Innovative pipe profile configurations for fast charging of phase change material in compact thermal storage systems for building heating applications

The depletion of fossil fuel reserves and growing energy demand have increased the need for renewable energy sources with suitable heat storage systems. Latent heat thermal energy storage (LHTES) using phase change materials (PCMs) provides high energy density and efficiency. However, heat transfer to the PCM core remains a challenge. This study investigates step, sinusoidal, and zigzag channel designs within a horizontal triple-tube LHTES system to enhance PCM charging rates. The step function geometry offered superior performance, increasing heat storage rate by 145 % and reducing melting time by 51 % versus straight channels. Detailed parametric analysis revealed that reducing step width from 15 mm to 5 mm improved heat storage rate by 18 % and shortened melting time by 14 %. Lengthening steps from 5 mm to 15 mm enhanced heat storage rate by 88 % and accelerated melting by 48 %. The novel step design improved temperature distrbution, drove recirculation enhancing convection, and increased surface area. These insights can guide engineering of efficient LHTES systems, advancing sustainable energy storage solutions.