Thermal performance of a pump-driven loop heat pipe as an air-to-air energy recovery device

A pump-driven loop heat pipe (PLHP) was proposed for energy recovery from exhaust air to reduce fresh air handling energy consumption of air conditioning systems. The influences of working fluid, mass flow rate, heat exchanging area and facing air velocity on heat transfer capacity, temperature effectiveness and coefficient of performance (COP) were studied experimentally under different working conditions. The optimum working fluid and value were obtained, respectively. Results indicate that the heat transfer capacity and COP increase with the temperature difference between indoor and outdoor air while the temperature effectiveness decreases. The general performance for R32 as working fluid was better than R22 and R152a. For summer condition, the heat transfer capacity was 4.09 kW and the COP was 9.26 when the mass flow rate was 250 kg h−1, the heat exchanging area was 58.0 m2 and the facing air velocity was 1.8 m s−1. For winter condition, the heat transfer capacity was 6.63 kW and the COP was 14.20 while the mass flow rate was 300 kg h−1, the heat exchanging area was 58.0 m2 and the facing air velocity was 1.8 m s−1. The tested device could meet the energy recovery need with remarkable energy savings.