The present work investigates the combined effect of varying gravity and heat flux direction with respect to gravity on the melting dynamics of Phase Change Material. Similar conditions are relevant to applications in space, at different space infrastructures, such as orbiting satellites, as well as various extraterrestrial surface assets, landers, and rovers. The numerical simulations are performed to study the melting dynamics of a paraffin-based phase change material with Prandtl number ≈ 71 and Stefan number ≈ 0.33 inside a differentially heated square enclosure. The mathematical model employs a control volume-based enthalpy porosity approach to simulate the melting process inside enclosure. The direction of the incoming heat flux relative to the gravity vector is defined in terms of an orientation angle, which is varying circularly with a step of 45°, whereas the gravity level is ranging from the terrestrial surface value to 0.2 to analyze the melting process over a wide range of Rayleigh number 100 ≤ ≤ 10. The study provides a detailed insight into the attributes of heat transfer, flow dynamics, and energy storage, along with a quantitative analysis of the transition between various melting regimes and temporal fluctuations in the performance parameters. The findings demonstrate that the mutual orientation between the directions of incoming heat flux and gravity, as well as the value of the latter, significantly affect features of the convective motion in the liquid phase, as well as the entire thermally driven heat transfer within the domain. In particular, for the oppositely directed gravity and heat flux, the melted fluid closely resembles Rayleigh-Bénard convection with the presence of multicellular flow structures, while at other orientation angles, except for a co-directed gravity and heat flux case, a circular convective motion of the melted fluid takes place. The results of numerical simulations reveal declining melting rates as the mutual orientation of gravity and heat flux changes from opposite to co-directed and vice versa. The low gravity conditions delay the onset of convection-driven melting, reducing the melting rate significantly.

中文翻译：

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研究不同重力和热通量方向对空间相变材料熔化动力学的综合影响

目前的工作研究了改变重力和相对于重力的热通量方向对相变材料熔化动力学的综合影响。类似的条件也适用于太空中不同空间基础设施的应用，例如轨道卫星以及各种外星表面资产、着陆器和漫游车。数值模拟的目的是研究石蜡基相变材料在差热方形外壳内的熔化动力学，该相变材料的普朗特数约为 71，斯特凡数约为 0.33。该数学模型采用基于控制体积的焓孔隙率方法来模拟外壳内的熔化过程。传入热通量相对于重力矢量的方向以方位角定义，以 45° 为步长循环变化，而重力水平范围从地表值到 0.2 来分析熔化过程在瑞利数 100 ≤ ≤ 10 的广泛范围内。该研究提供了对传热、流动动力学和能量存储属性的详细了解，并对各种熔化状态之间的转变和性能的时间波动进行了定量分析参数。研究结果表明，传入热通量方向和重力方向之间的相互方向以及后者的值显着影响液相中对流运动的特征，以及域内的整个热驱动传热。特别是，对于相反方向的重力和热通量，熔化的流体非常类似于瑞利-贝纳德对流，存在多细胞流动结构，而在其他方向角度，除了同向重力和热通量情况外，圆形对流熔化的流体发生运动。数值模拟的结果表明，随着重力和热通量的相互方向从相反方向变为同向，反之亦然，熔化速率会下降。低重力条件延迟了对流驱动熔化的开始，显着降低了熔化速率。