Melting performance enhancement of a phase change material using branched fins and nanoparticles for energy storage applications

This study presents the application of branched fins and nanoparticles to enhance the melting of phase change material (PCM) placed in a horizontally configured latent heat thermal energy storage (LHTES) unit. The mathematical model governing the transient melting of PCM is numerically solved for 2D planar geometries. The numerical solution procedure is validated against literature as well as our experimental results. First, the effects of different fin designs on melting performance are analyzed using pure PCM. All-straight, single-branched and double-branched fin designs are seen to enhance melting through efficient heat transfer resulting in time savings of 22.9%, 35.4% and 45.9%, respectively, as compared to a Y-oriented triple-fin Base Case. Additionally, the energy storage capacity is observed to increase in the same order with the double-branched design storing the highest at ∼3600 kJ. Next, the combined effects of the most efficient double-branched fin design and Al2O3 nanoparticles on melting performance are assessed. An addition of 1%, 5% and 10% nanoparticles by volume in the PCM results in an additional time savings of 11.5%, 19.2% and 26.8%, respectively, taking pure PCM case as the reference. The corresponding energy storage, however, is seen to decrease with an increase in the nanoparticles concentration. •Branched fins and nanoparticles are used to enhance melting of PCM.•Double branched fin design reduces the melting time by 45.9%.•Addition of 10% Al2O3 nanoparticles further reduces melting time by 26.8%.•Effects of heat transfer fluid temperature on heat storage rates are quantified.•Correlations are proposed for melting time and average Nusselt number.