Preparation and thermal performance of expanded graphite/paraffin composite phase change materials for solar thermal storage
In order to improve the performance of phase change material(PCM)for solar thermal storage,composite PCMs with good thermal performance were prepared using paraffin by adding dispersants and different mass fractions of expanded graphite(EG).The temperature changes were tested experimentally during melting and solidification,in order to analyze the heat storage and release characteristics of composite PCMs.And the main thermophysical parameters were obtained using the T-History method.Numerical simulation was carried out to study the solid-liquid phase change and flow field of composite PCMs during melting process,and the numerical temperature were compared with experimental data.The results show that the heat transfer,heat storage,and release perfor-mance of PCM are enhanced by adding EG.The thermal conductivity of PCM with 1.5％EG is 1.49 times that of pure PCM.As the EG additive amount increases,the viscosity of composite PCM increases,which weakens the convective heat transfer intensity.And the latent heat of composite PCM also decreases,which decreases the heat storage capacity.The composite PCM with 1％EG addition has the best heat storage and release performance,and its heat release time is shortened by 38.06％compared that of to pure PCM.The higher the amount of EG added,the faster the melting rate of composite PCM.The composite PCM with 1％EG addition has the best heat storage and release performance.
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