Abstract
Traditional defrosting methods applied to solve frosting problems of air-source heat pumps operating in cold periods may reduce heat capacity of the system and decrease indoor thermal comfort. In order to improve the performance of air-source heat pump (ASHP) and maintain indoor temperature in defrosting conditions, an air-source heat pump combined with a refrigerant direct-condensation radiant floor heating system with phase change material is proposed and evaluated in this study. Two radiant floor heating terminals with and without composite phase change material modules were compared through experiments. A composite phase change material based on dodecanoic acid-tetradecanol-hexadecanol mixture and expanded graphite was investigated for this application. Experimental results indicate that both heat fluxes of two comparing terminals are higher than 70 W/m2 in heating condition. At the same time, the floor surface temperature, indoor air temperature, and heating capacity of the terminal with composite phase change material modules are higher than those without composite phase change material modules in defrosting condition. This suggests that the proposed system with composite phase change material modules can improve indoor thermal comfort in defrosting condition as well as satisfy the heating requirement in heating condition.
Highlights
With the energy shortage and environmental deterioration, the air-source heat pump (ASHP) has been used worldwide instead of consumption of fossil fuels for space heating [1]
The heat flux of radiant floor heating terminal with composite phase change material (CPCM) modules is 64.6 W/m2, which is 19.2% higher than that without CPCM
The heat flux of radiant floor heating terminal with CPCM modules is 64.6 W/m2, which is 19.2% higher than that without CPCM modules
Summary
With the energy shortage and environmental deterioration, the air-source heat pump (ASHP) has been used worldwide instead of consumption of fossil fuels for space heating [1]. The ASHP systems are gaining increasing attention owing to the advantages of energy-saving, flexibility, and environmental friendliness, and are available to supply cooling and heating for residential and commercial buildings [2]. A fan coil unit is the traditional heating terminal of the ASHP system, which may generate strong draft sensation and affect the comfort and health of occupants [3]. The ASHP system experiences the frosting problem of the outdoor evaporator when operating in severe cold regions, thereby causing the decrease of indoor temperature [4]. The heating terminals could be categorized into two main types: fan coils and radiant heating terminals. Compared with the fan coils system, the radiant heating system could avoid
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