Performance optimization of urban sewage source heat pump units

Based on the technical status, in aspects as valve switch on refrigerants side and dual purpose heat exchanger for evaporating and condensation, and the existed problems, points out the development trends and research direction. Discusses the crucial techniques of innovation design such as waste water entering the unit directly, variable frequency screw compressor and variable inner volume ratio of compressor. The performance can be significantly improved by adopting the above techniques.