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首页> 外文期刊>International Journal of Heat and Mass Transfer >Effect of channel sidewalls on Joule heating induced sample dispersion in rectangular ducts
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Effect of channel sidewalls on Joule heating induced sample dispersion in rectangular ducts

机译：通道侧壁对焦耳热诱导矩形管中样品分散的影响

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In this article, we analyze the effect of channel sidewalls on the broadening of analyte bands resulting from Joule heating during their electrokinetic migration through a rectangular conduit. A method-of-moments formulation has been used to numerically evaluate the Taylor-Aris dispersivity of sample zones under these conditions for thin electrical double layers applicable to a majority of microfluidic assays. Our analysis shows that the larger surface area to volume ratio around the side regions of a rectangular channel causes these corners to stay cooler than the rest of the conduit. While such a thermal profile does not modify the electroosmotic flow in the system for a fixed temperature at the channel walls, it reduces the electrophoretic transport rate by about 10% for small temperature differentials across the channel cross-section (＜ 10 ℃). The effect of these thermal gradients on the hydrodynamic dispersion of analyte bands is more significant however, increasing such band broadening by nearly an order of magnitude in large aspect ratio designs. Our analyses further show that the trends noted above are magnified when a fixed heat transfer coefficient is assumed at the channel walls, in which case, the temperature along this boundary is no longer constant. The non-isothermal channel walls combined with the temperature dependence of zeta potential and other material properties in this situation leads to a non-uniform electroosmotic slip velocity in the system modifying both fluid and analyte transport rates. Again, while the resulting solute flow profile reduces the migration velocity of sample zones only to a moderate extent, it is found to increase the hydrodynamic dispersion of analyte bands by several orders of magnitude in large aspect ratio rectangular channels.
机译：在本文中，我们分析了在通过矩形导管进行电迁移过程中，焦耳加热导致通道侧壁对分析物谱带拓宽的影响。在这些条件下，对于适用于大多数微流体分析的薄双电层，采用矩量法公式来数值评估样品区的泰勒-阿里斯分散性。我们的分析表明，矩形通道的侧面区域周围较大的表面积与体积之比使这些角比其余的导管保持凉爽。尽管对于通道壁上的固定温度而言，这种热分布不会改变系统中的电渗流，但对于跨通道横截面的较小温差（＜10℃），它将使电泳迁移率降低约10％。这些热梯度对分析物谱带水动力分散的影响更为显着，但在大长宽比设计中，这种谱带展宽增加了近一个数量级。我们的分析进一步表明，当在通道壁处采用固定的传热系数时，上述趋势会放大，在这种情况下，沿该边界的温度不再恒定。在这种情况下，非等温通道壁与Zeta电位和其他材料特性的温度依赖性相结合，导致系统中的电渗滑移速度不均匀，从而改变了流体和分析物的传输速率。再次，虽然所得的溶质流剖面仅将样品区的迁移速度降低到中等程度，但发现在长宽比较大的矩形通道中，分析物谱带的水动力分散性增加了几个数量级。

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