In a boiling heat transfer setup, the two commonly used methods to heat the test section wall are electric heating and fluid heating, and a discrepancy of boiling heat transfer characteristics exists between the two heating methods. For the purpose of investigating boiling heat transfer under the condition of the fluid heating method, visualization research was conducted on saturated flow boiling water in vertical annular ducts heated by water. By combining an annular flow model with a theory of flooding and a turbulent Prandtl Number, a heat transfer model was given. The duct widths were 5mm and 3mm, and the mass flux ranges were 16.8 ～55.3 kg/(m2s) andl5.3～62.1 kg/(m２s) ,respectively. It was shown that chum flow takes up nearly the whole saturated area. Flooding is the mechanism of the formation of churn flow, and it is the churn motion that enhances the heat transport between steam and water. The proposed model can sufficiently predict the experimental results.%在沸腾传热实验中,一般壁面的加热方式有电加热和流体加热两种,在两种方式下的沸腾传热特性存在差异.针对流体加热方式下的沸腾传热问题,采用水加热方法,对水在竖直环形流道内的流动沸腾传热特性进行了可视化研究,并结合环状流模型、液泛原理和紊流普朗特数理论,给出了传热计算模型.实验段环隙宽度有5和3 mm两种,质量流速分别为16.8～55.3 kg/(m2s)和15.3～62.1 kg/(m2s).实验结果表明,饱和沸腾区域以搅混流为主,液泛现象是搅混流形成的内在机理,搅混使传热得以增强;基于环状流模型的计算结果和实验结果符合较好.
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