Views:6 Author:Site Editor Publish Time: 2019-05-10 Origin:Site
Refrigerant is a working substance that is continuously cyclically changed in a refrigeration system to achieve refrigeration, also called a working fluid. The refrigerant is vaporized in the evaporator to absorb the heat of the cold object and is cooled, and the heat is released into the surrounding environment medium in the condenser, and becomes a liquid refrigerant again, thereby continuously performing the refrigeration cycle.
At present, there are dozens of refrigerants, but there are more than ten kinds of refrigerants commonly used in industry.
According to the chemical composition of the refrigerant, it can be classified into an inorganic compound refrigerant, a Freon-based refrigerant, an azeotropic solution refrigerant, and a hydrocarbon refrigerant.
For the convenience of writing, the international system - the letter "R" and a group of numbers following it are used as a shorthand for the refrigerant. The letter "R" indicates the refrigeration system, and the latter numbers are written according to the molecular composition of the refrigerant according to certain rules.
Such refrigerants have long been used. Ammonia and water are still commonly used refrigerants, and they are eliminated due to high working pressure, low critical temperature and low cooling capacity, such as carbon dioxide.
Their code is coded as follows: The first digit after "R" is 7 and the last two digits are the integer part of the molecular weight of the substance. For example, ammonia is R 7 177, water is R 7 1 8 , carbon dioxide is R 7 4 4 , and the like.
This type of refrigerant has appeared in the 1930s and is gradually being used.
Many, the thermal properties have a big difference. They are all derivatives of methane and ethane. These derivatives
Substituting all or a part of the hydrogen atoms in the original compound with atoms of fluorine, chlorine and bromine.
If the number of fluorine atoms is increased, the less the toxicity of Freon, the higher the chemical stability; the fewer the number of hydrogen atoms,
The less likely it is to burn and explode; the more chlorine atoms there are, the higher the evaporation temperature.
3. Azeotropic solution
Azeotropic solution refrigerant is composed of two or more different refrigerants in a certain proportion
a mixture of mutually dissolved. They are steamed under a certain pressure like a single compound.
The hair temperature is also certain.
Compared with a single refrigerant, the azeotropic solution has some obvious advantages, such as evaporation temperature.
Low cooling capacity under the same working conditions and low exhaust gas temperature. Azeotropy
Solution refrigerants can improve the thermal properties of the refrigerant. Currently commonly used R 5 0 0, R502
Hydrocarbon refrigerants have methane, ethane, propane, ethylene and propylene, etc., their thermal properties
See Table 2-4. These refrigerants are mainly used in the petrochemical industry, and their advantages are easy to obtain.
Low price, low solidification temperature, etc. However, it is poor in safety, easy to burn and explode.