Temperature effects on the effective thermal conductivity of phase change materials with two distinctive phases

This study reports on an analytical estimation of the effective thermal conductivity of phase change materials (PCMs) and its dependence upon temperature. During the phase change process, two distinctive phases (solid to liquid) co-exist and the effective thermal conductivity of the PCM varies significantly with temperature. To analytically estimate the variation, the classical Series model assuming one-dimensional (1D) heat conduction normal to the solid–liquid interface was employed. For model validation, experimental measurements with paraffin were conducted covering a wide range of temperature (including the phase change temperature). It was demonstrated that the effective thermal conductivity varies mainly with the fraction of liquid (or solid) phase, bounded by the solid phase conductivity as well as the liquid phase conductivity, whilst the fraction of the liquid phase increased non-linearly with increasing temperature.