Gerardi Craig, Buongiorno Jacopo, Hu Lin-Wen, McKrell Thomas
Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave,, Cambridge, MA 02139 USA.
Nanoscale Res Lett. 2011 Mar 16;6(1):232. doi: 10.1186/1556-276X-6-232.
Infrared thermometry was used to obtain first-of-a-kind, time- and space-resolved data for pool boiling phenomena in water-based nanofluids with diamond and silica nanoparticles at low concentration (<0.1 vol.%). In addition to macroscopic parameters like the average heat transfer coefficient and critical heat flux [CHF] value, more fundamental parameters such as the bubble departure diameter and frequency, growth and wait times, and nucleation site density [NSD] were directly measured for a thin, resistively heated, indium-tin-oxide surface deposited onto a sapphire substrate. Consistent with other nanofluid studies, the nanoparticles caused deterioration in the nucleate boiling heat transfer (by as much as 50%) and an increase in the CHF (by as much as 100%). The bubble departure frequency and NSD were found to be lower in nanofluids compared with water for the same wall superheat. Furthermore, it was found that a porous layer of nanoparticles built up on the heater surface during nucleate boiling, which improved surface wettability compared with the water-boiled surfaces. Using the prevalent nucleate boiling models, it was possible to correlate this improved surface wettability to the experimentally observed reductions in the bubble departure frequency, NSD, and ultimately to the deterioration in the nucleate boiling heat transfer and the CHF enhancement.
采用红外热成像技术，首次获得了低浓度（<0.1体积%）含金刚石和二氧化硅纳米颗粒的水基纳米流体池沸腾现象的时空分辨数据。除了平均传热系数和临界热流密度[CHF]值等宏观参数外，还直接测量了沉积在蓝宝石衬底上的薄电阻加热氧化铟锡表面的气泡脱离直径、频率、生长和等待时间以及成核点密度[NSD]等更基本的参数。与其他纳米流体研究一致，纳米颗粒导致核态沸腾传热恶化（高达50%），CHF增加（高达100%）。在相同的壁面过热度下，发现纳米流体中的气泡脱离频率和NSD比水低。此外，还发现核态沸腾过程中加热器表面会形成一层纳米颗粒多孔层，与水煮表面相比提高了表面润湿性。利用普遍的核态沸腾模型，可以将这种改善的表面润湿性与实验观察到的气泡脱离频率、NSD降低相关联，并最终与核态沸腾传热恶化和CHF增强相关联。
