Experimental Investigation On The Thermal Performance Of Solar Phase Change Energy Material In Solar Systems

With increasing demand for energy resource,development and utilization of energy resource has become a hot topic centered on the.Phase change energy storage material,an emerging material and technology,has attracted considerable attention from both academic and industrial field for its great utility value and overwhelming advantage in building energy conservation,solar energy storage and ecological sustainable development.Phase change energy storage material can solve the contradiction of energy supply imbalance in space and time,so as to improve the efficiency of energy utilization.Phase transition enthalpy of current commercially available solar phase change materials is generally lower than 200 J/g.Low temperature phase change materials containing oxygen and nitrogen were investigated,DSC and TG analyses were carried out for sebacic acid,adipic acid,acetamide,the results show that the phase change latent heat of sebacic acid is 235.9 J/g without obvious supercooling phenomenon,meanwhile,it exhibited satisfying thermal stability.However,severe supercooling phenomenon was observed for adipic acid,which made phase transition difficult.To make better use of phase change materials,eutectic point of four binary systems,namely LA-SeA,StA-SeA,AAA-SeA,AAA-StA,were calculated so as to further plot cooling curves and obtain the phase diagram.For AAA-SeA and AAA-StA binary systems,composite phase change materials with AAA contents of 70%and 40%were analyzed using phase diagram and DSC,the results show that the two solid phase basically formed solid dispersion and a single endothermic peak was observed.AAA-SeA and AAA-StA binary systems show a phase transition temperature of 62 ? with a phase transition enthalpy of 234 J/g and 55 ? with a phase transition enthalpy of 217 J/g,respectively,and exhibited considerable thermal stability.The volume of expanded graphite prepared by microwave heating method was 30 mL/g larger compared with that of conventional heating methods,and time needed to reach the maximum expand volume is also shorter,which result in a more energy saving and convenient preparation process.Thermal conductivity of phase transition materials modified by expanded graphite was enhanced compared with that of pure graphite.AAA-SeA,AAA-StA composite materials were prepared by adding 10 wt%expanded graphite,the resulting materials show almost constant phase transition temperature and improved compatibility,and their thermal conductivity can be increased by more than 25%.Their phase transition enthalpy were 214 J/g and 205 J/g,respectively.AAA-SeA and AAA-StA composite phase transition materials has a phase change enthalpy of about 200 J/g,with good thermal conductivity and thermal stability,can be used as a solar phase change materials.