A heat pump type two-stage compression defrosting device

Abstract

The present invention provides a heat pump type two-stage compression defrosting device. In the device of the present invention, a heat pump system is added to a traditional cold storage refrigeration system, and the high-temperature heat source of the low-pressure stage compressor refrigeration cycle is transformed into the low-temperature heat source of the high-pressure stage compressor cycle. The kinetic energy input into the high-pressure stage compressor in the system is used to increase the exhaust temperature for rapid defrosting. This method is more energy-saving compared to directly using electric heating for defrosting, and the condensation heat of the low-pressure stage compressor refrigeration cycle is recovered, which is of energy-saving significance for the entire system.

Description

Technical Field

[0001] The present invention relates to the technical field of refrigeration and heat transfer, and particularly to a heat pump type two-stage compression defrosting device. Background Art

[0002] At present, cold storages mainly use the principle of evaporation refrigeration for cooling. Since the interior of the cold storage is in a low-temperature and high-humidity state for a long time, the saturated partial pressure of water vapor on the surface of the evaporator becomes smaller, and the relative humidity reaches 100%. As a result, water vapor precipitates and frost forms on the surface of the evaporator. The thickness of the frost layer affects the heat transfer effect of the evaporator. For air-coolers, the frost layer reduces the air flow area, increases the gas resistance, and increases the power consumption of the fan. In addition, it also affects the flow characteristics of the lubricating oil in the compressor, resulting in a reduction in the energy efficiency of the entire refrigeration system, temperature fluctuations in the cold storage, causing energy waste and a decline in the quality of frozen products.

[0003] To improve the heat transfer condition on the surface of the evaporator, regular defrosting has become a necessary process in the refrigeration process. The defrosting methods currently in use mainly include electric heating defrosting method, hot gas defrosting method, energy storage defrosting method, liquid refrigerant defrosting method, and continuous defrosting method, etc. However, each defrosting method has its own advantages and disadvantages. The problems that need to be urgently solved in the defrosting process of cold storages at present are to reduce the temperature fluctuations in the cold storage and shorten the defrosting time.

[0004] Manual defrosting: A traditional defrosting method. In some cold storages using evaporator coils for refrigeration, to prevent the moisture generated by hot gas defrosting from contaminating frozen products, the manual defrosting method is generally used. Usually, special personnel need to hold defrosting tools to work in the cold storage. This method does not require additional devices, has a short defrosting time, and small indoor temperature fluctuations. However, it will increase the labor cost, and the working environment of the staff is also poor. In recent years, the manual defrosting method is combined with other defrosting methods and is suitable for small and medium-sized refrigeration systems.

[0005] Water flushing defrosting: The ceiling-mounted air-cooler is equipped with a water spraying device, and the kinetic energy generated by high-pressure water flow is used to peel off the frost layer on the coil. The working process of water flushing defrosting is divided into three processes: refrigerant evacuation, water flushing defrosting, and drainage. Therefore, the defrosting time is relatively long, and a large amount of water is required. It is suitable for areas with sufficient water sources. This method is simple to operate and is suitable for the situation where the air-cooler has a slow frosting speed and a relatively thin frost layer.

[0006] Electric heating defrosting: Heating rods are inserted into the evaporator coils of the air-cooler, and the heat energy converted from electric energy is used to melt the frost layer on the evaporator. The defrosting time of electric heating defrosting is short, the system is simple, and automatic control can be achieved. However, the defrosting process consumes too much energy, is prone to the risk of secondary frosting, and has a greater impact on the temperature of the cold storage.

[0007] Air defrosting: The biggest feature of air defrosting is that the installation form of the air cooler is different from other methods. The air cooler in the air defrosting system is placed in a sealed cavity, and this cavity is connected to the cold storage and the outside through valves respectively. When refrigerating, the valve connected to the outside is closed, and the valve connected to the cold storage is opened. The air in the cold storage passes through the air cooler to complete the refrigeration cycle; when defrosting, the valve connected to the outside is opened, the valve connected to the cold storage is closed, and the fan keeps running to realize the defrosting process by using the outside temperature. This method does not require additional energy consumption and is simple to operate; however, it has high requirements for the airtight heat preservation effect of the valves and is only applicable to mild regions where the outside temperature in winter is not lower than 2°C.

[0008] Hot gas defrosting: This defrosting method uses the high-temperature and high-pressure gas before the condenser in the refrigeration cycle, and introduces the gas into the evaporator that needs to be defrosted to condense and release heat. This system recovers and uses the heat of the condenser for defrosting, which has the significance of energy conservation. And the liquid temperature is high, and the defrosting time is short. Correspondingly, this method has a greater impact on the temperature fluctuation in the cold storage. This system has complex pipelines and generally requires a liquid discharge container. This method is widely used in cold storage defrosting.

[0009] Energy storage defrosting: This method is an improved method for hot gas defrosting. An energy storage device is added to the hot gas defrosting system, and the stored heat is used for defrosting. The defrosting time is shorter than that of a simple hot gas defrosting system, but the system structure is complex, and the materials of the heat storage device limit the application of this method.

[0010] Liquid refrigerant defrosting: Liquid refrigerant defrosting is similar to hot gas defrosting, both using the high-temperature and high-pressure gas after the compressor for heat dissipation and defrosting. The difference in liquid refrigerant defrosting is that the evaporator that needs to be defrosted is connected in series after the condenser, and the liquid refrigerant obtains a higher degree of subcooling during the defrosting process, converting the defrosting cooling capacity into a degree of subcooling, which can improve the overall efficiency of the refrigeration system. This system requires more than two evaporators to work in parallel, and the system setting is also relatively complex. However, the temperature fluctuation in the cold storage is small and the system efficiency is high.

[0011] Continuous defrosting: The continuous defrosting method is also an improved method for hot gas defrosting. The continuous defrosting system needs to set up multiple evaporators. When one of the evaporators needs to be defrosted, the high-temperature and high-pressure gas that has not entered the condenser at the compressor outlet is first allowed to flow into the defrosting evaporator by using valve control. This method has a fast defrosting speed and a complex system. However, it will cause temperature fluctuations in the cold storage when the frosting is small.

[0012] The above several defrosting methods have all been applied. Among them, the liquid refrigerant defrosting and continuous defrosting methods can use the condenser as a heat source for defrosting, without the need for other heat sources, and can achieve energy-saving effects. Moreover, these two methods have a high degree of automation and are easy to control, which are the defrosting methods promoted in recent years. However, no matter which method is used, there are certain defects. At present, there is an urgent need for a defrosting device with a fast defrosting speed, small room temperature fluctuations, and the ability to utilize the condensation heat. Summary of the Invention

[0013] The object of the present invention is to solve the problems in the prior art, and a heat pump type two-stage compression defrosting device is proposed. The device can shorten the defrosting time, avoid temperature fluctuations, has a high defrosting efficiency, and can utilize a refrigeration defrosting system with the high-pressure stage compressor as the kinetic energy. At the same time, the device has a high defrosting efficiency, small temperature fluctuations, stable operation, and can recover the heat discharged by the condenser for defrosting, reducing energy consumption.

[0014] The present invention is realized through the following technical solutions. The present invention proposes a heat pump type two-stage compression defrosting device, which includes a first evaporator, a second evaporator, a condenser, a low-pressure stage compressor, a high-pressure stage compressor, an intermediate cooler, a gas-liquid separator, a first thermostatic expansion valve, a second thermostatic expansion valve, a third thermostatic expansion valve, a first solenoid valve, a second solenoid valve, a third solenoid valve, a fourth solenoid valve, a fifth solenoid valve, a sixth solenoid valve, a seventh solenoid valve, an eighth solenoid valve, a ninth solenoid valve, a tenth solenoid valve, an eleventh solenoid valve, a twelfth solenoid valve, a thirteenth solenoid valve, a first check valve, a second check valve, a third check valve, a dryer, a sight glass, a defrosting controller, a first fan and a second fan;

[0015] The first interface of the intermediate cooler is connected to the inlet of the high-pressure stage compressor through a third one-way valve. The first interfaces of the first evaporator and the second evaporator are respectively connected to the outlet of the high-pressure stage compressor in parallel after passing through a sixth solenoid valve and an eighth solenoid valve. The second interfaces of the first evaporator and the second evaporator are respectively connected to the third interface of the intermediate cooler and the second connection port of the defrost controller in parallel after passing through a fifth solenoid valve and a seventh solenoid valve. When connected to the third interface of the intermediate cooler, it passes through an eleventh solenoid valve and a third thermostatic expansion valve. When connected to the second connection port of the defrost controller, it passes through a thirteenth solenoid valve. The second interface of the intermediate cooler is connected to the outlet of the low-pressure stage compressor and the inlet of the condenser through a second one-way valve and a tenth solenoid valve. When the second interface of the intermediate cooler is connected to the inlet of the condenser, it passes through a ninth solenoid valve and a first one-way valve. The outlet of the condenser is connected to the inlet of the first connection port of the defrost controller through a twelfth solenoid valve. The outlet of the defrost controller is connected to the inlet of the dryer. The outlet of the dryer is connected to the inlet of the sight glass. The outlet of the sight glass is connected to the first interfaces of the first evaporator and the second evaporator. When the outlet of the sight glass is connected to the first evaporator, it passes through a second solenoid valve and a first thermostatic expansion valve. When the outlet of the sight glass is connected to the second evaporator, it passes through a fourth solenoid valve and a second thermostatic expansion valve. The second interfaces of the first evaporator and the second evaporator are respectively connected to the inlet of the gas-liquid separator in parallel after passing through a first solenoid valve and a third solenoid valve. The outlet of the gas-liquid separator is connected to the inlet of the low-pressure stage compressor; the first evaporator is provided with a first fan, and the second evaporator is provided with a second fan; the defrost controller is respectively connected to the first fan, the second fan, the tenth solenoid valve, the twelfth solenoid valve, the thirteenth solenoid valve, and the dryer, and controls the opening and closing of the valves and the fans to realize the refrigeration and defrosting working conditions.

[0016] Further, when the device is in the refrigeration working condition, the fifth solenoid valve, the sixth solenoid valve, the seventh solenoid valve, the eighth solenoid valve, the eleventh solenoid valve, and the thirteenth solenoid valve are closed, and the other solenoid valves are opened; the first evaporator and the second evaporator are evaporators; the condenser is a condenser; the defrost controller controls the first fan and the second fan to be turned on; the low-temperature and low-pressure refrigerant flowing out from the outlets of the first evaporator and the second evaporator enters the gas-liquid separator through the first solenoid valve and the third solenoid valve. The gaseous refrigerant separated by the gas-liquid separator is sucked by the low-pressure stage compressor and compressed into a medium-temperature and medium-pressure gas and discharged. The excess liquid refrigerant is stored in the gas-liquid separator; the gas enters the condenser through the ninth solenoid valve and the first one-way valve to release heat and condense into a saturated state, and then passes through the twelfth solenoid valve, the defrost controller, the dryer, the sight glass, the first thermostatic expansion valve, the second thermostatic expansion valve, the second solenoid valve, and the fourth solenoid valve to enter the first evaporator and the second evaporator to evaporate and absorb heat to complete refrigeration, and then flows out from the outlets of the first evaporator and the second evaporator to enter the next cycle.

[0017] Further, when the device defrosts the first evaporator, the first solenoid valve, the second solenoid valve, the seventh solenoid valve, the eighth solenoid valve, the ninth solenoid valve, and the twelfth solenoid valve are closed, and other solenoid valves are opened; the first evaporator serves as a condenser; the second evaporator serves as an evaporator; the condenser is closed; the defrost controller controls the first fan to close and the second fan to open; the low-temperature and low-pressure refrigerant flowing out of the second evaporator outlet enters the gas-liquid separator through the third solenoid valve. The gaseous refrigerant separated by the gas-liquid separator is sucked into the low-pressure stage compressor and compressed into medium-temperature and medium-pressure gas and discharged. The excess liquid refrigerant is stored in the gas-liquid separator; the medium-temperature and medium-pressure gas passes through the tenth solenoid valve and the second check valve and enters the intercooler. The gas separated from the intercooler passes through the third check valve and is sucked into the high-pressure stage compressor and compressed into high-temperature and high-pressure gas; the high-temperature and high-pressure gas enters the first evaporator through the sixth solenoid valve to perform a defrosting action on the first evaporator. At this time, the first fan is closed, effectively avoiding the exposure of hot air and affecting the temperature fluctuation of the cold storage; after the heat release process is completed in the first evaporator, it is divided into two paths after passing through the fifth solenoid valve. One path passes through the third thermostatic expansion valve and the eleventh solenoid valve and enters the intercooler. After separating the gas, it enters the high-pressure stage compressor for high-pressure circulation; the other path exchanges heat with the liquid in the intercooler to become a subcooled liquid. The subcooled liquid passes through the thirteenth solenoid valve, the defrost controller, the dryer, the sight glass, the fourth solenoid valve, and the second thermostatic expansion valve and enters the second evaporator to evaporate and absorb heat for refrigeration to ensure the room temperature requirement of the cold storage; the refrigerant flows out of the second evaporator outlet to form a closed cycle.

[0018] Further, when the device defrosts the second evaporator, the third solenoid valve, the fourth solenoid valve, the fifth solenoid valve, the sixth solenoid valve, the ninth solenoid valve, and the twelfth solenoid valve are closed, and other solenoid valves are opened; the second evaporator serves as a condenser; the first evaporator serves as an evaporator; the condenser is closed; the defrost controller controls the first blower to close and the second blower to open; the low-temperature and low-pressure refrigerant flowing out of the first evaporator outlet enters the gas-liquid separator through the first solenoid valve. The gas refrigerant separated by the gas-liquid separator is sucked and compressed by the low-stage compressor into medium-temperature and medium-pressure gas and discharged, and the excess liquid refrigerant is stored in the gas-liquid separator; the medium-temperature and medium-pressure gas passes through the tenth solenoid valve and the second check valve and enters the intercooler. The gas separated from the intercooler passes through the third check valve and is sucked and compressed by the high-stage compressor into high-temperature and high-pressure gas; the high-temperature and high-pressure gas enters the second evaporator through the eighth solenoid valve to perform a defrosting operation on the second evaporator. At this time, the second blower is closed, effectively avoiding the exposure of hot gas and affecting the temperature fluctuation in the cold storage; after completing the heat release process in the second evaporator, it is divided into two paths after passing through the seventh solenoid valve. One path passes through the third thermal expansion valve and the eleventh solenoid valve and enters the intercooler, and after separating the gas, it enters the high-stage compressor for high-pressure circulation; the other path exchanges heat with the liquid in the intercooler to become a subcooled liquid, and the subcooled liquid passes through the thirteenth solenoid valve, the defrost controller, the dryer, the sight glass, the second solenoid valve, and the first thermal expansion valve and enters the first evaporator to evaporate and absorb heat for refrigeration to ensure the room temperature requirement in the cold storage; the refrigerant flows out of the first evaporator outlet to form a closed cycle.

[0019] The beneficial effects of the present invention are as follows:

[0020] The main factors for judging the defrosting effect in the cold storage are mainly three aspects: 1. Defrosting time; 2. Room temperature fluctuation; 3. Energy consumption. Starting from these three factors, the present invention seeks a defrosting device with fast defrosting speed, small room temperature fluctuation, and condensable heat utilization. The heat pump type two-stage compression defrosting device proposed by the present invention has the following three characteristics:

[0021] 1. The present invention adds a high-stage compressor to form a heat pump cycle system and uses a relatively high exhaust temperature to defrost the cold storage. The exhaust temperature of a single-stage compression refrigeration system is generally 35°C to 40°C, and the temperature of the system entering the defrost evaporator using the continuous defrosting method does not exceed 40°C; while the exhaust temperature of a two-stage compression refrigeration system can reach 55°C to 60°C, and the defrosting speed is faster at this temperature. Taking the refrigerant temperature at the defrost evaporator outlet as the target, the automatic control of the system is realized. Under this control method, the defrosting time of the two-stage compression refrigeration system is only 64% of that of the single-stage compression refrigeration system, greatly shortening the time.

[0022] 2. Under the two cycles of separate refrigeration and defrosting, the low-pressure stage compression system is responsible for continuously refrigerating the environment. However, during defrosting, due to the addition of an intermediate cooler in the cycle, the subcooling degree obtained by the liquid refrigerant during defrosting is increased, resulting in the left shift of the state point entering the refrigeration evaporator in the pressure-enthalpy diagram, and the refrigeration capacity of the refrigeration system becomes larger. This additional refrigeration capacity can reduce the room temperature fluctuation in the environment and keep the temperature in the entire cold storage within a stable range.

[0023] 3. The device of the present invention adds a heat pump system to the traditional cold storage refrigeration system, converting the medium-temperature heat source of the low-pressure stage compressor refrigeration cycle into the low-temperature heat source of the high-pressure stage compressor cycle. The kinetic energy input into the high-pressure stage compressor in the system is used to increase the exhaust temperature for rapid defrosting. This method is more energy-saving compared to directly using electric heating for defrosting, and it also recovers the condensation heat of the low-pressure stage compressor refrigeration cycle, which is of energy-saving significance for the entire system. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic structural diagram of a heat pump type two-stage compression defrosting device described in the present invention.

[0025] Description of the marks in the figure:

[0026] The first evaporator 1, the second evaporator 2, the condenser 3, the low-pressure stage compressor 4, the high-pressure stage compressor 5, the intermediate cooler 6, the gas-liquid separator 7, the first thermostatic expansion valve 8, the second thermostatic expansion valve 9, the third thermostatic expansion valve 10, the first solenoid valve 11, the second solenoid valve 12, the third solenoid valve 13, the fourth solenoid valve 14, the fifth solenoid valve 15, the sixth solenoid valve 16, the seventh solenoid valve 17, the eighth solenoid valve 18, the ninth solenoid valve 19, the tenth solenoid valve 20, the eleventh solenoid valve 21, the twelfth solenoid valve 22, the thirteenth solenoid valve 23, the first check valve 24, the second check valve 25, the third check valve 26, the dryer 27, the sight glass 28, the defrost controller 29, the first fan 30, the second fan 31. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0028] Combined with Figure 1, the present invention provides a heat pump type two-stage compression defrosting device, which includes a first evaporator 1, a second evaporator 2, a condenser 3, a low-pressure stage compressor 4, a high-pressure stage compressor 5, an intermediate cooler 6, a gas-liquid separator 7, a first thermostatic expansion valve 8, a second thermostatic expansion valve 9, a third thermostatic expansion valve 10, a first solenoid valve 11, a second solenoid valve 12, a third solenoid valve 13, a fourth solenoid valve 14, a fifth solenoid valve 15, a sixth solenoid valve 16, a seventh solenoid valve 17, an eighth solenoid valve 18, a ninth solenoid valve 19, a tenth solenoid valve 20, an eleventh solenoid valve 21, a twelfth solenoid valve 22, a thirteenth solenoid valve 23, a first check valve 24, a second check valve 25, a third check valve 26, a dryer 27, a sight glass 28, a defrost controller 29, a first fan 30 and a second fan 31.

[0029] The first interface of the intermediate cooler 6 is connected to the inlet of the high-pressure stage compressor 5 through the third check valve 26. The first interfaces of the first evaporator 1 and the second evaporator 2 are respectively connected to the outlet of the high-pressure stage compressor 5 in parallel after passing through the sixth solenoid valve 16 and the eighth solenoid valve 18. The second interfaces of the first evaporator 1 and the second evaporator 2 are respectively connected to the third interface of the intermediate cooler 6 and the second connection port of the defrost controller 29 in parallel after passing through the fifth solenoid valve 15 and the seventh solenoid valve 17. When connected to the third interface of the intermediate cooler 6, it passes through the eleventh solenoid valve 21 and the third thermostatic expansion valve 10. When connected to the second connection port of the defrost controller 29, it passes through the thirteenth solenoid valve 23. The second interface of the intermediate cooler 6 is connected to the outlet of the low-pressure stage compressor 4 and the inlet of the condenser 3 through the second check valve 25, the tenth solenoid valve 20. When the second interface of the intermediate cooler 6 is connected to the inlet of the condenser 3, it passes through the ninth solenoid valve 19 and the first check valve 24. The outlet of the condenser 3 is connected to the inlet of the first connection port of the defrost controller 29 through the twelfth solenoid valve 22. The outlet of the defrost controller 29 is connected to the inlet of the dryer 27. The outlet of the dryer 27 is connected to the inlet of the sight glass 28. The outlet of the sight glass 28 is connected to the first interfaces of the first evaporator 1 and the second evaporator 2. When the outlet of the sight glass 28 is connected to the first evaporator 1, it passes through the second solenoid valve 12 and the first thermostatic expansion valve 8. When the outlet of the sight glass 28 is connected to the second evaporator 2, it passes through the fourth solenoid valve 14 and the second thermostatic expansion valve 9. The second interfaces of the first evaporator 1 and the second evaporator 2 are respectively connected to the inlet of the gas-liquid separator 7 in parallel after passing through the first solenoid valve 11 and the third solenoid valve 13. The outlet of the gas-liquid separator 7 is connected to the inlet of the low-pressure stage compressor 4. Among them, the intermediate cooler 6 and the gas-liquid separator 7 have the functions of gas-liquid separation and storage, which can prevent liquid from entering the low-pressure stage compressor 4 and the high-pressure stage compressor 5, thereby increasing the service life of the compressor. In addition, when the high-pressure liquid refrigerant taken out from the evaporator that needs defrosting is depressurized to a certain intermediate pressure, gas-liquid separation occurs in the intermediate cooler 6. The separated flash vapor is compressed by the high-pressure stage compressor 5, and the liquid part is throttled and depressurized again to absorb heat and refrigerate in the evaporator, which can achieve the purpose of saving the power consumption of the compressor.

[0030] The first evaporator 1 is provided with a first fan 30, and the second evaporator 2 is provided with a second fan 31. The defrost controller 29 is respectively connected to the first fan 30, the second fan 31, the tenth solenoid valve 20, the twelfth solenoid valve 22, the thirteenth solenoid valve 23 and the dryer 27, and controls the opening and closing of the valves and the fans to realize the refrigeration and defrosting working conditions.

[0031] When the device is in the refrigeration mode, the fifth solenoid valve 15, the sixth solenoid valve 16, the seventh solenoid valve 17, the eighth solenoid valve 18, the eleventh solenoid valve 21, and the thirteenth solenoid valve 23 are closed, and other solenoid valves are open. The first evaporator 1 and the second evaporator 2 are evaporators; the condenser 3 is a condenser. The defrost controller 29 controls the first fan 30 and the second fan 31 to turn on. The low-temperature and low-pressure refrigerant flowing out from the outlets of the first evaporator 1 and the second evaporator 2 enters the gas-liquid separator 7 through the first solenoid valve 11 and the third solenoid valve 13. The gaseous refrigerant separated by the gas-liquid separator 7 is sucked by the low-stage compressor 4 and compressed into a medium-temperature and medium-pressure gas and discharged. The excess liquid refrigerant is stored in the gas-liquid separator 7. The gas enters the condenser 3 through the ninth solenoid valve 19 and the first check valve 24 to release heat and condense into a saturated state, and then passes through the twelfth solenoid valve 22, the defrost controller 29, the dryer 27, the sight glass 28, the first thermostatic expansion valve 8, the second thermostatic expansion valve 9, the second solenoid valve 12, and the fourth solenoid valve 14 to enter the first evaporator 1 and the second evaporator 2 to evaporate and absorb heat to complete refrigeration, and then flows out from the outlets of the first evaporator 1 and the second evaporator 2 to enter the next cycle.

[0032] When the device defrosts the first evaporator 1, the first solenoid valve 11, the second solenoid valve 12, the seventh solenoid valve 17, the eighth solenoid valve 18, the ninth solenoid valve 19, and the twelfth solenoid valve 22 are closed, and other solenoid valves are open. The first evaporator 1 is a condenser; the second evaporator 2 is an evaporator; the condenser 3 is closed. The defrost controller 29 controls the first fan 30 to turn off and the second fan 31 to turn on. The low-temperature and low-pressure refrigerant flowing out from the outlet of the second evaporator 2 enters the gas-liquid separator 7 through the third solenoid valve 13. The gaseous refrigerant separated by the gas-liquid separator 7 is sucked by the low-stage compressor 4 and compressed into a medium-temperature and medium-pressure gas and discharged. The excess liquid refrigerant is stored in the gas-liquid separator 7. The medium-temperature and medium-pressure gas passes through the tenth solenoid valve 20 and the second check valve 25 to enter the intercooler 6. The gas separated from the intercooler 6 passes through the third check valve 26 and is sucked by the high-stage compressor 5 and compressed into a high-temperature and high-pressure gas. The high-temperature and high-pressure gas enters the first evaporator 1 through the sixth solenoid valve 16 to perform a defrosting operation on the first evaporator 1. At this time, the first fan 30 is turned off, effectively avoiding the exposure of hot air and affecting the temperature fluctuation of the cold storage. After the heat release process is completed in the first evaporator 1, it is divided into two paths after passing through the fifth solenoid valve 15. One path passes through the third thermostatic expansion valve 10 and the eleventh solenoid valve 21 to enter the intercooler 6, and after separating the gas, it enters the high-stage compressor 5 for high-pressure circulation; the other path exchanges heat with the liquid in the intercooler 6 to become a subcooled liquid. The subcooled liquid passes through the thirteenth solenoid valve 23, the defrost controller 29, the dryer 27, the sight glass 28, the fourth solenoid valve 14, and the second thermostatic expansion valve 9 to enter the second evaporator 2 to evaporate and absorb heat for refrigeration to ensure the room temperature requirement of the cold storage. The refrigerant flows out from the outlet of the second evaporator 2 to form a closed cycle.

[0033] When the device defrosts the second evaporator 2, the third solenoid valve 13, the fourth solenoid valve 14, the fifth solenoid valve 15, the sixth solenoid valve 16, the ninth solenoid valve 19, and the twelfth solenoid valve 22 are closed, and other solenoid valves are opened. The second evaporator 2 serves as a condenser; the first evaporator 1 serves as an evaporator; the condenser 3 is closed. The defrost controller 29 controls the second fan 31 to close and the first fan 30 to open. The low-temperature and low-pressure refrigerant flowing out of the outlet of the first evaporator 1 enters the gas-liquid separator 7 through the first solenoid valve 11. The gaseous refrigerant separated by the gas-liquid separator 7 is sucked in and compressed by the low-stage compressor 4 into medium-temperature and medium-pressure gas and discharged. The excess liquid refrigerant is stored in the gas-liquid separator 7. The medium-temperature and medium-pressure gas passes through the tenth solenoid valve 20 and the second check valve 25 and enters the intermediate cooler 6. The gas separated from the intermediate cooler 6 passes through the third check valve 26 and is sucked in and compressed by the high-stage compressor 5 into high-temperature and high-pressure gas. The high-temperature and high-pressure gas enters the second evaporator 2 through the eighth solenoid valve 18 to perform a defrosting operation on the second evaporator 2. At this time, the second fan 31 is closed, effectively avoiding the exposure of hot gas and affecting the temperature fluctuation of the cold storage. After completing the heat release process in the second evaporator 2, it is divided into two paths after passing through the seventh solenoid valve 17. One path passes through the third thermal expansion valve 10 and the eleventh solenoid valve 21 and enters the intermediate cooler 6. After separating the gas, it enters the high-stage compressor 5 for high-pressure circulation; the other path exchanges heat with the liquid in the intermediate cooler 6 to become subcooled liquid. The subcooled liquid passes through the thirteenth solenoid valve 23, the defrost controller 29, the dryer 27, the sight glass 28, the second solenoid valve 12, and the first thermal expansion valve 8 and enters the first evaporator 1 to evaporate and absorb heat for refrigeration to ensure the room temperature requirement of the cold storage. The refrigerant flows out of the outlet of the first evaporator 1 to form a closed cycle.

[0034] During the operation of the refrigeration device of the present invention, the conversion between the refrigeration of the low-stage compressor and the defrost mode of the high-stage compressor is realized through the switching of valves. In the defrost mode, the low-stage compressor is used to absorb the condensation heat from the refrigeration function to realize the defrost function of the evaporator. The condensation heat discharged to the environment is recovered, realizing the secondary utilization of energy and saving energy.

[0035] At the initial stage of the device operation, when both evaporators are refrigerating simultaneously, the entire device operates in a single-stage compression cycle; when a certain evaporator needs to be defrosted, the high-stage compressor is started, and the cycle during defrosting is a two-stage compression cycle. Furthermore, a dynamic and continuous refrigeration device is formed, which is more flexible and convenient to use, has a high defrosting efficiency, and saves energy.

[0036] During the defrosting process, the high-stage compressor is started, and the entire device is transformed into a heat pump type two-stage vapor compression refrigeration cycle. Ensure that the working state of the low-stage compressor is within medium pressure, the working pressure difference between the suction and discharge of the compressor in the low-stage cycle changes less, the compressor dissipates heat better, which is beneficial to protecting the compressor and extending its service life.

[0037] The defrosting refrigeration device compresses the refrigerant in series "relay" with two compressors. The compression ratio, exhaust temperature, etc. of each stage can meet the operating conditions of the compressor, and a lower evaporation temperature can be obtained. The refrigeration device is larger than a single-stage refrigeration cycle with the same refrigeration capacity, so it is more economical.

[0038] In the present invention, the defrosting heat comes from the condensation heat of the high-pressure stage compressor and the input power of the low- and high-pressure stage compressors. The defrosting and refrigeration processes can be continuous without interruption, and the defrosting efficiency is higher, which is suitable for cold storages that need to ensure the indoor temperature.

[0039] When a traditional continuous defrosting refrigeration system defrosts a certain evaporator, the passage of its evaporator is closed, and the refrigerant undergoes a refrigeration cycle through other evaporators. The refrigerant flow rate in the evaporator undergoing the refrigeration cycle will increase, but the evaporation temperature remains unchanged. At this time, during the defrosting process, heat is transferred to the indoor radiator, and the temperature fluctuation in the cold storage is relatively large. In contrast, the evaporation temperature of the two-stage compression system with a high-pressure stage compressor is lower than that of a single refrigeration cycle. The refrigerant flow rate in the evaporator of the refrigeration cycle increases, and more refrigeration capacity can be obtained. The disadvantage of lacking an evaporator system can be compensated, and the temperature fluctuation in the cold storage can be ignored.

[0040] In the present invention, the compression ratio of the two-stage compression system increases, the temperature of the high-pressure working medium discharged from the high-pressure stage compressor is higher, the temperature of the working medium entering the evaporator for defrosting is higher, and the defrosting time is shorter, the speed is faster, and the efficiency is higher.

[0041] The defrosting device of the present invention uses the reverse cycle heat pump method of the evaporator to heat from the inside of the evaporator. The frost layer is more likely to fall off from the surface, causing large pieces of ice to fall off, reducing the formation of water vapor, and lowering the air humidity. Internal heating defrosting can achieve the effect with the least amount of heat, has the least heat exchange with the surrounding environment, and the highest defrosting efficiency. Therefore, the device described in the present invention can obtain different evaporation temperatures and is suitable for different requirements of cold storages.

[0042] The above embodiments are merely examples given for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A heat pump type two-stage compression defrosting device, characterized in that, The device includes a first evaporator, a second evaporator, a condenser, a low-pressure stage compressor, a high-pressure stage compressor, an intermediate cooler, a gas-liquid separator, a first thermostatic expansion valve, a second thermostatic expansion valve, a third thermostatic expansion valve, a first solenoid valve, a second solenoid valve, a third solenoid valve, a fourth solenoid valve, a fifth solenoid valve, a sixth solenoid valve, a seventh solenoid valve, an eighth solenoid valve, a ninth solenoid valve, a tenth solenoid valve, an eleventh solenoid valve, a twelfth solenoid valve, a thirteenth solenoid valve, a first check valve, a second check valve, a third check valve, a dryer, a sight glass, a defrost controller, a first fan and a second fan; The first interface of the intermediate cooler is connected to the inlet of the high-pressure stage compressor through the third check valve. The first interfaces of the first evaporator and the second evaporator are respectively connected to the outlet of the high-pressure stage compressor in parallel after passing through the sixth solenoid valve and the eighth solenoid valve. The second interfaces of the first evaporator and the second evaporator are respectively connected to the third interface of the intermediate cooler and the second connection port of the defrost controller in parallel after passing through the fifth solenoid valve and the seventh solenoid valve. When connected to the third interface of the intermediate cooler, it passes through the eleventh solenoid valve and the third thermostatic expansion valve, and when connected to the second connection port of the defrost controller, it passes through the thirteenth solenoid valve. The second interface of the intermediate cooler is connected to the outlet of the low-pressure stage compressor and the inlet of the condenser through the second check valve and the tenth solenoid valve. When the second interface of the intermediate cooler is connected to the inlet of the condenser, it passes through the ninth solenoid valve and the first check valve. The outlet of the condenser is connected to the inlet of the first connection port of the defrost controller through the twelfth solenoid valve. The outlet of the defrost controller is connected to the inlet of the dryer. The outlet of the dryer is connected to the inlet of the sight glass. The outlet of the sight glass is connected to the first interfaces of the first evaporator and the second evaporator. When the outlet of the sight glass is connected to the first evaporator, it passes through the second solenoid valve and the first thermostatic expansion valve, and when the outlet of the sight glass is connected to the second evaporator, it passes through the fourth solenoid valve and the second thermostatic expansion valve. The second interfaces of the first evaporator and the second evaporator are respectively connected to the inlet of the gas-liquid separator in parallel after passing through the first solenoid valve and the third solenoid valve. The outlet of the gas-liquid separator is connected to the inlet of the low-pressure stage compressor; The first evaporator is provided with a first fan, and the second evaporator is provided with a second fan; The defrost controller is respectively connected to the first fan, the second fan, the tenth solenoid valve, the twelfth solenoid valve, the thirteenth solenoid valve, and the dryer, and controls the opening and closing of the valves and the fans to realize the refrigeration and defrosting working conditions.

2. The defrosting device according to claim 1, characterized in that: When the device operates in the refrigeration mode, the fifth solenoid valve, the sixth solenoid valve, the seventh solenoid valve, the eighth solenoid valve, the eleventh solenoid valve, and the thirteenth solenoid valve are closed, and other solenoid valves are open; the first evaporator and the second evaporator are evaporators; the condenser is the condenser; the defrost controller controls the first fan and the second fan to be turned on; the low-temperature and low-pressure refrigerant flowing out of the outlets of the first evaporator and the second evaporator enters the gas-liquid separator through the first solenoid valve and the third solenoid valve. The gaseous refrigerant separated by the gas-liquid separator is sucked in by the low-stage compressor, compressed into a medium-temperature and medium-pressure gas and discharged. The excess liquid refrigerant is stored in the gas-liquid separator; the gas enters the condenser through the ninth solenoid valve and the first check valve to release heat and condense into a saturated state, and then passes through the twelfth solenoid valve, the defrost controller, the dryer, the sight glass, the first thermostatic expansion valve, the second thermostatic expansion valve, the second solenoid valve, and the fourth solenoid valve to enter the first evaporator and the second evaporator to evaporate and absorb heat to complete refrigeration, and then flows out of the outlets of the first evaporator and the second evaporator to enter the next cycle.

3. The defrosting device according to claim 1, characterized in that: When the device defrosts the first evaporator, the first solenoid valve, the second solenoid valve, the seventh solenoid valve, the eighth solenoid valve, the ninth solenoid valve, and the twelfth solenoid valve are closed, and other solenoid valves are open; the first evaporator is the condenser; the second evaporator is the evaporator; the condenser is closed; the defrost controller controls the first fan to be turned off and the second fan to be turned on; the low-temperature and low-pressure refrigerant flowing out of the outlet of the second evaporator enters the gas-liquid separator through the third solenoid valve. The gaseous refrigerant separated by the gas-liquid separator is sucked in by the low-stage compressor, compressed into a medium-temperature and medium-pressure gas and discharged. The excess liquid refrigerant is stored in the gas-liquid separator; the medium-temperature and medium-pressure gas passes through the tenth solenoid valve and the second check valve to enter the intercooler. The gas separated from the intercooler passes through the third check valve and is sucked in by the high-stage compressor and compressed into a high-temperature and high-pressure gas; the high-temperature and high-pressure gas enters the first evaporator through the sixth solenoid valve to perform a defrosting action on the first evaporator. At this time, the first fan is turned off, effectively avoiding the exposure of hot air and affecting the temperature fluctuation of the cold storage; after completing the heat release process in the first evaporator, it is divided into two paths after passing through the fifth solenoid valve. One path passes through the third thermostatic expansion valve and the eleventh solenoid valve to enter the intercooler, and after separating the gas, it enters the high-stage compressor for high-pressure circulation; the other path exchanges heat with the liquid in the intercooler to become a subcooled liquid, and the subcooled liquid passes through the thirteenth solenoid valve, the defrost controller, the dryer, the sight glass, the fourth solenoid valve, and the second thermostatic expansion valve to enter the second evaporator to evaporate and absorb heat for refrigeration to ensure the room temperature requirement of the cold storage; the refrigerant flows out of the outlet of the second evaporator to form a closed cycle.

4. The defrosting device according to claim 1, characterized in that: When the device defrosts the second evaporator, the third solenoid valve, the fourth solenoid valve, the fifth solenoid valve, the sixth solenoid valve, the ninth solenoid valve, and the twelfth solenoid valve are closed, and other solenoid valves are open; the second evaporator serves as a condenser; the first evaporator serves as an evaporator; the condenser is closed; the defrost controller controls the first fan to close and the second fan to open; the low-temperature and low-pressure refrigerant flowing out of the first evaporator outlet enters the gas-liquid separator through the first solenoid valve. The gaseous refrigerant separated by the gas-liquid separator is sucked by the low-stage compressor and compressed into a medium-temperature and medium-pressure gas and discharged. The excess liquid refrigerant is stored in the gas-liquid separator; the medium-temperature and medium-pressure gas passes through the tenth solenoid valve and the second check valve and enters the intermediate cooler. The gas separated from the intermediate cooler passes through the third check valve and is sucked by the high-stage compressor and compressed into a high-temperature and high-pressure gas; the high-temperature and high-pressure gas enters the second evaporator through the eighth solenoid valve to perform a defrosting operation on the second evaporator. At this time, the second fan is closed, effectively avoiding the exposure of hot air and affecting the temperature fluctuation of the cold storage; after completing the heat release process in the second evaporator, it is divided into two paths after passing through the seventh solenoid valve. One path passes through the third thermal expansion valve and the eleventh solenoid valve and enters the intermediate cooler. After separating the gas, it enters the high-stage compressor for high-pressure circulation; the other path exchanges heat with the liquid in the intermediate cooler to become a subcooled liquid. The subcooled liquid passes through the thirteenth solenoid valve, the defrost controller, the dryer, the sight glass, the second solenoid valve, and the first thermal expansion valve and enters the first evaporator to evaporate and absorb heat for refrigeration to ensure the room temperature requirement of the cold storage; the refrigerant flows out of the first evaporator outlet to form a closed cycle.

Images