The technology of refrigerants has developed to the fourth generation, and we all know that the fourth generation of refrigerants is environmentally friendly refrigerants, mainly solving the negative impact of the first three generations of products on ozone layer destruction and global warming. Since the first-generation refrigerants have not yet been applied in commercial refrigeration, we mainly focus on the evolution process and future development trends of the second, third, and fourth-generation refrigerants. Second-Generation Refrigerants (1930s–1990s) Examples: CFCs (Chlorofluorocarbons): R-12 (CFC-12), R-11 (CFC-11) HCFCs (Hydrochlorofluorocarbons): R-22 (HCFC-22) Advantages Enhanced Safety Non-toxic and non-flammable: Solved critical safety issues of first-generation refrigerants (e.g., ammonia toxicity, methyl chloride flammability), enabling widespread use in households and commercial settings. High