Numerical analysis of thermal performance in Phase Change Material (PCM) melting within rectangular and square enclosures: Impact of design parameters

This study numerically investigates the impact of fin configuration including fin division and positioning on the melting dynamics of lauric acid. The primary objectives are to develop advanced benchmark solutions, generate a contemporary dataset for validating Computational Fluid Dynamics (CFD) models, and gain deeper insights into the mechanisms driving the melting process. To discretize the governing equations, including mass, momentum, and energy, a third-order Total Variation Diminishing (TVD) scheme is employed for handling the convection terms while the PISOC algorithm is applied to address the pressure-velocity coupling inherent in incompressible fluid flow. Once the developed code is validated, the investigation examines the effects of design parameters on the melting rate of lauric acid. These parameters include dividing a thick conductive fin into thinner ones, the orientation of the heated pipe embedded in the energy storage chamber, and the position of the conductive fin on the heated surface. The results showed that dividing thick conductive fin into thinner fins enhances the melting rate of lauric acid. However, there is a threshold beyond which further segmenting the fins does not significantly impact the melting rate. Furthermore, in scenarios involving heating from below, the formation of Rayleigh-Bénard convection cells near the bottom wall was observed, which promotes the development of unstable circulation eddies and subsequently results in the emergence of a wavy interface within the computational domain. Additionally, it was observed that changing the orientation of the hot pipe embedded within the energy storage system from horizontal to vertical significantly increases the melting rate. Moreover, the predicted results showed that, in the case of simultaneous heating from the bottom and side walls, attaching conductive fin to the bottom hot surface leads to a moderate enhancement of the melting process compared to placing it on the adjacent vertical hot surface. Finally, the results showed that, in general, the melting process driven by convection continues as long as the solid PCM remains above the hot surface or pipe. Once the solid PCM drops below the level of the hot surfaces, the melting rate slows down due to a transition from convection-dominated to conduction-dominated heat transfer. The results obtained from this study are presented in forms of temperature field, volume fraction contours, and profiles of the transient melting process, with each aspect discussed in detail in separate subsections.