Study On Preperation And Thermal Properties Of Composite Phase Change Building Temperature Regulating Materials Based On Expanded Perlite

Integrating phase change materials into building envelope can not only reduce the cold/heat load of building,but also realize the transfer of peak load,which helps to maintain a comfortable indoor thermal environment and achieve energy-saving effect.In this paper,expanded perlite/capric acid and expanded perlite/eutectic hydrated salts form-stable phase change materials are prepared with expanded perlite as supporting materials.The phase transformation temperature,latent heat and thermal conductivity of these two kinds of form-stable phase change materials are tested and analyzed.The heat transfer characteristics of phase change insulating panels prepared by these two kinds of form-stable phase change materials were studied.The main conclusions are as follows:(1)Expanded perlite/capric acid form-stable phase change materials were prepared by vacuum impregnation and solvent evaporation with capric acid as phase change material and three kinds of expanded perlite(20-30 mesh,30-50 mesh and 50-70 mesh)as support material.Based on the experimental results of volume enthalpy and leakage of expanded perlite/capric acid form-stable phase change materials,50% capric acid mass fraction and expanded perlite 30-50 mesh were selected as phase change building temperature control materials.Its phase change temperature and volume enthalpy were 31.46°C and 13.02J/cm3 during melting.The thermal conductivity of expanded perlite/capric acid at 20°C,25°C and 30°C were tested,the results show that the thermal conductivity of phase change material is the highest at 30°C,which is 0.38W/(m·K).Thermogravimetric and cyclic experiments show that the expanded perlite/capric acid form-stable phase change material has good thermal stability and cyclic stability.(2)Binary eutectic hydrated salts were prepared by evaporation crystallization with sodium carbonate decahydrate and disodium hydrogen phosphate dodecahydrate as units.Expanded perlite/eutectic hydrated salts form-stable phase change materials were prepared with eutectic hydrated salts as phase change material and three kinds of expanded perlite as support material.Based on the experimental results of volume enthalpy and leakage of expanded perlite/eutectic hydrated salts form-stable phase change materials,70% eutectic hydrated salts mass fraction and expanded perlite 30-50 mesh were selected as phase change building temperature control materials.The phase change temperature and volume enthalpy of it were 26.81°C and 36.34 J/cm3 during melting.The thermal conductivity of expanded perlite/eutectic hydrated salts form-stable phase change materials at 20°C,35°C and 30°C were tested,the result show that the thermal conductivity of phase change materials is the highest at 25°C,which is 0.44W/(m·K).Thermal cycling experiments show that the expanded perlite/eutectic hydrated salts form-stable phase change material has good stability in 500 thermal cycles.(3)Two single-layer PCM insulation panels and one double-layer PCM insulation panels were prepared with expanded perlite/eutectic hydrated salt and expanded perlite/capric acid form-stable PCM.The heat transfer characteristics of PCM insulation panels were studied in an experimental room.The results show that after 6.5 hours of illumination,comparing with the reference room,the time delay of using expanded perlite/capric acid phase change insulation board,expanded perlite/eutectic hydrated salts phase change insulation board and double-layer phase change insulation board is 2.8 h,2.1 h and 3.9 h,and the attenuation factors are 0.76,0.90 and 0.60,respectively.Compared with the expanded perlite thermal insulation board,the three phase change thermal insulation boards have greater thermal inertia,which can reduce the fluctuation of indoor temperature and improve indoor thermal comfort.In addition,the thermal performance of double-layer thermal insulation board is better than that of expanded perlite/decanoic acid phase change thermal insulation board.