Assembly and attachment methods for extended aluminum fins onto steel tubes for high temperature latent heat storage units

High temperature latent heat storages are being developed for both concentrating solar thermal power applications as well as integration in industrial processes. One of the concepts being developed is an extended finned-tube in a shell-and-tube assembly. This concept can be used at high pressures for steam applications and be built at a large scale. The design of the extended fins allowing for independent thermal expansion of the steel tubes and the aluminum fins with a physically possible assembly has not thus far been optimized. Due to the large fin surfaces necessary for storing large amounts of heat, conventional finned-tube assemblies have to date not been applicable for thermal energy storage systems. Designs using spring steel clips on axial fins have been proven, using conservatively high numbers of clips. In this paper, various fin and tube diameters with spring steel clips as well as other mounting methods are compared. Experiments were conducted to analyze the mechanical strength of the assembly; these are described and the results discussed. In addition, two assembly methods were tested using the same fin geometry and testing environment, allowing for a thermodynamic comparison of the assemblies. The tests have shown that while the steel clips allow for the best heat transfer, the crimping method has a higher bond strength. These results can be used for reducing costs and optimizing design of high temperature latent heat storages.