Effects of Several Roughness Elements on an Insulated Wall for Heat Transfer From the Opposite Smooth Heated Surface in a Parallel Plate Duct

Experiments were carried out to examine the effects of several roughness elements on the insulated wall opposite the smooth heated plate for the heat transfer with air flowing through a parallel plate duct. The local heat transfer coefficient, the velocity distribution, the turbulence intensity, and the pressure drop were measured. An optimum pitch of roughness elements for the augmentation of heat transfer exists for each space between two parallel plates. Additionally, the correspondence between the heat transfer and the flow situation is also examined. Acceleration and turbulence produced by roughness elements contribute to the increase of the local heat transfer coefficients on the smooth heated plate. Thermal performance is evaluated at constant pumping power.