铜基双尺度多孔表面厚度对沸腾传热的影响

Effects of Copper Micro-Nano Bi-Porous Surface Thickness on Boiling

多孔表面在强化沸腾领域有重要应用。本文制备了系列孔径相近但厚度不同的铜基微纳双尺度多孔表面,这些样品表面上都有一系列直径约为130μm的微孔,而孔壁上则是纳米(亚微米)孔隙。以纯水为工质的池沸腾实验显示,当热流密度较低时,存在最优厚度使得沸腾换热性能最佳;样品CHF随着厚度增加而增加。双尺度多孔表面有着区别于一般的多孔表面的重要特性,当壁面过热度较低时,只有大孔可以形成活化中心;但当壁面过热度到达一定温度后,其孔壁上的纳米尺度(亚微米)尺度结构形成大量的活化中心,其壁面过热度几乎不再随着热流密度的上升而上升。随着厚度的增加,其壁面可以形成的活化穴直径在减小,造成活化所需要的壁面过热度升高。

porous surface is very important in enhancing boiling heat transfer.Herein,series of Copper Micro-Nano bi-porous surface（Cu-MNBPS） with the same pore diameter but with different height are made.The SEM photography indicated that the Cu-MNBPS consists of micro pore around 130 μm,and the dendritic wall has nano gaps.The pool boiling experimental results show that there is an optimal thickness for enhancing pool boiling at low heat flux.And the CHF of Cu-MNBPS increases with the height of porous layer.Different from the traditional porous surface,only the micro pores in Cu-MNBPS can be activated to be nucleation site at low heat flux,but the nano gaps at the dendrite wall in Cu-MNBPS will be nucleated at a higher super heat and the super heat doesn’t increase with the increasing heat flux anymore.With increasing the layer thickness,the activated nucleation site formed at the wall become smaller,and lead to higher wall superheat.