Convection Heat Transfer for Turbulent Flow in Subsonic Diffusers

Heat-transfer rates from a heated, plane-wall, symmetrical, two-dimensional, subsonic diffuser to air were measured at total divergence angles ranging from 0 to 45 deg, at diffuser-wall, length-to-throat width ratios ranging from 6 to 18 and at Reynolds numbers based on throat velocity and throat width ranging from approximately 40,000 to 300,000. Diffuser flow conditions developed were: No “appreciable” separation, large transitory stall (separation) and fully developed, two-dimensional stall. Fluid boundary layers on the diffuser walls were always turbulent and were assumed to be incompressible. Flow studies were made in conjunction with the heat-transfer measurements by observing flow patterns with tufts and smoke. Velocity measurements were made in fully developed, two-dimensional stall. Predictions of heat transfer were made for the conditions of no “appreciable” separation and fully developed two-dimensional stall.