The role and development history of refrigerants

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(1) Function: Refrigerant: The working substance that circulates to provide cooling in a refrigeration system. (2) Development history: 1834 – Diethyl ether; 1866 – Windhausen proposed the use of CO2; 1870 – Cart Linde used NH3 as a refrigerant; 1874 – Raul Pictel employed SO2 as a refrigerant; 1955 – Freons (CmHnFxClyBrz). Currently, there is ongoing development of alternative refrigerants. Historically, the evolution of refrigerants has gone through three stages: The first stage, from 1830 to 1930, saw the use of NH3, HC, SO2, CO2, air, etc., as refrigerants. Some of these were toxic, some were flammable, and some had very low efficiency, primarily due to safety concerns. Despite being in use for a century, when CFC and HCFC refrigerants appeared, a decisive action was taken, leading to the first major transition. 　　In the second phase, from 1930 to 1990, CFC and HCFC refrigerants were primarily used. After 60 years of use, it was realized that these refrigerants are harmful to the environment, and substitutes began to be sought for environmental reasons. 　　In the third phase, from 1990 to the present, it has entered an era dominated by HFC refrigerants. Our country completely banned fluorocarbon substances as of January 1, 2010.