Effect of fin location on constrained melting heat transfer of phase change material in a spherical capsule: A numerical study

The present work is focussed on numerical investigation of the constrained melting of phase change material (n-octadecane) in a circumferentially finned spherical capsule keeping the base and volume of the fins equal in all cases. Four different fin shapes, namely straight, trapezoidal converging, stepped, stepped inverse, located at the center of the spherical capsule are considered for the study A series of two-dimensional transient numerical simulations are carried out. Present numerical results are validated with the existing experimental results of Fan et al. [5]. Various thermal performance parameters is used for comparative analysis. Baseline comparison of fin and no fin case have also been discussed. The least melting time of PCM is 114 min for the stepped fin, while the maximum melting time is 120 min and is reported for the straight fin. The surface area to volume ratio (S/V) of fins has been calculated for every case. Irrespective of the lower S/V ratio, the melting time of inverse stepped fin is lower than straight fin because of the excellent melting performance of inverse stepped fin in weak convection region. From the results, it has been concluded that changing the shape of fin from the base case of straight fin does not change the melting time significantly for fin volume considered in the present study. This research could be used as a reference for LHTES unit fin design optimization in the industrial setting.