Latent heat thermal energy storage (LHTES) systems face critical limitations from low thermal conductivity of Phase Change Materials (PCMs) and uneven temperature distribution, constraining their efficiency in renewable energy applications requiring rapid thermal response. This study introduces a novel horizontal shell-and-tube LHTES configuration featuring void-embedded twisted inner tubes, numerically evaluated through validated mathematical modeling using the enthalpy-porosity method. Seven geometrical configurations were analyzed, examining void number (3-5), void height (18-20 mm), helical pitches (2-4), HTF flow rate (6-24 cm 3 s -1 ), and void distribution patterns on melting and solidification performance. The optimal configuration with five 20 mm-high voids and four helical pitches achieved remarkable enhancements compared to the void-free baseline: melting rate increased by 115% (from 74.45 to 160.33 W), solidification rate improved by 67% (from 58.94 to 98.51 W), melting time reduced by 52.8% (2579 to 1217 s), and solidification time decreased by 53.8% (4278 to 1976 s). Uniform void distribution at 72° spacing outperformed non-uniform layouts by over 30% in heat recovery rate. Unlike conventional approaches that sacrifice PCM volume, this light-weight void design preserves storage capacity while delivering transformative performance through synergistic surface area enhancement, swirl-induced secondary flow and mixing in the HTF, and shortened conduction paths. This work establishes the first comprehensive framework for void-enhanced LHTES design, providing a scalable pathway for high-performance thermal energy storage in renewable energy integration and industrial applications.
Salih et al. (Wed,) studied this question.