Experiment of Heat Transfer to Supercritical Water Flowing in Vertical Annular Channels
Experiment of Heat Transfer to Supercritical Water Flowing in Vertical Annular Channels
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DOI：
10.1115/1.4023224
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发表时间：
2013-04
影响因子：
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通讯作者：
Zhendong Yang;Q. Bi;H. Wang;G. Wu;R. Hu
中科院分区：
文献类型：
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作者：
Zhendong Yang;Q. Bi;H. Wang;G. Wu;R. Hu
在西安交通大学进行了超临界水传热的垂直环形管实验研究。环形测试段构造有2 mm的环形间隙和8 mm外径的内部加热器。实验参数包括压力为23和25 MPa，质量通量为700和1000 kg/m2 s，热通量为200-1000 kW/m2。实验数据分别取自下向流和上向流。两种流动方向的换热特性存在差异。与上升流相比，下降流的换热系数增大。无论流动方向如何，在环空中装置下游的位置处观察到间隔物对传热的强烈影响。在低热流密度下，隔板效应减弱了浮力效应，但在大热流密度下，隔板效应不减弱浮力效应。超临界水中的强迫对流和混合对流是由于各种热物理性质和重力的影响而形成的复杂现象。间隔物效应的影响区域取决于流动条件。本文对浮力效应进行了定性分析，并讨论了传热损伤可忽略的判据。四个相关性与实验数据进行了比较，斯文森相关预测近的实验数据，但略高估的传热系数。
An experimental study of heat transfer to supercritical water has been performed at Xi'an Jiaotong University with a vertical annular tube. The annular test sections were constructed with an annular gap of 2 mm and an internal heater of 8 mm outer diameter. Experimental parameter covered pressures of 23 and 25 MPa, mass fluxes of 700 and 1000 kg/m2s, and heat fluxes of 200–1000 kW/m2. Experimental data were acquired from downward flow and upward flow, respectively. There were differences of heat-transfer characteristics between the two flow directions. Compared to upward flow, the heat-transfer coefficient increased at downward flow. A strong effect of spacer on heat transfer is observed at locations downstream of the device in the annuli regardless of flow direction. The spacer effect impaired the buoyancy effect at low heat flux, but not for large heat flux. Complex of forced convection and mixed convection in supercritical water is due to various thermophysical properties and the gravity. The affected zone of the spacer effect depends on the flow conditions. The buoyancy effect was analyzed qualitatively in this study and the criterionfor negligible heat-transfer impairment was discussed. Four correlations were compared with the experimental data; the Swenson correlation predicted nearly the experimental data but overpredicted slightly the heat-transfer coefficients.