Influence of fin parameters on the melting behavior in a horizontal shell-and-tube latent heat storage unit with longitudinal fins

Abstract

Adding longitudinal fins is an efficient method to enhance the melting behavior of a horizontal heat-storage tube. Nevertheless, the inhomogeneous heat transfer intensity, which is brought by the natural convection of liquid phase change material, causes a hard-melting region in the bottom half of the tube. In this study, two-dimensional models considering natural convection have been established to investigate the melting of phase change material in the latent heat storage unit with longitudinal fins. Optimization of the structural parameters, including fin-thickness and fin-length, are conducted and numerically calculated to accelerate the melting process. To enhance the charging of the hard-melting region, four strategies are employed and compared with the conventional model 1, whose fin length and fin thickness are constant. It is observed that the intensity of heat transfer is higher in the top-half domain, and it is lower in the bottom half. Moreover, thickening the bottom fins and thinning the top fins can efficiently enhance the charging process. An 8.7% reduction in the complete melting time can be realized by model 6 with the thickest bottom fins as compared to model 1 with equal length and equal thickness fins. Meanwhile, model 9, who has the longest bottom fins, can reduce the complete melting time by 47.1% as compared to model 1, so that the method of lengthening the bottom fins and shortening the top fins is likewise useful in accelerating the melting process. Based on the two strategies, we proposed an optimal model 10, who has the thickest and longest bottom fins, is conducted, and the complete melting time can be reduced by 54.1% compared with the original model 1. Consequently, the key limitation of heat storage in the horizontal tube is located in the bottom half, which is defined as hard-melting region, and thickening and lengthening the bottom fins is conducive to enhance the heat storage in the horizontal tube.