Two-phase flow structure in dual discharges – Stereo PIV measurements

Abstract

The discharge of two-phase flow from a stratified region through single or multiple branches is an important process in many industrial applications including the pumping of fluid from storage tanks, shell-and-tube heat exchangers, and the fluid flow through header to the cooling channels, feeder’s tube, of nuclear reactors during loss-of-coolant accidents (LOCA). Knowledge of the flow phenomena involved along with the quality and mass flow rate of the discharging stream(s) is necessary to adequately predict the different phenomena associated with the process. Stereoscopic Particle Image Velocimetry (SPIV) was used to provide detailed measurements of the flow patterns involving distributions of mean velocity, vorticity field, and flow structure. The experimental investigation was carried out to simulate two-phase discharge from a stratified region through branches located on a quarter-circular wall configuration exposed to a stratified gas–liquid environment. The quarter-circular test section is in close dimensional resemblance with that of a CANDU header–feeder system, with branches mounted at orientation angles of zero, 45° and 90° degrees from the horizontal. The experimental data for the phase development (mean velocity, flow structure, etc.) was collected during dual discharge through the horizontal branch and the 45° or 90° branch from an air–water stratified region over two selected Froude numbers in the horizontal branch while maintaining the Froude number in the other branch constant. These measurements were used to describe the effect of outlet flow conditions on phase redistribution in headers and understand the entrainment phenomena.