In the present study, a new numerical model is proposed to analyze solid-liquid phase change heat transfer in a complicated geometry. The present model can treat the solid/liquid phase change heat transfer with/without porous media, as well as conventional transient natural convection with/without porous media. Solidification calculations of pure water (without porous media) around a single cylinder and two cylinders were performed to check the validity of the model; The interaction of two solidification layers were examined, and the effects of natural convection in the melt on the solidification process were also studied. The numerical results were found to be in excellent agreement with experimental data. It was also shown that for the initial mater-temperature, T-i, of 0 degrees C the solidification progresses more rapidly for the single cylinder than that for the two cylinders, but the reverse is true for T-i greater than or equal to 4 degrees C.