Void fraction measurement and calculation model of vertical upward co-current air-water slug flow

The focus of this paper is on the measurement and calculation model of void fraction for the vertical upward co-current air-water slug flow in a circular tube of 15 mm inner diameter. High-speed photog-raphy and optical probes were utilized, with water superficial velocity ranging from 0.089 to 0.65 m.s-1 and gas superficial velocity ranging from 0.049 to 0.65 m?s?1. A new void fraction model based on the local parameters was proposed, disposing the slug flow as a combination of Taylor bubbles and liquid slugs. In the Taylor bubble region, correction factors of liquid film thickness Cd and nose shape CZ* were proposed to calculate aTB. In the liquid slug region, the radial void fraction distribution profiles were obtained to calculate aLS, by employing the image processing technique based on supervised machine learning. Results showed that the void fraction proportion in Taylor bubbles occupied crucial contribu-tion to the overall void fraction. Multiple types of void fraction predictive correlations were assessed using the present data. The performance of the Schmidt model was optimal, while some models for slug flow performed not outstanding. Additionally, a predictive correlation was correlated between the central local void fraction and the cross-sectional averaged void fraction, as a straightforward form of the void fraction calculation model. The predictive correlation showed a good agreement with the present exper-imental data, as well as the data of Olerni et al., indicating that the new model was effective and appli-cable under the slug flow conditions. (c) 2021 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd.

Automated summary

The paper focuses on the measurement and calculation model of void fraction for the vertical upward co-current air-water slug flow in a circular tube. A new void fraction model based on the local parameters was proposed. The research results showed that the void fraction proportion in Taylor bubbles was crucial to the overall void fraction.