Experimental and numerical investigation of thermal performance enhancement in shell-and-tube latent heat storage systems: effects of fins, eccentricity, and shell geometry

Latent heat storage (LHS) systems are integral to achieving efficient and low-emission energy solutions. However, the inherently low thermal conductivity of most phase change materials (PCMs) limits heat transfer rate, necessitating advanced enhancement techniques to improve thermal response and overall system performance. This study investigates the combined effects of fin addition, tube eccentricity, and shell geometry on the thermal performance of shell-and-tube LHS units. Eight transparent LHS units with circular and obround shell geometries were fabricated, incorporating tube eccentricities of 0, 0.2, 0.4, and 0.6. Each unit featured a different fin arrangement while maintaining constant fin and PCM volumes. Experimental visualization and numerical simulations were employed to evaluate key thermal performance metrics, including melting time, heat transfer rate, and time-averaged heat transfer rate. The results revealed that increasing the tube eccentricity factor from 0 to 0.6 reduced the melting time by 58 % and 29 %, and improved the time-averaged heat transfer rate by 109 % and 33 % for circular and obround shells, respectively. Comparing the melting times between the two geometries at constant eccentricity factors demonstrated that obround shells exhibited significantly shorter melting times than circular shells. However, this advantage diminished with increasing eccentricity. At eccentricity factors of 0 %, 0.2 %, and 0.4 %, the melting times of obround shells were 40 %, 22 %, and 10 % shorter than those of circular shells, with corresponding improvements in time-averaged heat transfer rates of 58 %, 9 %, and 2 %, respectively. At an eccentricity factor of 0.6, there was no significant difference in melting times between the two shell geometries.