Basic Research For Application On Straw Shape-stabilized PCMs

As the indoor environment comfort the people demands is increasing, building energy consumption also increases. Data shows that about35%of building energy consumption accounts for the total energy consumption in the referendum. Select the appropriate phase change material(PCM), through a certain method of making encapsulated in building walls, ceilings and floors, you can reduce the indoor temperature fluctuations, increase the comfort of the body, reduce building cooling and heating energy consume. On the other hand, crop straw is a renewable resource. China’s annual production of straw is about700million t and most of the straw was burned, causing serious pollution to the environment. The lightweight, porous characteristics of the straw make it have good insulation properties. Therefore, this study is to prepare the wall material with insulation characteristics and carry out the research of phase change material of straw.Using rice straw as the support and packaging material of the phase change material, with Na2SO4·10H2O as phase change materials, cement of specific composition as cementing agent, phase change materials were prepared. The affection of the ratio of the rice straw, Na2SO4·10H2O and cement on the quality of phase change material properties was studied and the results show that when the straw content is1:3and water-cement ratio is0.45, the phase change material integrated best performance, when the straw content reduced from1:2.5to1:6, phase change materials dry density increased by126.8%. When the water-cement ratio is0.45, the compressive strength of the phase change material is0.7MPa.Given the best insulation performance of Phase change material as targets, the influence of the molding pressure, curing time on the change material properties were studied. The results showed that when the insulation performance molding pressure is23KPa, and the curing time is14d, the insulation performance of the phase change materials was the best. On this condition, the dry density and thermal conductivity of the prepared straw phase change material were595kg/m3and0.07368W/m·K.Using homemade insulation performance testing device measure the thermal properties of the straw phase material, compared with the more hollow concrete block, when the temperature of the straw phase change holding plate on the heating surface is continuously at80℃and inner surface starting temperature is at14℃, inner surface reaching25℃needs15.5h,7.5h more extended than hollow concrete blocks. When phase change material was heated8h, the temperature between the two inner plate surface temperature phase was largest the inner plate temperature was6.5℃ower than transition block;2.0℃higher than concrete slabs when reduced to inner plate temperature after48h. DSC measurement showed that latent heat of rice straw composite phase change material is96.7J/g, the phase transition temperature is33.25℃.The pore size and distribution of the status quo straw and straw loaded with Na2SO4·10H2O were observed by SEM, and according to pore size and Young-Laplace equation the existing additional pressure of the straw pore on liquid phase was calculated and results show that when pore diameter is200μm, the additional pressure is1.458KPa. Analysis indicates due to surface tension and capillary force of the adsorbent the phase change material in the pores makes the phase change material no leak in the endothermic and exothermic process.