Vapor compression multifunctional heat pumps in China: A review of configurations and operational modes

With the growing concerns about worldwide energy and environmental sustainability, heat pump water heaters and solar water heaters became popular in China after 2000. The combinations between the heat pump air conditioner, heat pump water heater and solar water heater brought about more energy saving operational modes besides those included in the above three appliances, which promoted the development of multifunctional heat pumps. The combinations also resulted in the higher utilization ratio and lower operational cost of the heat pump, then the payback time can be shortened greatly. The rapid development of multifunctional heat pumps at the beginning of the 21st century in China indicates its promising application prospect.The heat pump air conditioner was the fundamental component of a multifunctional heat pump. Versatile configurations of multifunctional heat pumps were evolved from the integration of the domestic water heat exchanger with the refrigerant loop of the heat pump air conditioner by various approaches. This paper reviewed the development of multifunctional heat pumps in China, mainly focusing on configuration features and operational modes of the heat pump. The configuration of a multifunctional heat pump fundamentally determines the initial cost, operating cost and operating reliability. Therefore, it is reasonable to make a compromise between the simplicity of the configuration and versatile operational modes in the design of the multifunctional heat pump under different application conditions.