Investigation of the enhancing thermal performance of phase change material in a double-tube heat exchanger using grid annular fins

Abstract

In the present paper, the enhancement of the thermal performance of the phase change material (PCM) in a double-tube heat exchanger using new grid annular fins is investigated. The grid annular fins, which consist of straight and circular strip components, are placed on the inner tube. To examine the thermal performance of the grid annular fins, a comparison with the conventional annular fins is conducted. To make the results comparable, the same volume of the conventional annular fins is converted to the grid annular fins. Moreover, the impact of fin spacing (longitudinal pitch) on the melting process time and the amount of energy storage of the PCM are studied and compared for the grids and conventional annular fins. According to the obtained results, the conversion of the annular fins to the new grid fins for the same fins volume at the longitudinal pitches of 125, 62.5, 31.25, and 15.625 mm reduces the melting time by 27, 37.5, 53.5, and 69.5%, respectively. Also, the comparison of the thermal performance of the new grid fins at different longitudinal pitches with the fins volume of 0.5% shows that the best thermal performance of the new grid fins occurs at fins spacing of 31.25 mm. The study demonstrates the importance of the arrangement of the grid annular fins components. In the longitudinal pitch 31.25 mm, the best-case scenario, the complete melting time of the PCM is improved 40% compared to the state with the 125 mm longitudinal pitch. Finally, the non-uniform distribution of grids for the annular grid fins also is considered in this study. The results show 16% improvement in full melting time compared to the best annular grid fins with uniform distribution of grids.