On the comparison of new pressure drop and hold-up data for horizontal air–water flow in a square cross-section channel against existing correlations and models

New data on pressure drop and liquid hold-up obtained in a horizontal square cross-section channel (H = 0.02425 m) were compared against several existing correlations and models for gas–liquid flow. The hold-up data were taken for conditions of wavy-stratified and pseudo-slug flow. Pressure drop results were only obtained for wavy-stratified flow. The correlation developed by Friedel correlates well the pressure drop results, according to the test method used. For the hold-up data, none of the correlations and models tested was able to predict the results. However, a modification in the constants of the model by Turner and Wallis was introduced, and the new expression fits the hold-up data well.