Originally it meant brine, but in refrigeration it means a secondary refrigerant used in indirect refrigeration methods and the freezing point must be at least 5-6℃ lower than the refrigerant used.
Brine is a heat transfer medium that does not change its phase and transfers heat according to the heat capacity of the sensible heat. It must have high specific heat, good conductivity, low viscosity, low freezing temperature, non-flammable, inert and non-corrosive, and calcium chloride solution, ethylene glycol solution and alcohol are used as brine.