Recovery of core annular flow structure in a horizontal T-pipe using CFD approach

Previous work about CAF through a T-pipe reported that CAF stability could not be maintained after passing the intersection. The current CFD study was expected to propose a strategy to recover the stability of CAF in a horizontal T-pipe without interrupting the flow process. A recirculation zone was detected in the area near the junction. Additional water with a certain design of insertion and water velocity is introduced at the intersection to support the recovery of CAF by suppressing fouling. This numerical work covered both qualitative evaluation of CAF consistency along the T-pipe and quantitative evaluation to analyze the attainable energy savings of the proposed strategy. From some candidates for water insertion geometries and velocities of additional water, the ducting insertion with a water velocity of 2 m/s showed a consistent CAF structure starting at about 200 mm from the intersection point to the final downstream exits. This proposed design was estimated to reduce pressure drop more than 98% compared to transportation without lubrication and 4% higher than design without additional water injection. The power reduction factor was computed at a value greater than 1 (30.3), indicating that the proposed system was energetically more advantageous than the single-phase oil system.