Mean statistics of a heated turbulent pipe flow at supercritical pressure
Mean statistics of a heated turbulent pipe flow at supercritical pressure
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DOI：
10.1016/j.ijheatmasstransfer.2014.12.039
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发表时间：
2015-04-01
影响因子：
5.2
通讯作者：
Pecnik, Rene
中科院分区：
文献类型：
--
作者：
Nemati, Hassan;Patel, Ashish;Pecnik, Rene
直接数值模拟（DNS）的加热湍流管流与流体在超临界压力下进行雷诺数Re-τ = 360，基于管道直径和摩擦速度在入口处。恒定的壁面热通量的应用和温度范围内的流域结合的热力学区域中发生的热物理性质的大的变化。这些属性的变化对平均流量的贡献进行了研究。与理想气体传热相比，平均流控制方程中出现了附加项。这些项可以显著地影响能量平衡，因为它们修改了平均壁热通量和靠近管壁的焓扩散。此外，平均的热物理性质，特别是等压热容c（p），显着偏离使用平均温度或焓评估。这是由于平均人为称为詹森不等式，所造成的焓波动和热物理性质相对于焓的非线性依赖。本文讨论了一个强迫对流和两个混合对流情形的湍流统计特性。湍流动能的减少被观察到的强制对流和低浮力的情况下，这会导致传热恶化表示的高壁温。对于高浮力的情况下，湍流活动首先减少（传热恶化），然后由于湍流恢复而增加。(C)2014爱思唯尔有限公司版权所有。
Direct numerical simulations (DNS) of a heated turbulent pipe flow with a fluid at supercritical pressure are performed at a Reynolds number of Re-tau = 360, based on pipe diameter and friction velocity at the inlet. A constant wall heat flux is applied and the temperature range within the flow domain incorporates the thermodynamic region where large variations in thermophysical properties occur. The contribution of these property variations on the mean flow is studied. As compared to ideal gas heat transfer, additional terms appear in the mean flow governing equations. These terms can significantly affect the energy balance, because they modify the averaged wall heat flux and the enthalpy diffusion close to the pipe wall. Furthermore, the averaged thermophysical properties, especially the isobaric heat capacity c(p), deviate significantly from those evaluated using the mean temperature or enthalpy. This is due to an averaging artifact called the Jensen inequality, caused by the enthalpy fluctuations and the non-linear dependence of thermophysical properties with respect to enthalpy. Turbulent statistics for one forced convection and two mixed convection cases in an upward flow are discussed. A decrease in turbulent kinetic energy is observed for the forced convection and the low buoyancy case, which cause heat transfer deterioration indicated by high wall temperatures. For the high buoyancy case the turbulence activity first reduces (heat transfer deterioration) and then increases due to turbulence recovery. (C) 2014 Elsevier Ltd. All rights reserved.