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.

添加纵向翅片是增强水平储热管熔化行为的有效方法。然而，由液相变化材料的自然对流带来的不均匀的传热强度会在管的下半部造成硬熔区。在这项研究中，建立了考虑自然对流的二维模型来研究具有纵向散热片的潜热存储单元中相变材料的熔化。进行结构参数的优化，包括翅片厚度和翅片长度，并进行数值计算以加快熔化过程。为了增强硬熔区的装料，采用了四种策略并将其与常规模型1（翅片长度和翅片厚度恒定）进行比较。可以看出，在上半部区域传热强度较高，在下半部区域传热强度较低。此外，加厚底部鳍片和使顶部鳍片变薄可以有效地增强充电过程。与具有相同长度和相同厚度翅片的模型1相比，具有最厚底部翅片的模型6可以实现8.7％的总熔化时间减少。同时，具有最长底部鳍片的模型9与模型1相比，可将完全熔化时间减少47.1％，因此，延长底部鳍片和缩短顶部鳍片的方法同样可用于加速熔化过程。基于这两种策略，我们提出了具有最厚和最长的底部鳍片的最优模型10，并且可以将整个熔化时间减少54分钟。