Transient heat transfer of impinging jets on superheated wetting and non-wetting surfaces
Transient heat transfer of impinging jets on superheated wetting and non-wetting surfaces
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DOI：
10.1016/j.ijheatmasstransfer.2021.121056
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发表时间：
2021-08
影响因子：
5.2
通讯作者：
D. Butterfield;Brian D. Iverson;Daniel Maynes;J. Crockett
中科院分区：
文献类型：
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作者：
D. Butterfield;Brian D. Iverson;Daniel Maynes;J. Crockett
超疏水(SH)表面由于润湿性低而具有理想的防污性能，但也已被证明在撞击射流的情况下减少了向过冷水的热传递。在这项工作中，具有不同润湿性(亲水性或HPI、疏水性或HPO、SH)的过热硅衬底被冲击水射流淬火，其中衬底温度高于饱和温度。硅片被氧化以形成HPI表面，涂上特氟龙以使表面HPO，或者被等离子蚀刻和涂层以产生所需的微结构以满足SH条件。所有晶片都集成了电阻加热器，然后加热到200-320∘C的温度，然后用不同指定流速的轴对称室温水射流撞击，产生喷流雷诺数在6,000和18,000之间。收集了高速可视数据，显示了受沸腾热破裂限制的层状液体接触区域如何随着表面冷却到低于饱和的温度而径向增长。该数据与使用热像仪记录在晶片背面的温度数据相关联。这项研究的结果证实了先前的猜想，即表面润湿性可以改变最大热通量，在所描述的情况下，最大热通量在这里量化为40%，并且还可以影响喷射薄膜扩散高达50%。提高初始表面温度降低了薄膜在所有表面上的铺展速度，并增加了除SH表面以外的所有表面上的换热。随着雷诺数的增加，热流密度增大，同时影响薄膜的扩散速率和薄膜区域的最大半径。
Superhydrophobic (SH) surfaces possess desirable anti-fouling properties due to low wettability, but have also been shown to reduce heat transfer to subcooled water in impinging jet scenarios. In this work, superheated silicon substrates with varying wettability (hydrophilic or HPi, hydrophobic or HPo, SH) are quenched by an impinging water jet, where the substrate temperature is above the saturation temperature. Silicon wafers are either oxidized to create HPi surfaces, coated with Teflon to make the surface HPo, or plasma-etched and coated to create the necessary micro-texture for SH conditions. All wafers are integrated with an electric resistance heater and then heated to temperatures of 200–320∘ C before impingement with an axisymmetric room temperature water jet of varying specified flow rates yielding jet Reynolds numbers between 6000 and 18,000. High-speed visual data is collected, showing how the lamellar liquid contact region, limited by thermal breakup due to boiling, grows radially as the surface cools to temperatures below saturation. This data is correlated to temperature data recorded on the back side of the wafer using a thermal camera. Results of this study confirm previous conjecture that surface wettability can alter maximum heat flux, which is quantified here for the described scenario by up to 40%, and can also affect jet thin film spreading by up to 50%. Increasing initial surface temperature decreases thin film spreading rate on all surfaces, and increases heat transfer on all but the SH surfaces. Increasing Reynolds number yields an increase in heat flux, and affects both the thin film spreading rate as well as the maximum radius of the thin film region.