Carbon dioxide transcritical refrigeration system with ejector for assisting hot gas defrosting

Abstract

The invention belongs to the technical field of air conditioning refrigeration, and relates to a carbon dioxide transcritical refrigeration system with an ejector for assisting hot gas defrosting, which comprises a main compressor and a parallel compressor, an inlet of the main compressor is connected with a circulating barrel, an outlet is connected with a gas cooler, an inlet of the parallel compressor is connected with a flash tank, and an outlet is connected with the gas cooler; an outlet of the gas cooler is respectively connected with a subcooler and an ejector; the subcooler is sequentially connected with a high-temperature throttle valve, a flash tank, a low-temperature throttle valve and a circulating barrel; the ejector is sequentially connected with the subcooler, the defrosting evaporator, the defrosting throttle valve and the flash tank. The ejector is adopted for assisting hot gas defrosting, and the power consumption of the parallel compressor is effectively reduced; meanwhile, the subcooler is adopted, the characteristic that the temperature of an outlet of the ejector is low is utilized, gas passing through the subcooler continues to be cooled, the mass of flash gas in the flash tank can be effectively reduced, more liquid enters the circulating barrel, the refrigerating capacity is increased, and the COP of the whole system is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of air conditioning and refrigeration technology, and relates to a transcritical CO2 multi-stage compression refrigeration and defrosting system, in particular to a transcritical CO2 refrigeration system with an ejector-assisted hot gas defrosting function. BACKGROUND

[0002] The transcritical CO2 refrigeration system is mainly applied to heat pump water heaters, automobile air conditioners, refrigeration and freezing systems, etc. When applied to supermarkets, as an environmentally friendly and efficient refrigeration technology, the defrosting mode of the transcritical CO2 refrigeration system directly affects the performance and energy efficiency of the system. The defrosting modes of the transcritical CO2 refrigeration system mainly include electric heating, water defrosting, natural defrosting, etc., and the hot gas defrosting is less used. In view of system simplification, the hot gas source in the hot gas defrosting mode is part of the hot gas drawn from the exhaust of the main compressor or the parallel compressor into the defrosting evaporator to perform hot gas defrosting. Although this method is similar to the defrosting cycle of the current ammonia refrigeration system when applied to large refrigeration and freezing systems, the gas is reduced from supercritical pressure to defrosting pressure, and the throttling loss is large, which causes high energy consumption. SUMMARY

[0003] The transcritical CO2 refrigeration system with the ejector-assisted hot gas defrosting function provided by the application can improve the energy efficiency of the system (by increasing the supercooling of the added ejector), and solve the problems of high energy consumption and energy waste existing in the current hot gas defrosting mode.

[0004] The technical scheme of the application is as follows:

[0005] The transcritical CO2 refrigeration system with the ejector-assisted hot gas defrosting function provided by the application comprises a main compressor and a parallel compressor, the inlet of the main compressor is connected with a circulation barrel, and the outlet of the main compressor is connected with a gas cooler; the inlet of the parallel compressor is connected with a flash tank, and the outlet of the parallel compressor is connected with the gas cooler.

[0006] The outlet of the gas cooler is connected with a supercooler and an ejector respectively, the supercooler is sequentially connected with a high-temperature throttling valve, a flash tank, a low-temperature throttling valve and the circulation barrel; the ejector is sequentially connected with the supercooler, a defrosting evaporator, a defrosting throttling valve and the flash tank.

[0007] Further, the ejector comprises a primary flow inlet, a secondary flow inlet and a mixed fluid outlet.

[0008] The flash tank comprises two inlets, two gas outlets and one liquid outlet.

[0009] The circulation barrel comprises two inlets, one gas outlet and one liquid outlet.

[0010] Further, the liquid outlet of the circulating barrel is connected with a pump and an evaporator in sequence, and the evaporator is connected with the gas inlet of the circulating barrel, forming a circulating loop.

[0011] Further, the outlet of the gas cooler is connected with the primary flow inlet of an ejector, the gas outlet of the evaporator is connected with the secondary flow inlet of the ejector, and the mixed fluid outlet of the ejector is connected with a subcooler, a defrosting evaporator, a defrosting throttle valve and the gas inlet of a flash tank in sequence.

[0012] Further, the outlet of the gas cooler is connected with the inlet of a subcooler, the outlet of the subcooler is connected with the gas inlet of a flash tank, a high-temperature throttle valve is arranged between the gas cooler and the flash tank, the liquid outlet of the flash tank is connected with the gas inlet of the circulating barrel, and a low-temperature throttle valve is arranged between the flash tank and the circulating barrel.

[0013] Further, the system comprises:

[0014] The refrigeration system: the gas from the gas outlet of the circulating barrel enters a main compressor for compression, and part of the gas from the gas outlet of the flash tank enters a parallel compressor for compression; the two streams of gas are mixed and then enter the gas cooler; after cooling, the gas is divided into two streams, one of which passes through the subcooler, the high-temperature throttle valve, the gas inlet of the flash tank, the liquid outlet of the flash tank, the low-temperature throttle valve and returns to the gas inlet of the circulating barrel in sequence; the liquid from the liquid outlet of the circulating barrel enters the evaporator through the pump and then returns to the gas inlet of the circulating barrel.

[0015] The defrosting system: the other stream of gas from the gas cooler enters the primary flow inlet of the ejector, and part of the gas from the gas outlet of the flash tank is injected into the secondary flow inlet of the ejector through the ejector; the two streams of gas are mixed and then sprayed out from the mixed fluid outlet of the ejector; after being superheated by the cooler, the gas enters the defrosting evaporator, and then enters the gas inlet of the flash tank through the defrosting throttle valve.

[0016] The beneficial effects of the present application are:

[0017] (1) The present application adopts the ejector to assist the hot gas defrosting, which can inject part of the gas in the flash tank, and the cold energy of the defrosting evaporator can be used to condense the gas into liquid; although part of the mass is flashed after passing through the defrosting throttle valve, about 85% of the gas is finally returned to the flash tank in the form of liquid. The mass of about 85% is originally required to be compressed by the parallel compressor, and after being cooled by the gas cooler and throttled by the high-temperature throttle valve, the liquid proportion in the flash tank is only about 60%. Therefore, the use of the ejector to assist the hot gas defrosting can effectively reduce the power consumption of the parallel compressor and improve the coefficient of performance COP (COP is the coefficient of performance of the refrigeration system).

[0018] (2) The present invention uses a subcooler, which takes advantage of the low temperature of the ejector outlet to exchange heat between the gas with the CO2 gas at the outlet of the gas cooler in the subcooler, so that the temperature of the CO2 gas before the high temperature throttle valve is further reduced, which can effectively reduce the mass of flash gas in the flash tank, allowing more liquid to enter the circulation tank, thereby increasing the cooling capacity and improving the system COP. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the transcritical carbon dioxide refrigeration system with ejector-assisted hot gas defrosting provided by the present invention.

[0020] In the diagram, 1. Gas cooler; 2. Parallel compressor; 3. Main compressor; 4. Evaporator; 5. Pump; 6. Subcooler; 7. Defrosting evaporator; 8. Ejector; 9. High-temperature throttling valve; 10. Defrosting throttling valve; 11. Flash tank; 12. Low-temperature throttling valve; 13. Circulation tank. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] To further understand the present invention, it will be further described in conjunction with the accompanying drawings and embodiments.

[0023] like Figure 1 As shown, this invention provides a transcritical carbon dioxide refrigeration system with ejector-assisted hot gas defrosting, including a main compressor 3, a parallel compressor 2, a circulation tank 13, and a flash tank 11. The circulation tank 13 is connected to the inlet of the main compressor 3, and the flash tank 11 is connected to the inlet of the parallel compressor 2. The outlets of the main compressor 3 and the parallel compressor 2 are simultaneously connected to a gas cooler 1. The gas in the circulation tank 13 and a portion of the gas in the flash tank 11 are compressed and then sent to the gas cooler 1 for cooling.

[0024] In this specific embodiment, port A of ejector 8 is the primary flow inlet, port C of ejector 8 is the secondary flow inlet, and port B of ejector 8 is the mixed fluid outlet.

[0025] The flash tank includes two inlets, two gas outlets, and one liquid outlet. Specifically, inlet D of the flash tank 11 is the inlet for a two-phase gas-liquid relationship, and inlet F is located in the gas phase region at the inlet end. Inlet E and inlet G of the flash tank 11 are located in the gas phase region at the outlet end and serve as two gas outlets; inlet H is located in the liquid phase region and serves as the liquid outlet.

[0026] The circulating barrel comprises two inlets, one gas outlet and one liquid outlet; wherein, the I inlet of the circulating barrel 13 is an inlet of gas-liquid two-phase state, the K inlet is located in the gas phase zone of the gas inlet end and is an inlet of gas; the J inlet of the circulating barrel 13 is located in the gas phase zone of the gas outlet end and is a gas outlet; and the L inlet is located in the liquid phase zone and is a liquid outlet.

[0027] Further, the outlet of the gas cooler 1 is connected to the primary flow inlet of the ejector 8, the gas outlet of the evaporator 4 is connected to the secondary flow inlet of the ejector 8, and the mixed fluid outlet of the ejector 8 is connected to the inlet of the supercooler 6, the defrosting evaporator 7, the defrosting throttle valve 10 and the flash tank 11 in sequence.

[0028] Further, the outlet of the gas cooler 1 is connected to the inlet of the supercooler 6, the outlet of the supercooler 6 is connected to the inlet of the flash tank 11, the high-temperature throttle valve 9 is arranged between the cooler and the flash tank 11, the liquid outlet of the flash tank 11 is connected to the inlet of the circulating barrel 13, and the low-temperature throttle valve 12 is arranged between the flash tank 11 and the circulating barrel 13.

[0029] In a specific embodiment, the liquid outlet of the circulating barrel 13 is connected to the pump 5 and the evaporator 4 in sequence, and the evaporator 4 is connected to the gas inlet of the circulating barrel 13, forming a circulating loop.

[0030] It can be understood that the refrigeration system is supplied with liquid by the pump 5 or directly expanded. In the embodiment, the pump 5 is used to supply liquid, and the refrigerant liquid in the circulating barrel 13 is delivered to the evaporator 4 through the pump 5. Alternatively, the direct expansion liquid supply mode can be used, and the pump 5 needs to be replaced by a throttle valve when the direct expansion liquid supply mode is used. The refrigerant liquid in the circulating barrel 13 is expanded through the throttle valve and then enters the evaporator 4.

[0031] In another embodiment, the high-temperature throttle valve 9 can also be replaced by an electronic expansion valve, an ejector or other throttling devices. When the throttle valve 9 is replaced by an ejector, the system loss can be reduced and the efficiency can be improved. This is different from the function of the original ejector 8 in the system, which is mainly used for supercooling the CO2 gas at the outlet of the gas cooler.

[0032] The carbon dioxide transcritical refrigeration system with the ejector 8 assisted hot gas defrosting provided in the embodiment comprises a refrigeration system and a defrosting system, wherein the refrigeration system is:

[0033] The gas from the J inlet of the circulating barrel 13 enters the main compressor 3 for compression, and part of the gas from the G inlet of the flash tank 11 enters the parallel compressor 2 for compression. The two streams of gas are mixed and then enter the gas cooler 1. The cooled gas is divided into two streams, one of which passes through the supercooler 6, the high-temperature throttle valve 9, the D inlet of the flash tank 11, the H inlet of the flash tank 11, the low-temperature throttle valve 12 and the I inlet of the circulating barrel 13 in sequence. The liquid at the L inlet of the circulating barrel 13 enters the evaporator 4 through the pump 5 and then returns to the K inlet of the circulating barrel 13.

[0034] The defrosting system is:

[0035] Another gas from the gas cooler 1 enters the A port of the ejector 8, and part of the gas from the E port of the flash tank 11 is injected into the C port of the ejector 8, and the two streams of gas are mixed and sprayed out from the B port of the ejector 8, and then enters the defrosting evaporator 7 after being superheated by the cold cooler 6, and then enters the F port of the flash tank 11 after being throttled by the defrosting throttle valve 10.

[0036] The above description is only the preferred embodiments of the present application, and is not a limitation on the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or make equivalent replacements to some of the technical features. Any modification, equivalent replacement, modification, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A transcritical carbon dioxide refrigeration system with ejector-assisted hot gas defrosting, characterized in that, It includes a main compressor and a parallel compressor. The inlet of the main compressor is connected to a circulation tank and the outlet is connected to a gas cooler. The inlet of the parallel compressor is connected to a flash tank and the outlet is connected to a gas cooler. The outlet of the gas cooler is connected to a subcooler and an ejector, respectively. The subcooler is connected in sequence to a high-temperature throttling valve, a flash tank, a low-temperature throttling valve, and a circulation tank. The ejector is connected in sequence to a subcooler, a defrosting evaporator, a defrosting throttling valve, and a flash tank.

2. A transcritical carbon dioxide refrigeration system with ejector-assisted hot gas defrosting according to claim 1, characterized in that, The ejector includes a primary flow inlet, a secondary flow inlet, and a mixed fluid outlet; The flash tank includes two inlets, two gas outlets, and one liquid outlet; The circulation tank includes two inlets, one air outlet, and one liquid outlet.

3. A transcritical carbon dioxide refrigeration system with ejector-assisted hot gas defrosting according to claim 2, characterized in that, The outlet of the circulation tank is connected in sequence to the pump and the evaporator, and the evaporator is then connected to the air inlet of the circulation tank to form a circulation loop.

4. A transcritical carbon dioxide refrigeration system with ejector-assisted hot gas defrosting according to claim 2, characterized in that, The outlet of the gas cooler is connected to the primary inlet of the ejector, the outlet of the evaporator is connected to the secondary inlet of the ejector, and the mixed fluid outlet of the ejector is sequentially connected to the inlet of the subcooler, the defrosting evaporator, the defrosting throttle valve, and the flash tank.

5. A transcritical carbon dioxide refrigeration system with ejector-assisted hot gas defrosting according to claim 1, characterized in that, The outlet of the gas cooler is connected to the inlet of the subcooler, the outlet of the subcooler is connected to the inlet of the flash tank, a high-temperature throttling valve is provided between the cooler and the flash tank, the liquid outlet of the flash tank is connected to the inlet of the circulation tank, and a low-temperature throttling valve is provided between the flash tank and the circulation tank.

6. A transcritical carbon dioxide refrigeration system with ejector-assisted hot gas defrosting according to any one of claims 1-5, characterized in that, include: Refrigeration system: The gas coming out of the outlet of the circulating tank enters the main compressor for compression, and a portion of the gas coming out of the outlet of the flash tank enters the parallel compressor for compression. The two gases are mixed and then enter the gas cooler. The cooled gas is divided into two paths. One path passes through the subcooler, high-temperature throttling valve, flash tank inlet, flash tank liquid outlet, and low-temperature throttling valve in sequence and returns to the inlet of the circulating tank. The liquid at the outlet of the circulating tank enters the evaporator through the pump and then returns to the inlet of the circulating tank. Defrosting system: Another stream of gas from the gas cooler enters the primary inlet of the ejector. Part of the gas is drawn from the outlet of the flash tank and enters the secondary inlet of the ejector. The two streams of gas mix and are ejected from the mixed fluid outlet of the ejector. After being superheated by the cooler, they enter the defrosting evaporator and then enter the flash tank inlet after being throttled by the defrosting throttling valve.

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