Abstract: The influence of inner tube shape on the heat storage and release performance of 1.5% graphene/paraffin composite phase change material which is filled into the casing heat exchangers with different inner tube shapes and the same heat exchange area is analyzed by numerical simulation. The results show that the melting and solidification rate of the paraffin composite phase change material can be effectively improved by the special-shaped tube. The melting rate of paraffin composite materials outside the drop tube is53% and 62% higher than that outside the elliptical tube and circular tube respectively,and the solidification rate of paraffin composite materials outside the drop tube is 6.7% and 9.8% higher than that outside the elliptical tube and circular tube respectively. Based on the field synergy principle,the mechanism of heat transfer enhancement of special-shaped tube in the process of the paraffin composite phase change materials phase transition is analyzed. The phase change rate of the paraffin composite phase change materials can be improved more effectively because the drop tube can make the temperature field and velocity field of composite phase change materials more consistent in the process of phase change.