What are refrigerant fluids?

A refrigerant fluid (or simply refrigerant) can be either a liquid or a gas that transfers heat from one system to another. Energy transfer can take place through latent heat exchange (evaporation, condensation) and/or through sensible heat exchange (heating, cooling).
Said fluids can be considered for other applications too. Starting from the market demand, refrigerant fluids that are used as blowing agents are reformulated to produce foams and aerosols, while solvents become a substitute for other fluids that cannot be used anymore.