Computational investigations of heat transfer to supercritical CO2 in a large horizontal tube
Computational investigations of heat transfer to supercritical CO2 in a large horizontal tube
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DOI：
10.1016/j.enconman.2017.12.046
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发表时间：
2018-02
影响因子：
10.4
通讯作者：
Jianyong Wang;Z. Guan;H. Gurgenci;K. Hooman;Anand Veeraragavan;Xin Kang
中科院分区：
文献类型：
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作者：
Jianyong Wang;Z. Guan;H. Gurgenci;K. Hooman;Anand Veeraragavan;Xin Kang
浮力对湍流sCO 2的流动和传热特性有重要影响。本文采用数值计算方法研究了sCO 2在水平大管内的湍流流动与换热特性，并考虑了浮力效应，对RNG和三种低雷诺数k-ε湍流模型进行了实验验证。利用已验证的CFD模型，揭示了浮力对水平管内sCO 2流动和传热的影响机理，并分析了热流密度的影响。与实验结果的比较表明，AKN低雷诺数模型具有最好的预测。浮力主要通过诱导二次环流来影响流场结构和湍流度。浮力效应在增加的热通量值时更强。二次循环在较高的热通量水平下变得明显，并增加了顶部和底部管表面之间的温差。在大的水平管中，在拟临界点附近的混合对流中观察到轻微的传热增强。然而，一个显着的恶化，发现在较高的热负荷密度。这与过去仅限于小直径管的报告相反。
Buoyancy has been found to have a significant influence on the flow and heat transfer behaviors of turbulent sCO 2. This paper uses the computational method to investigate the flow and heat transfer characteristics of turbulent sCO 2 in a large horizontal tube with the buoyancy effects taken into account, RNG and three selected low-Reynolds number k-ε turbulence models have been validated against experiments published in literatures. Using the validated CFD model, the buoyancy mechanisms affecting sCO 2 flow and heat transfer within large horizontal tubes are revealed, and the effect of the heat flux have been analyzed. Comparison against experimental results suggests that AKN low-Reynolds number model exhibits the best prediction. Buoyancy influences the flow structure and turbulence levels mainly via the induced secondary circulation. Buoyancy effects are stronger at increased heat flux values. The secondary circulation becomes pronounced at higher heat flux levels and increases the temperature difference between the top and bottom tube surfaces. In large horizontal tubes, slight heat transfer enhancements in the mixed convection are observed near the pseudocritical point. However, a significant deterioration is found at higher heat load density. This is a result contrary to past reports confined to small diameter tubes.