Axial bent fins for the phase-change heat transfer enhancement in triplex-tube ice storage systems

• Bent fins are introduced to enhance freezing rates without fabrication complexity • Triplex-tube ice storage units are studied for the first time • Bent fins improve the phase change rate by up to 45.01% compared to finless case • Compared to conventional straight fins, 7.98% faster freezing rate is obtained • Comparison is done at constant heat transfer surface and PCM volume Fins are known as effective tools to compensate for the low thermal conductivity of phase change materials (PCMs) and increase the phase change rate in latent thermal energy storage devices. Numerous innovative fins have been designed and introduced in previous studies; however, fabrication complexity usually hinders these fins from entering the industry. The current work introduces a practical yet effective axial bent fin configuration to improve the rate of ice formation, saving time and operational costs in a triplex-tube ice storage system without imposing any complicated fabrication process for the fins. Through transient computational simulations, the influence of various fin parameters, such as the bend angle (30°, 60°, and 90°), direction (unidirectional and bidirectional), and location (near the roots, in the middle, and near the tips), on solidification is studied. It is essential to note that during these examinations, not only the PCM volume but also the heat transfer surface is kept constant. Based on the results, bending the fins with an angle of 60° in a bidirectional configuration and with a bend formed near the roots yields the best solidification rate. The findings reveal that the bend fins can offer up to 45.03% acceleration in the solidification rate compared to the finless case and up to 7.98% improvement compared to the case with conventional straight fins with the same heat transfer surface area and PCM volume. Considering that the fins are not complex, this approach can be a practical solution for industrial and commercial applications in thermal energy storage.