Nucleate boiling enhancement of FC-72 on the carbon nanotube buckypaper for two-phase immersion cooling

To further develop the two-phase immersion cooling technology with dielectric liquids and accelerate their applications in industrial practices, a comparative experimental study on saturated pool boiling heat transfer of FC-72 on the carbon nanotube (CNT) buckypaper and the smooth indium tin oxide (ITO) film is performed at atmospheric pressure in the present work. The commercially available buckypaper is selected as the nanostructured reinforced surface because of its low-cost, highly -scalable and mass -producible advantages. It achieves enhancements of CHF and maximum HTC up to 74.2 % and 102 %, compared to the smooth ITO surface. The underlying mechanism is well elucidated from the perspectives of surface characteristics, capillary wicking capability and bubble dynamics. The interconnected nanoporous network structure of CNT buckypaper can significantly improve bubble dynamics behavior and induce a marked nanoscale capillary wicking effect. The outstanding wickability can provide additional liquid replenishment on the boiling surface, facilitating the rapid generation and departure of bubbles as well as delaying film boiling. Interestingly, in terms of dielectric fluid (FC-72), it is found that the markedly increased bubble departure frequency on the CNT buckypaper surface primarily arises from a substantial reduction in the bubble waiting period. The present work not only provides an in-depth insight into the enhanced pool boiling characteristics of dielectric liquids on nanostructured surfaces, but also opens opportunities for the industrial applications of state-of-the-art two-phase immersion cooling technology based on nanostructures.