TURBULENT-FLOW AND PRESSURE LOSSES BEHIND OBLIQUE HIGH-DRAG HEAT-EXCHANGERS

A theoretical study is made of the flow downstream of very high-drag porous plates aligned obliquely to the ultimate flow direction, representing common oblique heat-exchanger arrangements in dry cooling towers, for example. Following a brief discussion of the flow between parallel porous plates, the flow in a V-shaped region formed by porous plates is analyzed. It is argued that eddy viscosity increases linearly with distance from the apex, permitting a self-similar solution. Pressure becomes infinite in the apex, and a concentrated jet appears on the centerline; turbulence acts near the centerline to limit the jet velocity there. Downstream of the V-opening, a narrowing of the flow occurs as it becomes parallel to the centerline, and finally, the velocity profile is fully diffused by turbulence. The velocity profiles, streamline patterns, pressures, and total head losses are fully described for this sequence of flow processes. It is shown that total-head losses can be eliminated by introducing a uniform cascade of airfoils just behind the plates. © 1979.