STUDY ON EFFECTIVE THERMAL CONDUCTIVITY OF FORM-STABLE PHASE CHANGE MATERIAL BY FRACTAL-CAVITY THEORY

摘要

In order to predict better effective thermal conductivity of form-stable phase change material (PCM), high density polyethylene (HDPE)/paraffin composites are studied in the paper. Based on the fractal theory, it describes the pore microstructure when the paraffin is extracted, and the volume change in phase transformation of paraffin and the cavity caused by manufacturing technology are also considered. Hence fractal-cavity model is established which includes fractal dimension d, cavity ratio v, volume shrinkage rate δ, porosity ε, and so on. The heat conduction model can prove to be well in reflecting the relation between thermal properties of the form-stable PCM and its true internal structure. The theoretical results are also agreed well with those of experiments. Furthermore, the influence of the several significant parameters on the effective thermal conductivity has been analyzed in the paper. The conclusion would have important guidance significance for the application of the form-stable PCM.