Experimental Study On The Preparation And Properties Of Composite Phase Change Materials

The contradiction between energy supply and demand is becoming more and more serious with the development of economy.How to improve energy efficiency is one of the main research direction.Using the latent heat energy storage technology,the phase change materials,combined with the building materials,can store energy when energy is not used and it release energy when energy is needed.This may reduce the building energy consumption.A kind of binary composite phase change material?PCM?is prepared by the melt blending method with myristic acid?MA?and tetradecyl alcohol?TD?as raw materials.The freezing points of the different components of the composite phase change materials is mersured by the cooling curve method.The eutectic point of MA-TD binary system is determined by phase diagram drawn according to the cooling curves.It is shown that MA-TD binary system achieved the eutectic point at about 32.7?when MA,TD quality ratio is 36:64.The DSC test results show that the phase change latent heat of MA-TD low eutectic is 227.08kJ/kg.The molecular structure of MA and TD in composite materials has not changed,and the two are physical recombination by FT-IR picture.After 500 times cold-heat cycle between 0to 60?,the phase transition temperature of the binary composite phase change material is basically unchanged.It indicates that the thermal stability of the binary composite phase change materials is good.Using the sol-gel method,MA-TD/SiO₂ composite phase change materials are prepared with the MA-TD binary low eutectic as energy storage unit and SiO₂ as carrier material.The best quality proportion of MA-TD phase change materials and TEOS is 1:2 by the diffusion-penetration method at 70??Scanning electron microscopy?SEM?is used to observe the appearance and structure of composite phase change materials.The composite material is nearly spherical in appearance and the energy storage unit is well fixed to the SiO₂ porous network.The DSC test results show that the initial phase transition temperature is 23.46?and the phase change latent heat of the composite phase change materials is 83.07kJ/kg.FT-IR test show that there is no new material between PCM and SiO₂.After 300 times cold-heat cycle between 0 to 60?,MA-TD/SiO₂ composite phase change materials still have good thermal stability.MA-TD/SiO₂ microcapsulated phase change materials are prepared.The appearance of the microcapsules is approximately spherical,and the phase change core material is well wrapped in the silica wall material by scanning SEM.The DSC test results show that the initial phase transition temperature is 29.93?and the phase change latent heat of the composite phase change materials is 98.78kJ/kg.FT-IR test show that no new groups appeare between PCM and SiO₂.They are only physical combination.The thermophysical properties of microcapsules changed slightly after 300 times cold-heat cycle from 0 to 60 C,the phase change core material does not leak out.The thermal stability of MA-TD/SiO₂ microcapsule is good.By comparing the moisture absorption experiment results of the shape-stabilized composite phase change materials and microcapsulated phase change materials,both of them have certain moisture-regulating ability.The moisture absorption ability of the shape-stabilized phase change materials is better.