Computational and experimental investigation of the drag reduction and the components of pressure drop in horizontal slug flow using liquids of different viscosities

Computational and experimental investigation in 10-cm ID horizontal pipes have been carried out utilizing carbon dioxide as the gas phase and two types of oil with different viscosities; namely 0.0025 Pa s and 0.05 Pa s, as the liquid phase. The influence of oil viscosity on the magnitude of total pressure drop and each of its components as well as the effectiveness of a drag reducing additive (DRA, CDR WS 500 M flow improver) in decreasing the pressure loss was investigated in two-phase oil–gas slug flow. The effects of changing oil viscosity on the contribution of frictional and accelerational components to total pressure drop in slug flow were also examined and analyzed. Computations of accelerational and frictional components of pressure drop were performed. The accelerational component of pressure drop was dominant in the 0.0025 Pa s oil while the frictional component had significant contributions in the 0.05 Pa s oil. Despite the fact that the magnitude of drag reduction was higher in the 0.05 Pa s oil, the DRA was more effective in reducing the total pressure drop and its components in the 0.0025 Pa s oil.