Heat Transfer and Flow Characteristics in Impinging Flows with Turbulators

The heat transfer characteristics in impinging flows with turbulators were experimentally investigated. The flow characteristics were also measured to elucidate the obtained heat transfer results. Uniform flows were generated at the inlet of a duct, and flowed out through the duct side-open slots near the duct end. A heat-transfer surface was located at the duct end, perpendicular to the incoming flow for heat transfer measurements. A pair of turbulator was mounted on the duct walls at the duct inlet, including rectangular-plate and triangular-plate turbulators, 45 degrees and 90 degrees angle of attacks. Temperatures on the heat-transfer surface were measured by thermocouples to obtain the average Nusselt number. Three-component mean and fluctuating velocity measurements by laser Doppler velocimetry were conducted to characterize the flow structures and to obtain the flow characteristics near the heat-transfer surface. Results show that the turbulators have the effect to increase the flow mean impinging velocity, axial vorticity and turbulent kinetic energy near the heat transfer surface and, thus, to augment the heat transfer. The 90 degrees rectangular-plate turbulator and 45 degrees delta-wing turbulator cause the largest and least heat transfer augmentation among the investigated turbulators, respectively.