The shell-and-helical-coil latent heat storage (LHS) unit filled with phase change material (PCM) offers high energy density and excellent charging/discharging capability for a wide range of temperatures. However, its thermal performance is often limited by suboptimal geometric configurations and the low thermal conductivity of PCMs. In this study, a three-dimensional CFD model was developed to evaluate the influence of helical coil diameter (60, 80, and 100 mm), multi-walled carbon nanotube (MWCNT) concentration (0.04, 0.06, and 0.08 wt%), and heat transfer fluid (HTF) inlet temperature (70, 75, and 80 °C) on the melting and solidification behaviour of paraffin wax in an SHT-LHS system. The model was validated against experimental results from the literature and showed good agreement. Temperature distribution, liquid fraction evolution, and stored/released energy were analysed. Results demonstrate that coil diameter, HTF temperature, and nanoparticle loading significantly affect melting/solidification rates. The optimal geometry and nanoparticle concentration were found at a coil-to-shell diameter ratio of 0.66 and 0.06 wt% MWCNT. At 80 °C inlet temperature, the melting time decreased by 10% and 34% compared with 75 °C and 70 °C, respectively. The maximum stored and released energy reached 476.22 kJ and 483.9 kJ for melting at 80 °C and solidification at 16 °C. • Three-dimensional CFD of shell and helical coil latent heat storage. • Optimal coil to shell diameter ratio of 0.66 reduces charging time. • Adding 0.06 wt% carbon nanotubes shortens melting time by 28%.
Al-Saaidi et al. (Fri,) studied this question.