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A study of heat transfer scaling of supercritical pressure water in horizontal tubes

机译：水平管中超临界水传热结垢的研究

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Understanding the role of the heat transfer scaling in supercritical utilities can help us obtain a better design for supercritical single phase thermosiphons. In this paper, heat transfer scaling analysis of supercritical pressure water in horizontal tubes with differential inside diameters are experimentally investigated. The operating conditions included mass flux of 100-600 kg/m~2 s and heat flux of up to 400 kW/m~2. The uneven circumferential temperature distributions are discussed firstly over a broad range of heat fluxes. A significant temperature discrepancy exists between the top and bottom surface in each pipe, deteriorated heat transfer occurs on the top surface but enhanced heat transfer happens in the bottom region. With the rise of heat flux, more severe deterioration appears on the higher domain. Then a qualitatively comparison on the heat transfer characteristic of supercritical flow in different pipes are implemented. Evidently, with the increase of tube diameter, the inner-wall temperature peak is much pronounced and the degree of deterioration at the top surface much severe due to the intensification of buoyancy force. The heat transfer mechanism of horizontal pipes is further discussed by comparing the effect of buoyancy and thermal acceleration. With the augment of diameter, free convection gradually intensifies due to its steeper density variation and expanded flow space, which leads to larger temperature deviation between the bottom and top region along the circumferential direction. On the contrary, thermal acceleration plays a relatively minor role in deteriorated heat transfer. Considering the scaling effect in various pipes, two heat transfer correlations are proposed respectively in both the bottom and top region of the horizontal flows.
机译：了解传热定标在超临界公用设施中的作用可以帮助我们获得针对超临界单相热虹吸管的更好设计。本文对内径不同的水平管中超临界压力水的传热结垢分析进行了实验研究。工作条件包括质量通量为100-600 kg / m〜2 s和热通量为400 kW / m〜2。首先讨论了不均匀的圆周温度分布，涉及的热通量范围很广。每根管子的顶面和底面之间存在明显的温度差异，在顶面上传热变差，而在底部区域传热增强。随着热通量的增加，在更高的区域出现更严重的恶化。然后对不同管道中超临界流的传热特性进行了定性比较。显然，随着管直径的增加，由于浮力的增强，内壁温度峰值显着增加，并且顶表面的劣化程度也更加严重。通过比较浮力和热加速度的影响，进一步讨论了水平管的传热机理。随着直径的增加，自由对流由于其更陡峭的密度变化和扩大的流动空间而逐渐增强，这导致底部和顶部区域之间沿圆周方向的较大温度偏差。相反，热加速在恶化的热传递中起相对较小的作用。考虑到各种管道的结垢效应，在水平流的底部和顶部分别提出了两种传热关系。

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