Void Fraction Measurement Based on Flow Transformation-NIR Array Sensors in Slug Flow

Slug flow is a typical gas-liquid two-phase flow pattern, and accurate measurement of the void fraction is of great significance for flow behavior analysis and the calculation of mixture average density. Near-infrared (NIR) optical array sensors are designed, and the transmission characteristics of NIR light are investigated within slug flow. Based on Lambert-Beer’s law and optical scattering theory, the relationship between the light intensity loss and the void fraction was derived, and a predictive correlation for the void fraction of slug flow was proposed. The experiment was conducted in a horizontal transparent pipeline with an inner diameter of 50 mm. Void fraction measurements had been obtained for 35 horizontal slug flow conditions. The laboratory results indicate that the proposed void fraction predictive correlation has good accuracy under experimental conditions, with an average absolute percentage error (MAPE) of 3.84%. The relative error of 97.14% of the data is within the ±10% band. These studies provide a reliable basis for the void fraction real-time monitoring of the slug flow.