关键词: 旋转圆柱体, 侧向冲击喷流, 湍流, 换热, 传质

Abstract: The heat transfer characteristics of a rotating cylinder under a side air impinging jet were experimentally investigated in this study. In practical industrial applications, such as food processing, textile and paper drying process, there are heat transfer and mass transfer problems on the side of the rotating cylinder under impinging jet flow. 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 local average temperature on the heated wall surface of the cylinder using thermocouples under stationary and rotating condition. The experimental results showed that the rotation 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_j and Re_r, 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.

Key words: rotating cylinder, side impinging air jet, turbulent flow, heat transfer, mass transfer