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 materialrn(PCM), high density polyethylene (HDPE)/paraffin composites are studied in the paper. Based onrnthe fractal theory, it describes the pore microstructure when the paraffin is extracted, and the volumernchange in phase transformation of paraffin and the cavity caused by manufacturing technology arernalso considered. Hence fractal-cavity model is established which includes fractal dimension d ,rncavity ratioυ , volume shrinkage rateδ , porosityε , and so on. The heat conduction model canrnprove to be well in reflecting the relation between thermal properties of the form-stable PCM and itsrntrue internal structure. The theoretical results are also agreed well with those of experiments.rnFurthermore, the influence of the several significant parameters on the effective thermalrnconductivity has been analyzed in the paper. The conclusion would have important guidancernsignificance for the application of the form-stable PCM.