Research On The Performance Of Modified Water Hyacinth Carbon-based Ternary Phase Change Energy Storage Materials And The Application Of Phase Change Shutter

Latent heat energy storage technology is an essential measure in the field of energy-efficient buildings.The application of phase change materials(PCMs)in the building envelope can improve the thermal comfort of building interiors,thereby reducing heating and cooling energy consumption and achieving energy efficiency in buildings.Based on the requirement of green energy saving,lauric acid-myristic acid-palmitic acid(LMPA)and lauric acid-myristic acid-paraffin section(LMPS)were prepared by melting and blending lauric acid(LA)and myristic acid(MA)with palmitic acid(PA)or paraffin section(PS,48-50℃)respectively.The waste water hyacinth was selected as the biomass material,and the porous carbon of water hyacinth was prepared by means of lyophilization and high temperature pyrolysis for encapsulation and thermal conductivity enhancement of phase change materials.The structural characteristics,phase change characteristics,thermal conductivity and stability of modified water hyacinth carbon-based composite phase change energy storage materials were studied,and the phase change louver model was built to analyze the effect of phase change louver on temperature control and energy conservation.The main research work is as follows:(1)The ternary eutectic phase diagrams of LMPA and LMPS are drawn by determining the optimal ratios of binary phase change materials.The mass ratios of LMPA and LMPS are59:26:15 and 51:28:21 respectively,the phase change temperatures are 32.24℃and 31.50℃,and the phase change latent heat are 160.41 J/g and 172.37 J/g respectively.At the same time,LMPA and LMPS are prepared by physical action without chemical reaction.LMPA and LMPS achieve initial degradation at temperatures of 164.69℃and 163.90℃,respectively,which have good thermal stability.After 500 thermal cycles,the latent heat of LMPA and LMPS is almost unchanged,among which,the change of phase change temperature of LMPA is relatively small,which has better thermal stability.(2)Lyophilization water hyacinth biochar(LWB)and vacuum-dried water hyacinth biochar(VWB)were prepared by chemical and physical modification,and the specific surface areas of LWB900 and VWB900 are up to 479.966 m~2/g and 364.488 m~2/g.The loading rates of LWB900 on LMPA and LMPS are as high as 80%and 75%,indicating that the modified water hyacinth carbon prepared by lyophilization combined with high temperature carbonization at900℃has the richest pores and the best encapsulation ability.The phase change temperatures of LMPA/LWB900 and LMPS/LWB900 are 26.17℃and 25.93℃,respectively,and the phase change latent heats are 105.16 J/g and 104.36 J/g,respectively.After 500 thermal cycles,it is found that the LMPA/LWB900 has the best thermal performance stability.The addition of modified water hyacinth carbon enhances the thermal conductivity of phase change materials.The thermal conductivity of LMPA/LWB900 is 0.3574 W/(m?K),which is 41.37%higher than that of LMPA.LMPA/LWB900 shows good temperature control performance in the process of heat storage and release,and has the effect of delaying temperature fluctuation.(3)LMPA/LWB900 is filled into the hollow louver and a phase change louver model is built,which is applied to the inside of the glass window.The phase change louver can store a large amount of heat while blocking the heat.Under different light distances,the peak values of its central temperature are 25.219℃and 28.918℃respectively(the louver angle is 90°),which is 1.914℃and 1.810℃lower than the traditional louver model,realizing the synergy of shading and energy storage and temperature control.Moreover,the peak time of shutter temperature and center temperature of phase change louver is later than that of traditional louver,and the cooling process is also slower.Phase change louvers have the function of delaying the rise and fall of temperature,reducing the temperature fluctuation,improving the thermal comfort of the environment,and realizing the sustainable use of biomass porous carbon-based phase change energy storage materials in the field of building energy conservation.