Falling film techniques are widely used in various chemical industrial devices because of their high heat and mass transfer coefficients. Since the coverage of a liquid film plays an important role in the heat and mass transfer, the liquid film coverage on different surfaces, including hydrophilic, ribbed, and untreated plates, had been investigated experimentally in this paper. Air flowed over the liquid surface, perpendicular to the direction of the liquid flow. The film coverage and flow patterns were analyzed through the infrared photo capture by an infrared camera. The effects of the mass flow rate, inlet air velocity, and heat flux were discussed. According to the experimental results, the specific water flow rate plays the most important role, while the inlet air velocity has little effect on the film coverage. When heated, the ribbed plate performs better because the ribs can stop the dry patches from spreading further. Moreover, the empirical correlation of the local water film coverage in the fully developed region and the nominal film coverage of the entire plate was developed.

中文翻译：

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通过亲水和结构化表面处理测量垂直板上的液膜覆盖率

降膜技术因其高的传热系数和传质系数而广泛用于各种化学工业设备中。由于液膜的覆盖率在传热和传质中起着重要的作用，因此本文通过实验研究了液膜在不同表面上的覆盖率，包括亲水性，肋状和未处理的板。空气垂直于液体流动方向流过液体表面。通过红外照相机的红外照片捕获来分析膜的覆盖率和流型。讨论了质量流量，进气速度和热通量的影响。根据实验结果，特定的水流量起着最重要的作用，而进气速度对薄膜的覆盖率影响很小。加热时 肋板的性能更好，因为肋板可以阻止干燥斑块进一步扩散。此外，还建立了完全发达区域的局部水膜覆盖率与整个板块的名义膜覆盖率之间的经验相关性。