Dual-temperature refrigerating system, air conditioning unit and defrosting control method

Abstract

The invention provides a dual-temperature refrigerating system, an air conditioning unit and a defrosting control method. The dual-temperature refrigerating system comprises a first compressor and a condenser; the low-temperature loop is provided with a low-temperature evaporator, and the low-temperature evaporator communicates with the first compressor and the condenser; the medium-temperature loop 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 which are connected in series, and the first evaporator and the second evaporator are arranged on the evaporator branch at an interval; and the controller is used for converting the refrigerant circulation 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. According to the double-temperature refrigerating system, the technical problems that in the related technology, the cost is increased and the practicability is poor due to the fact that two independent refrigerating systems are adopted in a double-temperature-zone system are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of refrigeration systems, and in particular to a dual-temperature refrigeration system, an air conditioning unit and a defrosting control method. Background Art

[0002] With the booming development of dual-temperature zone supermarkets and dual-temperature zone cold storage industries, the refrigeration industry has also grown rapidly. For dual-temperature zone system design, two independent refrigeration systems are usually used. However, this method not only increases equipment investment and refrigeration system operating costs, but also occupies a large amount of refrigeration room space, greatly reducing the practicality of the unit in this refrigeration environment.

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

[0004] In addition, for the storage needs of food and agricultural products, medicines and chemicals, a low temperature and low humidity environment is required to extend the storage time of the materials. However, the low temperature and low humidity environment will cause serious frosting of the evaporator, thus affecting the overall performance of the refrigeration system. However, the use of electric heating defrosting will result in uneven defrosting and slow defrosting, and will also cause large temperature fluctuations in the warehouse, thereby affecting the storage quality of food in the cold storage. In response to the above problems, effective energy-saving measures are proposed, and rapid defrosting can effectively improve the overall refrigeration performance of the unit, and at the same time can better ensure the storage quality of food in the cold storage.

[0005] Therefore, the prior art needs to be further developed. Summary of the invention

[0006] The purpose of the present invention is to overcome the above technical deficiencies and provide a dual-temperature refrigeration system, an air-conditioning unit and a defrost control method to solve the technical problems in the related art that the dual-temperature zone system uses two independent refrigeration systems, resulting in increased costs and poor practicality.

[0007] To achieve the above technical objectives, the present invention adopts the following technical scheme: a dual-temperature refrigeration system is provided, including: a first compressor and a condenser; a low-temperature circuit, a low-temperature evaporator is arranged on the low-temperature circuit, and the low-temperature evaporator is respectively connected to the first compressor and the condenser; a medium-temperature circuit, the medium-temperature circuit includes an evaporator branch and a medium-temperature evaporator arranged on the evaporator branch, and the evaporator branch is respectively connected to the first compressor and the condenser; the medium-temperature evaporator includes a first evaporator and a second evaporator arranged in series, and the first evaporator and the second evaporator are arranged on the evaporator branch at intervals; a first throttle valve is arranged on the evaporator branch, and the first throttle valve is located between the first evaporator and the second evaporator; a controller, the controller changes 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] Furthermore, a four-way valve is provided on the evaporator branch, a first port of the four-way valve is connected to the inlet of the evaporator branch, a second port of the four-way valve is connected to the first evaporator, a third port of the four-way valve is connected to the second evaporator, and a fourth port of the four-way valve is connected to the outlet of the evaporator branch.

[0009] Furthermore, the medium temperature circuit includes: an ejector, the active flow inlet of the ejector is connected to the condenser, the induced flow inlet of the ejector is connected to the outlet of the evaporator branch, and the ejector outlet of the ejector is connected to the inlet of the gas-liquid separator; a gas-liquid separator, the gas outlet of the gas-liquid separator is connected to the first compressor, and the liquid outlet of the gas-liquid separator is connected to the inlet of the evaporator branch.

[0010] Furthermore, the dual-temperature refrigeration system includes a first three-way valve, an inlet of the first three-way valve is connected to the condenser, a first outlet of the first three-way valve is connected to the active flow inlet of the ejector, and a second outlet of the first three-way valve is connected to the low-temperature evaporator.

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

[0012] Furthermore, the low-temperature circuit includes a second compressor, and two ends of the second compressor are respectively connected to the low-temperature evaporator and the first compressor.

[0013] Furthermore, the low-temperature circuit includes: a defrost branch, the inlet of the defrost branch is connected to the liquid outlet of the gas-liquid separator, the outlet of the defrost branch is connected to the inlet of the evaporator branch, the defrost branch flows through the low-temperature evaporator to exchange heat in the low-temperature evaporator; a first control switch, the first control switch is located at the inlet of the defrost branch to open and close the inlet of the defrost branch; and a second control switch is located at the outlet of the defrost branch to open and close the outlet of the defrost branch.

[0014] Furthermore, the dual-temperature refrigeration system includes a first economizer, which includes: a first flow path that exchanges heat with each other, the first flow path is arranged in the low-temperature circuit, and the two ends of the first flow path are respectively connected to the condenser and the second throttle valve; a second flow path, the second flow path is arranged in the medium-temperature circuit, and the two ends of the second flow path are respectively connected to the outlet of the evaporator branch and the injection flow inlet of the ejector.

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

[0016] Furthermore, the dual-temperature refrigeration system includes a first temperature sensor, which is located at the liquid outlet of the gas-liquid separator and is respectively connected to the first control switch and the second control switch signal.

[0017] Furthermore, the dual-temperature refrigeration system includes a second temperature sensor, which is located at the first port of the four-way valve, and the second temperature sensor is signal-connected to the four-way valve.

[0018] An air conditioning unit comprises the above-mentioned dual-temperature refrigeration system.

[0019] A defrost control method is applicable to the above-mentioned dual-temperature refrigeration system, and the defrost control method includes:

[0020] Monitor the frosting condition of medium temperature evaporator;

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

[0022] Furthermore, it also includes:

[0023] Monitor the frost condition of low temperature evaporator;

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

[0025] Further, when the low-temperature evaporator reaches the maximum frost thickness, the defrost branch is opened to defrost the low-temperature evaporator, including:

[0026] Turn on the first control switch to open the inlet of the defrost branch;

[0027] Turn on the second control switch to open the outlet of the defrost branch.

[0028] Beneficial effects:

[0029] 1. In the dual-temperature refrigeration system of the present embodiment, the medium-temperature circuit and the low-temperature circuit share a set of compressors and condensers, thereby realizing the function of one system controlling two temperature zones, thereby effectively reducing equipment costs, system operating costs and installation space of the refrigeration room, and greatly improving the practicality of the unit; by providing the first evaporator and the second evaporator, when one of the evaporators is defrosting, the other evaporator can still continue to refrigerate, maintaining the refrigeration function of the system, and the first evaporator and the second evaporator realize the functions of simultaneous defrosting and refrigeration. When one of the evaporators is severely frosted, the flow direction of the refrigerant can be changed, thereby changing the working state of the first evaporator and the second evaporator, thereby ensuring the reliability of the unit operation. At the same time, the defrosting process of the unit is also more energy-efficient, solving the technical problems of the dual-temperature zone system in the related art that uses two independent refrigeration systems, resulting in increased costs and poor practicality.

[0030] 2. Replacing traditional electric compression with compression-injection coupling can reduce irreversible losses and increase the suction pressure of the compressor, thereby reducing the compressor pressure ratio and effectively reducing the compression work, thereby improving the problem of excessive compression work in traditional compression systems.

[0031] 3. By setting the first economizer and the second economizer, and alternately defrosting the medium-temperature evaporator (the first evaporator or the second evaporator), the refrigerant before the throttle valve that is about to enter the medium-temperature evaporator or the low-temperature evaporator can be effectively supercooled, thereby effectively improving the refrigeration performance of the unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 1 is a schematic structural diagram of a dual-temperature refrigeration system in working condition 1 adopted in an embodiment of the present invention;

[0033] Figure 2 is a pressure-enthalpy diagram of the dual-temperature refrigeration system used in the embodiment of the present invention when it is in working condition one;

[0034] Figure 3 is a structural schematic diagram of the dual-temperature refrigeration system used in an embodiment of the present invention in working condition 2;

[0035] Figure 4 is a pressure-enthalpy diagram of the dual-temperature refrigeration system used in the embodiment of the present invention when in working condition 2;

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

[0037] The above drawings include the following reference numerals:

[0038] 100, first compressor; 200, condenser; 300, low-temperature circuit; 310, low-temperature evaporator; 320, second throttle valve; 330, second compressor; 340, defrost 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, active flow inlet; 442, induced flow inlet; 443, ejector outlet; 444, throat; 445, suction chamber; 446, mixing chamber; 447, pressure diffusion chamber; 450, gas-liquid separator; 500, first three-way valve; 600, first economizer; 700, second economizer. DETAILED DESCRIPTION

[0039] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work 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. Figures 1 to 5 , including: a first compressor 100 and a condenser 200; a low-temperature circuit 300, on which a low-temperature evaporator 310 is disposed, and the low-temperature evaporator 310 is communicated with the first compressor 100 and the condenser 200 respectively; a medium-temperature circuit 400, the medium-temperature circuit 400 includes an evaporator branch and a medium-temperature evaporator 410 disposed on the evaporator branch, and the evaporator branch is communicated with 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 arranged on the evaporator branch at intervals; the evaporator branch is provided with a first throttle valve 420, and the first throttle valve 420 is located between the first evaporator 411 and the second evaporator 412; the controller converts 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 to defrost the first evaporator 411 or the second evaporator 412.

[0042] In the dual-temperature refrigeration system of the present embodiment, the medium-temperature circuit 400 and the low-temperature circuit 300 share a set of compressors and condensers, thereby realizing the function of one system controlling two temperature zones, thereby effectively reducing equipment costs, system operating costs and installation space of the refrigeration room, and greatly improving the practicality of the unit; by providing the first evaporator 411 and the second evaporator 412, when one of the evaporators is defrosting, the other evaporator can still continue to refrigerate, maintaining the refrigeration function of the system, and the first evaporator 411 and the second evaporator 412 realize the functions of simultaneous defrosting and refrigeration. When one of the evaporators is severely frosted, the flow direction of the refrigerant can be changed to change the working state of the first evaporator 411 and the second evaporator 412, thereby ensuring the reliability of the unit operation. At the same time, the defrosting process of the unit is also more energy-efficient, solving the technical problems of the dual-temperature zone system in the related art that uses two independent refrigeration systems, resulting in increased costs and poor practicality.

[0043] It can be understood that in the dual-temperature refrigeration system of the present embodiment, by designing a medium-temperature evaporator 410 (for example, a design temperature of -7°C) and a low-temperature evaporator 310 (for example, a design temperature of -23°C) in one system, the effect of providing cooling at any time in the medium-temperature zone (0°C) and the low-temperature zone (-18°C) 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] It can be understood that compared with single evaporator refrigeration, the use of dual evaporator refrigeration with medium-temperature evaporator 410 and low-temperature evaporator 310 can effectively expand the application space of the refrigeration system, while the cost and operating expenses are also relatively small. In addition, compared with the problems of uneven defrosting, slow defrosting and high energy consumption of the evaporator of the traditional low-temperature refrigeration system, the system adopts thermal fluorine defrosting to achieve fast and uniform defrosting, and is also more energy-efficient.

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

[0046] By providing the 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 alternating switching of the working states of the first evaporator 411 and the second evaporator 412 .

[0047] See also Figure 1-Figure 2 , Figure 1 and Figure 2They are respectively a structural schematic diagram and a pressure-enthalpy diagram of the dual-temperature refrigeration system in working condition one. At this time, the refrigerant first passes through the second evaporator 412 and is supercooled by the frost layer outside the second evaporator 412, is throttled and reduced in pressure by the first throttle valve 420, and then enters the first evaporator 411 to evaporate and cool and become a gas refrigerant. Therefore, in working condition one, the first evaporator 411 is frosted for cooling and dehumidification, and the second evaporator 412 is defrosted and supercooled.

[0048] See also Figure 3-Figure 4 , Figure 3 and Figure 4 They are respectively a structural schematic diagram and a pressure-enthalpy diagram of the dual-temperature refrigeration system in working condition two. At this time, the refrigerant passes through the first evaporator 411 and is supercooled by the frost layer outside the first evaporator 411, and is throttled and reduced in pressure by the first throttle valve 420, and then enters the second evaporator 412 to evaporate and cool to become a gas refrigerant. Therefore, in working condition two, the second evaporator 412 is frosted and cools and dehumidifies, and the first evaporator 411 is defrosted and supercooled.

[0049] It can be understood that when passing through the first medium-temperature evaporator, the refrigerant is supercooled by the frost layer outside the evaporator and becomes a more supercooled liquid, thereby reducing 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 medium temperature circuit 400 includes: an ejector 440, an active flow inlet 441 of the ejector 440 is connected to the condenser 200, an induced flow inlet 442 of the ejector 440 is connected to the outlet of the evaporator branch, and an ejector outlet 443 of the ejector 440 is connected to the inlet of a gas-liquid separator 450; a gas-liquid separator 450, an air outlet of the gas-liquid separator 450 is connected to the first compressor 100, and a liquid outlet of the gas-liquid separator 450 is connected to the inlet of the evaporator branch.

[0051] Specifically, see Figure 5 , the ejector is mainly divided into three parts: the suction chamber 445, the mixing chamber 446 and the diffusion chamber 447. Among them, the suction chamber 445 includes an injection section and an ejection section. The high-pressure refrigerant coming out of the condenser 200 is used as the primary flow, and the low-pressure refrigerant coming out of the evaporator branch is used as the secondary flow. After the primary flow enters the injection section, it undergoes a process of reducing pressure and increasing speed until the primary flow pressure at the tail of the injection section reaches the minimum. At this time, the primary flow pressure is lower than the secondary flow pressure at the inlet of the ejection section. Therefore, under the action of suction, the secondary flow is sucked into the ejector and mixed with the primary flow at equal pressure. The mixed fluid enters the mixing chamber 446 to continue to be fully mixed, and then enters the diffusion chamber 447 and undergoes a process of increasing pressure and decreasing speed, thereby converting part of the kinetic energy of the refrigerant into pressure energy, thereby increasing the suction port pressure of the first compressor 100.

[0052] By providing the ejector 440, compared with the expansion valve working alone, a portion of the potential energy in 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 and reduces the irreversible loss caused by the refrigerant passing through the expansion valve or the capillary tube. The mixed fluid enters the diffusion chamber 447 for pressure increase and speed reduction. After gas-liquid separation in the gas-liquid separator 450, the gaseous refrigerant with increased pressure enters the first compressor 100 and is compressed, thereby increasing the suction pressure of the compressor, thereby reducing the pressure ratio and compression work of the compressor, and further improving the problem of excessive compression work of the traditional compression system.

[0053] It can be understood that in the dual-temperature refrigeration system of this embodiment, compression-injection coupling is used to replace traditional electric compression, thereby reducing irreversible losses and increasing the compressor suction pressure, thereby reducing the compressor pressure ratio and effectively reducing the compression work, thereby 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, an inlet of the first three-way valve 500 is connected to the condenser 200, a first outlet of the first three-way valve 500 is connected to the active flow inlet 441 of the ejector 440, and a 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 refrigerant flow rate entering the low-temperature circuit 300 or the medium-temperature circuit 400 can be controlled by the first three-way valve 500.

[0055] In the dual-temperature refrigeration system of this embodiment, see Figure 1 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. By disposing the second throttle 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, and both ends of the second compressor 330 are respectively connected to the low temperature evaporator 310 and the first compressor 100. By providing the second compressor 330, the refrigeration capacity in the low temperature circuit 300 is increased to meet the refrigeration demand of the low temperature zone.

[0057] It should be noted that the second compressor 330 is a low-pressure compressor, and the first compressor 100 is a high-pressure compressor. The refrigerant in the low-temperature circuit 300 is compressed twice, 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 defrost branch 340, the inlet of the defrost branch 340 is connected to the liquid outlet of the gas-liquid separator 450, the outlet of the defrost branch 340 is connected to the inlet of the evaporator branch, and the defrost branch 340 flows through the low temperature evaporator 310 to exchange heat in the low temperature evaporator 310; a first control switch 341, the first control switch 341 is located at the inlet of the defrost branch 340 to open and close the inlet of the defrost branch 340; a second control switch 342, the second control switch 342 is located at the outlet of the defrost branch 340 to open and close the outlet of the defrost branch 340. Through the above arrangement, the relatively high temperature refrigerant in the gas-liquid separator 450 can be led out to defrost the low temperature evaporator 310, which solves the defrosting problem of the low temperature evaporator 310, and this defrosting method is more energy-saving and environmentally friendly.

[0059] It is understandable that the defrost branch 340 is usually kept closed, and when it is detected that the frost layer of the low-temperature evaporator 310 reaches the maximum thickness, the defrost branch 340 is controlled to open for defrosting.

[0060] It can be understood that the system can achieve rapid and uniform defrosting of the surface of the low-temperature evaporator 310 and the medium-temperature evaporator 410 through the 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 respectively connected to the liquid outlet of the gas-liquid separator 450 and the third flow path inlet of the second economizer. For example, the remaining two ports of the second control switch 342 are respectively connected to the third flow path outlet of the second economizer and the first port of the four-way valve 430.

[0062] In the dual-temperature refrigeration system of this embodiment, see Figure 1The dual-temperature refrigeration system includes a first economizer 600, which includes: a first flow path that exchanges heat with each other, the first flow path is arranged 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; a second flow path, the second flow path is arranged 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 injection flow inlet 442 of the ejector 440. By setting the first economizer 600, the refrigerants at a certain node in the low-temperature circuit 300 and the medium-temperature circuit 400 can exchange heat with each other. In the low-temperature circuit 300, the high-temperature refrigerant flowing out of the condenser 200 can be cooled by the low-temperature refrigerant flowing out of the evaporator branch in the medium-temperature circuit 400. The refrigerant is effectively supercooled before the throttle 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 flow inlet 442 of the ejector 440. The refrigerant is heated by the first economizer 600 to be a superheated working medium, which can effectively increase the cooling capacity of the unit, thereby improving 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 arranged 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; a fourth flow path, which is arranged 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. By setting up the second economizer 700, the refrigerants at a certain node in the low-temperature circuit 300 and the medium-temperature circuit 400 are heat-exchanged with each other. 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, and enters the second compressor 330 and the first compressor 100 after being heated to superheated gas. 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, and the liquid refrigerant is cooled to a supercooled liquid, which is then supercooled by the frost layer on the outside of the first medium-temperature evaporator and becomes a more supercooled liquid. It then enters the second medium-temperature evaporator for evaporative cooling, which can effectively increase the cooling capacity of the unit, thereby improving the overall cooling performance of the unit.

[0064] By providing the first economizer 600 and the second economizer 700, and alternately defrosting the medium-temperature evaporator (the first evaporator 411 or the second evaporator 412), the refrigerant before the throttle valve that is about to enter the medium-temperature evaporator or the low-temperature evaporator can be effectively supercooled, thereby effectively improving the refrigeration performance of the unit.

[0065] In the dual-temperature refrigeration system of this embodiment, see Figure 1 The dual-temperature refrigeration system includes a first temperature sensor, which is 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 by signal. By setting the first temperature sensor, the refrigerant at the liquid outlet of the gas-liquid separator 450 is detected. When the refrigerant temperature is too low, for example, when the refrigerant temperature is lower than 0°, it is not suitable for defrosting. At this time, the system does not turn on the defrosting function, and the first control switch 341 and the second control switch 342 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, which is located at the first port of the four-way valve 430 and is signal-connected to the four-way valve 430. The first temperature sensor is provided to detect the refrigerant at the first port of the four-way valve 430. When the refrigerant temperature is too low, for example, when the refrigerant temperature is lower than 0°, it is not suitable for defrosting, and the system does not start the defrosting function.

[0067] In the dual-temperature refrigeration system of this embodiment, compared with the traditional electric compression refrigeration, the compression-injection coupling technology is applied to the low-temperature dehumidification system, which can effectively reduce the irreversible loss of the throttling process, and at the same time increase the suction pressure of the compressor, thereby improving the energy efficiency of the system; compared with the single evaporator refrigeration, the dual evaporator refrigeration can effectively expand the application space of the refrigeration system, and the initial investment and operating costs are also small. Compared with the problems of uneven defrosting, slow defrosting and high energy consumption of the evaporator of the traditional low-temperature refrigeration system, this system adopts the hot fluorine defrosting method to achieve fast and uniform defrosting, and is also more energy-saving; by supercooling the refrigerant before throttling the medium and low temperature evaporators, the refrigeration performance of the unit is effectively improved.

[0068] Example 2

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

[0070] In the air-conditioning unit of the present embodiment, the medium-temperature circuit 400 and the low-temperature circuit 300 share a set of compressors and condensers, thereby realizing the function of one system controlling two temperature zones, thereby effectively reducing the cost of the air-conditioning unit, the system operating costs and the installation space of the refrigeration room, and greatly improving the practicality of the air-conditioning unit; by setting the first evaporator 411 and the second evaporator 412, when one of the evaporators is defrosting, the other evaporator can still continue to refrigerate, maintaining the refrigeration function of the system, and the first evaporator 411 and the second evaporator 412 realize the functions of simultaneous defrosting and refrigeration. When one of the evaporators is severely frosted, the flow direction of the refrigerant can be changed to change the working state of the first evaporator 411 and the second evaporator 412, thereby ensuring the reliability of the unit operation. At the same time, the defrosting process of the unit is also more energy-efficient, which solves the technical problems of the dual-temperature zone system using two independent refrigeration systems in the related art, resulting in increased costs and poor practicality.

[0071] Example 3

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

[0073] Monitor the frosting condition of 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 switched to defrost the first evaporator 411 or the second evaporator 412 .

[0075] Specifically, the time when the medium-temperature evaporator 410 reaches the maximum frost thickness is determined through experiments. When the first evaporator 411 or the second evaporator 412 reaches the maximum frost thickness, the corresponding evaporator stops refrigeration and frost formation, and the direction of the four-way valve 430 is changed. The refrigerant flow direction between the first evaporator 411 and the second evaporator 412 is changed. The evaporator that was originally frosted and dehumidified is now defrosted and overcooled, and the evaporator that was originally defrosted is now frosted and dehumidified, so that the medium-temperature cold storage can achieve refrigeration and defrosting without stopping the unit.

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

[0077] Monitoring 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 refrigeration, and the defrost branch 340 is opened to defrost the low-temperature evaporator 310.

[0079] Specifically, the time when the low temperature evaporator reaches the maximum frost thickness is determined by experiments. When the low temperature evaporator 310 reaches the maximum frost thickness, the first three-way valve 500 is closed, the low temperature circuit 300 stops refrigeration, and the first control switch 341 is opened to achieve rapid defrosting.

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

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

[0082] The second control switch 342 is turned on to open the outlet of the defrost branch 340 .

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

[0084] In the defrost control method of this embodiment, in order to ensure stable defrost operation, a defrost control logic should be set, and temperature sensors should be 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 proceeds smoothly, and when the temperature is lower than 0°C, defrosting cannot be performed.

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

[0086] See also Figure 1-2 , Figure 5 When the dual-temperature refrigeration system is in working condition 1, high-temperature and high-pressure liquid refrigerant flows out from the condenser 200 ( Figure 2The state point 1) is divided into two paths, one path enters the ejector 440 to reduce the pressure and speed to become low-temperature low-pressure wet steam (state point 1'); the low-temperature low-pressure gas refrigerant flows out from the first evaporator 411 (state point 13 or 14), then enters the first economizer 600 to be heated to superheated working medium (state point 2), and then enters the ejector 440 ejector section to reduce the pressure and speed to become a relatively low-pressure refrigerant (state point 2'); the two refrigerants (state point 1' and state point 2') are in the ejector mixing chamber 4 46 is uniformly mixed at equal pressure to form refrigerant (state point 3'), and then enters the ejector 440 diffusion chamber 447 to reduce speed and increase pressure to form medium-pressure wet steam (state point 3); then enters the gas-liquid separator 450 to produce liquid refrigerant (state point 7) and gas refrigerant (state point 4); the liquid refrigerant (state point 7) passes through the second economizer 700 to be cooled to a subcooled liquid (state point 8), and then is subcooled by the frost layer outside the second evaporator 412, and then becomes a more subcooled liquid ( state point 11); then it passes through the first throttle valve 420 to become a low-temperature and low-pressure refrigerant (state point 12); then it enters the first evaporator 411 to evaporate and cool to become a gas refrigerant (state point 13 or 14); another high-temperature refrigerant (state point 1) coming out of the condenser 200 enters the first economizer 600 to be cooled to a supercooled liquid (state point 15), passes through the second throttle valve 320 to become a low-pressure working medium (state point 16), then enters the evaporator 2 to evaporate and absorb heat to become a gas working medium (state point 17), then enters the second economizer 700 to be heated to a superheated gas (state point 18), then enters the second compressor 330 to become a medium-temperature and medium-pressure working medium (state point 19), state point 4 and state point 19 are isobarically mixed to become a superheated working medium (state point 5), then enters the first compressor 100 to become a refrigerant (state point 6), then enters the condenser 200 to isobarically dissipate heat to become a liquid refrigerant (state point 1), and finally completes the entire refrigeration cycle.

[0087] See also Figure 3-4 , Figure 5When the dual-temperature refrigeration system is in working condition 2, the high-temperature and high-pressure liquid refrigerant (state point 1) flowing out of the condenser 200 is divided into two paths, one path enters the ejector 440 to reduce the pressure and increase the speed to become low-temperature and low-pressure wet steam (state point 1'); the low-temperature and low-pressure gas refrigerant (state point 10 or 14) flows out from the second evaporator 412, then enters the first economizer 600 to be heated to become a superheated working medium (state point 2), and then enters the ejector 440 ejector section to reduce the pressure and increase the speed to become a relatively low-pressure refrigerant (state point 2'); The two refrigerants (state point 1' and state point 2') are uniformly mixed at equal pressure in the ejector mixing chamber 446 to form a refrigerant (state point 3'), and then enter the ejector diffusion chamber 447 to reduce speed and increase pressure to form medium-pressure wet steam (state point 3); then enter the gas-liquid separator 450 to produce liquid refrigerant (state point 7) and gas refrigerant (state point 4); the liquid refrigerant (state point 7) passes through the gas-liquid separator 450 and is cooled to form a subcooled liquid (state point 8), and then is discharged from the first evaporator 411. The frost layer at the bottom is supercooled and then becomes a more supercooled liquid (state point 12); then it passes through the first throttle valve 420 to become a low-temperature and low-pressure refrigerant (state point 11); then it enters the second evaporator 412 for evaporation and refrigeration to become a gas refrigerant (state point 10 or 14); another high-temperature refrigerant (state point 1) coming out of the condenser 200 enters the economizer and is cooled to a supercooled liquid (state point 15), passes through the second throttle valve 320 to become a low-pressure working fluid (state point 16), and then enters the evaporator 2 evaporates and absorbs heat to become a gaseous working medium (state point 17), then enters the second economizer 700 to be heated to become a superheated gas (state point 18), then enters the second compressor 330 to become a medium-temperature and medium-pressure working medium (state point 19), state point 4 and state point 19 are isobarically mixed to become a superheated working medium (state point 5), then enters the first compressor 100 to become a refrigerant (state point 6), then enters the condenser 200 to dissipate heat at an isobaric pressure to become a liquid refrigerant (state point 1), and finally completes the entire refrigeration cycle.

[0088] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

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

[0090] The serial numbers of the above-mentioned embodiments of the present application are for description only and do not represent the advantages or disadvantages of the embodiments.

[0091] In the above embodiments of the present application, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, please refer to the relevant description of other embodiments.

[0092] The above is only a preferred implementation of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A dual-temperature refrigeration system, characterized in that: include: A first compressor (100) and a condenser (200); A low-temperature circuit (300), wherein a low-temperature evaporator (310) is provided on the low-temperature circuit (300), and the low-temperature evaporator (310) is respectively connected to the first compressor (100) and the condenser (200); A medium-temperature circuit (400), the medium-temperature circuit (400) comprising an evaporator branch and a medium-temperature evaporator (410) arranged on the evaporator branch, the evaporator branch being respectively connected to the first compressor (100) and the condenser (200); the medium-temperature evaporator (410) comprising a first evaporator (411) and a second evaporator (412) arranged in series, the first evaporator (411) and the second evaporator (412) being arranged at intervals on the evaporator branch; a first throttle valve (420) being arranged on the evaporator branch, the first throttle valve (420) being located between the first evaporator (411) and the second evaporator (412); A controller, wherein the controller switches 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).

2. The dual-temperature refrigeration system according to claim 1, characterized in that: A four-way valve (430) is provided on the evaporator branch, a first port of the four-way valve (430) is connected to the inlet of the evaporator branch, a second port of the four-way valve (430) is connected to the first evaporator (411), a third port of the four-way valve (430) is connected to the second evaporator (412), and a 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 medium temperature circuit (400) comprises: An ejector (440), wherein an active flow inlet (441) of the ejector (440) is in communication with the condenser (200), an ejector flow inlet (442) of the ejector (440) is in communication with an outlet of the evaporator branch, and an ejector outlet (443) of the ejector (440) is in communication with an inlet of a gas-liquid separator (450); The gas-liquid separator (450), the gas outlet of the gas-liquid separator (450) is connected to the first compressor (100), and the liquid outlet of the gas-liquid separator (450) is 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 comprises a first three-way valve (500), wherein an inlet of the first three-way valve (500) is connected to the condenser (200), a first outlet of the first three-way valve (500) is connected to an active flow inlet (441) of the ejector (440), and a second outlet of the first three-way valve (500) 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), and the second throttle valve (320) is arranged 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), and two ends of the second compressor (330) are respectively connected to the low-temperature evaporator (310) and the first compressor (100).

7. The dual-temperature refrigeration system according to claim 3, characterized in that: The low temperature circuit (300) comprises: a defrost branch (340), wherein the inlet of the defrost branch (340) is connected to the liquid outlet of the gas-liquid separator (450), the outlet of the defrost branch (340) is connected to the inlet of the evaporator branch, and the defrost branch (340) flows through the low-temperature evaporator (310) to generate heat exchange in the low-temperature evaporator (310); A first control switch (341), the first control switch (341) being located at the inlet of the defrost branch (340) to open and close the inlet of the defrost branch (340); A second control switch (342), the second control switch (342) is located at the outlet of the defrost branch (340) to open and close the outlet of the defrost branch (340).

8. The dual-temperature refrigeration system according to claim 5, characterized in that: The dual-temperature refrigeration system comprises a first economizer (600), wherein the first economizer (600) comprises: a first flow path, the first flow path being arranged in the low-temperature circuit (300), and two ends of the first flow path being respectively connected to the condenser (200) and the second throttle valve (320); A second flow path, wherein the second flow path is arranged in the medium temperature circuit (400), and two ends of the second flow path are respectively connected to the outlet of the evaporator branch and the ejector flow inlet (442) of the ejector (440).

9. The dual-temperature refrigeration system according to claim 6, characterized in that: The dual-temperature refrigeration system comprises a second economizer (700), wherein the second economizer (700) comprises: a third flow path, the third flow path being arranged in the low-temperature circuit (300), and two ends of the third flow path being respectively connected to a refrigerant outlet of the low-temperature evaporator (310) and the second compressor (330); A fourth flow path, wherein the fourth flow path is arranged in the medium temperature circuit (400), and 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 comprises a first temperature sensor, the first temperature sensor is located at the liquid outlet of the gas-liquid separator (450), and the first temperature sensor is respectively connected to the first control switch (341) and the second control switch (342) by signals.

11. The dual-temperature refrigeration system according to claim 2, characterized in that: 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 (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 comprises a dual-temperature refrigeration system according to any one of claims 1 to 11.

13. A defrost control method, characterized in that: The defrost control method is applicable to the dual-temperature refrigeration system according to any one of claims 1 to 11, and the defrost control method comprises: Monitor the frosting condition of 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 changed to defrost the first evaporator (411) or the second evaporator (412).

14. The defrost control method according to claim 13, characterized in that: Also includes: Monitoring 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 refrigeration and opens the defrost branch (340) to defrost the low-temperature evaporator (310).

15. The defrost control method according to claim 14, characterized in that: When the low-temperature evaporator (310) reaches the maximum frost thickness, the defrost branch (340) is opened to defrost the low-temperature evaporator (310), comprising: Turning on the first control switch (341) to open the inlet of the defrost branch (340); The second control switch (342) is turned on to open the outlet of the defrost branch (340).

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