Effects of different thermal conductivity enhancers on the thermal performance of two organic phase-change materials: Paraffinwax RT42 and RT25

Using metal thermal conductivity enhancer (TCE) to improve the thermal conductivity of a phasechange material (PCM) is one effective technique. The heat transfer enhancements of TCEs in different PCMs during melting and solidification processes are studied by comparing the melting and solidification time to that of pure PCM. Two PCMs (paraffin wax RT25 and RT42) and four metal TCEs: vertical fin (volume fraction = 1.8%), horizontal fin (1.8%), honeycomb structure (2.7%) and square cell structure (3.6%) are studied. The experimental results show that the metal TCEs can improve the heat transfer greatly even with a small volume fraction (<4%), especially for PCM with lower melting temperature. However, adding more TCE would not always give a satisfactory improvement in heat transfer rate particularly during the solidification process when PCM has higher phasechanging temperature. Even with the same volume fraction, the TCE's effect on the PCM thermal performance will be different owing to the varied distributions. The experimental results show that the efficiency of TCEs in RT25 is higher than that for RT42 by an efficiency factor of 2 during the melting process, and is 5 times higher during the solidification process.