Preparation And Performance Improvement Of Paraffin Composite Phase Change Heat Storage Materials

In recent years,heat storage devices developed based on phase change materials(PCMs)have attracted more and more attention,providing effective technical means for reducing energy waste.As an important part of the heat storage device,PCM collects and releases heat through the latent heat of phase change during melting and solidification.Organic PCM has the advantages of large latent heat of phase change,small volume change,stable properties,and non-corrosive.However,low thermal conductivity and easy leakage are the main defects of organic PCM.Improving the thermal conductivity of PCM and reducing leakage in the molten state have practical guiding significance for the realization of large-scale applications,especially the recovery and reuse of waste heat in chemical production,and indirectly promote energy saving and emission reduction.In this work,paraffin(PA)was used as PCM,and high-density polyethylene(HDPE)was selected as the packaging material to reduce the leakage of paraffin in the molten state.We prepared PA/HDPE composite PCM.And the leakage test at 70? showed that the leakage rate of sample is about 15%when the mass ratio of HDPE is 20%.Combined with the phase change enthalpy of the composite PCM which measured by DSC,we optimized the mass ratio range of HDPE to 10-20%.Additionally,the results of FT-IR and TG show that the material has good chemical compatibility and thermal stability.In order to improve the thermal conductivity of the composite PCM,expanded graphite(EG)and foamed copper(Cu Foam)were added by melt blending and vacuum impregnation to prepare a shape-stable and high thermal conductivity composite PCM.By comprehensively comparing the thermal conductivity and latent heat,we prefer the sample PCM 10-5(HDPE:10 wt%,EG:5 wt%),which has a thermal conductivity of 2.7 times that of pure paraffin and an increase in temperature response speed of about 25.9%.The latent heat of PCM10-5 is 119 J/g(pure paraffin:139 J/g).After 120 thermal cycles,the heat loss of PCM 10-5 is about 5%,showing good thermal cycle stability.In addition,the thermal conductivity of the sample PCM-CuF(EG/Cu Foam as the thermal conductive filler)is 14.3 times that of pure paraffin.However,its latent heat is only about 43%of pure paraffin.For composite PCM used for heat storage,we only recommend copper foam as an alternative material.