Enhanced wickability of single-columnar, non-uniform pore-size wick using Lattice Boltzmann Method
Enhanced wickability of single-columnar, non-uniform pore-size wick using Lattice Boltzmann Method
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DOI：
10.1016/j.compfluid.2022.105376
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发表时间：
2022-04
期刊：
影响因子：
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通讯作者：
Mohammad Borumand;Taehun Lee;G. Hwang
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文献类型：
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作者：
Mohammad Borumand;Taehun Lee;G. Hwang
优化灯芯设计对于开发高热流密度的两相热管理系统至关重要，包括小型化电力电子、能源、高动力电池和航天器系统等各种应用，因为它们既需要大渗透率，又需要提高毛细压力，即增强可折性。使用非均匀孔径芯来检测增强的渗透性，而较大的孔隙增加渗透率，较小的孔隙提高毛管压力。采用基于自由能的两相单组分晶格玻尔兹曼方法（LBM）研究了芯层的孔隙尺度上升速率。在给定孔隙率（ε= 0.67和0.8）和孔径比（lr= 1.3和2.6）的情况下，预测了均匀和非均匀孔径芯在两个平行板之间的单柱颗粒的上升速率。研究表明，与均匀孔径芯相比，非均匀孔径芯提高了大孔隙的渗透率，增加了小孔隙的毛细管泵送能力，提高了毛细管压力的上升速率和上升幅度，分别达到298和157%。在一定孔隙度下，孔隙度随孔隙度比的增大而增大，随孔隙度比的减小而增大。非均匀孔径芯材的最大/最小无因次液高和液饱和度的累积增强分别为90、114和112%，atε= 0.67和lr= 2.6。非均匀粒径芯的毛细压力增强是由于小孔隙的存在。此外，垂直分级芯由于其顶部孔隙较小而增加了毛细压力，而在给定孔隙度和孔径比下，与非均匀孔径芯相比，垂直分级芯略微降低了毛细压力的上升速率。模拟结果为高热流密度两相热管理系统的最佳薄芯结构提供了新的思路。
Optimal wick designs are essential to develop high heat flux two-phase thermal management systems in various applications including miniaturized power electronics, energy, high power battery, and spacecraft systems, as they require both large permeability and improved capillary pressure, i.e., enhanced wickability. The enhanced wickability is examined using non-uniform pore size wicks, while the larger pores increase the permeability and the smaller pores improve the capillary pressure. A two-phase single component free-energy-based Lattice Boltzmann Method (LBM) is employed to study the enhanced wickability, i.e., pore-scale rate-of-rise through wicks. The rate-of-rise is predicted for uniform and non-uniform pore size wicks having a single-column-particle between the two parallel plates for given porosities (ε= 0.67 and 0.8) and pore size ratios (lr= 1.3 and 2.6). The study shows that the non-uniform pore size wicks enhance the rate-of-rise and capillary pressure up to 298 and 157%, respectively, compared to those of the uniform pore size wicks, by improving the permeability through larger pores and increased capillary pumping capability through smaller pores. Also, the wickability enhances as the pore size ratios increase at given porosity or the porosity decreases at given pore size ratio. The cumulative enhancements of the maximum/minimum dimensionless liquid heights and the liquid saturation of non-uniform pore size wick are found to be up to 90, 114, and 112%, respectively, atε= 0.67 andlr= 2.6. The capillary pressure enhancement of non-uniform particle size wicks results from the presence of the small pores. Also, the vertically graded wicks increase the capillary pressure due to the smaller pores at the top of the wicks, while they marginally decrease the rate-of-rise compared to the non-uniform pore size wicks at given porosity and pore size ratio. The simulation results provide insights into the optimal thin wick structures for high heat flux two-phase thermal management system by enhancing the wickability through the non-uniform pore sizes.