Review on heat pump energy recovery technologies and their integrated systems for building ventilation

Heat pump energy recovery ventilators have been widely implemented for energy saving technologies in buildings. Researchers have been exploring methods for the most effective use of heat pump systems for fresh air supply in building. Currently, the improvement of the heat pump energy recovery ventilation units mainly focuses on the two aspects: (1) Adopting a multi-loop system and a multi-heat exchanger system to reduce the irreversible loss in the heat exchange process and improve the system performance. (2) Using the passive energy recovery units (including rotary wheels, fixed-plate heat exchangers, run-around and heat pipe heat exchangers) coupled with heat pump system to enhance thermal efficiency of the whole equipment. This paper focuses on the performance of various system configurations and develops proper control strategies for the heat pump and their integrated systems to work efficiently under different weather conditions. The review notes that various configurations, parameters and evaluation indicators may lead to significant inconsistency that increase the complexity of comparing and analyzing different system studies. The development of heat pump systems with multi-functions features, including cooling, heating, dehumidification, humidification, fresh air and air-cleaning, have also been presented.