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Melting and resolidification of a phase change material around two cylindrical heat exchangers spaced vertically have been investigated experimentally. Experiments have been performed to examine the effects of the cylinder surface temperatures on heat transfer during the melting and freezing cycle. The processes have been clarified on the basis of observations of timewise variations in the solid/liquid interface and of temperature distribution measurements in the phase change material. The results show that the solid/liquid interface contour during the melting and resolidification of the liquid from the upper cylinder is greatly affected by the surface temperature of the lower cylinder. The results show that multiple liquid regions may develop in the phase change material around the embedded heat sources/sinks, and the temperature swings and melting and freezing periods need to be selected properly in order to effectively utilize the phase change material in a latent heat energy storage unit.

Numerical calculations were performed for the melJing of phase change material in a rectangular cavity to examine the possibility of using the melting process for cooling of a surface healed at a constant rate. Two orienuuions of the heated surface, i.e., tu the bottom and at the side of the cavity, were examined. In additwn, the effects of uniform-and discrete-heating conditions on the cooling of the heated surface were stndied. Because of strong natural convection, the temperature of the heated surface was kept almost constant for a long period, and the value was smaller for the heated surface located at the bottom of the cavity than at the side. The discrete arrangement of the heated portions strongly affected the cooling of the surface.

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