CN210861850U - Double-stage throttling non-azeotropic working medium mechanical supercooling CO2Transcritical refrigeration cycle system - Google Patents

Abstract

The utility model discloses a double-stage throttling non-azeotropic working fluid mechanical subcooling CO ₂ transcritical refrigeration cycle system. The _CO2 transcritical refrigeration cycle system of the utility model comprises a gas cooler, a medium temperature stage cooling evaporator, a low temperature stage cooling evaporator, an expansion valve, an evaporator and a compressor; a non-azeotropic working fluid mechanical subcooling two-stage throttling cycle system Including medium temperature stage compressor, condenser, liquid accumulator, medium temperature stage throttle valve, low temperature stage throttle valve, low temperature stage compressor. The CO ₂ fluid at the outlet of the CO ₂ circulating gas cooler can be cooled for the first time and the second time through the non-azeotropic working fluid pressurization mechanical circulation, which reduces the throttling loss and improves the overall energy efficiency of the system. Through the double-stage throttling non-azeotropic working fluid mechanically assisted subcooling cycle, the heat exchange forms a better temperature matching, reduces the heat transfer temperature difference, reduces the irreversible loss of the process, and further reduces the condenser and evaporator. The irreversible loss of heat transfer increases the efficiency of the refrigeration cycle.

Description

Two-stage throttling non-azeotropic working fluid mechanical subcooling CO2 transcritical refrigeration cycle system

technical field

The utility model relates to the technical field of refrigeration, in particular to a double-stage throttling non-azeotropic working fluid mechanical supercooling CO ₂ transcritical refrigeration cycle system.

Background technique

With the increasingly prominent environmental problems such as global warming and the destruction of the ozone layer, in order to replace the CFCs, HCFCs, HFCs and other working fluids that have a damaging effect on the ozone layer and produce a greenhouse effect, the search for new and friendly natural refrigeration refrigerants has become the field of refrigeration and air conditioning. research focus. Among them, CO ₂ has attracted widespread attention due to its advantages of non-toxicity, non-flammability, safety and environmental protection.

However, due to the lower critical temperature and higher critical pressure of _CO2 , the throttling loss is large and the refrigeration efficiency is low, especially when the ambient temperature is high, the refrigeration capacity of _CO2 drops sharply. If the _CO2 fluid at the outlet of the gas cooler is subcooled, with the increase of subcooling degree, the throttling loss decreases, the circulating cooling capacity increases, and the circulating COP is improved. The subcooling of the _CO2 refrigeration cycle can be achieved by means of internal heat exchangers, mechanical subcooling, thermoelectric subcooling, etc. Some scholars have carried out theoretical research on the use of mechanical subcooling for _CO2 transcritical refrigeration cycle, that is, _CO2 at the outlet of the gas cooler of the main cycle ( _CO2 transcritical refrigeration cycle) is cooled by a vapor compression refrigeration cycle. Mechanical subcooling can not only increase the cooling capacity, but also reduce the operating high pressure of the main cycle, reduce the compressor discharge pressure, and prolong the service life of the compressor

Conventional mechanical subcooling cycles use pure working fluid, and the temperature during the evaporative phase change remains unchanged, but the cooling process of supercritical CO ₂ fluid is a cooling process, and the temperature of the two heat exchange processes does not match, resulting in large irreversible losses in the heat exchange process. And for applications with high ambient temperature and low evaporation temperature, the CO ₂ subcooling degree is as high as 20°C or more. The condensing side of the mechanical subcooling refrigeration cycle exchanges heat with the air, and the evaporation side exchanges heat with the _CO2 fluid. The temperature rise of the air side generally does not exceed 8 °C, while the temperature drop of _CO2 is about 20 °C.

If the mechanical subcooling cycle adopts a non-azeotropic working medium, the temperature glide of the evaporation and condensation phase change process is close, and the condensation side and the evaporation side cannot form a good temperature match with the air and _CO at the same time, which will cause a larger temperature. irreversible loss.

Utility model content

The purpose of the present utility model is to provide a double-stage throttling non-azeotropic working fluid mechanical subcooling CO ₂ transcritical refrigeration cycle system in order to overcome the above-mentioned deficiencies in the prior art.

The utility model is composed of a mechanical subcooling refrigeration cycle and a _CO2 transcritical refrigeration cycle, wherein the mechanical subcooling refrigeration cycle is a vapor compression refrigeration cycle with two evaporation pressures, and the refrigerant is a mixed refrigerant _CO2 /R1234ze with reasonable temperature glide , CO ₂ /R1234yf, R41/R1234ze, R41/R1234yf, R32/R1234ze, R32/R1234yf or R32/R600a.

The circulation system of the utility model is composed of the coupling of a non-azeotropic working fluid mechanical subcooling _two -stage throttling circulation system and a CO2 transcritical refrigeration circulation system;

The _CO2 transcritical refrigeration cycle system includes a gas cooler, a medium temperature stage cooling evaporator, a low temperature stage cooling evaporator, an expansion valve, an evaporator, and a compressor; the compressor outlet is connected to the gas cooler inlet, and the gas cooler The outlet is connected to the inlet of the medium temperature cooling evaporator, the outlet of the medium temperature cooling evaporator is connected to the inlet of the low temperature cooling evaporator, the outlet of the low temperature cooling evaporator is connected to the inlet of the expansion valve, the outlet of the expansion valve is connected to the inlet of the evaporator, and the evaporator The inlet is connected to the compressor;

The non-azeotropic working fluid mechanical subcooling two-stage throttling cycle system includes a medium temperature stage compressor, a condenser, a liquid accumulator, a medium temperature stage throttle valve, a low temperature stage throttle valve, and a low temperature stage compressor; the medium temperature stage The outlet of the compressor is connected to the inlet of the condenser, the outlet of the condenser is first connected to the medium temperature throttle valve and the low temperature throttle valve after passing through the accumulator, the outlet of the medium temperature throttle valve is connected to the inlet of the medium temperature cooling evaporator, and the outlet of the medium temperature cooling evaporator is connected to the medium temperature throttle valve. The inlet of the medium temperature compressor is connected to form a first circuit; the outlet of the low temperature throttle valve is connected with the inlet of the low temperature cooling evaporator, the outlet of the low temperature cooling evaporator is connected with the inlet of the low temperature stage compressor, and the outlet of the low temperature stage compressor is connected with the inlet of the medium temperature stage compressor connected to form a second loop.

The medium temperature cooling evaporator and the low temperature cooling evaporator are both counter-flow heat exchangers.

The CO ₂ transcritical refrigeration cycle refrigerant adopts natural working medium CO ₂ , and the non-azeotropic working medium mechanical subcooling two-stage throttling cycle refrigerant is CO ₂ /R1234ze, CO ₂ /R1234yf, R41/R1234ze, R41/R1234yf, R32 /R1234ze, R32/R1234yf or R32/R600a.

The advantages and positive effects that the utility model has are:

(1) The refrigerant of the CO ₂ refrigeration system is the natural working medium CO ₂ . The GWP of _{CO 2} is ₁ , and the ODP is 0. It is safe, non-toxic, non-flammable, cheap and easy to obtain, and does not decompose to produce harmful gases under high temperature conditions. R1234ze, R41/R1234yf, R32/R1234ze, R32/R1234yf or R32/R600a have a lower GWP and the refrigerants used in the system are all environmentally friendly refrigerants.

(2) The mechanical subcooling cycle uses non-azeotropic refrigerant CO ₂ /R1234ze, CO ₂ /R1234yf, R41/R1234ze, R41/R1234yf, R32/R1234ze, R32/R1234yf or R32/R600a as the working fluid. A good temperature match is formed with the air in the condenser. The refrigerant is throttled twice, and there are two evaporation processes with different high and low temperatures in the cycle. Among them, the evaporation process of higher temperature forms a good temperature match with the primary subcooling of CO ₂ , and the evaporation process of lower temperature is compatible with the secondary CO ₂ . Subcooling allows for better temperature matching, which ultimately reduces the _CO2 gas cooler outlet temperature further. The irreversible loss of heat exchange on the evaporation side and the condensation side of the mechanical subcooling cycle is reduced, and the overall performance of the cycle is improved.

(3) The _CO2 at the outlet of the _CO2 system gas cooler is subcooled by the mechanical subcooling system to reduce the _CO2 temperature before entering the expansion valve, reduce the expansion loss, and further reduce the _CO2 operating high pressure.

Description of drawings

Fig. 1 is the temperature enthalpy diagram of the _CO transcritical refrigeration cycle of the _dual -stage throttling non-azeotropic working fluid mechanical subcooling CO transcritical refrigeration cycle system of the present invention;

Fig. 2 is the temperature enthalpy diagram of the double-stage throttling non-azeotropic working fluid mechanical subcooling of the dual-stage throttling non-azeotropic working fluid mechanical subcooling CO ₂ transcritical refrigeration cycle system of the present invention;

Figure 3 is a schematic diagram of the dual-stage throttling non-azeotropic working fluid mechanical subcooling CO ₂ transcritical refrigeration cycle system of the present invention.

Detailed ways

The present utility model will be further described below in conjunction with the accompanying drawings.

As shown in Figure 1, the utility model includes a two-stage throttling non-azeotropic working fluid mechanical subcooling cycle system and a _CO2 transcritical refrigeration cycle system, the thick solid line is the CO2 transcritical cycle (1'- _2' -3 '-4'-5'-6'-1'), the thin solid line is the low temperature evaporation process (8-1) and the high temperature evaporation process (7-3) of the double-stage throttle non-azeotropic working fluid mechanical subcooling cycle . Fig. 2 is the temperature-enthalpy diagram of the auxiliary subcooling refrigeration cycle of the non-azeotropic working fluid supercharging mechanical subcooling _CO2 transcritical refrigeration cycle system of the present invention, wherein 3'-4' are the primary subcooling process of _CO2 , 4'-5' is the secondary subcooling process of _CO2 .

The utility model system is shown in Figure 3:

Step 1: The compressor 1 inhales the low-temperature and low-pressure saturated _CO2 gas at the outlet of the evaporator 6, compresses it into high-temperature and high-pressure gas, exchanges heat with the air in the gas cooler 2, and the temperature decreases, and then flows through the gas cooler 2 respectively. The medium temperature cooling evaporator 3 and the low temperature cooling evaporator 4 exchange heat with the non-azeotropic mixed refrigerant to realize the subcooling of the _CO2 fluid, and then enter the throttle valve 5 to throttle and depressurize, and become a gas-liquid two-phase state. After the evaporator 6 evaporates and absorbs heat, it becomes superheated gas and enters the compressor to complete the CO ₂ transcritical cycle.

The second step: the mechanical subcooling cycle low temperature stage compressor 12 absorbs the low temperature and low pressure refrigerant at the outlet of the low temperature cooling evaporator 4, compresses it into a superheated gas of medium temperature and medium pressure, and mixes it with the saturated gas at the outlet of the medium temperature cooling evaporator 3 Enter the medium temperature stage compressor 7, compress it into high temperature and high pressure gas, and enter the condenser 8 to exchange heat with the air. Afterwards, the refrigerant enters the accumulator 9, one way passes through the medium-temperature stage throttle valve 10 for expansion and throttling, and then becomes a gas-liquid two-phase fluid of medium temperature and medium pressure, and the other way passes through the low-temperature stage throttle valve 11 and becomes a low temperature and low pressure after expansion and throttling. gas-liquid two-phase fluid.

The third step: the non-azeotropic working medium gas-liquid two-phase fluid of the medium temperature and medium pressure in the mechanical subcooling cycle undergoes a heat exchange with CO ₂ through the medium temperature cooling evaporator 3 and becomes a saturated gas, and the low temperature and low pressure gas-liquid two-phase fluid passes through the low temperature. The cooling evaporator 4 exchanges heat with CO ₂ , further reduces the temperature of the CO ₂ fluid, and the non-azeotropic working medium finally becomes a saturated gas.

Although the preferred embodiments of the present utility model have been described above in conjunction with the accompanying drawings, the present utility model is not limited to the above-mentioned specific embodiments, which are only illustrative and not restrictive. Under the inspiration of the present utility model, those of ordinary skill can also make many forms without departing from the scope of protection of the present utility model and the claims, which all belong to the protection scope of the present utility model.

Claims (3)

1. Double-stage throttling non-azeotropic working medium mechanical supercooling CO₂The transcritical circulation refrigeration system is characterized in that the circulation system consists of a non-azeotropic working medium mechanical supercooling two-stage throttling circulation system and CO₂A transcritical refrigeration cycle system;

the CO is₂The transcritical refrigeration cycle system comprises a gas cooler, a medium-temperature-stage cooling evaporator, a low-temperature-stage cooling evaporator, an expansion valve, an evaporator and a compressor; the outlet of the compressor is connected with the inlet of the gas cooler, the outlet of the gas cooler is connected with the inlet of the medium-temperature-stage cooling evaporator, the outlet of the medium-temperature-stage cooling evaporator is connected with the inlet of the low-temperature-stage cooling evaporator, the outlet of the low-temperature-stage cooling evaporator is connected with the inlet of the expansion valve, the outlet of the expansion valve is connected with the inlet of the evaporator, and the inlet of the evaporator is connected with the compressor;

the non-azeotropic working medium mechanical supercooling two-stage throttling circulation system comprises a medium-temperature-stage compressor, a condenser, a liquid storage device, a medium-temperature-stage throttling valve, a low-temperature-stage throttling valve and a low-temperature-stage compressor; the outlet of the medium-temperature stage compressor is connected with the inlet of the condenser, the outlet of the condenser is connected with the medium-temperature throttling valve and the low-temperature throttling valve respectively after passing through the liquid storage device, the outlet of the medium-temperature throttling valve is connected with the inlet of the medium-temperature cooling evaporator, and the outlet of the medium-temperature cooling evaporator is connected with the inlet of the medium-temperature compressor; the outlet of the low-temperature throttling valve is connected with the inlet of a low-temperature cooling evaporator, the outlet of the low-temperature cooling evaporator is connected with the inlet of a low-temperature stage compressor, and the outlet of the low-temperature stage compressor is connected with the inlet of a medium-temperature stage compressor.

2. The dual stage throttling non-azeotropic working medium mechanical subcooling CO according to claim 1₂The transcritical circulation refrigeration system is characterized in that the medium-temperature cooling evaporator and the low-temperature cooling evaporator are both counterflow heat exchangers.

3. The dual stage throttle of claim 1Mechanical super-cooling CO of non-azeotropic working medium₂Transcritical cycle refrigeration system, characterized by CO₂Natural working medium CO is adopted as transcritical refrigeration cycle refrigerant₂The non-azeotropic working medium mechanical supercooling two-stage throttling circulating refrigerant is CO₂/R1234ze、CO₂R1234yf, R41/R1234ze, R41/R1234yf, R32/R1234ze, R32/R1234yf or R32/R600 a.

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