Heat transfer characteristics of a rotating cylinder with a lateral air impinging jet

This study experimentally investigated the heat transfer characteristics of a rotating cylinder under lateral air impinging jet. The height and diameter of the cylinder were fixed, and the variable parameters were as follows: (1) the jet Reynolds number (Re-j = 655-60237); (2) the rotational Reynolds number (Re-r = 1975-7899); (3) the ratio of the cylinder diameter (D) to the nozzle width (w) (D/w = 2-16); (4) the relative jet-impinging distance (L/w = 1-16, L is the shortest nozzle-to-cylinder distance). This experiment measured detailed temperature on the heated wall surface of the cylinder using an infrared thermo tracer, and observed the smoke flow characteristics of the stationary and rotating cylinder under impinging jet flow using visualization technique. The experimental results showed that the rotation changed the separation position of impinging jet flow on the cylinder, and allowed the surface temperature of the cylinder to tend towards uniformity along the circumferential direction of the cylinder. In addition, the heat transfer experiment included the pure rotating condition, the pure jet-flow condition and the coexistent condition of rotation and jet flow. The results showed that the average Nusselt number (Nu) increased with the increase of Re, and Rer, and decreased with the increase of D/w. The influence of D/w on Nu decreased with the increase of L/w, and Nu first increased and then decreased with the increase of L/w. In other words, there is a critical L/w value that can produce the highest Nu, and the critical L/w value increased with D/w. Finally, this study proposed reasonable and accurate empirical correlations of Nu in view of three test conditions. All the results can provide reference for practical design of the cooling system in relevant power machinery. (C) 2013 Elsevier Ltd. All rights reserved.