Refrigerant R12 (CF2Cl2) used in refrigerators, freezers, car air conditioners, etc. is the Class A first group of controlled substances specified in 5 Montreal Protocol 6. Developed countries have ceased to use in 1996 and developing countries should also be deactivated in 2010. Due to the destruction of the atmospheric ozone layer by R12 and the greenhouse effect, it will be replaced by other refrigerants.

China has joined the WTO, in order to expand the export of refrigeration products to eliminate foreign trade / green barriers 0, forcing us to carry out the replacement of controlled refrigerants such as R12 as soon as possible. At present, China's production enterprises do not adopt a unified standard scheme for substitutes of raw refrigerants, and the refrigerants used by various enterprises are not the same. For example, if a refrigerator uses the open type compressor 2F10 type, due to the crack at the inlet elbow of the air-cooled condenser and multiple repair welding, the heat resistance of the condenser and the flow resistance of the refrigerant increase the heat exchange amount. The cooling efficiency is reduced. The author changed the condenser during the maintenance process and changed the refrigerant R12 used in the original system to R134a (CH2FCF3). The drying filter and connecting pipe of the original system were also replaced. After the system was modified, the operating noise of the compressor was changed. Compared with the original R12 system, there is no significant difference. The suction pressure is about 0.2MPa lower than the original system, the exhaust pressure is about 0.1MPa, and the evaporator frost is slower than the original system, which can meet the refrigeration performance requirements. The physical and chemical properties and thermodynamic properties of the refrigerant are the basic knowledge that must be mastered by the installation and maintenance personnel. It is very important to master the characteristics of the refrigerant and related parameters in the operation of the refrigeration system. The R134a refrigeration system can also refer to the parameters of the R12 system during actual maintenance.