This research aims to further improve the thermal performance and the heat charge and discharge efficiency of the developed vertical phase change thermal energy storage device (VPCTESD) in order to adapt the application of VPCTESD in solar energy utilization technology and waste heat utilization technology. Based on the developed heat transfer model of VPCTESD, with experiment and numerical simulation methods, this paper proposes the optimization design parameters of VPCTESD filled with PCMs (called DX-53), including the gap between DX-53 slabs, the velocity of HTF (water) in heat transfer unit's flow passage, the thickness of DX-53, the filling height of DX-53 and divergent length of entrance region. The research result provides the reference methods for evaluation of the thermal performance of VPCTESD. (C) 2013 Elsevier B.V. All rights reserved.