Do you know which refrigerants are commonly used in cold storage?

　　【】Cold storage is widely used in our daily production and life, such as food, liquids, chemicals, medicine, vaccines, scientific experiments, etc., through the control of temperature and humidity to achieve the function of heat preservation and protection, and when building a cold storage, Refrigeration is its most important control program. It uses a chemical substance with a very low boiling point under normal temperature and pressure as the working medium to perform physical changes in heat absorption and heat release in a working system, and to air in a relatively space Cool down.

　　 refrigerant is also called refrigeration working medium. It is the working medium of the refrigeration cycle, also called refrigerant, refrigerant, and refrigerant. It is the medium substance used to complete energy conversion in various heat engines. At present, there are more than 80 kinds of substances that can be used as refrigerants, among which ammonia and Freon are the most commonly used in cold storage.

　　1. Ammonia large-scale cold storage

　　Ammonia is currently the most widely used medium pressure and medium temperature refrigerant. The solidification temperature of ammonia is -77.7°C, and the standard evaporation temperature is -33.3°C.

The advantages of 　　 are: easy to obtain, low price, moderate pressure, large unit refrigeration capacity, high heat release coefficient and small flow resistance.

The shortcomings of 　　 are: pungent odor, toxic, combustible and explosive, and corrosive to copper and copper alloys.

　　2. Freon-22 (code: R22) is applicable to most cold storages

　　 R22 is also a halogenated substance of alkanes, the scientific name is difluoromonochloromethane, the molecular formula is CHClF2, and the standard evaporation The temperature is about -41°C, and the solidification temperature is about -160°C.

The advantages of 　　 are: the condensing pressure is similar to ammonia, and the standard refrigeration capacity per unit volume is about 454kcal/m. It is widely used in two-stage compression or air-conditioning refrigeration systems at -40～-60℃.

　　The shortcomings are: it destroys the ozone layer and has a greenhouse effect. China will also completely phase out and ban its use in 2030.

　　3. R-404A refrigerant small low-temperature cold storage

　　R-404A refrigerant chemical composition: It is a mixture of pentafluoroethane/trifluoroethane/tetrafluoroethane, Physical and chemical properties: R404A is a non-azeotropic mixed refrigerant without chlorine. It is a colorless gas at room temperature and pressure. It is a compressed liquefied gas stored in a cylinder.

The advantage of 　　 is: it is an environmentally friendly refrigerant that does not destroy the ozone layer of the atmosphere. It is mainly used to replace R22. It has the characteristics of clean, low toxicity, non-combustibility, and good cooling effect. It is widely used in medium and low temperature refrigeration systems.

The disadvantage of 　　 is: the production cost is high, and the price is more expensive.

　　According to statistics, the cold storages built before the 1980s currently account for about half of the country’s cold storage capacity. Most cold storages have a service life of more than 30 years. However, many companies have failed to recover the cold storage overhaul in time and in full. Funds have led to long-term disrepair of many cold storages. Some cold storage refrigeration systems even leak ammonia refrigerant. This caused many major safety accidents. Therefore, in the daily operation of the cold storage, it is necessary to pay attention to daily inspections, regularly record pressure, temperature and other data, and conduct regular safety inspections, especially the inspection of various items of special pressure-bearing equipment.