Refrigerant, also known as refrigerant, is the core medium in the refrigeration cycle. Its working principle is based on phase change, that is, it absorbs heat when vaporizing in the evaporator and releases heat when condensing in the condenser. At present, there are many kinds of refrigerants available, up to more than 80 kinds, among which ammonia, Freon, water and a few hydrogen compounds are the most common.
Among the many refrigerants, inorganic compounds have a long history, such as ammonia and water are still widely used. However, some refrigerants such as carbon dioxide are gradually eliminated due to problems such as working pressure, critical temperature and cooling capacity. On the other hand, Freon refrigerants have gradually become mainstream since their advent in the 1930s. There are many kinds of such refrigerants with different thermodynamic properties. They are based on methane and ethane and synthesized by substitution reactions of fluorine, chlorine and bromine atoms.
It is worth noting that the more fluorine atoms there are, the lower the toxicity and chemical stability of Freon; and the fewer hydrogen atoms there are, the lower the risk of combustion and explosion. At the same time, the number of chlorine atoms directly affects the evaporation temperature.
In addition, azeotropic refrigerants are made by mixing two or more refrigerants in a specific ratio. They are similar to single compounds and have a constant evaporation temperature at a constant pressure. On the other hand, hydrocarbon refrigerants such as methane and ethane are widely used in the petrochemical industry. This type of refrigerant is cheap, easy to obtain and has a low freezing temperature, but attention should be paid to its safety and flammable and explosive properties.
Finally, R-404A, as a chlorine-free non-azeotropic mixed refrigerant, is a colorless gas at room temperature and pressure. When stored in a cylinder, it is a compressed liquefied gas.
1. Refrigerant: An indispensable refrigeration cycle medium
Refrigerant, also known as refrigerant, is an indispensable medium in the refrigeration cycle. Its working principle is based on phase change. It absorbs heat when vaporizing in the evaporator, thereby taking away heat; while it releases heat when condensing in the condenser, releasing heat to the environment. At present, there are many types of refrigerants available on the market, among which ammonia, Freon, water and a few hydrogen compounds are the more common ones.
Among the many refrigerants, inorganic compounds have a long history, such as ammonia and water, which are still widely used. However, some refrigerants such as carbon dioxide are gradually being eliminated due to problems such as working pressure, critical temperature and cooling capacity. On the other hand, Freon refrigerants have gradually become the mainstream of the market since they came out in the 1930s. There are many types of such refrigerants with different thermodynamic properties. They are based on methane and ethane and synthesized by substitution reactions of fluorine, chlorine and bromine atoms. It is worth noting that the more fluorine atoms there are, the lower the toxicity and chemical stability of Freon; and the fewer hydrogen atoms there are, the lower the risk of combustion and explosion. At the same time, the number of chlorine atoms directly affects the evaporation temperature.
In addition, azeotropic solution refrigerants are mixed with two or more refrigerants in a specific proportion. They are similar to single compounds and have a constant evaporation temperature under constant pressure. On the other hand, hydrocarbon refrigerants such as methane and ethane are widely used in the petrochemical field. These refrigerants are cheap, easy to obtain and have a low solidification temperature, but special attention should be paid to their safety and flammable and explosive properties.
Finally, R-404A is a chlorine-free non-azeotropic mixed refrigerant that is a colorless gas at room temperature and pressure. When stored in a cylinder, it appears as a compressed liquefied gas.
2. High-temperature refrigerant
Also known as low-pressure refrigerant, its evaporation temperature is higher than 0°C and its condensation pressure is lower than 0.3MPa. This type of refrigerant is suitable for air-conditioning systems with centrifugal compressors, such as R21.
3. Medium-temperature refrigerant
Or called medium-pressure refrigerant, its evaporation temperature range is between -500°C and the condensation pressure is between 1.52.0MPa. This type of refrigerant is widely used, including refrigerators with piston compressors, small canteen cold storages, refrigeration systems for air conditioners, and large cold storages. For example, R22 belongs to this category.
4. Low-temperature refrigerant
Also known as high-pressure refrigerant, its evaporation temperature is lower than -50°C and its condensation pressure is in the range of 2.0~4.0MPa.
This type of refrigerant is mainly suitable for low-temperature refrigeration equipment, such as cascade low-temperature refrigeration devices, of which R13 and R14 are typical representatives.
