Principal Investigator Jacopo Buongiorno
Increasing the performance of phase-change heat transfer phenomena is key to the development of next-generation electronics, as well as power generation systems and chemical processing components. Surface-engineering techniques could be successfully deployed to achieve this goal. For instance, by engineering micro/nano-scale features, such as pillars, on the boiling surface, it is possible to attain 100% enhancement in pool boiling critical heat flux (CHF). Researchers have been working on several CHF enhancing micro- and nano-structured surfaces for years. However, due to the complexity of CHF phenomena, there is still no general agreement on the enhancement mechanism. An investigation of the effect of micropillar height on surface capillary wicking and the associated pool boiling CHF enhancement has been conducted. Several 1 cm × 1 cm silicon micropillar surfaces with different micro-pillar heights have been fabricated using MTL's photolithography and DRIE facilities.
The surfaces were characterized using MTL's Scanning Electron Microscope (SEM). The surfaces were then characterized by measuring the capillary wicking rate using high-speed imaging and a custom-built capillary tube approach as presented. The capillary wicking experimental results are presented is demonstrating the increase in liquid transport capability by increasing the micro-pillar heights.
Finally, the performances of such structures were characterized through traditional pool boiling experiments and compared with a flat silicon heater. The surfaces were tested at atmospheric pressure and saturation temperature using DI water as the working fluid. The results demonstrate the benefits of wicking promoted by these structures in terms of CHF enhancement.