Institute of Thermal Process Engineering, Thin Film Technology, Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany.
Lab Chip. 2014 Feb 21;14(4):771-8. doi: 10.1039/c3lc50892g.
The evaporation of water from open u-shaped microchannel grooves was investigated with particular emphasis on the roles of channel width and air flow conditions. Given the small dimensions of the microchannels, all measurements were conducted in a range where convection and diffusion are of equal importance and known correlations for the calculation of mass transfer coefficients cannot be applied. The evaporation rates were measured using a new optical method and a gravimetric method. Both measurement methods yielded mass transfer coefficients that are in agreement with each other. The observed relation between mass transfer coefficient, air velocity and channel width vastly differs from the predictions obtained from macroscopic structures. With respect to diagnostic devices we conclude that analyte concentration in an open microchannel groove strongly increases even within short times due to the evaporation process and we show that wider channels are more favourable in terms of minimizing the relative evaporation rate.
本文特别研究了空气流动条件和 U 型微通道槽宽度对水蒸发的影响。由于微通道的尺寸很小，所有测量都在对流和扩散同等重要的范围内进行，并且无法应用已知的传质系数计算关联式。采用一种新的光学方法和重量法测量了蒸发速率。两种测量方法得到的传质系数彼此吻合。观察到的传质系数、空气速度和通道宽度之间的关系与从宏观结构获得的预测结果有很大的不同。关于诊断设备，我们得出结论，即使在短时间内，由于蒸发过程，开放微通道槽中的分析物浓度也会强烈增加，并且我们表明，较宽的通道在最小化相对蒸发率方面更为有利。
