Performance study and heating simulation on novel latent heat thermal energy storage device suit for air source heat pump

Abstract

Latent heat thermal energy storage (LHTES) technology can solve the problem of limited performance improvement of air source heat pump (ASHP) systems due to the time mismatch between building energy demand and operational efficiency in low temperatures. Therefore, this paper proposes a LHTES device suitable for the ASHP system. Firstly, the internal structure is obtained by ANSYS numerical simulation. Furthermore, experiments are carried out to verify the heat storage and release performance of the proposed device under different inlet water temperatures and flow rates. Finally, the operational effects of the ASHP-LHTES combined heating system are analyzed by TRNSYS. The design results show that a liquid phase ratio of 97.24 % is achieved with a pipe diameter of 16 mm, tube pitch of 70 mm, and 1/2 horizontal tube fins. Experiment results exhibit that the proposed device performs excellently under optimal conditions, with 89.7 % effective heat storage efficiency and 92.5 % available heat release efficiency. TRNSYS results indicate that the annual operating cost of the combined heating system saves 32.9 % compared with the single ASHP heating system, although the power consumption increases by 24.4 %. This study can provide theoretical support for the application of low-temperature LHTES devices in the ASHP system.