Preparation of the PCM Roofbrick and Study on Its Thermal Insulation Properties

The Hot Summer and Warm Winter Zone of our country, has a long summer, strong solarradiation. For the roof, due to direct sunlight for a long time, and the heat transferred from roofto the room is more than walls. If the roof does not have good thermal insulation to block theheat into the room, hot roof will give rise to a strong sense of baking. To maintain thermalcomfort of indoor thermal environment, it usually will require air-conditioning for cooling, andit also caused a corresponding increase in building energy consumption.In addition, overheatingis a major problem in many modern buildings due to the utilization of lightweight constructionswith low heat storing capacity. Therefore, some useful technology of thermal insulation shouldbe used. Phase change roof as a new style roof is presented on the basis of the importance ofroof insulation.a possible answer to the problem of insulation is the emplacement of phasechange materials (PCM).These materials change their state of aggregation within a definedtemperature range. Useful PCM for roof show a phase transition from solid to liquid and viceversa. The thermal mass of the materials is increased by the latent heat.In this paper, by analyzing and comparing the characteristics of different phase changematerials, two solid paraffin waxes with different melting point and liquid paraffin wereselected to make up16composite phase change materials．The phase change temperatures，phase change latent heats of paraffin mixtures were studied experimentally by DifferentialScanning Calorimetry(DSC)．One composite PCM with appropriate phase change temperatureand higher phase change latent heat were selected according to the requirements in theperformance．Shape-stabilized phase change material constituted phase change material andsupport material were preparation to solve the liquid phase flow problem when phasetransition．The phase change temperatures，phase change latent heats of shape-stabilized phasechange materials were studied experimentally by DSC.In this paper, a PCM roofbrick was designed. This brick was placed on the outside of theroof and phase change roof formed. According to its production method,200PCM roofbrickwere producted and applied to practice. Through the testing and comparison with not insulatedroof, EPS roof and green roof, insulation performance of PCM room was analysed. The testresult showed that thermal insulation performance of not insulated roof was increased by using PCM roofbrick. And thermal insulation performance of phase change roof was as well as geenroof, and slightly better than EPS roof.The study of heat transfer across phase change roof has assimilated experience from theheat transfer across walls at home and abroad,and made innovation from. Finally, Fluentsoftware was used to do heat transfer analysis of phase change roof. The autor first presentedthat using liquid fraction to evaluate phase change effect of PCM. Optimal phase transitiontemperature and phase change layer thickness in the process of phase change heat transfer wereproposed. Numerical simulation shows that phase change roof was a new roof that had goodthermal insulation performance in the day and fast heat dissipation in the evening. When theoptimal phase transition temperature is33～35℃and the optimal phase change layer thicknessis35mm, phase transition from solid to liquid and vice versa could be completed in a day, andphase change latent heat could be used completely. Meanwhile, phase change roof had bestthermal insulation performance.