Effect of proportions of fins with radial branches on the lauric acid melting process in an annular cavity

Abstract

Energy storage systems with phase change materials (PCM) are characterized by high energy density, with a low thermal and volumetric variation. However, the usual low thermal conductivity increases energy charging and discharging times. An established solution to enhance heat exchange is the use of fins. The objective of the present work is to analyze the effect of innovative fin geometry on the melting process of Lauric acid PCM in an annular cavity. In the case studies, the fins cross-sectional areas were considered constant, then varying the proportions and positioning of the fin branches for two different area fractions between the fin and cavity. The numerical model, validated with experimental data from reference works, consisted of the continuity, momentum, and energy conservation equations complemented by an enthalpy-porosity phase change model. The results showed that the melting rate effectiveness reached average values up to 146% compared to a finless system. The increase in branches intensified the natural convection while its positioning was decisive for total melting time reduction. Positioning the branches close to the heated inner core or outer cavity wall reduced the melting rate due to the fluid circulation inhibition.