A dual-temperature refrigeration system, air conditioning unit and defrosting control method

Abstract

The application provides a dual-temperature refrigeration system, an air conditioning unit and a defrosting control method, which comprises a first compressor and a condenser; a low-temperature circuit, wherein a low-temperature evaporator is arranged on the low-temperature circuit, and the low-temperature evaporator is in communication with the first compressor and the condenser respectively; a medium-temperature circuit, wherein the medium-temperature circuit comprises an evaporator branch and a medium-temperature evaporator arranged on the evaporator branch; the medium-temperature evaporator comprises a first evaporator and a second evaporator arranged in series, and the first evaporator and the second evaporator are arranged at intervals on the evaporator branch; and a controller, which converts the refrigerant flow direction between the first evaporator and the second evaporator according to the frosting condition of the first evaporator or the second evaporator, so as to defrost the first evaporator or the second evaporator. The dual-temperature refrigeration system solves the technical problems of cost increase and poor practicability caused by the two independent refrigeration systems in the related art.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of refrigeration systems, and particularly relates to a dual-temperature refrigeration system, an air conditioning unit and a defrosting control method. BACKGROUND

[0002] With the vigorous development of dual-temperature commercial superstores and dual-temperature cold storage industries, the refrigeration industry has also rapidly expanded. For dual-temperature system design, two independent refrigeration systems are usually used, however, this method not only increases equipment investment and refrigeration system operation costs, but also occupies a large amount of refrigeration room space, greatly reducing the practicability of the unit in the refrigeration environment.

[0003] In a traditional direct expansion refrigeration system, the refrigerant needs to undergo an isenthalpic process from the condensing pressure to the evaporation pressure, which is achieved through an expansion valve or a capillary tube. However, compared with an ideal reverse Carnot cycle, this results in a large irreversible loss. At the same time, for low-temperature refrigeration systems, the first compressor has a large compression ratio and a large compression work, so the system has a low energy efficiency.

[0004] In addition, for the storage of food and agricultural products, pharmaceuticals and chemical substances, a low-temperature and low-humidity environment is needed to extend the storage time of the substances. However, a low-temperature and low-humidity environment can cause serious frosting problems of the evaporator, thereby affecting the overall performance of the refrigeration system. However, using electric heating defrosting can cause uneven defrosting and slow defrosting, and can also cause large temperature fluctuations in the warehouse, thereby affecting the storage quality of food in the cold storage. To solve the above problems, effective energy-saving measures and fast defrosting can effectively improve the overall refrigeration performance of the unit, and can also better ensure the storage quality of food in the cold storage.

[0005] Therefore, the prior art needs to be further developed. SUMMARY

[0006] The present application aims to overcome the above technical deficiencies, and provides a dual-temperature refrigeration system, an air conditioning unit and a defrosting control method, to solve the technical problems of cost increase and poor practicability caused by the use of two independent refrigeration systems in the related art.

[0007] To achieve the above technical purposes, the present application adopts the following technical scheme: a dual-temperature refrigeration system is provided, comprising: a first compressor and a condenser; a low-temperature circuit, wherein a low-temperature evaporator is arranged on the low-temperature circuit, and the low-temperature evaporator is in communication with the first compressor and the condenser respectively; a medium-temperature circuit, wherein the medium-temperature circuit comprises an evaporator branch and a medium-temperature evaporator arranged on the evaporator branch, and the evaporator branch is in communication with the first compressor and the condenser respectively; the medium-temperature evaporator comprises a first evaporator and a second evaporator arranged in series, and the first evaporator and the second evaporator are arranged at intervals on the evaporator branch; a first throttling valve is arranged on the evaporator branch, and the first throttling valve is located between the first evaporator and the second evaporator; and a controller, wherein the controller converts the refrigerant flow direction between the first evaporator and the second evaporator according to the frosting condition of the first evaporator or the second evaporator, so as to defrost the first evaporator or the second evaporator.

[0008] Further, a four-way valve is arranged on the evaporator branch, a first port of the four-way valve is in communication with the inlet of the evaporator branch, a second port of the four-way valve is in communication with the first evaporator, a third port of the four-way valve is in communication with the second evaporator, and a fourth port of the four-way valve is in communication with the outlet of the evaporator branch.

[0009] Further, the medium-temperature circuit comprises: an ejector, wherein a motive flow inlet of the ejector is in communication with the condenser, a suction flow inlet of the ejector is in communication with the outlet of the evaporator branch, and an ejector outlet of the ejector is in communication with an inlet of a gas-liquid separator; and the gas-liquid separator, wherein a gas outlet of the gas-liquid separator is in communication with the first compressor, and a liquid outlet of the gas-liquid separator is in communication with the inlet of the evaporator branch.

[0010] Further, the dual-temperature refrigeration system comprises a first three-way valve, wherein the inlet of the first three-way valve is in communication with the condenser, a first outlet of the first three-way valve is in communication with the motive flow inlet of the ejector, and a second outlet of the first three-way valve is in communication with the low-temperature evaporator.

[0011] Further, the low-temperature circuit comprises a second throttling valve, and the second throttling valve is arranged between the second outlet of the first three-way valve and the low-temperature evaporator.

[0012] Further, the low-temperature circuit comprises a second compressor, and two ends of the second compressor are in communication with the low-temperature evaporator and the first compressor respectively.

[0013] Further, the low-temperature circuit comprises: a defrosting branch, wherein the inlet of the defrosting branch is in communication with the liquid outlet of the gas-liquid separator, the outlet of the defrosting branch is in communication with the inlet of the evaporator branch, and the defrosting branch flows through the low-temperature evaporator to exchange heat in the low-temperature evaporator; a first control switch, wherein the first control switch is located at the inlet of the defrosting branch to open and close the inlet of the defrosting branch; and a second control switch, wherein the second control switch is located at the outlet of the defrosting branch to open and close the outlet of the defrosting branch.

[0014] Further, the dual-temperature refrigeration system comprises a first economizer, the first economizer comprises a first flow path and a second flow path which exchange heat with each other, the first flow path is arranged in the low-temperature circuit, and two ends of the first flow path are in communication with the condenser and the second throttling valve respectively; the second flow path is arranged in the medium-temperature circuit, and two ends of the second flow path are in communication with the outlet of the evaporator branch and the suction inlet of the ejector respectively.

[0015] Further, the dual-temperature refrigeration system comprises a second economizer, the second economizer comprises a third flow path and a fourth flow path which exchange heat with each other, the third flow path is arranged in the low-temperature circuit, and two ends of the third flow path are in communication with the refrigerant outlet of the low-temperature evaporator and the second compressor respectively; the fourth flow path is arranged in the medium-temperature circuit, and two ends of the fourth flow path are in communication with the liquid outlet of the gas-liquid separator and the inlet of the evaporator branch respectively.

[0016] Further, the dual-temperature refrigeration system comprises a first temperature sensor, the first temperature sensor is located at the liquid outlet of the gas-liquid separator, and the first temperature sensor is in signal connection with the first control switch and the second control switch respectively.

[0017] Further, the dual-temperature refrigeration system comprises a second temperature sensor, the second temperature sensor is located at the first port of the four-way valve, and the second temperature sensor is in signal connection with the four-way valve.

[0018] An air conditioning unit, the air conditioning unit comprising the dual-temperature refrigeration system.

[0019] A defrosting control method, the defrosting control method being applicable to the dual-temperature refrigeration system, and the defrosting control method comprising:

[0020] Monitoring the frosting condition of the medium-temperature evaporator;

[0021] When the first evaporator or the second evaporator reaches the maximum frosting thickness, the flow direction of the refrigerant between the first evaporator and the second evaporator is switched to defrost the first evaporator or the second evaporator.

[0022] Further, the defrosting control method further comprises:

[0023] Monitoring the frosting condition of the low-temperature evaporator;

[0024] When the low-temperature evaporator reaches the maximum frosting thickness, the low-temperature evaporator stops refrigeration, and the defrosting branch is opened to defrost the low-temperature evaporator.

[0025] Further, when the low-temperature evaporator reaches the maximum frosting thickness, the defrosting branch is opened to defrost the low-temperature evaporator, and the method comprises:

[0026] Opening the first control switch to open the inlet of the defrosting branch;

[0027] The second control switch is opened to open the outlet of the defrost branch.

[0028] Advantages:

[0029] 1. In the dual-temperature refrigeration system of the embodiment, the medium-temperature circuit and the low-temperature circuit share a set of compressor and condenser, thereby realizing the function of controlling two temperature zones by one system, effectively reducing the equipment cost, system operation cost and refrigeration machine room installation space, and greatly improving the practicability of the unit; by setting the first evaporator and the second evaporator, when one of the evaporators defrosts, the other evaporator can still continue to refrigerate, maintaining the refrigeration function of the system, the first evaporator and the second evaporator realize the functions of simultaneous defrosting and refrigerating, and when one of the evaporators is seriously frosted, the flow direction of the refrigerant can be converted, thereby converting the working state of the first evaporator and the second evaporator, ensuring the reliability of the unit operation, and the defrosting process of the unit is also more energy-saving, solving the technical problems of cost increase and poor practicability caused by the use of two independent refrigeration systems in the related art dual-temperature zone system.

[0030] 2. The compression-ejection coupling is used to replace the traditional electric compression, thereby reducing the irreversible loss, increasing the suction pressure of the compressor, reducing the compression ratio of the compressor, effectively reducing the compression power, and further improving the problem of excessively high compression power of the traditional compression system.

[0031] 3. By setting the first economizer and the second economizer, and the medium-temperature evaporator (the first evaporator or the second evaporator) alternately defrosting, the refrigerant before the throttling valve entering the medium-temperature evaporator or the low-temperature evaporator can be effectively supercooled, and the refrigeration performance of the unit is effectively improved. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 is a structure schematic diagram of the dual-temperature refrigeration system in working condition one adopted by the embodiment of the present application;

[0033] Figure 2 is a pressure-enthalpy diagram of the dual-temperature refrigeration system in working condition one adopted by the embodiment of the present application;

[0034] Figure 3 is a structure schematic diagram of the dual-temperature refrigeration system in working condition two adopted by the embodiment of the present application;

[0035] Figure 4 is a pressure-enthalpy diagram of the dual-temperature refrigeration system in working condition two adopted by the embodiment of the present application;

[0036] Figure 5 is a pressure and velocity distribution schematic diagram of the ejector in the dual-temperature refrigeration system adopted by the embodiment of the present application.

[0037] Among them, the above drawings include the following reference signs:

[0038] 100, First compressor; 200, Condenser; 300, Low-temperature circuit; 310, Low-temperature evaporator; 320, Second throttle valve; 330, Second compressor; 340, Defrosting branch; 341, First control switch; 342, Second control switch; 400, Medium-temperature circuit; 410, Medium-temperature evaporator; 411, First evaporator; 412, Second evaporator; 420, First throttle valve; 430, Four-way valve; 440, Ejector; 441, Main flow inlet; 442, Jet flow inlet; 443, Ejector outlet; 444, Throat; 445, Suction chamber; 446, Mixing chamber; 447, Diffuser chamber; 450, Gas-liquid separator; 500, First three-way valve; 600, First economizer; 700, Second economizer. Detailed Implementation

[0039] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0040] Example 1

[0041] According to an embodiment of the present invention, a dual-temperature refrigeration system is provided. Please refer to [link / reference]. Figures 1 to 5 The system includes: a first compressor 100 and a condenser 200; a low-temperature circuit 300, on which a low-temperature evaporator 310 is provided, the low-temperature evaporator 310 being connected to the first compressor 100 and the condenser 200 respectively; and a medium-temperature circuit 400, which includes an evaporator branch and a medium-temperature evaporator 410 disposed on the evaporator branch, the evaporator branch being connected to the first compressor 100 and the condenser 200 respectively; the medium-temperature evaporator 410 includes a first evaporator 411 and a second evaporator 410 arranged in series. Evaporator 412, first evaporator 411 and second evaporator 412 are arranged alternately on evaporator branch; evaporator branch is provided with a first throttle valve 420, the first throttle valve 420 is located between the first evaporator 411 and the second evaporator 412; controller, the controller changes the refrigerant flow direction between the first evaporator 411 and the second evaporator 412 according to the frosting condition of the first evaporator 411 or the second evaporator 412, so as to defrost the first evaporator 411 or the second evaporator 412.

[0042] In the dual-temperature refrigeration system of this embodiment, the medium-temperature circuit 400 and the low-temperature circuit 300 share a single compressor and condenser, thereby enabling one system to control two temperature zones. This effectively reduces equipment costs, system operating expenses, and refrigeration room installation space, greatly improving the practicality of the unit. By setting up a first evaporator 411 and a second evaporator 412, when one evaporator is defrosting, the other evaporator can continue to refrigerate, maintaining the system's refrigeration function. The first evaporator 411 and the second evaporator 412 achieve simultaneous defrosting and refrigeration. When one evaporator is severely frosted, the working state of the first evaporator 411 and the second evaporator 412 can be switched by changing the direction of refrigerant flow, ensuring the reliability of the unit's operation. At the same time, the unit's defrosting process is also more energy-efficient, solving the technical problems of increased costs and poor practicality caused by using two independent refrigeration systems in related technologies for dual-temperature zone systems.

[0043] It is understood that in the dual-temperature refrigeration system of this embodiment, by designing a medium-temperature evaporator 410 (e.g., design temperature -7℃) and a low-temperature evaporator 310 (e.g., design temperature -23℃) within the system, the effect of providing cooling at any time in the medium-temperature zone (0℃) and the low-temperature zone (-18℃) can be achieved, thereby effectively reducing the initial investment in equipment, system operating costs and refrigeration room space, and greatly improving the practicality of the unit.

[0044] Understandably, compared to single-evaporator refrigeration, using dual-evaporator refrigeration with a medium-temperature evaporator 410 and a low-temperature evaporator 310 can effectively expand the application scope of the refrigeration system, while also reducing costs and operating expenses. In addition, compared to the problems of uneven defrosting, slow defrosting, and high energy consumption of traditional low-temperature refrigeration systems, this system uses a hot fluorine defrosting method to achieve fast and uniform defrosting, which is also more energy-efficient.

[0045] In the dual-temperature refrigeration system of this embodiment, see Figure 1 A four-way valve 430 is installed on the evaporator branch. The first port of the four-way valve 430 is connected to the inlet of the evaporator branch, the second port of the four-way valve 430 is connected to the first evaporator 411, the third port of the four-way valve 430 is connected to the second evaporator 412, and the fourth port of the four-way valve 430 is connected to the outlet of the evaporator branch.

[0046] By setting a four-way valve 430 and adjusting the connection direction of the four-way valve 430, the refrigerant flow direction between the first evaporator 411 and the second evaporator 412 can be switched, thereby realizing the alternating switching of the working state of the first evaporator 411 and the second evaporator 412.

[0047] See Figures 1-2 , Figure 1 and Figure 2The diagrams show the structure and pressure-enthalpy diagram of the dual-temperature refrigeration system under operating condition one. At this time, the refrigerant first passes through the second evaporator 412 and is subcooled by the frost layer on the outside of the second evaporator 412. It then passes through the first throttling valve 420 to reduce the pressure and enters the first evaporator 411 to evaporate and cool, becoming a gaseous refrigerant. Therefore, under operating condition one, the first evaporator 411 frosts for cooling and dehumidification, while the second evaporator 412 defrosts for subcooling.

[0048] See Figures 3-4 , Figure 3 and Figure 4 The diagrams show the structure and pressure-enthalpy diagram of the dual-temperature refrigeration system under operating condition two. At this time, the refrigerant is subcooled by the frost layer outside the first evaporator 411, and its pressure is reduced by the first throttling valve 420. Then it enters the second evaporator 412 to evaporate and cool, becoming a gaseous refrigerant. Therefore, under operating condition two, the second evaporator 412 frosts and cools and dehumidifies, while the first evaporator 411 defrosts and subcools.

[0049] It is understandable that when the refrigerant passes through the first medium-temperature evaporator, it is subcooled by the frost layer on the outside of the evaporator, becoming an even subcooled liquid. This lowers the temperature of the refrigerant entering the second medium-temperature evaporator, which can effectively increase the cooling capacity of the unit and thus improve the overall cooling performance of the unit.

[0050] In the dual-temperature refrigeration system of this embodiment, see Figure 1 The intermediate temperature circuit 400 includes: an ejector 440, the main flow inlet 441 of the ejector 440 being connected to the condenser 200, the jet flow inlet 442 of the ejector 440 being connected to the outlet of the evaporator branch, and the ejector outlet 443 of the ejector 440 being connected to the inlet of the gas-liquid separator 450; the gas-liquid separator 450, the gas outlet of the gas-liquid separator 450 being connected to the first compressor 100, and the liquid outlet of the gas-liquid separator 450 being connected to the inlet of the evaporator branch.

[0051] Specifically, see Figure 5 The ejector is mainly divided into three parts: suction chamber 445, mixing chamber 446, and diffuser chamber 447. Suction chamber 445 includes a spray section and an ejector section. High-pressure refrigerant from condenser 200 is the primary flow, and low-pressure refrigerant from the evaporator branch is the secondary flow. After entering the spray section, the primary flow undergoes a pressure reduction and acceleration process until the primary flow pressure reaches its lowest point at the tail of the spray section. At this point, the primary flow pressure is lower than the secondary flow pressure at the inlet of the ejector section. Therefore, under suction, the secondary flow is drawn into the ejector and mixed with the primary flow at equal pressure. The mixed fluid enters mixing chamber 446 for further thorough mixing, and then enters diffuser chamber 447, undergoing a pressure increase and acceleration decrease process, thereby converting some of the refrigerant's kinetic energy into pressure energy and increasing the suction port pressure of the first compressor 100.

[0052] By setting the ejector 440, compared to the expansion valve working alone, a portion of the potential energy of the refrigerant flowing out of the condenser 200 is not lost through the expansion valve. This portion of potential energy reduces the pressure ratio of the first compressor 100, reducing the irreversible loss of the refrigerant caused by the expansion valve or capillary tube. The mixed fluid enters the diffuser 447 for pressurization and deceleration. After gas-liquid separation by the gas-liquid separator 450, the gaseous refrigerant with increased pressure enters the first compressor 100 and is compressed, increasing the compressor suction pressure, thereby reducing the compressor pressure ratio and compression work, and thus improving the problem of excessive compression work in traditional compression systems.

[0053] It is understood that in the dual-temperature refrigeration system of this embodiment, compression-jet coupling replaces traditional electric compression, thereby reducing irreversible losses and increasing the compressor suction pressure, thereby reducing the compressor pressure ratio and effectively reducing compression work, thus improving the problem of excessive compression work in traditional compression systems.

[0054] In the dual-temperature refrigeration system of this embodiment, see Figure 1 The dual-temperature refrigeration system includes a first three-way valve 500. The inlet of the first three-way valve 500 is connected to the condenser 200, the first outlet of the first three-way valve 500 is connected to the active flow inlet 441 of the ejector 440, and the second outlet of the first three-way valve 500 is connected to the low-temperature evaporator 310. By setting the first three-way valve 500, the flow rate of refrigerant entering the low-temperature circuit 300 or the medium-temperature circuit 400 can be controlled.

[0055] In the dual-temperature refrigeration system of this embodiment, see Figure 1 The low-temperature circuit 300 includes a second throttling valve 320, which is located between the second outlet of the first three-way valve 500 and the low-temperature evaporator 310. By setting the second throttling valve 320, the refrigerant is throttled and depressurized before entering the low-temperature evaporator 310.

[0056] In the dual-temperature refrigeration system of this embodiment, see Figure 1 The low-temperature circuit 300 includes a second compressor 330, whose two ends are connected to the low-temperature evaporator 310 and the first compressor 100, respectively. By setting up the second compressor 330, the cooling capacity in the low-temperature circuit 300 is increased to meet the cooling needs of the low-temperature zone.

[0057] It should be noted that the second compressor 330 is a low-pressure stage compressor, while the first compressor 100 is a high-pressure stage compressor. The refrigerant in the low-temperature circuit 300 undergoes two compressions, thereby increasing the cooling capacity of the low-temperature circuit 300.

[0058] In the dual-temperature refrigeration system of this embodiment, see Figure 1The low-temperature circuit 300 includes: a defrosting branch 340, the inlet of which is connected to the liquid outlet of the gas-liquid separator 450, and the outlet of which is connected to the inlet of the evaporator branch. The defrosting branch 340 flows through the low-temperature evaporator 310 for heat exchange. A first control switch 341 is located at the inlet of the defrosting branch 340 to open and close it. A second control switch 342 is located at the outlet of the defrosting branch 340 to open and close it. Through this configuration, the relatively high-temperature refrigerant in the gas-liquid separator 450 can be drawn out to defrost the low-temperature evaporator 310, solving the defrosting problem of the low-temperature evaporator 310. Furthermore, this defrosting method is more energy-efficient and environmentally friendly.

[0059] Understandably, the defrosting branch 340 is usually kept closed, and when the frost layer on the low-temperature evaporator 310 is detected to reach its maximum thickness, the defrosting branch 340 is controlled to open for defrosting.

[0060] Understandably, this system can achieve rapid and uniform defrosting of the surfaces of the low-temperature evaporator 310 and the medium-temperature evaporator 410 through hot fluorine defrosting technology, effectively ensuring the reliability of the unit operation, while the unit defrosting process is also more energy-efficient.

[0061] In some embodiments, the first control switch 341 and the second control switch 342 are both three-way valves. For example, the remaining two ports of the first control switch 341 are connected to the liquid outlet of the gas-liquid separator 450 and the third flow path inlet of the second economizer, respectively. For example, the remaining two ports of the second control switch 342 are connected to the third flow path outlet of the second economizer and the first port of the four-way valve 430, respectively.

[0062] In the dual-temperature refrigeration system of this embodiment, see Figure 1The dual-temperature refrigeration system includes a first economizer 600, which includes two flow paths that exchange heat with each other: a first flow path located in the low-temperature circuit 300, with its two ends connected to the condenser 200 and the second throttle valve 320, respectively; and a second flow path located in the medium-temperature circuit 400, with its two ends connected to the outlet of the evaporator branch and the jet inlet 442 of the ejector 440, respectively. By setting up the first economizer 600, heat exchange occurs between the refrigerants at a certain node in the low-temperature circuit 300 and the medium-temperature circuit 400. In the low-temperature circuit 300, the low-temperature refrigerant flowing out of the evaporator branch in the medium-temperature circuit 400 can cool the high-temperature refrigerant flowing out of the condenser 200, effectively subcooling the refrigerant before the expansion valve, thereby reducing the temperature of the refrigerant about to enter the low-temperature evaporator 310. In the medium-temperature circuit 400, the high-temperature refrigerant flowing out of the condenser 200 can increase the temperature of the refrigerant entering the ejector inlet 442 of the ejector 440. The refrigerant is heated into a superheated working fluid by the first economizer 600, which can effectively increase the cooling capacity of the unit and thus improve the overall cooling performance of the unit.

[0063] In the dual-temperature refrigeration system of this embodiment, see Figure 1 The dual-temperature refrigeration system includes a second economizer 700, which includes a third flow path that exchanges heat with each other. The third flow path is located in the low-temperature circuit 300, and its two ends are connected to the refrigerant outlet of the low-temperature evaporator 310 and the second compressor 330, respectively. The fourth flow path is located in the medium-temperature circuit 400, and its two ends are connected to the liquid outlet of the gas-liquid separator 450 and the inlet of the evaporator branch, respectively. By setting up a second economizer 700, heat exchange occurs between the refrigerants at a certain node in the low-temperature circuit 300 and the medium-temperature circuit 400. In the low-temperature circuit 300, the refrigerant flowing out of the liquid outlet of the gas-liquid separator 450 heats the low-temperature refrigerant flowing out of the refrigerant outlet of the low-temperature evaporator 310. After being heated into superheated gas, it enters the second compressor 330 and the first compressor 100. In the medium-temperature circuit 400, the low-temperature refrigerant flowing out of the refrigerant outlet of the low-temperature evaporator 310 cools the refrigerant flowing out of the liquid outlet of the gas-liquid separator 450. The liquid refrigerant is cooled into a subcooled liquid, and then subcooled by the frost layer outside the first medium-temperature evaporator, becoming an even subcooled liquid, and then entering the second medium-temperature evaporator for evaporative cooling. This can effectively increase the cooling capacity of the unit, thereby improving the overall cooling performance of the unit.

[0064] By setting up a first economizer 600 and a second economizer 700, and alternating defrosting of the medium-temperature evaporator (first evaporator 411 or second evaporator 412), effective subcooling of the refrigerant before the throttling valve that is about to enter the medium-temperature evaporator or low-temperature evaporator can be achieved, thereby effectively improving the unit's cooling performance.

[0065] In the dual-temperature refrigeration system of this embodiment, see Figure 1 The dual-temperature refrigeration system includes a first temperature sensor located at the liquid outlet of the gas-liquid separator 450. The first temperature sensor is connected to both a first control switch 341 and a second control switch 342. By using the first temperature sensor, the refrigerant temperature at the liquid outlet of the gas-liquid separator 450 is monitored. When the refrigerant temperature is too low, for example, below 0°C, defrosting is not suitable, and the system does not activate the defrosting function; both the first and second control switches remain closed.

[0066] In the dual-temperature refrigeration system of this embodiment, see Figure 1 The dual-temperature refrigeration system includes a second temperature sensor located at the first port of the four-way valve 430, and the second temperature sensor is signal-connected to the four-way valve 430. By setting the first temperature sensor, the refrigerant at the first port of the four-way valve 430 is detected. When the refrigerant temperature is too low, for example, when the refrigerant temperature is below 0°C, it is not suitable for defrosting, and the system will not activate the defrosting function at this time.

[0067] In this dual-temperature refrigeration system, compared to traditional electric compression refrigeration, applying compression-jet coupling technology to the low-temperature dehumidification system can effectively reduce irreversible losses during the throttling process, while increasing the compressor suction pressure, thereby improving system energy efficiency. Compared to single-evaporator refrigeration, dual-evaporator refrigeration can effectively expand the application scope of the refrigeration system, while also having lower initial investment and operating costs. Compared to the problems of uneven defrosting, slow defrosting, and high energy consumption of evaporators in traditional low-temperature refrigeration systems, this system uses thermal refrigerant defrosting to achieve fast and uniform defrosting, while also being more energy-efficient. By subcooling the refrigerant before throttling in the medium and low-temperature evaporators, the unit's refrigeration performance is effectively improved.

[0068] Example 2

[0069] In this embodiment, the air conditioning unit includes the aforementioned dual-temperature refrigeration system.

[0070] In this embodiment of the air conditioning unit, the medium-temperature circuit 400 and the low-temperature circuit 300 share a single compressor and condenser, thereby achieving the function of controlling two temperature zones with one system. This effectively reduces the cost of the air conditioning unit, system operating costs, and installation space in the refrigeration room, greatly improving the practicality of the air conditioning unit. By setting up a first evaporator 411 and a second evaporator 412, when one evaporator is defrosting, the other evaporator can continue to cool, maintaining the cooling function of the system. The first evaporator 411 and the second evaporator 412 achieve simultaneous defrosting and cooling functions. When one evaporator is severely frosted, the working state of the first evaporator 411 and the second evaporator 412 can be switched by changing the direction of refrigerant flow, ensuring the reliability of the unit's operation. At the same time, the unit's defrosting process is also more energy-efficient, solving the technical problems of increased cost and poor practicality caused by using two independent refrigeration systems in dual-temperature zone systems in related technologies.

[0071] Example 3

[0072] In this embodiment of the defrosting control method, the defrosting control method is applicable to the above-mentioned dual-temperature refrigeration system, and the defrosting control method includes:

[0073] Monitor the frosting condition of the medium-temperature evaporator;

[0074] When the first evaporator 411 or the second evaporator 412 reaches the maximum frost thickness, the refrigerant flow direction between the first evaporator 411 and the second evaporator 412 is reversed to defrost the first evaporator 411 or the second evaporator 412.

[0075] Specifically, the time it takes for the medium-temperature evaporator 410 to reach its maximum frost thickness is determined through experiments. When either the first evaporator 411 or the second evaporator 412 reaches its maximum frost thickness, the corresponding evaporator stops cooling and frosting. The direction of the four-way valve 430 is changed, altering the refrigerant flow direction between the first evaporator 411 and the second evaporator 412. The evaporator that was previously frosting and dehumidifying now defrosts and overcools, while the evaporator that was previously defrosting now frosts and dehumidifies. This allows the medium-temperature cold storage to achieve both cooling and defrosting without shutting down the unit.

[0076] In the defrosting control method of this embodiment, the defrosting control method includes:

[0077] Monitor the frosting condition of the low-temperature evaporator 310;

[0078] When the low-temperature evaporator 310 reaches the maximum frost thickness, the low-temperature evaporator 310 stops cooling and the defrosting branch 340 is turned on to defrost the low-temperature evaporator 310.

[0079] Specifically, the time required for each low-temperature evaporator to reach its maximum frost thickness was determined through experiments. When the low-temperature evaporator 310 reaches its maximum frost thickness, the first three-way valve 500 is closed, the low-temperature circuit 300 stops cooling, and the first control switch 341 is turned on to achieve rapid defrosting.

[0080] In the defrosting control method of this embodiment, when the low-temperature evaporator 310 reaches the maximum frost thickness, the defrosting branch 340 is activated to defrost the low-temperature evaporator 310, including:

[0081] Turn on the first control switch 341 to open the inlet of the defrosting branch 340;

[0082] Turn on the second control switch 342 to open the outlet of the defrosting branch 340.

[0083] Specifically, the opening and closing of the defrosting branch 340 is controlled by controlling the first control switch 341 and the second control switch 342.

[0084] In the defrosting control method of this embodiment, in order to ensure stable defrosting operation, defrosting control logic should be set up. Temperature sensors are set at the liquid outlet of the gas-liquid separator 450 and the first port of the four-way valve 430. When the temperature is higher than 0°C, defrosting can be carried out smoothly, and when the temperature is lower than 0°C, defrosting cannot be carried out.

[0085] Combined with appendix Figures 1-4 The working principle of the dual-temperature refrigeration system in this embodiment is as follows:

[0086] See Figures 1-2 , Figure 5 When the dual-temperature refrigeration system is operating under condition one, high-temperature and high-pressure liquid refrigerant flows out from condenser 200. Figure 2The refrigerant at state point 1) splits into two streams. One stream enters ejector 440, where it is depressurized and accelerated to become low-temperature, low-pressure wet steam (state point 1'). Low-temperature, low-pressure gaseous refrigerant (state point 13 or 14) flows out from the first evaporator 411 and then enters the first economizer 600 to be heated into superheated working fluid (state point 2). It then enters the ejector section of ejector 440, where it is depressurized and accelerated to become lower-pressure refrigerant (state point 2'). The two refrigerants (state points 1' and 2') mix in the ejector mixing chamber 4. The refrigerant is uniformly mixed at isobaric pressure within the evaporator 46 (state point 3'), then enters the diffuser chamber 447 of the ejector 440, where it is depressurized and pressurized into medium-pressure wet vapor (state point 3); subsequently, it enters the gas-liquid separator 450, producing liquid refrigerant (state point 7) and gaseous refrigerant (state point 4); the liquid refrigerant (state point 7) is cooled to subcooled liquid (state point 8) by the second economizer 700, then further subcooled by the frost layer outside the second evaporator 412, becoming an even more subcooled liquid. State point 11); then it passes through the first throttling valve 420 to become a low-temperature, low-pressure refrigerant (state point 12); then it enters the first evaporator 411 for evaporation and cooling to become a gaseous refrigerant (state point 13 or 14); another high-temperature refrigerant from the condenser 200 (state point 1) enters the first economizer 600 and is cooled to a subcooled liquid (state point 15), passes through the second throttling valve 320 to become a low-pressure working fluid (state point 16), then enters the evaporator 2 for evaporation and heat absorption to become a gaseous working fluid (state point 17), then enters the second economizer 700 for heating to become a superheated gas (state point 18), then enters the second compressor 330 to become a medium-temperature, medium-pressure working fluid (state point 19), state point 4 and state point 19 are mixed at the same pressure to become a superheated working fluid (state point 5), then enter the first compressor 100 to become a refrigerant (state point 6), then enter the condenser 200 for isobaric heat dissipation to become a liquid refrigerant (state point 1), finally completing the entire refrigeration cycle.

[0087] See Figures 3-4 , Figure 5When the dual-temperature refrigeration system is in operating condition two, the high-temperature and high-pressure liquid refrigerant flowing out of the condenser 200 (state point 1) is divided into two paths. One path enters the ejector 440, where the pressure is reduced and the speed is increased to become low-temperature and low-pressure wet steam (state point 1'). The low-temperature and low-pressure gaseous refrigerant flowing out of the second evaporator 412 (state point 10 or 14) then enters the first economizer 600 and is heated to become superheated working fluid (state point 2). It then enters the ejector section of the ejector 440, where the pressure is reduced and the speed is increased to become low-pressure refrigerant (state point 2'). Two refrigerants (state points 1' and 2') are uniformly mixed at isobaric pressure in the ejector mixing chamber 446 to form a refrigerant (state point 3'), which then enters the ejector diffuser chamber 447 to decelerate and pressurize into medium-pressure wet vapor (state point 3); subsequently, it enters the gas-liquid separator 450 to produce liquid refrigerant (state point 7) and gaseous refrigerant (state point 4); the liquid refrigerant (state point 7) is cooled to subcooled liquid (state point 8) in the gas-liquid separator 450, and then discharged from the first evaporator 411. The frost layer in the condenser becomes subcooled and then turns into an even subcooled liquid (state point 12); it then passes through the first throttling valve 420 to become a low-temperature, low-pressure refrigerant (state point 11); it then enters the second evaporator 412 for evaporation and cooling to become a gaseous refrigerant (state point 10 or 14); another path of high-temperature refrigerant from the condenser 200 (state point 1) enters the economizer and is cooled into a subcooled liquid (state point 15), passes through the second throttling valve 320 to become a low-pressure working fluid (state point 16), and then enters the evaporator. 2. Evaporation absorbs heat and becomes a gaseous working fluid (state point 17), then enters the second economizer 700 and is heated into a superheated gas (state point 18), then enters the second compressor 330 and becomes a medium-temperature and medium-pressure working fluid (state point 19), state point 4 and state point 19 are mixed at isobaric pressure to become a superheated working fluid (state point 5), then enters the first compressor 100 and becomes a refrigerant (state point 6), then enters the condenser 200 and dissipates heat at isobaric pressure to become a liquid refrigerant (state point 1), finally completing the entire refrigeration cycle.

[0088] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0089] Optionally, specific examples in this embodiment can refer to the examples described in the above embodiments, and will not be repeated here.

[0090] The sequence numbers of the embodiments in this application are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0091] In the above embodiments of this application, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0092] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A dual-temperature refrigeration system, characterized in that, include: First compressor (100) and condenser (200); A low-temperature circuit (300) is provided, and a low-temperature evaporator (310) is provided on the low-temperature circuit (300), and the low-temperature evaporator (310) is connected to the first compressor (100) and the condenser (200) respectively; A medium-temperature circuit (400) includes an evaporator branch and a medium-temperature evaporator (410) disposed on the evaporator branch. The evaporator branch is connected to the first compressor (100) and the condenser (200) respectively. The medium-temperature evaporator (410) includes a first evaporator (411) and a second evaporator (412) disposed in series. The first evaporator (411) and the second evaporator (412) are disposed at intervals on the evaporator branch. A first throttle valve (420) is disposed on the evaporator branch between the first evaporator (411) and the second evaporator (412). The controller, based on the frosting condition of the first evaporator (411) or the second evaporator (412), reverses the refrigerant flow direction between the first evaporator (411) and the second evaporator (412) to defrost the first evaporator (411) or the second evaporator (412).

2. The dual-temperature refrigeration system according to claim 1, characterized in that, A four-way valve (430) is provided on the evaporator branch. The first port of the four-way valve (430) is connected to the inlet of the evaporator branch, the second port of the four-way valve (430) is connected to the first evaporator (411), the third port of the four-way valve (430) is connected to the second evaporator (412), and the fourth port of the four-way valve (430) is connected to the outlet of the evaporator branch.

3. The dual-temperature refrigeration system according to claim 1, characterized in that, The intermediate temperature circuit (400) includes: The ejector (440) has its main flow inlet (441) connected to the condenser (200), its jet inlet (442) connected to the outlet of the evaporator branch, and its ejector outlet (443) connected to the inlet of the gas-liquid separator (450). The gas-liquid separator (450) has its gas outlet connected to the first compressor (100) and its liquid outlet connected to the inlet of the evaporator branch.

4. The dual-temperature refrigeration system according to claim 3, characterized in that, The dual-temperature refrigeration system includes a first three-way valve (500), the inlet of which is connected to the condenser (200), the first outlet of which is connected to the active flow inlet (441) of the ejector (440), and the second outlet of which is connected to the low-temperature evaporator (310).

5. The dual-temperature refrigeration system according to claim 4, characterized in that, The low-temperature circuit (300) includes a second throttle valve (320), which is disposed between the second outlet of the first three-way valve (500) and the low-temperature evaporator (310).

6. The dual-temperature refrigeration system according to claim 3, characterized in that, The low-temperature circuit (300) includes a second compressor (330), the two ends of which are connected to the low-temperature evaporator (310) and the first compressor (100), respectively.

7. The dual-temperature refrigeration system according to claim 3, characterized in that, The cryogenic circuit (300) includes: The defrosting branch (340) has its inlet connected to the liquid outlet of the gas-liquid separator (450) and its outlet connected to the inlet of the evaporator branch. The defrosting branch (340) flows through the low-temperature evaporator (310) to conduct heat exchange within the low-temperature evaporator (310). A first control switch (341) is located at the inlet of the defrosting branch (340) to open or close the inlet of the defrosting branch (340); A second control switch (342) is located at the outlet of the defrosting branch (340) to open or close the outlet of the defrosting branch (340).

8. The dual-temperature refrigeration system according to claim 5, characterized in that, The dual-temperature refrigeration system includes a first economizer (600), which includes components that exchange heat with each other. The first flow path is disposed in the low temperature circuit (300), and the two ends of the first flow path are respectively connected to the condenser (200) and the second throttle valve (320); The second flow path is provided in the medium temperature circuit (400), and the two ends of the second flow path are respectively connected to the outlet of the evaporator branch and the jet inlet (442) of the ejector (440).

9. The dual-temperature refrigeration system according to claim 6, characterized in that, The dual-temperature refrigeration system includes a second economizer (700), which includes components that exchange heat with each other. The third flow path is provided in the low-temperature circuit (300), and the two ends of the third flow path are respectively connected to the refrigerant outlet of the low-temperature evaporator (310) and the second compressor (330); The fourth flow path is provided in the medium temperature circuit (400), and the two ends of the fourth flow path are respectively connected to the liquid outlet of the gas-liquid separator (450) and the inlet of the evaporator branch.

10. The dual-temperature refrigeration system according to claim 7, characterized in that, The dual-temperature refrigeration system includes a first temperature sensor located at the liquid outlet of the gas-liquid separator (450). The first temperature sensor is connected to the first control switch (341) and the second control switch (342) respectively.

11. The dual-temperature refrigeration system according to claim 2, characterized in that, The dual-temperature refrigeration system includes a second temperature sensor located at the first port of the four-way valve (430), and the second temperature sensor is signal-connected to the four-way valve (430).

12. An air conditioning unit, characterized in that, The air conditioning unit includes a dual-temperature refrigeration system as described in any one of claims 1 to 11.

13. A defrosting control method, characterized in that, The defrosting control method is applicable to the dual-temperature refrigeration system as described in any one of claims 1 to 11, and the defrosting control method includes: Monitor the frosting condition of the medium-temperature evaporator; When the first evaporator (411) or the second evaporator (412) reaches the maximum frost thickness, the refrigerant flow direction between the first evaporator (411) and the second evaporator (412) is reversed to defrost the first evaporator (411) or the second evaporator (412).

14. The defrosting control method according to claim 13, characterized in that, Also includes: Monitor the frosting condition of the low-temperature evaporator (310); When the low-temperature evaporator (310) reaches the maximum frost thickness, the low-temperature evaporator (310) stops cooling and starts the defrosting branch (340) to defrost the low-temperature evaporator (310).

15. The defrosting control method according to claim 14, characterized in that, When the low-temperature evaporator (310) reaches its maximum frosting thickness, the defrosting branch (340) is activated to defrost the low-temperature evaporator (310), including: Turn on the first control switch (341) to open the inlet of the defrosting branch (340); Turn on the second control switch (342) to open the outlet of the defrosting branch (340).

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