Abstract
Nowadays, phase change materials (PCMs) have gained further importance as they are the main substance in thermal energy storage systems. The observations indicated that the rate of thermal storage is related to the rate of melting and thermal distribution within these materials, where it has been concluded in almost works that convection is an effective contributor to boosting heat transfer, mainly in the upper layers of PCM capsules unlike in the lower layers. This article aims to accelerate heat distribution and fusion rates of NEPCM inside rectangular capsules by using novel fins in the shape of dendrites planted in the lower region of the capsule. Three different cases are considered and analyzed; in the first case without fins, in the second case fin branches length is decreasing downward (type 1), and in the third case, fin branches length is increasing downward (type 2). The porosity enthalpy method is used in modeling heat transfer during phase change. The impact of nanoparticles volume fraction is investigated by three different concentrations (phi = 0, 3%, and 6%). The findings indicated that enriching the weight of the nano-elements and using fins yield improving the thermal conductivity characteristic of the base PCM, besides, integrating the fin in the lower region of the PCM, i.e. under the heat source extends the heat transfer area, particularly where the dominated heat transfer in the low region is conduction, thereupon, as a result, both the thermal resistance and fusion time diminish. The maximum heat transfer rate and shorter fusion time were achieved by case 3 (fin type 2) with phi = 6%, where, fin-type 2 increased the melting rate by 33% compared to no fin case due to the largest branch of the fin is located in the bottom area, whereas the conduction is more dominated as approaching the lower wall. Finally, it is recommended to further investigate the dimension characteristic of this new kind of fins, for instance, the number of branches, spacing between the fin branches, and the branches' angle.