Buoyancy effects on coupled heat transfer of supercritical pressure CO2 in horizontal semicircular channels
Buoyancy effects on coupled heat transfer of supercritical pressure CO2 in horizontal semicircular channels
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水平半圆通道内超临界压力CO2耦合传热的浮力效应
DOI：
10.1016/j.ijheatmasstransfer.2019.01.045
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发表时间：
2019-05
影响因子：
5.2
通讯作者：
Keyong Cheng
中科院分区：
文献类型：
--
作者：
Haiyan Zhang;Jiangfeng Guo;Xiu Lan Huai;Xinying Cui;Keyong Cheng
浮力对超临界流体的对流换热有很大影响，在拟临界点附近流体的热物性发生剧烈变化。因此，本文对超临界压力CO2（S-CO2）在水平半圆形通道内的耦合换热特性进行了数值研究。详细分析了浮力引起的二次流对局部热性能的影响，并采用无量纲数Se来描述二次流，估算浮力效应。数值计算结果表明，随着质量流量的增加，浮力效应逐渐减小，在低质量流量下，非对称流动的传热性能上级对称流动。浮力可以显著改善热侧上壁的热性能，但会恶化热侧下壁的热性能，而冷侧正好相反。壁面局部换热的增强主要是由于二次流导致的热边界层变薄，能积耗散理论可以很好地解释壁面局部换热行为。与现有标准相比，该标准Se/Regions可以更好地预测浮力对整体和局部传热的影响。
The buoyancy has great influence on the convective heat transfer of supercritical pressure fluids whose thermal properties change drastically near the pseudocritical point. Thus, numerical investigations on the coupled heat transfer characteristics of supercritical pressure CO2(S-CO2) in horizontal semicircular channels are conducted in the present study. The effect of the secondary flow induced by buoyancy on the local thermal performance is analyzed in detail, and the dimensionless numberSe, which represents the absolute vorticity flux in the main flow, is employed to describe the secondary flow and estimate the buoyancy effect. The numerical results show that the buoyancy effect gets smaller with the increase of the mass flow rate, and the heat transfer performance in the asymmetric flow is superior to that in symmetric flows at low mass flow rate. The buoyancy could significantly improve the thermal performance on the top wall but deteriorate that on the bottom wall in the hot side, which is exactly opposite in the cold side. The local wall heat transfer enhancement could be attributed to thinner thermal boundary layer due to the secondary flow, and the entransy dissipation theory could well explain the local heat transfer behavior. The criterionSe/Regives better prediction for the buoyancy effect on both overall and local heat transfer than the existing ones.
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DOI：
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