Refrigerant Air Working Medium

The air working medium has been applied in residential buildings, vehicles, and air conditioning and/or cooling systems of turboplanes. The reason why air as a working medium is not widely used is because it is generally believed that air has low efficiency as a working medium and is not a practical working medium.
However, with appropriate compression and expansion techniques, the efficiency of the air working medium can be improved, in which case air is the working medium that can be used in practice. The advantage of air working medium is that it does not pollute or damage the environment, and the potential harm to animals and plants is very small (existing air cooling methods discharge trace amounts of oil or lubricants into the atmosphere).