Introduction of Household Air Conditioning Refrigerants
Currently, most of the refrigerants used in household air conditioners are R22, and a few countries have begun to use two environmentally friendly refrigerants, R407c and R410a. Because the R22 molecule contains chlorine atoms, it will destroy the ozone layer of the atmosphere. There are two main types of substitutes for refrigerants such as R22, namely hydrofluorocarbons (HFCs) and hydrocarbons (HCs). A more mature alternative to R22 hydrofluorocarbon refrigerant.
1.R407C
R407C is a mixture of R32, R125 and R134a. The mixing ratio (mass ratio) is: R32 accounts for 32%, R125 accounts for 25%, and R134a Accounted for 52%. R407c is used to replace R22 and is currently used more. After the original R22 refrigeration equipment is converted to R407C, except for replacing the lubricating oil and adjusting the system refrigerant
charging amount and throttling components, the compressor and other equipment can not be changed, but the cavity The cooling capacity and energy efficiency ratio of are slightly lower than R22, and it is expected to be similar to R22 after structural optimization.
2.R410a
R410a is a mixture of R32 and R125. The mixing ratio of R410a is: R32 accounts for 50% and R125 accounts for 50%. Its thermodynamic performance is very close to a single working fluid, which is convenient for thermal calculation and maintenance. When it is used to replace R22, the structure of the air-conditioning equipment needs to be changed, and the condensing pressure and refrigeration volume of the refrigeration system are increased.
Nearly 500, the energy efficiency ratio is similar to R22.
3. Natural alternative working fluid
Natural Refi-igerant refers to the substances that can be used as refrigerants that are not artificially synthesized, such as water, air, and nitrogen. , Hydrocarbons (methane, propane, butane, etc.), ammonia, carbon dioxide, helium, etc. Nitrogen, methane, air, helium, etc. are mainly used in low-temperature engineering due to the low standard evaporation temperature, and the rest can be used in refrigeration engineering. Artificially synthesized compounds are released into the surrounding environment in large quantities, often resulting in unpredictable consequences. Replacing CFC with HFC can alleviate the damage to the ozone layer, but it does not solve another problem that endangers the ecological balance of the earth, the greenhouse effect. While ammonia, propane, butane and carbon dioxide are used as refrigerants, there are many oxygen-bursting layers that do not produce the greenhouse effect (the CO2 used as the refrigerant is taken from the atmosphere and does not increase the content of CO in the atmosphere), low price, and traditional Lubricating oil and so on. Of course, due to flammability and toxicity issues, when using hydrocarbons and ammonia, you must pay attention to safety issues; with c01, the compressor and refrigeration system must be redesigned. These problems can be solved through continuous improvement in technology.
1.CO, the characteristics of refrigerant
Co2 refrigerant has been used in refrigeration and air conditioning for more than 100 years. Although Co2 refrigerant has many excellent characteristics, the large volume loss, low system efficiency, and high operating pressure during operation in a high temperature environment are problems that have not been solved in the past. When the research on using CFC as a refrigerant was started in 1930, no advantages were found, such as good thermal properties and no damage to the odorous environment. Therefore, CFC refrigerants gradually replaced the more restrictive refrigerants (such as Ammonia is toxic, hydrocarbons are flammable, CO2 is inefficient, etc.). By the 1950s, the international use of CO2 as a refrigerant ceased.
After more than half a century of development, but also due to environmental protection requirements, new research has begun in the field of CO2 refrigerant application. In 1993, Norway’s G. Lorentzen and I. Pettersens* first proposed the application of CO refrigerant to automobile air-conditioning refrigeration systems, and carried out some experimental studies on
. Compared with R12 refrigerant, CO2 has the following properties:
(1) The critical temperature of CO2 is low (31.1℃),
If CO is used as a refrigerant for compression, its The exothermic zone will exceed the critical point temperature and work in the supercritical point area.
(2)0 has a high I critical point pressure (738MPa), which is about 1.8 times that of R12. However, due to its low critical point temperature, its working pressure will be higher during the compression cycle. CO2 heat release in the supercritical point area has a considerable temperature difference that can be achieved. Therefore, this feature is very suitable for high-efficiency heat pump systems.
CO2 has a high adiabatic coefficient, which will cause compression The temperature of the engine exhaust increases. But the compression ratio is low enough to offset the negative effect brought by the adiabatic coefficient, and can reduce the loss of compressor clearance volume re-expansion. Specific heat capacity, latent heat of vaporization, thermal conductivity, and dynamic viscosity are important performance parameters related to heat exchange and pressure drop. In terms of these performance parameters, CO: is better than halogenated hydrocarbons.
In addition, from a practical point of view, CO: Compared with halogenated hydrocarbon refrigerants, there are the following advantages:
1) Compared with various lubricating oils and common machine parts Compatible materials;
2) It is easy to obtain, without supply restrictions;
3) Convenient operation and maintenance, no need to recycle, low price
2. The characteristics of propane refrigerant
Propane is widely present in petroleum and natural gas. It is easy to refine and cheap, and it is widely used in the petrochemical industry. Propane is a very cheap natural refrigerant, and its ODP and GW P values u200bu200bare both zero. Propane (P, 290) is a saturated hydrocarbon, chemically very inactive and hardly soluble in water. It can dissolve the lubricating oil and reduce the viscosity of the lubricating oil. Therefore, a lubricating oil with a higher viscosity should be selected. Propane is a medium-temperature refrigerant. The standard evaporation temperature is lower than 0℃ and higher than -60℃, and the condensing pressure is higher than 0.3MPa and lower than 2.0MPa.
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