What are the air-conditioning refrigerants?
Refrigerant is a working fluid that transfers heat energy and produces cooling and heating effects in the air-conditioning system.
The ideal refrigerant should be: non-toxic, non-explosive, non-corrosive to metals and non-metals, non-flammable, easy to detect when leaking, chemically stable, non-destructive to lubricating oil, has a large latent heat of evaporation, and has no effect on the environment. Harmful.
Understanding the physical properties of refrigerants should have the following characteristics:
1. The evaporation pressure should be high: if the evaporation pressure of the refrigerant is lower than the atmospheric pressure, the air will easily penetrate into the system, and the system processing is more difficult. Therefore, it is hoped that the evaporation pressure of the refrigerant can be higher than the atmospheric pressure when the refrigerant evaporates at a low temperature.
2. The latent heat of evaporation should be large: the latent heat of evaporation of the refrigerant is large, which means that a large amount of heat can be absorbed by using less refrigerant.
3. The critical temperature should be high: if the critical temperature is high, it means that the condensation temperature of the refrigerant is high, and the air or water at room temperature can be used to cool the refrigerant to achieve the effect of condensation and liquefaction.
4. The condensing pressure should be low: the condensing pressure is low, which means that the refrigerant can be liquefied with a lower pressure, and the compression ratio of the compressor is small, which can save the horsepower of the compressor.
5. The freezing temperature should be low: the freezing point of the refrigerant should be low, otherwise the refrigerant will freeze in the evaporator and cannot be circulated.
6. The specific volume of the gaseous refrigerant should be small: the smaller the specific volume of the gaseous refrigerant, the better, the volume of the compressor can be reduced to reduce the cost, and the suction pipe and the exhaust pipe can be piped with smaller refrigerants.
7. The density of the liquid refrigerant should be higher: the higher the density of the liquid refrigerant, the smaller the liquid pipe can be.
8. It is soluble in refrigeration oil, so the system does not need to install an oil separator.
Understanding the chemical properties of refrigerants should have the following characteristics:
1. Stable chemical properties: The evaporation temperature will change with the application temperature. For example, the evaporation temperature of the chiller is about 0~5℃. In the refrigeration cycle system, the refrigerant only changes physically, but not chemically, and does not decompose.
2. Non-corrosive: It is non-corrosive to steel and metal, and ammonia is corrosive to copper. Therefore, copper pipes should not be used in the ammonia refrigeration system. The insulation should be good, otherwise it will destroy the insulation of the compressor motor. Therefore, ammonia should not be used in airtight applications. type compressor to avoid direct contact with the copper coil.
3. No environmental pollution: harmless to the natural environment, does not destroy the ozone layer, and has low greenhouse effect.
5. Not explosive and flammable.
Because it is an ideal refrigerant, we are constantly striving for a perfect refrigerant, but at least it should not have: toxic, flammable, explosive, easy to leak and more destructive to the environment.
Classification and characteristics of conventional refrigerants1. Inorganic compounds: Refrigerants belonging to inorganic compounds include ammonia, water, carbon dioxide, etc. The serial number of the inorganic compound is represented by 700, and the molecular weight of the compound (integer part) plus 700 is the number of the refrigerant. For example, the integer part of the molecular weight of ammonia (NH3) is 17, and its number is R-717. The numbers for water and carbon dioxide are R-718 and R-744, respectively.
2. Fluorocarbons: including CFC, HCFC, HFC, etc.
3. Hydrocarbons: including saturated hydrocarbons (methane, ethane, etc.) and unsaturated hydrocarbons (ethylene, propylene, etc.).
4. Mixed refrigerant.