The natural convection of phase change material (PCM) in a two-dimensional square cavity is numerically analyzed. consists heat surface with constant total heated area and adiabatic wall. Grashof Prandtl numbers for the PCM (n-eicosane melting temperature, Tmelt=36°C) basic LHS system are 9 × 10^5 62.7, respectively, at 350.15K. mass, momentum energy balance equations were considered. Three hea...