Flow and heat transfer measurements in the laminar wake region of semi-circular cylinder embedded within a rectangular channel

Abstract Flow and heat transfer in the wake region of a semi-circular cylinder embedded within a rectangular channel have been studied experimentally using non-intrusive techniques. The semi-circular cylinder embedded within the channel with a blockage ratio of 0.45 (d/H) acts as an obstacle to the incoming fully developed laminar flow and creates a wake region in its downstream side. The velocity field in the downstream wake region is mapped using PIV (particle image velocimetry) technique with water as the working medium. The fluctuating shear layers and the vortices shed by the cylinder interact with the bottom heated wall of the channel. The influence of the wake region of the cylinder manifests on the heat transfer characteristics of the bottom wall of the channel and acts in a way to passively improve the overall heat transfer characteristics. The resulting whole field temperature values are captured using interferometry and augmentation in heat transfer rates vis-a-vis a channel without cylinder are compared. The dominant frequencies of the downstream unsteady flow in the wake of the cylinder are captured using schlieren technique. Heat transfer enhancement up to 42 percentage is observed in the case of the presence of the semi-circular cylinder in the channel in comparison with the flow in a plain channel for the Reynolds number range of 75–200 under which the experiments are performed.