Hi'/> Effects of heat flux, mass flux and two-phase inlet quality on flow boiling in a vertical superhydrophilic microchannel
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首页> 外文期刊>International Journal of Heat and Mass Transfer >Effects of heat flux, mass flux and two-phase inlet quality on flow boiling in a vertical superhydrophilic microchannel
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Effects of heat flux, mass flux and two-phase inlet quality on flow boiling in a vertical superhydrophilic microchannel

机译：垂直超亲水微通道中热通量，质量通量和两相入口质量对流动沸腾的影响

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Highlights•Microchannel flow boiling experiments of various surface wettability are conducted.•Effects of experimental operation conditions are discussed comprehensively.•Flow visualizations are provided to explain trends of heat transfer performance.AbstractSaturated flow boiling experiments were conducted to investigate the influence of surface wettability on the hydraulic and thermal transport performance in a large width-to-height aspect ratio, one-sided heated rectangular microchannel with deionized water as the working fluid. The contact angles of the bare silicon wafer surface and superhydrophilic surface after deposited by a thin film of 100-nm-thickness silicon dioxide were 65° ± 3° and less than 5° respectively, both of which were utilized as heated surfaces of the microchannel. Parametric experimental studies were carried out with the inlet vapor quality varied from 0.03 to 0.1 and the wall heat fluxes spanned from 4 W/cm2to 20 W/cm2, at various mass fluxes ranging from 120 to 360 kg/m2 s. High speed flow visualizations were conducted coupled with instrumental measurements to illustrate the effects of heat flux, mass flux and two phase inlet quality on the local heat transfer coefficient, averaged heat transfer performance, two phase flow structure and pressure drop characteristics for surfaces with distinct surface wettability characteristics in the microchannel. Experimental results showed that the local heat transfer coefficient decreased first until approaching a minimum value and then increased towards the exit along the flow direction. Severe heat transfer deterioration was obtained for the bared silicon wafer surface with increased inlet vapor quality and heat flux, resulting from the local dryout phenomenon as can be verified by the flow visualization. While the heat transfer performance of the superhydrophilic surface was relatively constant due to continuous and uniform distribution of the thin liquid film on the heated surface during annular flow dominance and subsequent delay to partial dryout occurrence, which outperformed the untreated hydrophilic surface without additional pressure drop penalty.
机译： 突出显示 • 进行了各种表面润湿性的微通道沸腾实验。 • 全面讨论了实验操作条件的影响。 • 流程提供可视化以解释传热性能的趋势。 摘要 进行了饱和流沸腾实验以去离子水为工作流体的单侧加热矩形微通道，研究了宽高比大的表面润湿性对水力和热传输性能的影响。用厚度为100nm的二氧化硅薄膜沉积后的裸硅晶片表面和超亲水表面的接触角分别为65°±±3°和小于5°，两者均用作微通道的加热表面。进行了参数实验研究，入口蒸汽质量从0.03到0.1不等，壁热通量从4 W / cm 2 到20 W / cm < ce：sup loc =“ post”> 2 ，质量通量范围为120至360 kg / m 2 s。进行了高速流动可视化和仪器测量，以说明热通量，质量通量和两相入口质量对具有不同表面的表面的局部传热系数，平均传热性能，两相流结构和压降特性的影响微通道中的润湿性特征。实验结果表明，局部传热系数先减小直到达到最小值，然后沿流动方向向出口增大。裸露的硅片表面由于入口蒸汽质量和热通量的增加而导致严重的传热恶化，这是由于局部变干现象所致，可以通过流动可视化验证。尽管超亲水性表面的传热性能相对稳定，这是因为在环形流动占主导地位期间，受热表面上的液体薄膜连续且均匀地分布，并且随后延迟了部分变干的发生，这优于未经处理的亲水性表面，而没有额外的压降损失。

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