Flow visualization and heat transfer experiments in a duct with a staggered array of cylinders

Abstract

Flow visualization and heat transfer measurements were made for flow between parallel plates with an insertion of a staggered array of cylinders. The Reynolds number ranged from 8000 to 60,000. The channel height was 50 mm, and the cylinder diameter was 10 mm. The streamwise cylinder pitch was kept constant at five times the cylinder diameter, but the space between the cylinder and the duct wall was changed in four step increments. The measured distribution of local Nusselt number was found to be similar in shape regardless of the Reynolds number. The heat transfer results are discussed in terms of the results of flow visualization. The flow visualization study was made at a Reynolds number of 8500, corresponding to the lowest bound of the Reynolds number range chosen in the heat transfer experiments. A high-speed camera was used to examine the unsteady behavior of the flow. One of the results obtained is that heat transfer is enhanced mainly due to the effect of intermittent reattachment of discrete vortices formed in the separation shear layer starting from the cylinder surface.