Quantitative Analysis of Drag Reduction in Horizontal Slug Flow

Abstract

Summary Calculations have been made to predict the components of pressure drop in slug flow. This analysis is aimed at understanding, in a quantitative manner, the contributions of both frictional and accelerational components to total pressure drop in horizontal slug flow and the effect of drag reducing agents (DRAs) on each component. Experimental results were in good agreement with predicted values. The DRA used in this study was effective in reducing both components of the pressure drop. The accelerational component was found to be dominant and formed more than 80% of the total pressure drop. It increased dramatically with increasing superficial gas velocity. With the addition of 20 ppm DRA, the accelerational and frictional components were noticed to decrease by a factor of 70%. At DRA concentration of 50 ppm, they decreased by a factor of 80%. Total drag reduction was found to generally decrease at higher superficial gas velocities. In sharp contrast with expectations, the drag reduction was recovered mainly from the accelerational component, indicating that the DRA worked not only in the buffer zone but also in the mixing zone in the slug body. The accelerational drag reduction reached values as high as 89% of total drag reduction.