Abstract: We numerically investigate the phase change melting enhancement in a shell-and-tube latent heat thermal energy storage unit by using ellipse. The schemes for ellipse shell or tube settings are proposed. The enthalpy approach is firstly employed to simulate the heat heat tranfer and flow mechanism of the phase change materials in traditional unit with round shell and tube. Then,the heat transfer enhancement for shell-and-tube latent heat thermal energy storage system by using ellipse is presented. The results showed that employing ellipse shell is an efficient way to enhance the heat transfer. The total melting time of unit with round tube and elliptical shell with aspect ratio of 2 can save about 53.5%. The influence of heating wall temperature,thermal conductivity and initial temperature of PCM on the melting process are all characterized. It is found that,the melting rate increases sharply,was the tempertaure increasing of heating wall. However,the thermal conductivity and initial temperature of PCM have negligible influence on thermal performance of the unit.