Phase change material (PCM) based Thermal Energy Storage (TES) system is a proven technology to store/release a large amount of energy as latent heat during the phase transition process. In spite of the advantages, a major weakness with PCMs is their low thermal conductivity in both solid and liquid phases which seriously affects the heat transfer rate. Over the past two decades various efforts have taken place to enhance the heat transfer rate during the melting/solidification process of phase change material (PCM) encapsulated in various shape of containers. However, very few attempts have been made on accounting the heat transfer augmentation in internally finned spherical capsule. In the present study, CFD analysis is carried out to explore and report the effect of fin orientation on heat transfer enhancement of a paraffin PCM filled in an internally finned spherical capsule. Keeping the same surface area of fin but oriented differently (orthogonal and circumferential) in spherical capsule is undertaken for the computational analysis. In addition, spherical capsule with no fin configuration is alsoconsidered in the present analysis to compare with finned configuration results. The CFD results showed that the orthogonally finned spherical capsule resulted in appreciable reduction in total time takenfor complete melting/solidification process than the circumferential fin and no fin configuration. Thesame computational study is performed experimentally in order to validate the CFD results.

Nomenclature  is Fluid Density, kg/m 3 ; E is Energy, J; p is Pressure, Pa; keff is Effective Conductivity, W/(m⋅K); T is Temperature, K; h is Sensible Enthalpy, J/kg; j J is Diffusion Flux, mol/(m 2 s); eff τ is Effective Viscous Stress N/m 2 ; V is Velocity Vector, m/s; Sh is Heat Source, J; qout,k is Energy Flux leaving the surface, J; k is Emissivity of the Surfaces, J/m 2 ;  is Stefan Boltzmann Constant; Tk is Temperature of the area, K; k is Density of the area, kg/m 3 ; qin,k is Energy Flux incident on the surface, J. Subscripts: eff -Effective; jindex of coordinate; hheat; ksurface.