自然循环窄矩形通道内过冷沸腾两相摩擦阻力特性

采用去离子水作为实验工质,在低压低流速自然循环工况下开展了单面加热可视化窄矩形通道内的过冷沸腾摩擦阻力特性实验研究。实验中测量了实验段内的压降数据,并通过高速摄影仪拍摄了窄矩形通道内的气液两相图像,提出了过冷沸腾条件下的两相摩擦压降的剥离计算方法。基于本实验中获得摩擦压降数据,对分别基于均相流模型和分液相模型的经典两相摩擦压降计算关系式进行了评估,实验结果表明:采用不同等效黏度计算方法的均相流模型计算结果比实验值明显偏小;而分相流模型中,Sun and Mishiba关系式和Tran关系式均能够较好地预测摩擦阻力,计算值与实验值的平均相对偏差在±15%以内。结合实验数据,以分相流模型方法为基础,考虑全液相Reynolds数、Martinelli参数和Laplace数的影响,获得了计算分液相折算系数的经验关系式,与实验数据符合较好,平均相对误差在10%范围内。

Subcooled flow boiling resistance characteristics in narrow rectangular channel under natural circulation condition

Using deionized water as the experimental working medium, an experimental study of the frictional resistance characteristics of subcooled boiling in a narrow rectangular channel under single-sided heating visualization was carried out under low pressure and low flow rate natural circulation conditions. In the experiment study, the pressure drop data in the narrow rectangular test section was measured, high-speed camera was used as well to capture the two-phase flow images, calculation method that separates the two-phase frictional pressure drop in subcooled flow boiling was brought out. Based on the experimental data obtained, evaluation study of classical two-phase frictional pressure drop correlations from homogeneous flow and separated flow modes were carried out. The experimental results indicates that correlations that based on two-phase equivalent viscosity from homogeneous flow models significantly under estimate the friction pressure drop. Sun and Mishiba correlations and Tran correlations from separated flow models can predict the friction pressure drop pretty well with mean relative error under 15% error bands. Based on the experimental data obtained, empirically correlations for two-phase multiplier was obtained by considering the effect of liquid only Reynolds number, Martinelli parameter and Laplace number. The mean relative error of predicted result with the experimental data is within 10% error band.