The solid-liquid phase-change melting of phase change material (PCM, paraffin wax) is simulated in a rectangular cavity with two isothermally partially active vertical walls. A concept of inverting the cavity at different stages during the melting process is proposed as a possible method for thermal behaviors enhancement in the latent heat thermal energy storage with PCM. The enthalpy-porosity model is employed to account for the corresponding phase change process and flow evolution at the PCM solid liquid interface, and the numerical model is validated by the existing data in the literature. It is confirmed that inverting the cavity is an effective method to improve the PCM thermal behaviors, and the maximum similar to 24.3% increase of the liquid fraction during the PCM melting process for the best case of inverting at 40% standard unit hour. On the other hand, the cavity inverted is also a simple technique to enhance the solid liquid phase-change melting heat transfer as compared to the available techniques reviewed. Furthermore, the concluded way is also suggested to incline the PCM cavity by a few degrees if a full inversion is not available in some situations. In conclusion, this proof of concept is expected to provide a novel development field of thermal transport enhancement in latent heat thermal energy storage. (C) 2018 Elsevier Ltd. All rights reserved.