Abstract: The heat transfer performance of the phase change materials used in free cooling and air conditioning applications is low, due to the poor thermal conductivity of the materials. The recent phenomenal advancement in nano technology provides an opportunity for an appreciable enhancement in the thermal conductivity of the phase change materials. In order to explore the possibilities of using nano technology for various applications, a detailed parametric study is carried out, to analyse the heat transfer enhancement potential with the thermal conductivity of the conventional phase change materials and nano enhanced phase change materials under various flow conditions of the heat transfer fluid. Initially, the theoretical equation, used to determine the time for outward cylindrical solidification of the phase change material, is validated with the experimental results. It is inferred from the parametric studies, that for paraffinic phase change materials with air as the heat transfer fluid, the first step should be to increase the heat transfer coefficient to the maximum extent, before making any attempt to increase the thermal conductivity of the phase change materials, with the addition of nano particles. When water is used as the phase change material, the addition of nano particles is recommended to achieve better heat transfer, when a liquid is used as the heat transfer fluid.

Key words: thermal storage, phase change material, nano particle, solidification time, building cooling