Numerical modeling and optimization of annual thermal characteristics of an office room with PCM active–passive coupling system

Abstract

Herein a numerical study was conducted on a PCM coupling room integrated with a PCM active–passive coupling system to optimize it annual thermal characteristics. In detail, four kinds of inorganic composite PCMs were simultaneously introduced into the wall, ventilation cavity and double-layer radiant floor to construct a PCM active–passive coupling system. The numerical model constructed by EnergyPlus was validated based on the experimental result. The simulation results shown that, compared with the room with common radiant floor, the PCM coupling room exhibited a lower annual energy consumption and a higher indoor thermal comfort rate, which was increased by 16.58%. Based on the thermal comfort evaluated by PMV-PPD method and annual energy consumption, a parameter optimization of the double-layer PCM radiant floor was performed, including the PCM thickness, the thermal conductivity and the location of the heat source. It was found that appropriately increasing the total thickness of the PCM layer could effectively enhance its heat storage capacity to improve the indoor temperature control effect. Specially, the total thickness and the thickness of the upper and lower PCM layers had optimal values. Furthermore, when the thermal conductivity of the upper PCM layer was fixed, increasing that of the lower PCM layer could improve the heat storage /release efficiency of the floor, while its enhancement effect gradually decreased. In addition, moving up or down the heat source would reduce the utilization rate of the PCMs. The radiant floor exhibited the optimal overall thermal performance when the heat source was placed between the two PCM layers. Finally, after parameter optimization, the PCM coupling room performed an indoor thermal comfort rate as high as 81.58%, while saving 20% of the electricity cost by utilizing the price difference between peak and valley electricity.