纳米TiO_(2)复合泡沫铜表面强化沸腾传热实验研究

Study on enhanced boiling heat transfer by nano-TiO_(2) composite copper foam surface

将纳米TiO_(2)按照质量分数2%分散在乙醇溶液中,通过沉积法将TiO_(2)沉积在泡沫铜骨架上,制备出纳米TiO_(2)复合泡沫铜表面。通过环境扫描电镜(SEM)观察其沉积情况,发现随着TiO_(2)沉积量的增加,泡沫铜骨架被覆盖的部分逐渐增加,其中沉积量为2.5 mL TiO_(2)的泡沫铜表面覆盖效果最好,其骨架完全被TiO_(2)颗粒覆盖且泡沫铜的孔隙没有被堵塞。以水为工质对复合表面进行沸腾性能测试,发现沉积TiO_(2)乙醇分散液体积为2.5 mL时表面传热性能最佳,传热系数是未沉积有TiO_(2)的泡沫铜表面的1.5倍,热通量增加了170 kW/m^(2)。通过沸腾可视化图像可看出,TiO_(2)沉积量为2.5 mL的泡沫铜表面产生的气泡数量多,且不易合并,说明沉积的纳米TiO_(2)增加了表面的核化点,且提高了表面的毛细吸力,加速了液体回流。

Nano-TiO_(2)is dispersed in ethanol solution at a 2%mass fraction,and deposited on a copper foam skeleton via the deposition method to prepare nano-TiO_(2)composite copper foam surface.The deposition situation is observed by means of scanning electron microscopy.It is found that the covered portion of copper foam skeleton increases gradually with the increase of the deposited TiO_(2)content.The surface coverage of copper foam with 2.5 mL of TiO_(2)deposited reaches the best,and the skeleton has been completely covered by TiO_(2)particles while the pores of copper foam are not blocked.Boiling performance of composite surface is tested with water as the working medium,and it is indicated that the composite surface prepared with 2.5 mL of TiO_(2)ethanol dispersion solution exhibits the best heat transfer performance,its heat transfer coefficient is 1.5 times that of the copper foam surface without TiO_(2)deposition,and its heat flux is 170 kW·m^(-2)higher.It can be seen from the boiling visualization images that the composite surface prepared with 2.5 mL of TiO_(2)ethanol dispersion solution produces a large number of bubbles that do not merge easily,indicating that the deposited titanium dioxide nanoparticles increases the nucleation sites on the surface,improves the capillary suction on the surface and accelerates the liquid reflux.