Gravity effects on subcooled flow boiling heat transfer
Gravity effects on subcooled flow boiling heat transfer
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DOI：
10.1016/j.ijheatmasstransfer.2018.09.011
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发表时间：
2019-01-01
影响因子：
5.2
通讯作者：
Kim, Jungho
中科院分区：
文献类型：
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作者：
Lebon, Michel T.;Hammer, Caleb F.;Kim, Jungho
使用HFE-7000的过冷流动沸腾测量在垂直的6 mm ID蓝宝石管中在包括超重力和微重力的各种重力水平下在向上和向下流动期间获得。采用涂敷在管内的温敏涂料（TSP）测量了管壁-流体界面处的时间和空间分辨的温度和传热分布，并将该数据沿着流动显示用于表征不同流型下的传热。时间平均传热系数进行了比较，在九个重力水平，四个质量通量，六个热通量，和两个过冷度。平均传热系数通常随热通量、质量通量和绝对重力水平的增加而增加。在微重力条件下，由于缺乏自然对流和气泡滑动速度，在低热通量下缺乏混合，导致传热系数与向下和向上条件相比有所下降。热传递强烈依赖于流态，导致高质量通量或低重力下的某些数据点偏离典型趋势，这是由于成核位点失活。随着质量通量和热流密度的增加，传热系数对重力的依赖性变小。流动状态对浮力和惯性力之间的竞争非常敏感，这反过来又影响了传热。讨论了在各种条件下传热的机制。(C)2018爱思唯尔有限公司版权所有。
Subcooled flow boiling measurements using HFE-7000 were obtained in a vertical 6 mm ID sapphire tube during upward and downward flow at various gravity levels including hypergravity and microgravity. Temperature sensitive paint (TSP) applied to the inside of the tube was used to measure time and space resolved temperature and heat transfer distributions at the wall-fluid interface, and this data along with flow visualization were used to characterize the heat transfer for different flow patterns. Time-averaged heat transfer coefficients were compared at nine gravity levels, four mass fluxes, six heat fluxes, and two subcoolings. The average heat transfer coefficient typically increased with heat flux, mass flux, and absolute gravity level. In microgravity, the lack of mixing at low heat fluxes due to the absence of natural convection and bubble slip velocity resulted in a decrease in heat transfer coefficient compared to downward and upward conditions. The heat transfer was strongly dependent on the flow regime, causing certain data points at high mass flux or low gravity to deviate from the typical trends due to deactivation of nucleation sites. The heat transfer coefficient became less dependent on gravity as the mass flux and heat flux increased. Flow regimes were very sensitive to the competition between buoyancy and inertial forces, which in turn affected the heat transfer. Mechanisms by which heat is transferred under various conditions are discussed. (C) 2018 Elsevier Ltd. All rights reserved.