Numerical investigation of heat transfer performance of a rotating latent heat thermal energy storage

Abstract

During charging and discharging process, due to natural convection, latent heat thermal energy storage (LHTES) experiences a non uniform heat transfer process in which higher heat transfer generally occurs at the upper area of LHTES. To overcome this issue, a rotating LHTES is proposed and is expected to have higher and more uniform heat transfer. Hence, this study is conducted to evaluate the potential of heat transfer enhancement of latent heat thermal energy storage by rotation. A computational fluid dynamics (CFD) model for conjugate heat transfer between heat transfer fluid (HTF) and phase change material (PCM) in the latent heat thermal energy storage which experiences charging-discharging process is developed and validated against the experimental measured data. An enthalpy-porosity formulation is adopted to take into account the melting and solidification process of the PCM. For performance evaluation, thermal enhancement ratio (TER) is introduced and defined as the ratio of heat transfer rate enhancement due to rotation to the heat transfer rate of the base case (stationary). This ratio takes into account the parasitic energy needed for rotation. The results reveal that rotation does increase the heat transfer performance of LHTES with up to 25% and 41% enhancement can be achieved during charging and discharging, respectively. In addition, it was found that rotational speed posses significant influence on the performance of rotating LHTES where, for the studied cases, higher rotation speed results in higher heat transfer rate. This study serves asa guideline in designing innovative high performance rotating LHTES.