Computational study of bubble, thin-film dynamics and heat transfer during flow boiling in non-circular microchannels
Computational study of bubble, thin-film dynamics and heat transfer during flow boiling in non-circular microchannels
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DOI：
10.1016/j.applthermaleng.2023.122039
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发表时间：
2024-02
影响因子：
6.4
通讯作者：
F. Municchi;C. N. Markides;O.K. Matar;M. Magnini
中科院分区：
文献类型：
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作者：
F. Municchi;C. N. Markides;O.K. Matar;M. Magnini
多微通道蒸发器的流动沸腾是高功率密度应用中最有效的热管理解决方案之一。然而，对这些装置中发生的两相传热传质过程的控制还缺乏了解，这导致基于第一性原理的适用沸腾换热预测方法和可靠的热设计工具的可用性有限。本文系统地分析了三面加热非圆微通道内流动沸腾过程中气泡及其周围液膜的动力学。该研究使用定制版本的ESI OpenFOAM v2106，采用几何流体体积法捕捉界面动力学，并结合了通过蒸发器壁面的共轭换热。渠道水力直径固定为Dh=0。229 mm，宽高宽高比范围ϵ=0。25−4被检查。我们研究了水、HFE7100、R1233zd(E)、R1234ze(E)和蒸发材料铜、铝、硅、不锈钢等不同的流体，在基面热流密度Qb=50−200kW/m2范围内，共轭换热使流道截面周围的温度分布更加均匀，而润滑膜的表面形貌和流道耗尽时形成的干汽斑的长度都依赖于流道的截面形状，并对换热性能有显著影响。对于高度潮湿的条件，ϵ=0的通道。25有利于提高换热速率，其空间平均努塞尔数比ϵ=1(正方形通道)时高50%，比ϵ=4时高10%。这是由于覆盖竖壁的延长蒸发膜，由于三面加热配置，对空间平均换热性能贡献了两倍。对于更疏水性的条件，当ϵ=0时，垂直壁上会形成较大的干燥斑块。25由于蒸发器温度较低，导致换热减少，在ϵ=0的范围内，热性能弱依赖于ϵ。5.−2.
Flow boiling in multi-microchannel evaporators is one of the most efficient thermal management solutions for high-power-density applications. However, there is still a lack of understanding of the governing two-phase heat and mass transfer processes that occur in these devices, which has resulted in a limited availability of applicable boiling heat transfer prediction methods based on first principles, and of reliable thermal design tools. This article presents a systematic analysis of the dynamics of bubbles and the surrounding liquid film during flow boiling in three-side-heated non-circular microchannels. The study is performed using a custom version of ESI OpenFOAM v2106 with a geometric volume-of-fluid method to capture the interface dynamics, also incorporating conjugate heat transfer through the evaporator walls. The hydraulic diameter of the channel is fixed to D h= 0. 229 mm and the range of width-to-height aspect ratios ϵ= 0. 25− 4 is examined. We investigate different fluids, namely water, HFE7100, R1233zd (E), R1234ze (E), and evaporator materials, namely copper, aluminium, silicon, stainless steel, with base heat fluxes in the range q b= 50− 200 kW/m 2. The results show that conjugate heat transfer acts to make the temperature distributions around the perimeter of the channel cross-section more uniform, and that the topography of the lubricating film and the extension of the dry vapour patches that develop while the film is depleted both depend on the cross-sectional channel shape and influence the heat transfer performance significantly. For highly wetting conditions, channels with ϵ= 0. 25 tend to allow enhanced heat transfer rates, with a spatially-averaged Nusselt number that is 50% higher than that obtained for ϵ= 1 (square channels) and 10% higher than that for ϵ= 4. This arises thanks to an extended evaporating film that covers the vertical walls which, owing to the three-side-heated configuration, contribute twice to the spatially-averaged heat transfer performance. For more hydrophobic conditions, large dry patches develop over the vertical walls for ϵ= 0. 25 due to the lower evaporator temperatures, leading to reduced heat transfer, with thermal performance weakly dependent on ϵ in the range ϵ= 0. 5− 2.