Prediction of non-uniform liquid film thickness distribution of gas–liquid annular flow in inclined and horizontal pipes

A new prediction model for the non-uniform distribution of liquid film thickness in inclined and horizontal pipes is established in this work. The model takes into account the pumping effect of disturbance waves and considers that the non-uniform distribution of liquid film in annular flow is caused by the circumferential pressure gradient induced by disturbance waves. Based on mathematical derivation and experimental data, an analytical closure relation that can be directly solved is established, avoiding complex iterative calculations. The model requires only the extreme values of the liquid film thickness at the bottom and top of the pipe to predict the liquid film thickness distribution in inclined and horizontal pipes. Model evaluation results show that the new model can well reproduce the liquid film profile and interface position, with an absolute relative error of 15.83% compared with experimental data, which verifies the accuracy of the model. Compared with published models, the new model also has a smaller relative error, with a reduction up to 57.16%, confirming that the new model has better prediction performance and can more accurately predict the circumferential liquid film thickness and distribution profile.