Boosting Solidification Rates in a Triplex-Tube Thermal Storage System Using Circular Fins: Novel Staggered and Inline Fin Arrangements

This article proposes a new staggered fin configuration in a vertical triple-tube heat storage unit to accelerate the discharging rate of phase change material (PCM) solidification. The proposed design consists of a staggered pattern of distribution fins, i.e. with fins on the outer tube oriented upwards and those on the inner tube oriented downwards, maximizes the heat removal potential through exposing fins to the higher flow rate tube. The solidification performance is assessed by modeling the transient heat transfer and fluid flow by using an enthalpy-porosity technique. The effects of fin dimensions, inlet temperature, and Reynolds number are analyzed to obtain the optimal configuration. Compared to the baseline case without fins, the optimized staggered arrangement reduces solidification time by 52% and increases the discharge rate by 30%. The staggered fins also outperform inline fins, cutting solidification time by 46% and boosting discharge rate by 16%. Furthermore, temperature contours reveal more uniform PCM cooling for the staggered design. Adding a fin at the top further improves performance by overcoming weak natural convection in that region. This study demonstrates that the proposed staggered fin arrangement significantly enhances the PCM discharge characteristics, offering major advantages over conventional inline or finless configurations.