Enhancing melting performance in multi-tube latent heat exchangers: Investigating the effect of inner tube number and arrangement

The latent heat energy storage system holds promising application prospects in the field of energy. However, the critical bottleneck remains the melting speed of phase change materials (PCMs). In this study, the melting dynamics of PCM within a triplex-tube heat exchange system are investigated, focusing on the effects of varying the number and arrangement of inner tubes. The system performance with four, five, six, and seven inner tubes is compared, revealing a decrease in melting time with an increasing number of inner tubes. However, excessive numbers do not yield more significant enhancement. A novel arrangement scheme is proposed, recommending six inner tubes. Additionally, the effects of inner tube spacing, upper angle and lower angle are explored. Increasing these parameters initially decreases melting time but then exhibits a reverse trend. Specifically, appropriate spacing enhances coverage area, expediting rapid connectivity of melting areas and thereby augmenting natural convection. While an increase in the upper angle delays PCM melting in the upper half, optimal arrangement enhances lower half PCM melting. Balancing melting rates of three difficult-to-melt areas in the lower half with proper lower angle achieves optimal performance. Compared with the base case, the proposed arrangement with the tube spacing of 40 mm, upper angle of 92 degrees, and lower angle of 62 degrees reduces melting time by 44.8 %. These findings provide a theoretical and experimental foundation for enhancing PCM-based energy storage system performance, offering valuable insights for engineering applications.