AbstractsEngineering

High pure water systems are used in pharmaceutical and chemical industries. Deadlegs are generally found at points of use in distribution systems. The FDA suggests that the 6D rule is sufficient to help prevent microbial contamination, due to stagnant water within the dead leg. However, more recently, industrial experts are designing systems with dead legs limited to 3D or less. The aim of this study is to examine the effects of entry length, drop loop bends, dead-leg length and mainflow velocity on flow patterns within a branch of a 50:50 mm equal tee. A 2D CFD analysis was carried out on a range of dead-leg configurations and the resulting data presented highlight the overall flow patterns with each branch. A rig was modified to carry out the dye injection tests, to verify CFD results. It was found that the entry length had a little effect on the flow velocity of the deadleg branch. However, when a bend was incorporated in the system, the entry length increase improved the flow patterns of all dead-leg branches. Different combinations of mainflow velocities, dead-leg lengths and length extensions were evaluated to investigate their effect on the flow pattern. It was observed that high mainflow velocities yielded better flow patterns in 2DL and 4DL when compared with 6DL. High mainflow velocities resulted in good flow patterns at only 2DL. At low mainflow velocities, 4DL and 6DL had better flow patterns compared with 2DL. Increasing the length of the extension resulted in better flow patterns in 6DL. At both, high and low mainflow velocities, 4DL sowed a reasonable flow pattern in the branch. Flow visualization studies were performed as well as a CFD simulation. The results of both studies were in good agreement in the case of 4DL branch length. However, for 2DL, an accelerated dye dispersion was observed, suggesting a higher fluid exchange between the mainstream flow and the branch.