Heat transfer enhancement of a channel flow by rotation circular cylinder

Heat transfer measurement has been done for a low speed water channel with an insertion of rotation circular cylinder in order to find an effective way to achieve high heat transfer enhancement by dynamic flow control method. In the present study, a ratio of the gap between the cylinder and heat transfer wall to the cylinder diameter was kept to be 0.6. The diameter based Reynolds number was set for 200 and 400. It was found that the cylinder rotation achieves remarkable heat transfer enhancement. Counter clockwise rotation, the direction of which accelerates the gap flow, intensifies the unsteady vortex in the shear layer above the low speed area downstream the circular cylinder and this enhances the wall heat transfer over the extensive downstream region. Heat transfer enhancement becomes large as the rotation speed becomes higher within the present experimental condition. Clockwise rotation suppresses the vortex formation, although high speed rotation induces the fast flow approaching near the wall and achieves large heat transfer enhancement there.