微通道中球窝/球凸强化传热特性研究

Heat Transfer Enhancement in Micro-channel with Dimples and Protrusions

为了解决微机电系统高热流密度的散热问题,采用数值方法对在宽度为50μm、高度为200μm的矩形截面微通道内布置球窝/球凸结构的传热特性进行了研究,通道的Re为100~900,流向间距为1.5到3.5倍的球窝直径,同时研究了球窝/球凸的叉排和顺排对微通道传热特性及流动规律的影响.结果表明：在微通道内布置球窝/球凸后,Nu与光滑微通道的Nu0比值为1.28~4.77,其数值基本和常规通道范围一致;范宁摩擦系数f同光滑微通道的f0比值范围为1.11~2.04,上限与常规通道的一致,下限较之常规通道的小.随着Re的增加,Nu/Nu0和f/f0近似线性增加;相同Re下,叉排的Nu/Nu0和f/f0大于顺排;相同排列方式下,随着流向间距的减小,Nu/Nu0和f/f0增加.叉排的热性能明显优于顺排;微通道中布置球窝/球凸的节能效果明显优于常规通道中布置球窝/球凸的情况.

The heat transfer characteristics in a rectangular micro-channel with dimples/protrusions were numerically studied to solve the problem of high flux heat removal of MEMS.The height and the width of the micro-channel were 200 μm and 50 μm,respectively.The Reynolds number ranged from 100 to 900,and the stream wise pitch was 1.5-3.5 times the dimple diameter.The influences of aligned or staggered arrangement of dimples/protrusions on the heat transfer and flow characteristics were also investigated.The results show that the normalized Nusselt number（Nu/Nu0） in the micro-channel with dimples/protrusions ranges from 1.28 to 4.77,almost the same as that in conventional channels.The normalized Fanning friction factor（f/f0） is in the range from 1.11 to 2.04,whose upper limit and lower limit are the same as that and smaller than that in conventional channels with dimples/protrusions,respectively.Both Nu/Nu0 and f/f0 values increase approximately linearly with an increase in Reynolds numbered.At the same Reynolds number,both Nu/Nu0 and f/f0 values for the staggered arrangement are greater than those for the aligned arrangement.Both Nu/Nu0 and f/f0 values increase with the decrease in the stream wise pitch at the same arrangement of dimples/protrusions.The thermal performance for the staggered arrangement is higher than that for the aligned arrangement.These findings confirm that the energy saving for micro-channels with dimples/protrusions is greater than that for conventional channels with dimples/protrusions.