ABSTRACT
This chapter briefly reviews the development history of heat pump technology, the types of heat pumps, and the composition and the types of air source heat pumps. It mainly introduces various technical problems of air source heat pump and its latest progress. Aiming at the technical problems of air source heat pump used in cold climate regions, a new variable volume ratio two-stage compression air source heat pump technology with a single-compressor is proposed, and its technical characteristics and advantages are introduced.
