Experimental study on the influence of PCM container height on heat transfer characteristics under constant heat flux condition

Rectangular encapsulation is the most widely used packaging form of latent heat storage (LHS). The geometry of the encapsulation, especially the height, may significantly affect the melting process of a phase change material (PCM). In this study, the effect of height variation of rectangular LHS encapsulation on the melting process of PCMs under constant heat flux is experimentally studied. The effect of container height on the melting process and Nusselt number (Nu) is presented by scale analysis. With the increase in container height, the overall melting time of the PCM becomes longer, the average PCM temperature increases, and the temperature stratification in the vertical direction of the container is more remarkable. The melting time is extended by 50% and the average temperature increases above 30 degrees C when the height of the container is increased from 12 to 48 cm. Results show that although the height of the PCM container contributes positively to the acceleration of PCM melting in the early stage, it caused more sensible heat accumulation at the top of the container during the solid shrinking regime, which prolongs the melting time of the PCM. Therefore, when designing an LHS system, the geometry of the PCM container must be optimised.