Similarity Curve in the Solidification Process of Latent Heat Energy Storage Unit with Straight Fins. 2nd Report. Effect of Heat Transfer Tube on the Formation of the Similarity Rule.

Abstract

The formation of the similarity rule that the relationship between a similarity function and frozen fraction is independent of the Biot number is known to have a connection with the uniformity of heat flux distribution on a heat transfer surface. The latent heat thermal energy storage unit with straight fins, which has the nature of losing such uniformity inherently, has been adopted to examine how the formation of the similarity rule will be affected by thickness and thermal conductivity of a heat transfer tube serving as the base of the straight fins. It is proved that, if a heat transfer tube is made of a high-thermal-conductivity material, the formation of the similarity rule can be assured over wide variations in thickness of the tube. On the other hand, if a heat transfer tube is made of a material of lower thermal conductivity, the similarity rule is valid only in the situation that the tube is considerably thick. The temperature distribution inside the storage unit, as well as the position of the solid-liquid interface, is shown for the purpose of discussing the results.