基于自润湿溶液的纳米表面传热性能

Nano-Surface Heat Transfer Performance Based on Self-Wetting Solution

采用阳极氧化法在钛板表面制备出TiO_2纳米管阵列,并以其为加热表面。以含不同浓度丁醇的自润湿溶液为实验工质,考察了自润湿溶液浓度变化对系统临界热流密度和传热系数的影响,并从气泡行为的不同分析了两者耦合强化传热的机理。结果表明:相比于光滑表面和蒸馏水的常规组合,TiO_2纳米管表面和自润湿溶液耦合传热使得系统的临界热流密度大幅度提高,随自润湿溶液浓度的升高,传热系数依次降低。具有超亲水性和较大粗糙度的纳米管表面与1%(质量分数,下同)自润湿性溶液相耦合时,其最大传热系数和临界热流密度分别为11.963 kW·m^(-2)·℃^(-1)与623.706 kW·m^(-2),比常规组合传热分别提高了84.1%和143.8%。由气泡可视化可知,耦合传热在沸腾过程中产生的气泡细小,脱离速度快,不易团聚,合并后的气泡易破碎,易形成微气泡,从而使系统进入剧烈的微气泡沸腾状态。气泡的高脱离频率和特殊有效的液体补充路径,是提高系统传热系数和临界热流密度的主要原因。

Titanium dioxide nanotube arrays served as the heat exchange surface were prepared by anodic oxidation on titanium surface. The influences of the butanol concentration on the critical heat flux and heat transfer coefficient of the system were investigated with the self-wetting solutions containing different concentrations of butanol, and the coupled heat transfer mechanism was also analyzed. The experimental results showed that the critical heat flux was greatly increased by the coupled heat transfer between the titanium dioxide nanotube surface and the self-wetting solution compared with the conventional smooth surface and distilled water coupling, and the heat transfer coefficient decreased with the increase of the concentration of the self-wetting solution. When the nanotube surface with super hydrophilicity and greater roughness was coupled with the 1% self-wetting solution, the maximum heat transfer coefficient and critical heat flux can be as high as 11.963 kW·m-2·℃-1 and 623.706 kW·m-2, respectively, which are increased by 84.1% and 143.8% compared with the conventional coupling. It is known from the bubble visualization that the bubbles produced by coupled heat transfer during the boiling process are small, quick to depart and not easy to reunite. The combined bubbles are easy to break and form the microbubbles, which makes the system enter a violent bubble boiling state. The high departure frequency of bubbles and special effective liquid replenishing paths are the main reason for improving the heat transfer coefficient and critical heat flux.