Research on working characteristics of composite two-stage ventilation heat recovery system with heat pipe and heat pump

In this paper, a composite two-stage ventilation heat recovery system with heat pipe and heat pump is proposed, heat pipe is used to recover the exhaust air energy to improve the operating performance of the system under all operating conditions. The split heat pipe heat exchanger is designed and manufactured, the working characteristics and performance of the composite heat recovery system under different working conditions are tested, and it is compared with the parallel-loop heat pump ventilation heat recovery system also. The results show that the optimal working fluid charge rate of the split heat pipe used in the composite system is 50 %–60 %, the temperature efficiency of the composite system in winter is higher than 64.31 %, the heating COP is up to 7.17, and the total heating capacity is 5.09 kW. Temperature efficiency and heating capacity of the system are 4.01 %–66.6 % and 7.68 %–67.19 % higher than that of the double loop heat pump heat recovery system, respectively. •A concept of new composite two-stage ventilation heat recovery system with heat pipe and heat pump is proposed.•The split heat pipe heat exchanger is manufactured, the composite heat recovery system are tested in environment chamber.•Compared with other system, temperature efficiency and heating capacity of the system increase 4.01%∼66.6% and 7.68%∼67.19%.