Solidification enhancement with multiple PCMs, cascaded metal foam and nanoparticles in the shell-and-tube energy storage system

The thermal response of the shell-and-tube energy storage system consisting of multiple segments holding separate phase-change materials (PCMs) of different melting points was studied. Nanoparticles in PCM of 5% volume fraction with cascaded (multiple-segment) metal foam of average porosity 0.95 were applied the heat-transfer enhancement. A simulation model that accounts for the non-Darcy effects of cascaded foam and Brownian motion of nanoparticles was developed and validated with previous experimental studies. The impact of using different arrangements of multiple PCMs, multiple PCMs with nanoparticles, and multiple PCMs with cascaded foam on the time-based solidification evolution was investigated. The module that combines multiple PCMs with cascaded foam showed the best thermal response rate. Compared to the module of single PCM with no nanoparticles or cascaded foam, the full solidification time saving was up to 94% depending on the number of multiple PCMs and number of cascaded foam segments. Although solidification time decreases as the number of foam segments and/or number of multiple PCMs increases, the choice of adequate small number of multiple PCMs and foam segments is recommended. This reduces design limitations associated with cascading of the containment vessel and does not significantly affect the positive role of natural convection during the early period of the solidification.