Research On Thermal Performances Of Phase Change Heat Storage Building Based On Coupled Heat Transfer Methods

An effective method of reducing energy consumption for heating a building is to incorporate phase change material(PCM) in building floors. Research on the way to improve the property of PCM, as well as thermal properties of PCM heat storage building does help to its generalization and application in building energy conservation.To improve the thermal conductivity and shape-stabilization of PCM, expanded graphite(EG) and high-density polyethylene(HDP) were used to formulate a new type of Shape-stabilized PCM(SSPCM) with increased thermal conductivity. A floor model equipped with SSPCM is developed. The model is used to analyze the thermal performance of the SSPCM floor with different heating positions and different kinds of heating methods. Results show that expanded graphite can not only improve the thermal conductivity of PCM effectively, but also have minute effect on the latent heat and melting temperature of SSPCM. It also can be found that when the heating position is in the middle of the SSPCM, the melting speed is faster and the melting degree of SSPCM is larger than when it is at the bottom. Furthermore, the floor temperature is more comfortable when the heating position is in the middle of the SSPCM.A full size two-dimensional heat transfer model is abstracted from a kind of under- floor electric heating system with SSPCM floor. By using the modeling, a dynamic simulation of the influence of various factors(thickness of SSPCM layer, under-heating flux, the thermal conductivity of SSPCM) on the room thermal performance was analyzed. Besides the calculation of heat transfer in the phase change from solid to liquid, a variety of heat transfer mechanism of the coupled problems are also considered in this model. The conclusion is that the thermal conductivity has obvious influence on indoor air temperature, and the higher thermal conductivity, the better heat diffusion. What’s more, indoor air temperature does not increase with the increment of thickness, and the heat storage time must be controlled in case that the floor temperature becomes too high when the SSPCM layer is less than 20 mm. Further more the lager is the under-heating flux, the higher indoor air temperature would be, but the investment and the indoor air comfort should be balanced.