制冷剂的性质（Properties of refrigerants）.docVIP

制冷剂的性质（Properties of refrigerants） Properties of refrigerants Properties of refrigerants There are many kinds of refrigerants in steam compression refrigeration. According to the composition of refrigerant, there is a single refrigerant and mixed refrigerant; According to the chemical categories of refrigerants, there are mainly three kinds: inorganic substances, freon and hydrocarbon. Selection criteria of chiller: 1, refrigeration performance We expect the condensation of refrigerant pressure is not too high, the evaporation at atmospheric pressure is more than atmospheric pressure low or not too much pressure, moderate, exhaust temperature is not too high, the refrigerating capacity per unit volume, the coefficient of performance of the high cycle. Good heat transfer. 2, practical refrigerant chemical stability and good thermal stability, in the refrigeration cycle process does not decompose, do not degenerate. Non-toxic, harmless. Wide source and cheap price. 3, environmental acceptability should meet the environmental protection requirements for the protection of the atmospheric ozone layer and the reduction of greenhouse benefits. The ozone damage index of refrigerants must be 0, and the greenhouse benefit index should be as small as possible. Two critical temperature: The critical temperature is the temperature at which the substance is at the critical point. It is the lowest temperature that the refrigerant can not pressurize and liquefy. At this temperature, even if the pressure of the refrigerant gas is increased, it can not be changed from gaseous to liquid. Three environmental impact indicators Atmospheric greenhouse effect, stratospheric ozone depletion and acid rain are three major environmental hazards. Ozone absorbs ultraviolet radiation from solar radiation, Protect the earths biology. Freon (chlorine and bromine) in the material if the atmosphere of long life, it is in the atmosphere. Emissions will rise to the ozone layer, excited by UV and ozone