Effect of graphene oxide coating on bubble dynamics and nucleate pool boiling heat transfer

Abstract

Materials coating has been proved to be an effective mean to increase the number of active nucleating sites, and therefore generate more vapor bubbles and lead to better poolboiling heat transfer performance. In this work, graphene oxide (GO) is coated on a boiling surface by self-assembly method, to enhance critical heat flux (CHF). The pool boiling is carried out on a smooth copper surface to study the effect of GO coating using distilled water as the working fluid along with bubble dynamic visualization. GO coating facilitates bubble nucleation by providing numerous microscale cavities. The visualization investigation of bubble dynamic behavior shows that the CO-coated surface exhibits a higher bubble departure frequency, a smaller bubble departure diameter and smaller bubble diameters in the pool, indicating greatly enhanced heat transfer effects. Meanwhile, the GO-coated surface exhibited a smaller contact angle than the copper surface, revealing that surface becomes more hydrophilic after GO coating. Consequently, GO-coated surface with a coating time of 4 h provides a CHF of 224.3 W/cm2 and a heat transfer coefficient (HTC) of 8.79 W/(cm2·K), representing an improvement of 94.0% in CHF and 83.5% in HTC compared to smooth copper surface.