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首页> 外文期刊>International Journal of Heat and Mass Transfer >Convective heat transfer in pressure-driven nitrogen slip flows in long microchannels: The effects of pressure work and viscous dissipation
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Convective heat transfer in pressure-driven nitrogen slip flows in long microchannels: The effects of pressure work and viscous dissipation

机译：压力驱动的氮气滑流在长微通道中的对流传热：压力功和粘性耗散的影响

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摘要

An analytical and numerical study is carried out to examine the convective heat transfer in two-dimensional pressure-driven nitrogen slip flows in long microchannels, whose length-to-height ratios are above 500. The momentum and the energy equations are solved, where variable properties, rarefaction that involves velocity slip, thermal creep and temperature jump, pressure work, and viscous dissipation are all taken into account. Nitrogen is assumed to be a perfect gas. The effects of pressure work and viscous dissipation, which are particularly significant for long microchannels, are examined by analyzing the uniform wall temperature and the uniform wall heat flux cases. It is found that the degree of rarefaction, which is characterized by the Knudsen number, is the key factor that determines the relative importance of pressure work and viscous dissipation. It is demonstrated that, for perfect gases, rarefaction promotes the conversion of internal energy to mechanical energy. Specifically, regardless of the fluid field development, pressure work and viscous dissipation cancel out in the absence of rarefaction, while pressure work is greater than viscous dissipation with rarefaction and its dominance increases as the Knudsen number increases. It is shown that the combination of pressure work and viscous dissipation makes a significant impact on the Nusselt number in both the continuum and the rarefaction cases. Therefore, it is concluded that for convective heat transfer in internal gas flows, both pressure work and viscous dissipation need to be considered in analysis.
机译：进行了分析和数值研究，研究了长高比大于500的长微通道中二维压力驱动的氮气滑流中的对流传热。求解了动量和能量方程，其中变量特性，涉及速度滑移的稀疏性，热蠕变和温度跃变，压力功和粘性耗散都已考虑在内。氮气被认为是一种完美的气体。通过分析均匀的壁温和均匀的壁热通量情况，检验了压力功和粘性耗散的影响（对于长微通道而言尤其重要）。发现以克努森数为特征的稀疏度是决定压力功和粘性耗散的相对重要性的关键因素。结果表明，对于完美的气体，稀疏化促进了内部能量向机械能的转化。具体而言，无论流体场的发展如何，在缺乏稀疏性的情况下，压力功和粘性耗散都会抵消，而在稀疏性的情况下，压力功大于粘性耗散，并且随着克努森数的增加，其主导地位会增加。结果表明，在连续和稀疏情况下，压力功和粘性耗散的结合对努塞尔数都有很大的影响。因此，可以得出结论，对于内部气流中的对流传热，在分析中需要同时考虑压力功和粘性耗散。

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