Analysis of heat transfer across phase change material filled reinforced cement concrete roof for thermal management

Analysis of heat transmission across three roof structures, namely, bare reinforced cement concrete roof, reinforced cement concrete roof with weathering coarse and reinforced cement concrete roof with phase change material above reinforced cement concrete are analysed. A transient numerical procedure is developed. The numerical procedure is validated against the available experimental data. The simulation is carried out on 365 days of year for these three roofs. The phase change material melts from 8 to 18 h and solidifies during the rest of the day. From March to August, the net heat entering into the room per day is positive, thus more and more phase change material melts and becomes liquid. The liquid portion of phase change material increases from March to August. During September to February, there is a net heat rejection per day, thus the melted phase change material becomes solid progressively, and at the end of February, almost all phase change material has become solid. Thus, there is melting cycle on daily basis and over the year. It takes care of all the external climatic variations and keeps the roof bottom surface temperature almost constant and closes to room air temperature. On yearly basis, about 56% reduction in heat transmission into the room is obtained with phase change material roof when compared to the conventional weathering coarse laid roof.