three-way valve (123), an outlet of the first three-way valve (15), an internal heat exchange pipeline of the gas-liquid separator (5), a hot side inlet of the first heat regenerator (4), a hot side outlet of the first heat regenerator (4), a hot side outlet of the second heat regenerator (6), an inlet of the low-pressure stage compressor (9), an outlet of the second three-way valve (113), an inlet of the high-pressure stage compressor (1), an outlet of the first temperature control valve (112), an inlet of the second temperature control valve (122), an outlet of the second temperature control valve (122), a cold side outlet of the second oil cooler (121), a hot side inlet of the heat recovery device (10), a cold side outlet of the heat recovery device (10), an inlet of a first water pump (101), an outlet of the first water pump (101), an inlet of a third temperature control valve (141) and an energy storage device (13).The third temperature control valve (141) and the outlet of the energy storage device (13) are connected with the inlet of the floor heat exchanger (14); the outlet of the floor heat exchanger (14) is connected with the cold side inlet of the heat recovery device (10); the water side outlet of the evaporative condenser (2) is connected with the inlet of the second water pump (202), and the water supply is connected with the water side inlet of the evaporative condenser (2); the inlet of the control device (16) is connected with the first pressure sensor (163) for measuring the outlet pressure of the high-pressure stage compressor (1), the second pressure sensor (162) for measuring the suction port pressure of the high-pressure stage compressor (1), the third pressure sensor (167) for measuring the outlet pressure of the evaporator (8), the first temperature sensor (161) for measuring the suction port temperature of the high-pressure stage compressor (1), the second temperature sensor (164) for measuring the oil return temperature at the inlet of the high-pressure stage compressor (1), the third temperature sensor (165) for measuring the oil return temperature at the inlet of the low-pressure stage compressor (9), the fourth temperature sensor (166) for measuring the water return temperature at the outlet of the floor heat exchanger (14), and the fifth temperature sensor (168) for measuring the outlet temperature of the evaporator (8); and the outlet of the control device (16) is connected with the adjustment mechanism of the second water pump (202), the first three-way valve (15), the second three-way valve (113), the third three-way valve (123), the first temperature control valve (112), the second temperature control valve (122), the third temperature control valve (141), the second electronic expansion valve (7), and the fan (201) arranged near the evaporative condenser (2).

2. The two-stage compression refrigeration system applied to a cold storage according to claim 1, characterized in that, The high-temperature and high-pressure exhaust gas of the high-pressure stage compressor (1) enters the evaporative condenser (2) after passing through the first oil separator (11); after cooling, it is throttled by the first electronic expansion valve (3) and enters the gas-liquid separator (5) after absorbing heat by the first heat exchanger (4); the gas phase of the gas-liquid separator (5) is mixed with the gas phase of the hot side outlet of the first heat exchanger (4) and then enters the high-pressure stage compressor (1); the liquid phase in the gas-liquid separator (5) is throttled by the second heat exchanger (6) and then enters the second electronic expansion valve (7); the throttled refrigerant absorbs heat in the evaporator (8) and then enters the second heat exchanger (6); the heat-absorbed refrigerant is pressurized and heated in the low-pressure stage compressor (9); the exhaust gas of the low-pressure stage compressor (9) enters the heat recovery device (10) after passing through the second oil separator (12); after cooling by the heat recovery device (10), it enters the first heat exchanger (4) to release heat and then enters the high-temperature stage compressor (1), completing the refrigeration cycle; in order to protect the lubrication characteristics of the compressor operation, the lubricating oil of the first oil separator (11) is cooled by the first oil cooler (111) and mixed with part of the oil return to meet the oil return temperature setting before entering the suction port of the high-pressure stage compressor (1); the cold source of the first oil cooler (111) comes from part of the refrigerant condensed by the evaporative condenser (2), which absorbs heat in the first oil cooler (111) and then enters the inlet of the evaporative condenser (2) to be cooled again; the lubricating oil of the second oil separator (12) is cooled by the second oil cooler (121) and mixed with part of the oil return to meet the oil return temperature setting before entering the suction port of the low-pressure stage compressor (9); the cold source of the second oil cooler (121) comes from part of the refrigerant condensed by the evaporative condenser (2), which absorbs heat in the second oil cooler (121) and then enters the inlet of the heat recovery device (10) to be cooled again; the cold side water of the heat recovery device (10) enters the floor heat exchanger (14) by the first water pump (101) and is intermittently fed into the energy storage device (13), which is cooled by the floor heat exchanger (14) and then enters the heat recovery device (10) to absorb heat; part of the refrigerant at the outlet of the heat recovery device (10) is connected to the heat exchange pipeline inside the gas-liquid separator (5) to prevent gas-liquid entrainment during the gas-liquid separation process.

3. The two-stage compression refrigeration system applied to a cold storage according to claim 1, characterized in that, The gas-liquid separator (5) is a cyclone gas-liquid separator, which includes a main pipe (504), a refrigerant inlet (501), a gas phase outlet (502), and a liquid phase outlet (503) arranged on the main pipe (504), a filament isolation net (506) and a refrigerant heat exchange pipeline (505) arranged in the upper space of the main pipe (504), and a spiral flow channel (507) and a conical structure arranged in the lower space of the main pipe (504), which are beneficial to forming a liquid seal.

4. The control method of a two-stage compression refrigeration system applied to a cold storage according to any one of claims 1 to 3, characterized in that, The control device (16) collects the outlet pressure of the high-pressure stage compressor (1), controls the start-stop of the fan (201) and the second water pump (202); the control device (16) collects the suction port pressure and temperature of the high-pressure stage compressor (1), controls the opening of the first three-way valve (15); the control device (16) collects the temperature and pressure at the outlet of the evaporator (8), controls the opening of the second electronic expansion valve (7); the control device (16) collects the oil return temperature at the inlet of the high-pressure stage compressor (1) and the low-pressure stage compressor (9), controls the opening of the second three-way valve (113), the third three-way valve (123), the first temperature control valve (112) and the second temperature control valve (122); the control device (16) collects the outlet temperature of the floor heat exchanger (14), controls the opening of the third temperature control valve (141), and ensures the stable operation of the refrigeration system; the outlet set pressure of the high-temperature stage compressor (1) is P10, and the deviation value is Δ10; the suction set pressure and set temperature of the high-temperature stage compressor (1) are P20 and T20, respectively, and the deviation values are Δ21 and Δ22; the set pressure and set temperature at the outlet of the evaporator (8) are P30 and T30, respectively, and the deviation values are Δ31 and Δ32; the oil return temperature of the high-pressure stage compressor (1) and the low-pressure stage compressor (9) is T40, and the deviation value is Δ40; the set temperature of the outlet temperature of the floor heat exchanger (14) is T50, and the deviation value is Δ50; the control method is as follows: 1) The control device (16) collects the signal P1 of the first pressure sensor (163) arranged at the outlet of the high-pressure stage compressor (1), when P1>P10+Δ10, the control device (16) controls the fan (201) and the second water pump (202) to start; when P1 2) The control device (16) collects the signal P2 of the second pressure sensor (162) arranged at the suction port of the high-pressure stage compressor (1) and the signal T1 of the first temperature sensor (161), when P2>P20+Δ21, T1>T20+Δ22, the control device (16) controls the first three-way valve (15) to reduce the flow into the gas-liquid separator (5); when P2 When P2P20-Δ21, T1T20-Δ22, the control device (16) controls the first three-way valve (15) to increase the flow into the gas-liquid separator (5), so that the state of the refrigerant at the inlet of the high-pressure stage compressor (1) is above the saturated temperature; when P20-Δ21P2P20+Δ21, T20-Δ22T1T20+Δ22, the opening of the first three-way valve (15) is unchanged. 3) The control device (16) collects the signal P3 of the third pressure sensor (167) and the signal T5 of the fifth temperature sensor (168) set at the outlet of the evaporator (8). When P3>P30+Δ31, T5>T30+Δ32, the control device (16) controls the second electronic expansion valve (7) to reduce the refrigerant flow into the evaporator (8) and lower the temperature in the evaporator. When P3P30-Δ31, T5T30-Δ32, the control device (16) controls the second electronic expansion valve (7) to increase the refrigerant flow in the evaporator (8) and raise the temperature in the evaporator. When P30-Δ31≤P3≤P30+Δ31, T30-Δ32≤T5≤T30+Δ32, the control device (16) controls the opening of the second electronic expansion valve (7) to remain unchanged; 4) The control device (16) collects the signal T2 of the second temperature sensor (164) set at the inlet of the high-pressure stage compressor (1) and the signal T3 of the third temperature sensor (165) set at the inlet of the low-pressure stage compressor (9). When T2>T40+Δ40, the control device (16) controls the opening of the second three-way valve (113) and the first temperature control valve (112) to adjust the oil return flow distribution and increase the refrigerant flow on the cold side of the first oil cooler (111). When T2T40-Δ40, the control device (16) controls the opening of the second three-way valve (113) and the first temperature control valve (112) to adjust the oil return flow distribution and decrease the refrigerant flow on the cold side of the first oil cooler (111). When T40-Δ40≤T2≤T40+Δ40, the control device (16) controls the opening of the second three-way valve (113) and the first temperature control valve (112) to remain unchanged. When T3>T40+Δ40, the control device (16) controls the opening of the third three-way valve (123) and the second temperature control valve (122) to adjust the oil return flow distribution and increase the refrigerant flow on the cold side of the second oil cooler (121). When T3T40-Δ40, the control device (16) controls the opening of the third three-way valve (123) and the second temperature control valve (122) to adjust the oil return flow distribution and decrease the refrigerant flow on the cold side of the second oil cooler (121). When T40-Δ40≤T3≤T40+Δ40, the control device (16) controls the opening of the third three-way valve (123) and the second temperature control valve (122) to remain unchanged. 5) The control device (16) collects the signal T4 of the fourth temperature sensor (166) arranged at the outlet of the floor heat exchanger (14); when T4>T50+Δ50, the control device (16) controls the opening of the third temperature control valve (141) to increase the circulating water flow in the floor heat exchanger (14) and put the energy storage device (13) into operation; when T4T50-Δ50, the control device (16) controls the opening of the third temperature control valve (141) to reduce the circulating water flow in the floor heat exchanger (14) and stop the energy storage device (13) from operating; when T50-Δ50≤T4≤T50+Δ50, the control device (16) maintains the opening of the third temperature control valve (141) unchanged and puts the energy storage device (13) into operation.

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