Experimental Investigation of Triplex‐Tube Latent Heat Thermal Energy Storage System Incorporating a Helical Coil for Thermal Performance Enhancement

Latent heat thermal energy storage (LHTES) systems are essential for efficient thermal energy storage. However, these devices are often constrained by long charging and short discharging periods. This study presents a novel triplex‐tube LHTES design incorporating a copper helical coil positioned between two concentric stainless‐steel shells. Stearic acid was used as the phase change material and water as the HTF, with two separate flow paths provided for charging and discharging. During charging, HTF is circulated through the outer shell at a higher mass flow rate to increase energy input and accelerate the charging process. During discharging, HTF flows through the inner helical copper coil at a reduced mass flow rate, increasing its residence time by 97.54%. This enhances the uniformity index and extends the discharge duration by 26.8% compared to a conventional concentric triplex‐tube design. Additionally, the discharge efficiency increases to 87.5% due to a 31.4% rise in heat‐transfer area and higher thermal conductivity of copper compared to stainless steel.