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What Refrigerants are Commonly Used in Cold Storage?
- September 17, 2022
- Fonsum
Cold storage widely exists in our daily production and life, such as food, liquid, chemical industry, medicine, vaccine, scientific experiment, etc. In the construction of cold storage, refrigeration is the most important control procedure. Using a chemical substance with a very low boiling point at normal temperature and pressure as the working medium, the physical changes of heat absorption and heat release are carried out in a working system, and the air is cooled in relative space.
Refrigerant, also known as refrigerating working medium, is the working medium of the refrigeration cycle and the medium material used to complete energy conversion in various heat engines. There are currently more than 80 substances that can be used as refrigerants. Among them, the most commonly used cold storage is ammonia, freon, and so on.
1. Ammonia - large cold storage
Ammonia is currently the most widely used medium-pressure medium-temperature refrigerant. The solidification temperature of ammonia is -77.7°C, and the standard evaporation temperature is -33.3°C.
The advantages are easy availability, low price, moderate pressure, large unit refrigeration capacity, high heat release coefficient, and small flow resistance.
The disadvantage is that it has a pungent odor, is toxic, can burn and explode, and has a corrosive effect on copper and copper alloys.
2. Freon-22 (R22) - applicable to most cold storages
R22 is also a halogenated alkane, the scientific name is difluoro-chloromethane, the molecular formula is CHClF2, the standard evaporation temperature is about -41 °C, and the solidification temperature is about -160 °C.
The advantage is that the condensation pressure is similar to that of ammonia, and the standard refrigeration capacity per unit volume is about 454kcal/m, which is widely used in two-stage compression or air-conditioning refrigeration systems at -40 to -60 °C.
The disadvantage is that it destroys the ozone layer and has a greenhouse effect. China will also completely phase out the ban by 2030.
3. R404A refrigerant - small low temperature cold storage
The chemical composition of R404A refrigerant is a mixture of pentafluoroethane, trifluoroethane, and tetrafluoroethane. R404A is a chlorine-free non-azeotropic refrigerant, which is a colorless gas at normal temperature and pressure. Stored in cylinders is a compressed liquefied gas.
The advantage is that it is an environmentally friendly refrigerant that does not destroy the atmospheric ozone layer, and is mainly used to replace R22. It has the characteristics of cleanliness, low toxicity, non-combustibility, and good refrigeration effect, and is widely used in medium and low-temperature refrigeration systems.
The disadvantage is that the production cost is high and the price is more expensive.
According to statistics, the cold storages built before the 1980s now account for about half of the national cold storage capacity, and most cold storages have a service life of more than 30 years. However, many enterprises failed to recover the funds for the cold storage overhaul in time and in full, resulting in many cold storages being in disrepair for a long time. Some cold storage refrigeration systems even leak ammonia refrigerant, resulting in many major safety accidents. Therefore, in the daily operation of cold storage, it is necessary to pay attention to daily inspections, regularly record data such as pressure and temperature, and conduct regular safety inspections.
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