狭槽式空气喷流冲击于旋转圆柱体侧面的换热特性

利用实验方法探讨旋转圆柱体受狭槽式空气喷流的换热特性，圆柱体的高度与直径为定值，变动参数为（1）喷流Reynolds数（Re_j）、（2）旋转Reynolds数（Re_r）、（3）圆柱体直径（D）与喷嘴宽度（w）的比例（D/w）、（4）相对喷流冲击距离 （L/w，L为喷嘴距圆柱体的最近距离）等。实验结果显示平均Nusselt数（Nu）随Re_j与Re_r增大而提升，而D/w增加会使Nu减小，且D/w对Nu的影响将随L/w增大而衰退，且存在一临界L/w值能产生最高的Nu，且临界L/w值将随D/w增大而增大，最后，提出合理而准确的经验公式。

Cooling effects of a rotating cylinder under a side impinging air slot jet

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.