NUMERICAL INVESTIGATION OF THE EFFECTS OF THE NUMBER OF RADIAL LONGITUDINAL FINS ON THE MELTING OF PARAFFIN WAX IN A CYLINDRICAL ANNULUS

A numerical simulation of the melting process of a phase-change material (PCM) in a horizontal cylindrical annulus has been studied with and without heat transfer enhancement techniques. In this study, longitudinal fins were used to enhance heat transfer in a cylindrical annulus. A numerical study was carried out for melting of paraffin wax, with and without fins, using the Fluent finite-volume code. Three configurations of a cylindrical annulus with a constant wall temperature of the inner pipe were studied: (1) without fins, (2) with four fins, and (3) with eight fins. To analyze the thermal behavior of the system, the results of the presented numerical simulation are used to show the movement of the melting front in the cylindrical annulus for the three aforementioned configurations. The results show that comparatively high heat transfer was achieved in the cases with eight and four fins compared to the plain annulus: 90% and 73% melt fractions were easily achieved in 1000 and 900 s in the cases of a cylindrical annulus with eight and four fins, respectively, and the heat transfer and melting rate become slower after theses time limits. To generalize the results, two dependent dimensionless parameters are used: The Nusselt number (Nu) and melt fraction of the PCM. The product of the Stefan and Fourier numbers (FoSte) takes into account the transient phase change and heat conduction and serves as an independent dimensionless parameter. The trends presents in the dimensional analysis are a step toward generalization and can be used in the design of PCM-based heat storage systems.