Mass transfer in back to back elbows arranged in an out of plane configuration under annular two phase flow conditions

• Mass transfer in back to back elbows in an out of plane configuration was measured.
• Tests were performed under annular two phase air–water conditions.
• Highest mass transfer was on the outer wall of the first elbow.
• The mass transfer on the second elbow was always less than that in the first elbow.
• The mass transfer increased with an increase in the air superficial velocity.

The mass transfer in back-to-back elbows arranged in an out of plane configuration has been measured under annular two phase air–water flow conditions. The measurements were performed using a wall dissolving technique with the elbow sections cast from gypsum. Experiments were performed to study the effect of increasing the water and air superficial velocities, and the effect of separation distance between the elbows. The highest mass transfer for all cases occurs on the outer wall of the first elbow, and the magnitude was not affected by the separation distance between the elbows. The maximum mass transfer in the second elbow was approximately 60 percent of the maximum value in the first elbow. The mass transfer increased with an increase in either the water or air superficial velocity, with the air velocity having a greater effect. The roughness development in the upstream pipe was modest, but was significant in the regions of high mass transfer on the first and second elbow.