Effect of fin placement on melting and solidification performance in double-tube energy storage with phase changing material

Energy storage technologies are becoming increasingly important for the efficient utilization of energy resources and sustainability. In this context, phase change materials (PCMs) stand out due to their high energy densities and ability to store energy at nearly constant temperatures. However, the low thermal conductivity of PCMs represents a significant limitation in practical and commercial applications. To address this issue, various methods have been developed to enhance thermal conductivity in PCM-based energy storage systems, including the use of fins, nanoparticle additives, and metal foams. In this study, fin utilization was selected as the enhancement method to improve energy storage performance. Unlike previous studies, fins were concentrated in different proportions in the upper and lower regions of the PCM enclosure. The effects of these varying concentration ratios on natural convection flow, energy storage efficiency, and charging and discharging durations were analyzed simultaneously. Within the scope of the study, six different fin placement configurations with varying inter-fin angles were modelled, and numerical analyses were conducted in a transient, two-dimensional framework. The enthalpy-porosity method was employed to simulate the melting and solidification processes. Parametric analyses revealed that the configuration where all fins were concentrated on the lower surface of the inner tube with an inter-fin angle of 45° (Model 6) exhibited the highest melting performance, reducing the charging time by 27,2% compared to the reference case. Since the average PCM temperatures across different fin configurations were relatively similar, it was concluded that fin placement had a minimal effect on energy storage capacity. In terms of solidification performance, the Model 6 configuration with a 30° inter-fin angle yielded the most significant improvement, increasing the discharging duration by 129,1% compared to the reference model. Moreover, when considering average PCM temperatures, the Model 6 configuration with a 60° inter-fin angle demonstrated the highest energy release capacity. Finally, energy storage efficiency calculations, which accounted for both melting and solidification performance, indicated that the highest efficiency of 87% was achieved with Model 6 at a 45° inter-fin angle. Keywords :Thermal Energy Storage, Renewable Resources, Phase Change Materials, Latent Heat, Fins