Based on chemical compositions, industrial chiller refrigerants can be divided into 5 categories: inorganic compound refrigerants, freon, saturated hydrocarbon refrigerants, unsaturated hydrocarbon refrigerants, and azeotropic mixture refrigerants. According to the condensing pressure, chiller refrigerants can be classified into 3 categories: high-temperature (low-pressure) refrigerants, medium-temperature (medium-pressure) refrigerants, and low-temperature (high-pressure) refrigerants. The refrigerants widely used in industrial chillers are ammonia, freon, and hydrocarbons.