A theoretical analysis is presented for the performance study of a Latent Heat Thermal Storage (LHTS) system that contains a phase change material (PCM) dispersed with high conductivity particles. The effect of fraction of dispersed particles in the PCM oil energy storage time and heat flux is presented for laminar and turbulent flows, and also analytical expressions are presented for various quantities of interest to study the energy storage capabilities. The combined effect of thermal and flow properties of both the heat transfer fluid (HTF) and the PCM-mixture is also included in the study. It is observed that there exists an optimum fraction of particles to be dispersed in the PCM,for maximum energy storage/extraction.