Numerical study of phase change heat accumulator with distribution of Hanoi tower-shaped fin

Abstract

Hanoi tower-shaped fin distribution was proposed to improve the shell-and-tube phase change accumulator's ability for heat storage. Unlike the common annular fin group, the fin spacing of the Hanoi tower-shaped fin distribution is distributed in an arithmetic sequence, the fin length increases in a fixed proportion, and the fin group's overall position changes with the bottommost spacing. In this paper, the effects of no fin, uniform fin distribution, and Hanoi tower-shaped fin distribution on the melting process were compared and analyzed. The single-factor effects of bottommost spacing, spacing tolerance, and length ratio were analyzed for the Hanoi tower-shaped fin distribution. The solid–liquid phase change frontier, melting time, temperature distribution, and streamline distribution were simulated and studied for different fin structures. Fins' combined effects on heat conduction and natural convection were examined. The Hanoi tower-shaped fins' structural parameters were optimized by applying response surface methodology (RSM). The results indicated that the Hanoi tower-shaped fin distribution considerably enhanced the phase change material's (PCM) melting rate and uniformity in the vertical circular tube heat accumulator. The significance levels of factors affecting the whole melting time were spacing tolerance (d) < length ratio (k) < bottommost spacing (P1). Within a certain range, the larger the bottommost spacing was, the synergistic heat transfer effect of natural convection and heat conduction was better. According to the RSM optimization results, when the length ratio was 1.2, the fin's bottommost spacing was 17.82 mm, and the spacing tolerance was 3.38 mm, the model had the shortest melting time. Compared with the uniform fin distribution, the total heat storage time was reduced by 18.04 %.