Geometric Optimization of Multitube Heat Exchangers for Enhanced Thermal Performance in PCM-based Energy Storage Systems

Abstract

This study investigates the thermal performance enhancement of phase change material (PCM)-based thermal energy storage systems via the geometric optimization of multitube heat exchangers. A numerical analysis performed using ANSYS Fluent evaluates configurations with 1, 2, 3, and 4 inner copper tubes while keeping the PCM mass and the heat-transfer fluid flow rate constant. Our results demonstrate that increasing the number of tubes significantly improves the charging efficiency of the PCM. In particular, the four-tube design achieves complete melting in 105 min, a 77% reduction compared with the single-tube benchmark (448 min). This improvement is attributed to an expanded heat-transfer surface area (an increase from 0.0703 to 0.1408 m²) and enhanced natural convection due to distributed heat sources and higher aspect ratios (28.57–57.14). The multitube configuration outperforms other augmentation strategies, such as nanoparticle additives and finned systems, by maintaining structural simplicity without adding material complexity. Notably, the design utilizes cost-effective Iraqi paraffin, underscoring its potential for localized applications. Although our simulations assume laminar flow and adiabatic boundaries, our findings highlight the viability of geometric optimization to overcome the intrinsic low thermal conductivity of PCMs. This study fills a critical research gap by quantifying the influence of tube multiplicity on PCM dynamics, offering a scalable solution for renewable energy storage. Future studies should validate these numerical results experimentally and investigate the effects of turbulent flow and economic feasibility.