Preparation and Application of Paraffin/Expanded Graphite-Based Phase Change Material Floor for Solar-Heat Pump Combined Radiant Heating Systems

Application of phase change material (PCM) floor as the thermal storage unit in a radiant heating system possesses the advantages of improving indoor comfort with high energy efficiency and favorable economic applicability. This work proposed a novel PCM floor by directly mixing the paraffin/expanded graphite composite PCM (CPCM) with building cements and then explored its practical application performance in a solar-heat pump combined radiant heating system. First, the mass fraction of CPCM was optimized, taking into account the thermal (thermal storage capacity, thermal conductivity, leakage analysis, thermal stability, and reliability) and mechanical properties (combined strength and flexural strength) that the PCM floor should have, and 35% was determined as the optimum mass fraction of CPCM for the PCM floor. Second, the application potential of the studied PCM floor was further evaluated by experimental measurements and TRNSYS simulations. The results showed that the thermal comfort satisfaction rate of the room based on the PCM floor reached 96.8%; by comparing the PCM floor room with the control one without a PCM layer installed in the floor, the enhancement of the PCM floor, that is, the indoor comfort improvement as well as the energy and economic impacts, was well interpreted.