Flow in Corners of Passages With Noncircular Cross Sections

Abstract

Conditions for convective heat transfer are known to be especially poor in the corner regions of noncircular passages. This situation causes the passage walls to become too hot in certain types of heat exchangers and directs attention to flow conditions in the corner regions. An experimental and theoretical investigation was conducted on the flow characteristics of triangular-shaped passages. Flow-visualization techniques revealed the remarkable fact that through a certain range of Reynolds numbers laminar and turbulent flows exist simultaneously side by side. Pressure measurements were made on two ducts to study the influence of the geometry on the hydrodynamic entrance length. The velocity field within the ducts was measured over a Reynolds number range from 500 to 43,000. An analytical study of the flow resulted in the development of a simple expression to describe the velocity field under the conditions of laminar fully developed flow in a narrow corner. This expression was confirmed experimentally using a sensitive micromanometer developed for this purpose.