Experimental investigation of flow structure and heat transfer characteristics for confined cylinders

In this work, the heat transfer characteristics and the flow structures for confined cylinders are presented. The aspect ratio of the confined cylinders was varied between 0.4 and 1; however, the ratio between the projected height of cylinders to the confinement height was kept constant as 0.25 in this work. The experiments were conducted to determine heat transfer rates for Reynolds numbers ranging from 200 to 1000. The results indicated that the highest heat transfer rate was achieved for the confined cylinder having the aspect ratio of 1. Both heat transfer rates and predicted drag coefficient reduce as the aspect ratio of the cylinders decreases. A particular concern is revealing the relations between flow physics and the heat transfer mechanisms by quantifying and examining instantaneous velocity patterns to state instantaneous data and time-mean data through confined cylinders using the technique of PIV for the different Reynolds numbers such as 360, 500, 600 and 750. According to the quantitative data obtained from the PIV system, the acceleration of the fluids particles due to the conservation of mass in the cross-streamwise direction when the flow encounters the blockage is the main consequence of confinement on the flow characteristics over the cylinders.