Thermal Properties And Applications Of Inorganic Porous-based Shape-stabilized Composite Phase Change Materials

In the 21st century,China’s economy is developing rapidly,and energy is also being consumed in large quantities.Among them,due to the increasing requirements of people on the building environment,building energy consumption is rising.Therefore,the use of phase change energy storage technology to integrate phase change materials in the building envelope to reduce the fluctuation of indoor temperature can achieve the purpose of improving energy utilization and reducing energy consumption.Fatty acid and paraffin wax phase change materials have become research hotspots in recent years due to their advantages of large latent heat,low cost and easy availability.Therefore,in order to reduce the energy consumption of building operation and improve the heat storage and release capacity of building roof.（1）In this paper,lauric acid（LA）,50^#paraffin wax（PW50）,myristic acid（MA）and 46^#paraffin wax（PW46）are used as raw materials to prepare two binary eutectic phase change materials（EPCMs）,namely LP50 and MP46.Four kinds of shape-stabilized phase change materials（SSPCMs）,LP50/EG,MP46/EG,LP50/EP and MP46/EP,are prepared by using EG and EP as supporting materials.The properties of the above two EPCMs and four SSPCMs are evaluated by step cooling curve method,penetration mass percentage determination method,penetration ring percentage determination method,SEM,DSC,FT-IR,XRD and TG methods.Then,the four SSPCMs and XPS are re-encapsulated by PVC plates to analyze the influence of different filling materials on the internal thermal performance of the building.（2）The mass ratio of LA to PW50 in LP50 was 70:30,and the mass ratio of MA to PW46 in MP46 was 69:41.It is confirmed by DSC that the mass ratio of the eutectic point is consistent with that obtained by the step cooling curve method,and the phase transition temperatures of LP50 and MP46 are 37.93℃ and 40.01℃,respectively,and the latent heats are 164.52 J/g and 169.57 J/g,respectively.Then through FT-IR and XRD,it is concluded that LP50 and MP46 are physical mixing.After 500 thermal cycles,the deviation of phase transition temperature and latent heat is less than 5%,and the type and position of functional groups and crystal structure have not changed,therefore,both MP46 and LP50 show good durability.Finally,by calculating the cost,the cost per 500g of LP50 and MP46 is lower than that of the binary fatty acid EPCM which is close to their latent heat.（3）The optimum mass ratios of supporting materials and EPCM in LP50/EG,MP46/EG,LP50/EP and MP46/EP were 1:11,1:10,35:65 and 40:60,respectively.The microstructure of four SSPCMs and two supporting materials are observed by SEM,and the correctness of the optimal adsorption ratio of four SSPCMs is qualitatively verified.The phase transition temperatures of LP50/EG,MP46/EG,LP50/EP and MP46/EP are 37.43℃,39.98℃,37.06℃ and 40.00℃,respectively.The latent heat of phase transition are 151.53 J/g,151.5 J/g,109.57 J/g and 99.02 J/g,respectively.The adsorption of LP50 and MP46 by EG or EP is physical mixing by FT-IR and XRD.Through the TG curve,it is concluded that the addition of the support material improves the heat resistance of SSPCMs.After 1000 thermal cycles,the deviation rate of phase transition temperature is less than 3.5%,the deviation rate of latent heat is less than10%,and the type and position of functional groups and crystal structure have not changed.Therefore,all four SSPCMs show good durability.Therefore,fatty acid-sliced paraffin/support materials（LP50/EG,LP50/EP,MP46/EG and MP46/EP）have good practical application prospects.（4）According to the ETR,AC and indoor temperature fluctuation values,the phase change plate with LP50/EG SSPCM as the filling material placed on the upper side of the building roof structure layer has best temperature control.The growth rate of is74.7%,the growth rate of is 60.9%,AC is 0.2365,and the indoor temperature fluctuation value is 11.2℃,which is 6.7℃ smaller than the control group A₀.