Preparation And Thermal Properties Of Eutectic Phase Change Energy Storage Composites

Phase change materials?PCM?can store energy and discharge energy by phase transition of PCMs,which is called latent heat storage.This technology can improve energy efficiency and achieve the goal of energy conservation and consumption reduction,now it has become an important means to solve the energy problem.PCMs have the advantages of smaller temperature difference at phase change progress,and higher storage density,smaller volume change,and no corrosion and no pollution.So it was widely used in building energy saving,waste heat utilization,solar energy storage,military and other fields.In this paper,the eutectic materials were prepared by melting method with tetradecanol?TD?,hexadecanol?HD?,palmitic acid?PA?and stearic acid?SA?as raw materials.According to the Schroeder formula,the molar composition and phase transition temperature of the eutectics were calculated.the eutectic mole composition of TD:PA=0.841:0.159?TD:SA=0.885:0.115 and HD:SA=0.81:0.19 was further determined by the step cooling curve method.By DSC test determination,the phase transition temperature of TD-PA,TD-SA and HD-SA were 34.07°C?33.30°C and45.83°C respectively,while phase change enthalpies of were 154.8 J/g?389.4 J/g and259.4 J/g respectively.Eutectic/silicon dioxide phase change energy storage composite materials?TD-PA/SiO₂ and HD-SA/SiO₂?were prepared by low heating solid state reaction,adopting eutectic as phase change body materials and sodium silicate as raw materials.The structure,morphology,and thermal performance of the composite were characterized by IR,ESEM,DSC,XRD.The results show that the prepared composite by SiO₂ coating had obvious silicon oxygen bond,and the alkane chains of the body eutectic materials were not changed.The two kinds of composite materials were irregular in shape,the SiO₂ matrix was dispersed uniformly,and the eutectics were imbedded effectively into the net of silicon dioxide.When the mass ratio of the eutectic materials and nine sodium silicate hydrate was 5:2,the eutectics can be effectively coated with SiO₂.The enthalpy of TD-PA/SiO₂ and HD-SA/SiO₂ composite were 87.07J/g and 79.69 J/g respectively,and the phase transition temperature were 34.07°C and43.88°C respectively.TD-PA/bamboo charcoal and HD-SA/bamboo charcoal composites were prepared by vacuum adsorption by using TD-PA and HD-SA as phase change materials,bamboo charcoal as matrix.Through the infrared and XRD test,it was found that the adsorption of bamboo charcoal to low eutectics was only physical adsorption depending on the intermolecular force without new chemical bonds.According to TGA test,the adsorption of bamboo charcoal to low eutectics increased the heat transfer performance of the eutectics and improved the thermal conductivity of the composites.The DSC test showed that the phase transition temperature of TD-PA/bamboo charcoal and HD-SA/bamboo charcoal were 34.17°C and 45.29°C respectively,and the enthalpy of transformation were 58.57 J/g and 68.85 J/g respectively.The eutectic phase change material was prepared by melt blending using hexahydrate magnesium nitrate and zinc nitrate hexahydrate as phase change materials.The DSC test showed that the phase transition temperature of the eutectic phase change material was 44.35°C,and the enthalpy of transformation was 139.9 J/g.