Comparison of 63 different void fraction correlations for different flow patterns, pipe inclinations, and liquid viscosities

Gas–liquid two-phase flow is commonly encountered in the oil industry, especially in transport pipelines. Thus, the correct prediction of operational parameters such as void fraction or pressure drop is necessary for the development of efficient processes and facility design. Nowadays, there are different studies focused on predicting the void fraction parameter with empirical correlations. This study was aimed at analyzing and comparing 63 different void fraction correlations in order to determine if there was a unique correlation capable of accurately predicting the void fraction for the different operational conditions of flow patterns, pipe inclinations, and liquid viscosity. For this reason, a database of 11,895 experimental points was used to compare the results against the different empirical correlations available in the literature and determine the best one using statistical analyses based on indicators, such as relative error, absolute average percent error, among others. It must be mentioned that the database was strictly filtered and divided depending on the flow pattern (i.e., slug, churn, bubbly, and annular), the different pipe inclinations (i.e., vertical, horizontal and inclined), and the liquid viscosities. The results showed that there was not a unique unified correlation to determine the void fraction accurately for the different operational conditions and fluid properties. However, the best correlations for each specific set of flow patterns, pipe inclinations, and intervals of liquid viscosities were determined according to the statistical indicators, the general assumptions of each correlation, and information reported in the literature. Moreover, it was possible to analyze and provide some recommendations for the patterns evaluated, taking into account that some specific cases require further study, as there was no correlation capable of providing reliable results for the prediction of void fraction.