Freon is a widely used refrigerant at present. It is the general term for saturated hydrocarbons. It is characterized by slight toxicity, odorless, non-combustible, no explosion hazard, good chemical stability, does not react with water, and has no corrosive effect on metals. . There are many types of Freon. To avoid the trouble of writing its molecular formula and to facilitate memory, people have developed a set of simplified codes to represent various Freon refrigerants, such as R12, Chlorodifluoromethane R-22, R502, etc. Let's take Chlorodifluoromethane R-22 as an example to introduce its characteristics. Other refrigerants are similar.
Chlorodifluoromethane R-22 is not easy to burn and not easy to explode. When Chlorodifluoromethane R-22 comes into contact with an open flame, it will decompose a toxic gas called (CoCl2). Therefore, when repairing the open flame for refrigeration compressors, the refrigeration system should be fully ventilated (blowing), and the environment should be ventilated during operation. Chlorodifluoromethane R -22 can work at a temperature of 135-150℃ for a long time in steel and copper containers, and it will gradually decompose when the temperature exceeds the temperature. It interacts with refrigerating oil, in addition to acid and water, it frees the carbon in the oil to form carbon deposits, and in the case of coexistence with iron, it will decompose when the temperature rises to 550°C.
The standard boiling point of Chlorodifluoromethane R-22 is -40. 8℃. Chlorodifluoromethane R-22 is a medium-temperature refrigerant. When water is used as a cooling medium, its condensing pressure should generally not exceed 1.53MPa; when it is cooled by air, its condensing pressure Generally, it should not exceed 2.16MPa (except for tropical air conditioners). The solubility of water in Chlorodifluoromethane R-22 is more than 10 times greater than that in R12 and the lower the temperature, the higher the proportion of its water content. Therefore, it is required that the water content in Chlorodifluoromethane R-22 does not exceed 40-60 mg/L (100 Ten Thousand Points). Chlorodifluoromethane R-22 and lubricating oil are slightly soluble, dissolve each other in the compressor casing and condenser, and separate in the evaporator and its solubility changes with the change of temperature.
Chlorodifluoromethane R-22 has strong permeability and is easier to leak than R12, so its tightness requirements are higher. The cooling capacity per unit volume is about 40% larger than R12. Chlorodifluoromethane R-22 has good electrical properties and excellent insulation properties, but the dielectric constant in the liquid phase is high, and the insulation resistance is low; the high dielectric constant means that the tendency of the insulation resistance to decrease due to trace impurities increases, just like lubrication If oil is mixed, the insulation strength will decrease sharply. Therefore, when using Scope 2 in a closed system, special attention should be paid to impurities in the electrical insulation material factory.