Numerical investigation of the thermal mechanism of the solid-liquid phase changing process

Latent heat thermal energy storage (LHTES) has been a hot research topic because of the advantage of coordinating the mismatch between energy supply and demand. This paper presents numerical investigation to study the thermal behavior of shell-and-tube LHTES system. The twodimensional physical model was considered to simplify. The three-dimensional physical model was also used to monitor outlet temperature and time needed to accomplish phase change. The enthalpy method was used to solve the energy equation in liquid and solid regions of phase change material (PCM). The natural convection (NC) in liquid PCM was considered by adopted Boussinesq approximation. The numerical model is validated by literature data. The result indicates that the inlet temperature of heat transfer fluid (HTF) has a significant influence during the phase change process. It also confirms that the melting process is significantly influenced by natural convection, vorticity distribution directly affects the heat exchange efficiency; and the thermal conduction plays a dominant role during the solidification process. The three-dimensional simulation shows that outlet temperature of HTF depends on the average Nusselt number at the tube, in the meantime, the horizontal arrangement of heat exchange tube has slightly lower heat transfer efficiency than vertical arrangement.