Abstract Unsteady laminar and turbulent pipe flows subjected to a constant temperature gradient in axial direction are investigated based on asymptotic considerations. The thermal boundary condition is that of a constant wall heat flux for a steady flow. The unsteadiness is induced by a sinusoidal pressure gradient with different amplitudes and frequencies. The asymptotic analysis is performed with the help of selected CFD simulations. The simulation model is a pipe which is assumed to be infinitely long with an ideal condition of fully developed flow at the pipe entrance. For laminar flows there is no effect with respect to the time averaged heat transfer performance. For turbulent flows appreciable heat transfer enhancement only occurs with large amplitudes and low frequencies. The asymptotic analysis with CFD results are in accordance with the conclusions according to full CFD simulations. Their computational costs, however, are several orders lower. The study shows that, prior to expensive CFD simulations, an asymptotic analysis with CFD simulations at ideal conditions can be considered to find the trend with respect to the parameters of interest.

中文翻译：

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脉动不稳定会增加管流中的对流传热吗？系统研究

摘要 基于渐近考虑，研究了轴向恒定温度梯度作用下的非定常层流和湍流管流。热边界条件是稳定流动的恒定壁热通量。不稳定是由具有不同幅度和频率的正弦压力梯度引起的。渐近分析是在选定的 CFD 模拟的帮助下进行的。模拟模型是假设无限长的管道，在管道入口处具有充分发展的流动的理想条件。对于层流，时间平均传热性能没有影响。对于湍流，显着的传热增强仅发生在大振幅和低频率下。CFD结果的渐近分析与全CFD模拟的结论一致。然而，它们的计算成本要低几个数量级。研究表明，在进行昂贵的 CFD 模拟之前，可以考虑在理想条件下使用 CFD 模拟进行渐近分析，以找出感兴趣参数的趋势。