Experimental investigation of heat-hydraulic characteristics of smooth and dimpled surfaces behind the cylinder

The drag and heat transfer coefficients of smooth and dimpled surfaces located in the wake of a cylinder are experimentally determined. The cylinder, 8 mm in diameter, was placed in a 30 mm-high slot channel. In the experiments the cylinder location along the channel height varied: the gap between the cylinder and the wall under consideration ranged from 0 to 21 mm. The cylinder was unheated. The drag coefficients of the smooth and dimpled surfaces were determined by directly weighing the models on a single-component strain-gauge balance. The local values of the heat transfer coefficients were determined by means of recording the rate of the model surface cooling using an infrared imager. The Reynolds analogy factor for the above-mentioned models ranged from 1.0 to 7.75 depending on the particular surface and the gap between the cylinder and the wall.