LES Simulation of Turbulent Supercritical CO2 Heat Transfer in Microchannels
LES Simulation of Turbulent Supercritical CO2 Heat Transfer in Microchannels
复制标题
DOI：
--
复制
发表时间：
2018
期刊：
影响因子：
--
通讯作者：
M. Nabil
中科院分区：
文献类型：
--
作者：
M. Nabil
尽管自20世纪60年代以来，超临界CO2（sCO 2）传热已被用于工业过程，但对高通量微尺度几何结构中的潜在传输现象（如可用于聚光太阳能接收器）知之甚少。迄今为止，几乎所有的超临界对流换热的实验研究和模拟都集中在大直径垂直通道和管束流动，这可能与微尺度超临界对流有很大不同。计算研究主要采用雷诺平均（RANS）湍流模拟方法，这可能无法捕捉到超临界流体急剧变化的性质趋势的影响。本文采用大涡模拟（LES）湍流模拟技术研究了微尺度换热器中sCO 2的传热特性。模拟几何结构由750 μm×737 μm横截面和5 mm长的微通道组成，从所有四个侧面加热。在减压= 1.1、质量通量= 1000 kg m·s、热通量= 1.7 - 8.9 W·cm-1和变化的入口温度：20 - 100°C下评估模拟情况。计算结果揭示了微尺度sCO 2流的热传输机制。结果与可用的超临界对流相关性[1-3]进行了比较，以确定最适用于微通道sCO 2热交换器工程的传热模型。
Although supercritical CO2 (sCO2) heat transfer has been employed in industrial process since the 1960s, the underlying transport phenomenon in high-flux microscale geometries, as could be employed in concentrating solar receivers, is poorly understood. To date, nearly all experimental studies and simulations of supercritical convective heat transfer have focused on large diameter vertical channel and tube bundle flows, which may differ dramatically from microscale supercritical convection. Computational studies have primarily employed Reynolds averaged (RANS) turbulence modeling approaches, which may not capture effects from the sharply varying property trends of supercritical fluids. In this study, large eddy simulation (LES) turbulence modeling techniques are employed to study heat transfer characteristics of sCO2 in microscale heat exchangers. The simulation geometry consists of a microchannel of 750 μm×737 μm cross-section and 5 mm length, heated from all four sides. Simulation cases are evaluated at reduced pressure = 1.1, mass flux = 1000 kg m s , heat flux = 1.7 − 8.9 W cm , and varying inlet temperature: 20 − 100°C. Computational results reveal thermal transport mechanisms specific to microscale sCO2 flows. Results have been compared with available supercritical convection correlations [1–3] to identify the most applicable heat transfer models for engineering of microchannel sCO2 heat exchangers.