Numerical Analysis of Fin Position Effects on PCM Melting and Natural Convection in a Rectangular Enclosure

The current numerical study focused on the influence of the location of the fin and the arrangement of the fins on the transient phase change characteristics of the phase change material (PCM) in a rectangular enclosure. The development of the liquid fraction and velocity field showed that the melting of PCM is initially conducted from the heated wall and as the liquid fraction grows, buoyancy-driven natural convection plays an increasing role. The contours of the liquid-fraction indicated that the melting started near the heated wall and gradually moved toward the bulk of the PCM as a function of time; and the melting front became more irregular as the natural-convection transport progressed. The velocity-field results also showed the development of buoyancy-induced circulation, where the heated liquid moving upwards along the heated wall, and relatively cooler liquid moving downwards enhancing heat transfer inside the melted region. The presence of the fins introduced an extra conductive pathway for heat transfer and changed the local convection pattern, leading to the formation of different melting features for the various fin configurations. A single fin at 0.50H caused a hot distribution above and below the fin, and led to a melting around the central region, while a single fin at 0.25H moved the heat transfer enhancement towards the lower part of the enclosure. The two fin configuration at 0.30H and 0.70H spread the enhancement in the conductive heat transfer over two vertical positions and thus modified the spatial evolution of the melting fronts. The comparison shows the fin location and number also has significant effect on the interaction of conduction and natural convection during PCM melting. The overall results illustrate that the proper placement of the fins can change the melting pattern, enhance thermal transport in the PCM, and eventually minimize the melting time by fins, which can serve as a guideline for the thermal design and optimization of fin-assisted latent heat thermal energy storage systems.

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