AUTHOR=Wang Haobo , Cheng Yuanda , Wang Dawei , Peng Weijin , Ai Zejian , Jia Jie , Duan Pengfei , Yang Jinming 

TITLE=Experimental and Numerical Study on Thermal Performance of a Novel Direct Expansion Air-Source Heat Pump Heating System

JOURNAL=Frontiers in Energy Research

VOLUME=Volume 9 - 2021

YEAR=2022

URL=https://www.frontiersin.org/journals/energy-research/articles/10.3389/fenrg.2021.765221

DOI=10.3389/fenrg.2021.765221

ISSN=2296-598X

ABSTRACT=In this paper, a novel direct expansion air source heat pump heating system with gravity- driven radiator as heating terminal was developed, for the purpose to reduce the energy consumption and improve the thermal comfort of indoor personnel. The thermal response speed of the system at start-up stage was experimentally studied firstly. The results showed that the thermal response speed of the developed system was slightly lower than that of traditional air-source heat pump heating system with convective heating terminal, but largely higher than that of air-source heat pump floor radiant heating system. When the outdoor air temperature fluctuated between -5.2℃ and -1.0℃, the average rising ratios of indoor air temperature at start-up stage for the developed heating system and the traditional system are 10.8℃/h and 13.8℃/h respectively. On this basis, optimization study was then conducted to further improve the thermal performance of the developed heating system. The numerical results indicated that integrating a cross-flow fan to the gravity-driven radiator is able to promote the thermal performance of the heating system obviously at start-up stage, due to the convention heat transfer of the radiator was highly enhanced. Among the simulation conditions, the time required for the air temperature at head height reach to designed temperature is shortest when the flow angle of fan is 0° with an air speed of 0.6m/s. While setting the flow angle of fan to -45° with an air speed of 0.4m/s is recommended to achieve the most thermal comfort for whole body.