Phase Transition Dynamics of Phase Change Material in the Grille-Capsule Packed Channel

Phase change thermal energy storage technology, with its high energy storage density and near-isothermal heat release characteristics, serves as an effective solution to address the intermittency and fluctuation issues in solar energy utilization, thereby significantly enhancing the stability and utilization efficiency of solar energy systems. The encapsulation of phase change material (PCM) within spherical capsules not only significantly enhances the specific heat transfer area but also effectively addresses the long-standing issues of leakage and corrosion during phase transition processes. Notably, the employment of a grid structure enables rapid and ordered layering of PCM capsules, which not only reduces the flow drag but also creates stable flow channels that enhance heat transfer performance. This study presents a numerical investigation on the phase-change process of PCM within grille-capsule packed channels, focusing on the effects of channel-to-particle diameter ratio (N). The results indicate that, under the same inlet Reynolds number (Re), the melting rate of the PCM inside the spherical capsules decreases as the N increases, while the synchronization of the melting process in spherical capsules at different positions improves. Compared to the channel with N = 1, the complete melting time of PCM at different positions increases by an average of 14.32 %, 31.26 % and 28.7 % for N=1.15, 1.3, and 1.47, respectively, which indicates that the N exerts a significant influence on the thermal transport characteristics.