<p>Latent heat thermal energy storage (LHTES) systems use a phase change material (PCM) to store and release heat, but their efficiency is limited by the low thermal conductivity of the PCM. Numerical simulations were conducted to investigate the effects of the tube arrangement on the melting behavior of the PCM in a LHTES system. An outer cylinder containing three internal tubes with the PCM filling the space between the cylinder and tubes was modeled, and the vertical offset and angle of the internal tubes were varied. Heat transfer was shown to transition from conduction-driven melting to convection-enhanced melting over time. At angles of 0° and 30°, increasing the vertical offset initially enhanced the heat transfer efficiency by delaying the merging of melting fronts. However, an excessive vertical offset hindered conduction efficiency, which limited further reduction of the melting time. At an angle of 60°, the melting fronts merged rapidly leading to unstable flow patterns, and sideways-directed convection delayed complete melting. These findings highlight the importance of the tube arrangement for maximizing the heat transfer efficiency of the PCM in a LHTES system.</p>