Geometry modification of a vertical shell-and-tube latent heat thermal energy storage system using a framed structure with different undulated shapes for the phase change material container during the melting process

This study aims to modify the melting performance of a vertical latent heat double-pipe heat exchanger by geometry modification of the phase change material (PCM) container. To modify the configuration of the PCM container placed in the outer tube, a framed structure is embedded in the inner surface of the outer tube. Different framed structures i.e. smooth, arc-shaped, reverse arc-shaped, and zigzag-shaped structures are examined and compared with that of the unframed enclosure. Moreover, different numbers of pitches are also examined. The results show that the melting duration drops by almost 55 % and the thermal energy storage rate improves by 115 % using a smooth framed structure for the PCM container compared with that of using an unframed structure. The thermal energy storage rate and melting time are-9.5 W and 244.4 min, respectively, for the system using an unframed structure. The analysis of the pitch number for the zigzag-shaped structure reveals that increasing the number of pitches from 0 to 11 enhances the thermal energy storage rate by 36.5 %. The evaluation of different shapes of the framed structure shows that the case with reverse arc-shaped structure is the most enhanced unit which has the thermal energy storage rate of-34 W and melting time of 63.15 min heated by water at the Reynolds number 1000 and inlet water temperature of 50 degrees C. The sensitivity analysis of the HTF characteristics reveals that by increasing the Re from 1000 to 2000, the thermal energy storage rate increases by around 6 W. Furthermore, by increasing the inlet temperature of HTF from 50 degrees C to 55 degrees C, the thermal energy storage rate enhances by around 10 W. This paper shows the capability of geometry modification in enhancing the thermal energy storage rate of the systems.