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首页> 外文期刊>Experimental Thermal and Fluid Science: International Journal of Experimental Heat Transfer, Thermodynamics, and Fluid Mechanics >Using viscous heating to determine the friction factor in microchannels - An experimental validation
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Using viscous heating to determine the friction factor in microchannels - An experimental validation

机译：使用粘性加热确定微通道中的摩擦系数-实验验证

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摘要

Many experimental works on forced convection through microchannels have evidenced deviations from conventional theory in fluid-dynamic and diabatic behaviour. Whereas often these anomalies were ascribed to "new" micro-effects, it can usually be shown that the explanations for different behaviour at microscale are hidden in the conventional theory. There is just the issue of scaling effects that cause certain phenomena that are negligible at macroscale to become influential when channel geometry is reduced below a certain limit. Such an effect also pertains to viscous dissipation, which becomes important especially in liquid microchannel flows. This paper focuses on the role of viscous heating in such flows, explaining its occurrence in the Navier-Stokes equations and verifying its presence in experimental validation. A criterion will be presented to draw the limit of significance for viscous dissipation effects in microchannel flows. The connection between viscous heating and the friction factor will be demonstrated, which will then provide the basis for comparison in an experimental context. The friction factor obtained through pressure measurements and through evaluation of the viscous heating are confronted. The results show an exceedingly good description of fluid-dynamic behaviour by the viscous heating method for diameters below 100 mu m, proving the validity of the principle of scaling effects. This implies that at extremely small diameters temperature measurements suffice to describe head loss, and that in diabatic experiments the viscous heating should be accounted for. (C) 2006 Elsevier Inc. All rights reserved.
机译：通过微通道进行强制对流的许多实验工作已证明在流体动力学和非绝热行为方面与传统理论有所不同。这些异常通常归因于“新的”微观效应，通常可以证明，对微观尺度上不同行为的解释被传统理论所掩盖。只是存在缩放效应的问题，当通道几何尺寸减小到特定限制以下时，缩放效应会导致某些在宏观尺度上可以忽略的现象变得有影响。这种效果也与粘性耗散有关，这在液体微通道流动中尤其重要。本文着重讨论了粘性加热在此类流中的作用，解释了它在Navier-Stokes方程中的出现，并在实验验证中验证了它的存在。将提出一个标准来画出微通道流中粘性耗散效应的重要性极限。将说明粘性加热与摩擦因数之间的关系，然后将为实验中的比较提供基础。面对通过压力测量和通过评估粘性加热获得的摩擦系数。结果表明，对于小于100微米的直径，通过粘性加热方法可以很好地描述流体动力学行为，证明了结垢效应原理的有效性。这意味着在极小的直径下，温度测量值足以描述水头损失，并且在非绝热实验中应考虑粘性加热。 （C）2006 Elsevier Inc.保留所有权利。

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