[China Refrigeration Network] Refrigerant is the working fluid in air-conditioning refrigeration equipment. It circulates in the air-conditioning refrigeration equipment system and exchanges energy with the outside world through the cyclic changes of its thermodynamic state. It achieves the purpose of refrigeration. Traditionally, it is also called refrigerant as refrigeration working medium or working medium for short.
Only substances that can vaporize and condense in the operating temperature range can be used as refrigerants. How did refrigerant develop?
Ether was the first refrigerant to be used in 1834. Its disadvantage is that it is flammable and explosive. The evaporation pressure at low temperature is lower than atmospheric pressure.
Weatherhausen proposed the use of carbon dioxide as refrigerant in 1866.
Kallind used ammonia as refrigerant in 1870.
In 1874, Raoul double eyelid Kurt used sulfur dioxide as refrigerant.
Sulfur dioxide and carbon dioxide used to be relatively important refrigerants in history. However, sulfur dioxide has great toxicity and has been used as an important refrigerant for 60 years. The extremely high pressure of carbon dioxide in the temperature range of use makes the structural design of the refrigeration compressor extremely heavy, but it is nontoxic and safe to use. It was used as a refrigerant in marine refrigeration units for 50 years before it was replaced by Freon in 1955. In recent years, carbon dioxide has received new attention from the people for its excellent thermal performance and environmental protection.
Azeotropic refrigerants began to be used in the 1950s.
Non-azeotropic Refrigerants Used in 1960s
In the 1980s, scientists confirmed CFC (chlorofluorocarbon) as a hazardous substance causing ozone layer destruction and greenhouse effect, and began the work of restricting and replacing HCFCs (chlorofluorocarbon) and hydrochlorofluorocarbons (hydrochlorofluorocarbons). At present, the most promising alternative refrigerant is HFCs (hydrofluorocarbons) in Freon.
In general, the development of refrigerants has gone through the following three stages:
The first stage (1830-1930):
Ammonia, carbon dioxide, sulfur dioxide and water are mainly used as refrigerants. Some of them are toxic, some are flammable and some are inefficient, which took about 100 years.
The second stage (1930-1990):
CFCs (hydrochlorofluorocarbons) and HCFCs (hydrochlorofluorocarbons) refrigerants are mainly used for about 60 years.
The third stage (since 1990):
It has entered a period dominated by HFCs.