Thermal enhancement of phase change material melting in double-tube heat exchangers using twisted tape inserts

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Abstract

This study explores the enhancement of phase change material (PCM) melting performance within a double-tube heat exchanger, a key factor in improving thermal energy storage and transfer efficiency. Optimizing PCM melting behavior is essential for efficient thermal management and sustainable energy applications. In this research, a novel double-tube energy storage system with twisted tape inserts is analyzed numerically, with findings validated through experimental data. The system utilizes twisted tapes with three pitch lengths (60 mm, 80 mm, and 100 mm) to investigate their impact on melting rates. The numerical results reveal significant improvements in charging time, with reductions of 34%, 46%, and 53% for twisted tapes with pitch lengths of 100 mm, 80 mm, and 60 mm, respectively, compared to a plain tube. The average PCM temperature shows a 13.7% increase with the 60-mm pitch length twisted tape. Furthermore, the system achieves a total energy storage of 260 kJ kg−1 in just 120 min with the twisted tape insert (60 mm pitch length), in contrast to 250 kJ kg-1 over 240 min in a plain tube setup. Temperature contours along the axial and radial directions indicate elevated temperatures near the twisted tape surface, promoting a higher melting fraction and accelerating the complete melting process. These findings underscore the potential of twisted tape inserts to significantly improve PCM-based thermal energy storage, offering promising applications in sustainable energy systems.