Two-phase air-water flow in a slot-type distributor

This study was a fundamental analysis of two-phase air-water flow through a slot-type distributor. Here a diverging manifold system was used to investigate the factors affecting crossflow. A slot was cut in the side of a vertical 1-in. diameter tube parallel to the tube axis and a controlled variable pressure drop perpendicular to the main stream flow was employed to remove a portion of the main stream. The distribution through the slot was studied with respect to the main stream quality and total mass flux, the length and width of the slot and the pressure drop across the slot. A six foot length of plexiglass tube was used as the main flow channel. Three slot lengths were used: 1.66-in., 4-in., and 6-in. while the slot width was varied from .012-in to .080-in. The total main stream mass flux was varied from 200,000 to 500,000 lbm/hr.ft 2 and the air quality ranged from 0.2 to 0.7 at system pressure of 50 psia. The orifice equation employing discharge coefficients was found to be successful for calculating crossflow rates. The air crossflow was virtually independent of the total mass flux while the water crossflow exhibited ogee behaviour passing from convex to concave shape with increasing mass flux. When the main stream quality was increased, while maintaining fixed values of the total mass flux and radial pressure drop, the mass flow rate of water decreased exponentially. The variation of air discharge rates with quality was much less as compared to the quality effect on water crossflow. The axial pressure gain across the slot was investigated and the value of k, the momentum correction factor, was obtained experimentally. The axial pressure drop across the test section was also examined and it was observed that the Lockhart-Martinelli correlation [20] fits the data very well in the low quality, low mass flux region.