Implication of Void Prediction in the Determination of Pressure Gradient in Vertical Pipes

Abstract

This research work mainly investigates the implication of void prediction in the estimation of total pressure gradient in vertical pipes for multiphase flow systems. Experimental data was collected for a multiphase flow system with silicone oil and air as the liquid and gas phases. The void fraction prediction was carried out using Microsoft Excel. Ten correlations were used for void estimation in chronological order to include statistical analysis of correlation performance. Nicklin et al. (1962) drift flux correlation gives the best void fraction for bubble flow. The prediction from this correlation shows a fairly constant average absolute error of about 20.98% for low gas rate flow (bubble). Greskovich and Cooper (1975) give the best prediction for void fraction in slug flow regime with about 4.84% average absolute error in void fraction prediction. Hassan and Kabir (1989), show progressively higher accuracy and stability in the direction of increasing gas rate with an average absolute error of 6.99% in the churn flow regime. Hence a good correlation for transitional flow region. Pressure gradient prediction was carried out using two separate approaches: the Homogeneous model and the Duns and Ros model (1963). The statistical parameters used in this study are percentage absolute average error, average absolute and relative error. The parameters calculated were compared to determine the performance of the different correlations evaluated. The realization of this work was used to develop a quality assurance flow scheme for vertical sections.