A CFD Study of the Convection Aspect of PCMs in the Water Tank of a Solar Combisystem

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Solid/liquid phase change process has received great attention for its capability to obtain high energy storage density. In this project, to analyze a simplified system undergoing liquid-solid phase change in presence of forced convection and natural convection, a commercial CFD code FLUENT has being utilized. The thermal and heat transfer characteristics of paraffin wax and sodium acetate plus graphite were investigated in simulation. The performance of these two phase change materials in the discharge process was characterized; the existence of natural convection during the solidification of paraffin wax was visualized and characterized. Solidification of paraffin wax and sodium acetate plus graphite were visualized and characterized by means of density changes. The simulation results indicate that paraffin wax and sodium acetate plus graphite have quite different thermal performance under the same working conditions; phase change of paraffin wax will affect the velocity of solid-liquid interface; porous graphite can greatly improve the heat transfer of sodium acetate/graphite composite. In the final part of this project, the num...