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首页> 外文期刊>International Journal of Heat and Fluid Flow >Size effect on single-phase channel flow and heat transfer at microscale
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Size effect on single-phase channel flow and heat transfer at microscale

机译：尺寸对单相通道流量和微观传热的影响

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摘要

The size effects on microscale single-phase fluid flow and heat transfer are reviewed and discussed. The physical mechanisms for the size effects on the microchannel flow and heat transfer were divided into two classifications: (a) The gas rarefaction effect occurs when the continuum assumption breaks down as the characteristic length of the flow becomes comparable to the mean free path of the molecules; (b) Variations of the predominant factors influence the relative importance of various phenomena on the flow and heat transfer as the characteristic length decreases, even if the continuum assumption is still valid. Due to the larger surface to volume ratio for microchannels, factors related to surface area have more impact to the microscale flow and heat transfer. Among them are: The surface friction induced flow compressibility in microchannels makes the fluid velocity profiles flatter and leads to higher friction factors and Nusselt numbers; The surface roughness of the microchannel is likely responsible for the early transition from laminar to turbulent flow and the increased friction factor and Nusselt number; The importance of viscous force in natural convection modifies the correlation between Nu and Ra for natural convection in a microenclosure and, other effects, such as the axial heat conduction in the channel wall, the channel surface geometry, and measurement errors as well, could lead to different flow and heat transfer behaviors from that at conventional scales.
机译：审查和讨论了尺寸对微尺度单相流体流动和传热的影响。尺寸影响微通道流动和传热的物理机制分为两类：（a）气体稀疏效应发生在连续假设被打破时，因为流动的特征长度变得与流动的平均自由程相当。分子（b）主要特征的变化会随着特征长度的减小而影响各种现象对流动和传热的相对重要性，即使连续假设仍然有效。由于微通道的表面积与体积之比较大，因此与表面积有关的因素对微米级流动和传热的影响更大。其中：微通道中表面摩擦引起的流动可压缩性使流体速度分布曲线更平坦，并导致更高的摩擦系数和Nusselt数；微通道的表面粗糙度可能是导致层流向湍流早期过渡以及摩擦系数和Nusselt值增加的原因。粘性力在自然对流中的重要性改变了微外壳中自然对流的Nu和Ra之间的相关性，其他影响（例如通道壁中的轴向热传导，通道表面几何形状以及测量误差）也可能导致不同于常规规模的流动和传热行为。

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