Pressure drop, void fraction and flow pattern of vertical air–silicone oil flows using differential pressure transducer and advanced instrumentation

New data for pressure drop, void fraction and flow pattern in a vertical riser using air–silicone oil as the system fluid are reported in this work. A differential pressure cell (DP cell) was used to measure the pressure drop. Also, void fraction data were recorded simultaneously by an electrical capacitance tomography (ECT) and wire mesh sensor (WMS). The observed flow patterns are the spherical cap bubble, slug and churn flows. However, only the slug flow without the presence of churn flow is seen within the transition line as predicted by the map. The characteristic probability density function (PDF) derived from void fraction data was used to determine the flow patterns. A comparison between present experimental results and the air–water data reported in the literature was carried out and various levels of agreement were achieved. The PDFs obtained from the DP cell signals for spherical cap bubble and slug flows significantly differ from those derived from the ECT and WMS outputs. Current void fraction and pressure gradient results were compared with the values predicted by ten empirical correlations selected from the literature. Statistical tools such as Mean Square Error (MSE), Root Mean Square Error (RMSE) and Mean Absolute Percentage Error (MAPE) were applied in the comparison. The Greskovich and Cooper correlation gave the least MSE, RMSE and MAPE values of 0.0007908, 0.013 and 3.05%, respectively for slug flow.