水平环形两相流的局域液体速度测量

2008/06/17   下载量： 90 次

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Two-phase annular flow is commonly used in both commercial and industrial heat transfer; however, we do not yet possess a thorough understanding of the nature of the fluid. Most analytical annular two-phase models are based on a relationship between the liquid film thickness, liquid film mass flux, and the axial pressure gradient or interfacial shear stress. The film thickness calculated from these models can then be utilized to determine the heat transfer coefficient of the flow. Although they are specific to certain flow regimes and fluids, empirical models remain more accurate than these analytical models. The key to understanding these flows lies with the liquid film. Therefore, to better understand the pressure drop and heat transfer of annular two-phase flow, this study involves the development of local, liquid velocity measurement techniques and their application to horizontal, wavy-annular two-phase flow. Two techniques, Bubble Streak Tracking (BST) and Thin Film Particle Image Velocimetry (TFPIV), have been developed in this study. Utilizing naturally occurring bubbles within the liquid film, the BST technique determines the liquid velocity by measuring reflected light streaks from the bubbles. A three-colored LED array creates directionally unambiguous streaks, while a strobe illuminates interfacial features that affect the liquid velocity. The TFPIV technique applies a typical micro-PIV system to a macroscopic flow with the addition of a non-trivial image processing algorithm. This algorithm successfully overcomes the image noise that occurs when applying PIV to a two-phase, thin film. Although difficulties arise when processing the BST data, the results of the BST and TFPIV methods are comparable, making BST an economical alternative to TFPIV for calculating liquid film velocities.

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下一篇 与自由流方向对准的磁支撑等直圆柱体的无张线式测量

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北京欧兰科技发展有限公司
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