Freon is the general name of chlorofluoromethane and chlorofluoroethane, so it is also called "chlorofluoromethane" or "chlorofluorocarbons", which can be expressed by the symbol "CFC". Freon contains more than 20 compounds, the most commonly used of which is Freon-12 (chemical formula CCl2F2), followed by Freon-11 (chemical formula CCl3F). Freon is an excellent refrigerant, which is widely used in household refrigerators and air conditioners.
At present, China's main consumption and consumption of seven controlled substances, such as Freon-12 Freon-11 Freon-113 and Halon-1211 Halon-1301 carbon tetrachloride 1,1,1-trichloroethane, etc.
Freon is a transparent, odorless, non-toxic, explosive and chemically stable refrigerant. Freon refrigerants with different chemical compositions and structures have different thermodynamic properties. They can be used in high temperature, medium temperature and low temperature refrigerators to meet the requirements of different refrigeration temperatures.
Freon has low solubility in water. When water enters the refrigeration unit, acidic substances will be produced. It is easy to form "ice jam" in the cryogenic system and block throttle valves or pipes. In addition, to avoid the effect of Freon and natural rubber, the device should use NBR as gasket or sealing ring.
Freon refrigerants commonly used are R12R22R502 and R1341a, which have been disabled or banned in the past due to other types of refrigerants. No explanation will be given here.
Freon 12 is one of the most widely used refrigerants. It is widely used in household refrigerators in small and medium-sized food stores and refrigeration devices such as water refrigeration and transportation. R12 has good thermodynamic properties and low refrigeration pressure. The air-cooled or natural condensation pressure is about 0.8-1.2KPa. The standard evaporation temperature of R12 is - 29 C, which belongs to medium temperature refrigerant. Low temperature of - 70 C can be obtained for medium and small piston compressors. For large centrifugal compressors, low temperature of - 80 C can be obtained. Recent years, the refrigerant substitute for refrigerator is R134a.
Freon 22 is one of the most widely used refrigerants in Freon refrigerants. It is mainly used in household air conditioning and cryogenic refrigerators. The thermodynamic properties of R22 are similar to that of ammonia. The standard gasification temperature is - 40.8 C, and the condensation pressure usually does not exceed 1.6 MPa. R22 is non-flammable and non-explosive. It is safer and more reliable than ammonia in operation. The unit volume of R22 is about 60% higher than that of R12, and its refrigeration capacity and saturation pressure at low temperature are higher than those of R12 and ammonia. In recent years, the refrigerant of large air conditioning chillers is mostly replaced by R134a.
It is an azeotropic solution mixed with R12R22 in 51.2% and 48.8% percentages. Compared with R115R22, R502 has better thermodynamic properties and is more suitable for low temperature. The standard evaporation temperature of R502 is - 45.6 C, and the normal working pressure is similar to that of R22. Under the same conditions, the unit volume refrigeration capacity is larger than that of R22, but the exhaust temperature is lower than that of R22. R502 is used for full blockade, semi-blockade or some small and medium refrigeration units. Its evaporation temperature can be as low as - 55 C. R502 is widely used in refrigerators.
It is a new refrigerant with evaporation temperature of - 26.5 C. Its main thermodynamic properties are similar to those of R12, which will not destroy the ozone layer in the air. It is an environmental friendly refrigerant advocated in recent years, but it will constitute a greenhouse effect. It is an ideal alternative refrigerant for R12.
The relationship between freon and water
Freon and water are almost insoluble and have very little solubility. The water entering the device from the low-temperature side is in the state of water vapor, which is compressed with the Freon vapor into the condenser, then condensed into liquid water. The water is strong mixed in the Freon liquid with droplets, and frozen into ice at the shrinkage valve due to the low temperature, blocking the valve, so that the refrigeration device can not work properly. Water can also cause the hydrolysis of Freon to produce acid, which can cause the phenomenon of "copper plating" in the refrigeration system.
Relation between Freon and Lubricating Oil
Freon is usually soluble in frozen oil, but at high temperatures, it is synthesized from frozen oil. So there are heaters in the fuel tanks of large chillers, which insist on a certain temperature to prevent the dissolution of freon.
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