Effect of fin bendiness on heat transfer and flow dynamics in phase change material-based systems

A phase change material-based system that can absorb and release energy is a crucial component in renewable energy applications. The performance of such a system can be improved by incorporating fins into the phase change material region of the system. Conventionally, the most common shape for these fins is straight and unbend. However, in this study, the impact of using wave-shaped bend fins has been explored instead of the unbend ones. Different cases have been analysed, with variations in their amplitude, which influences the degree of bendiness. For the considered cases, a transient analysis computer simulation model was developed and validated against published experimental data. Using this model, the charging and discharging processes of the PCM were analysed based on liquefied portion and temperature variation. The findings demonstrate that bend fins significantly enhance heat transfer and PCM flow dynamics. For the wave-shaped fin with the highest amplitude, the charging and discharging times were reduced by 35.55% and 37.82%, respectively, compared to straight unbend fins. The thermal-fluid behaviour of the material was further evaluated based on phase change time, as well as variations in temperature and velocity of the PCM at critical points (locations below the first and second peaks of the horizontally oriented wave-shaped bend fin). The results reveal that increased fin bendiness (higher amplitude of the wave-shaped fin) delays the initiation of phase change at these critical points. Additionally, PCM flow dynamics near critical points were significantly improved with bend fins.