Influence of angular orientation of fins on thermal charging and discharging performance of latent heat storage unit

In this paper, numerical and experimental investigations of influence of fin orientations on thermal performance of a horizontal shell and tube latent heat storage unit having were performed for charging and discharging cycles. Stearic acid was used as a phase change material which was placed between annulus of shell and tube. A buoyancy driven transient numerical methodology was adopted to analyze three different angular orientations of external fins of tube carrying heat transfer fluid $(30^{\circ}\le \theta \le 90^{\circ})$. The angle $\theta = 90^{\circ}$ produced $\lambda$-fin configuration while $\theta = 30^{\circ}$ yielded Y-fin configuration. During charging cycle, a significant increase in heat transfer rate was observed for Y-fin configuration due to enhanced natural convection effects. The Y-fin configuration, for an heat transfer fluid of $358$ K, improved the complete charging process by $51\%$ along with $10\%$ enhancement in total heat storage capacity of the latent heat storage unit as compared to $\lambda$-fin configuration. The Y-fin latent heat storage unit also resulted in augmentation of overall charging and discharging heat transfer rates by $13.7$ and $4.8\%$, respectively. The heat transfer fluid temperature increase of $7.6\%$ intensified the charging and discharging performance of Y-fin latent heat storage unit correspondingly by $80$ and $12.9\%$. Lastly, correlations of charging and discharging time and Nusselt numbers were proposed as functions of Stefan number and Rayleigh number, respectively.