Experimental and Numerical Investigation of Micro/Mini Channel Flow-Boiling Heat Transfer with Non-Uniform Circumferential Heat Fluxes at Different Rotational Orientations
Experimental and Numerical Investigation of Micro/Mini Channel Flow-Boiling Heat Transfer with Non-Uniform Circumferential Heat Fluxes at Different Rotational Orientations
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DOI：
10.1016/j.ijheatmasstransfer.2020.119948
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发表时间：
2020-09
影响因子：
5.2
通讯作者：
M. Vermaak;Jarryd Potgieter;J. Dirker;M. Moghimi;P. Valluri;K. Sefiane;J. Meyer
中科院分区：
文献类型：
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作者：
M. Vermaak;Jarryd Potgieter;J. Dirker;M. Moghimi;P. Valluri;K. Sefiane;J. Meyer
对水平微小通道内全氟己烷（FC-72）在不同重力旋转方向下的流动沸腾进行了实验研究和数值模拟。在实验中考虑了单侧均匀通道加热，旋转角度范围为0°（从下方加热）至180°（从上方加热），增量为30°。微/迷你通道具有10（5 mm X 0.5mm）的高纵横比和909μ π ι的水力直径。记录通道内流动可视化，并在56 °C的饱和温度下确定质量通量为10、20和40 kg/m2 s的传热系数。施加合适的热通量以跨越通道内的核态沸腾的开始到接近干燥的条件。结果表明，旋转角度对气泡分离的影响，对传热性能有显着的影响。底部加热的情况下（0°方向）导致局部传热系数高达201%，高于任何其他旋转方向。60°（倾斜加热表面）和90°（从侧面加热）的通道取向通常产生最低的局部传热系数。通过二维和三维数值模拟，深入了解了重力取向对成核和脱离区域内单个气泡生长的影响。分离后的气泡行为及其对传热的影响也进行了短暂的研究，直到分离。数值模拟反映了实验的趋势，它被发现，不断增长的气泡的存在中断的速度流线和热边界层下游的成核网站。
Flow-boiling of Perfluorohexane (FC-72) in horizontal micro/mini channels was investigated experimentally and numerically at different rotational orientations in terms of gravity. One-sided uniform channel heating was considered experimentally for rotational angles ranging from 0° (heating from below) to 180° (heating from above) in increments of 30°. The micro/mini channel had a high aspect ratio of 10 (5 mm x 0.5 mm) and a hydraulic diameter of 909μm. In-channel flow visualisations were recorded and heat transfer coefficients were determined for mass fluxes of 10, 20 and 40 kg/m2s at a saturation temperature of 56 °C. Suitable heat fluxes were applied to span the onset of nucleate boiling to near dry-out conditions within the channel. It was found that the rotational angle had a significant influence on the heat transfer performance due to its influence on bubble detachment. Bottom-heated cases (0° orientation) resulted in local heat transfer coefficients that were up to 201% higher than for any other rotational orientation. Channel orientations of 60° (slanted heating surface) and 90° (heating from the side) generally produced the lowest local heat transfer coefficients. Insight into the influence of the gravitational orientation on single-bubble growth within the nucleation and detachment region was obtained via two- and three-dimensional numerical simulations. Bubble behaviour after detachment and its effect on heat transfer were also investigated transiently until detachment. The numerical simulations mirrored the experimental trends and it was found that the presence of growing bubbles interrupted the velocity streamlines and the thermal boundary layer downstream of the nucleation site.