具有边缘倒圆凹陷涡发生器换热性能实验

Experimental of turbulent flow heat transfer of dimple vortex generators with rounded edge

使用瞬态液晶(TLC)热像传热测试技术,对具有边缘倒圆的凹陷涡发生器局部传热特征和流动阻力进行了实验研究。凹陷边缘倒圆方案有2种:凹陷前边缘倒圆和凹陷边缘全部倒圆。凹陷的投影直径与通道高度比为1.0,凹陷深度与直径比为0.2,实验雷诺数范围为10 000~60 000。实验结果表明,在选取的雷诺数下,相比于光滑通道,边缘无倒圆的常规球型凹陷涡发生器阵列表面对流换热性能提升了约62.0%,相应的摩擦因子也增大了约73.0%。与无倒圆的常规球型凹陷涡发生器相比,边缘全倒圆的凹陷涡发生器换热性能提升了约3.6%,摩擦因子降低了约4.6%;前边缘倒圆的凹陷涡发生器换热性能提升了约11.0%,摩擦因子提高了约5.2%。综合看来,边缘倒圆使得凹陷涡发生器内部表面传热更加均匀;前边缘倒圆的凹陷涡发生器综合换热性能最高,比边缘无倒圆的常规凹陷涡发生器高出约9.6%;而边缘全部倒圆的凹陷涡发生器的综合换热性能比常规凹陷涡发生器高出近4.4%。

An experimental study of the local heat transfer performance and flow friction characteristics in a channel with spherical dimples with rounded edge is conducted using a transient liquid crystal（TLC）thermography technique.Two different rounding schemes for the dimple edge are investigated：the front edge rounding,and the whole edge rounding.The ratio of the dimple print diameter to the duct height is 1.0,the ratio of the dimple depth to diameter is 0.2,and the Reynolds number ranges from 10 000 to 60 000.As is shown in the experiment,the Nussult number of the channel with conventional dimples is about 62.0%higher than that of the smooth channel,with the friction factor being about 73.0%higher than that of the latter.Compared with the conventional dimples,the Nussult number of the dimples with the whole edge rounded is about3.6% higher,with the friction factor being about 4.6%lower;the Nussult number of the dimples with the front edge rounding is about 11.0% higher,with the friction factor being about 5.2% higher.It is still found that the existence of dimple edge rounding can improve the heat transfer uniformity on the surface of the dimples.The overall thermal performance of the dimples with the front edge rounding is the best,which is about 9.6% higher than that of the normal dimples;while the dimples with the whole edge rounding is about 4.4% higher than that of the normal dimples.