Preparation And Heat Transfer Characteristics Of Composite Phase Change Cement Board

With the severe energy situation, the high frequency of el nino phenomenon after global warming and the improvement of requirements on thermal comfort in indoor environment, the building energy saving and indoor temperature control have gradually become hot research topics in recent years. The phase change materials (PCMs) have attracted much attention in building energy saving with the advantages of constant storage temperature, large energy storage density, easy controlled process and multiplicating reutilization. By combining with traditional construction materials for phase change building materials (PCBMs), in maintaining the original functional and structural properties, it has also characteristics of thermal storage, thermoregulation, retarding the fluctuation of indoor temperature and reducing the heating/ cooling energy consumption. In this paper, a kind of phase change material used for thermal insulation of external wall is prepared to achieve the purpose of energy saving and temperature control.Regarding the capric acid (CA) as phase change materials, and expanded perlite (EP) which has rich mesopores and micropores as porous supporting material, the stabilized composite phase change materials can be prepared by vacuum absorption method, and the maximum adsorption capacity of EP was 55wt%. A comprehensive study of the microstructure, compatibility, thermal properties, thermal stability and thermal reliability was conducted through the Scanning Electron Microscopy (SEM), Fourier Transfor Infrared Spectoscopy (FT-IR), Diffenrential Scanning Calorimetry (DSC), Thermogravimetric analyzer (TG) and accelerated thermal cycling test. The results show that, the phase change temperature and latent heat are about 30 ℃,72 kJ/kg, respectively; The surface tension for split surface of EP and the capillarity effect for internal cellular structure can adsorb CA well to prevent the leakage of molten PCM; The CA/EP has good thermal stability and thermal reliability.By mixing the cement mortar and the stabilized composite phase change materials, the phase change cement board was prepared using the self-made mould. The test system of constant power plane heat source was set up. The equivalent thermal conductivity and heat storage coefficient of the common/phase change cement board were tested, and the influence of temperature and PCM content on these thermal physical properties was analyzed. The results show that, under the same temperature, the higher the content of PCM, the lower the equivalent thermal conductivity and heat storage coefficient, the higher the thermal inertia coefficient; but with the increase of temperature, these thermal physical properties would also increase.Regard the west orientation typical room of high-rise buildings as simulation object, the indoor temperature, the temperature and heat flux of inner surface of two external envelope structure for ordinary cement wall and 20wt％ CA/EP phase change cement wall was simulated and analyzed. The simulation results show that, compared with the ordinary cement walls, the phase change cement wall could reduct 2.7℃ for temperature of the inner surface and weaken the heat flux of inner surface for 53.94%, it could also reduce the indoor temperature 1.51℃ and delay the peak time of indoor temperature for 2 hours.