Synergistic enhancement strategy on the heat charging process of a shell-and-tube thermal storage device based on close-contact melting mechanism and nano-enhanced phase change material

Abstract

Nano-enhanced phase change materials (NePCM) exhibit immense potential for thermal energy storage (TES) applications, due to its improved thermal conductivity. However, its high viscosity can cause a significant deterioration in natural convection. In some cases, even a decrease in the total heat transfer rate can occur in shell-and-tube TES devices after nano-additives loading. Close-contact melting (CCM), featuring heat conduction through micro-liquid film, is regarded as a viable pathway to maximize the advantage of NePCM's high thermal conductivity and weaken the adverse effect of high viscosity on convection. To reveal the synergistic impacts of CCM and NePCM on the charging process of TES device, this study achieved the regulation of CCM by changing the fin configuration, and further analyzed the charging process of NePCM samples with three nano-additives loadings (0 wt%, 1 wt%, and 3 wt%) in TES devices with three different fin configurations. It was shown that expanding the CCM surface can significantly enhance CCM and weaken the contribution ratio of natural convection to the total heat transfer process. Under the experimental conditions established in this study, the best enhancement effect based on the synergistic strategy of NePCM and CCM was achieved, with a remarkable boost of >100 % in power density and a significant shortening of the total melting time to only 52.7 % of the original case. The introduction of CCM in LHTES through reasonable fin configuration is thus regarded as a highly applicable improvement method to enhance the power density, especially used in conjunction with NePCM, exhibiting great potential in the field of high-power-density latent heat storage and thermal management.