Enhanced subcooled flow boiling in microchannels integrated with nanoporous graphene coatings of distinctive wettability

Subcooled flow boiling in microchannel presents a promising solution for efficient electronics cooling. This study explores the use of graphene nanoplatelets (GNPs) as a nanoporous surface coating to leverage the ultrafast water permeation and variable wettability properties of graphene in subcooled flow boiling through microchannels. The performance of GNPs coatings is evaluated using metrics such as the Nusselt number, pumping power, flow resistance, and performance evaluation criterion. The results demonstrate that the base GNPs coating, exhibiting dual wetting characteristics due to its synergistic combination of hydrophobicity and high surface roughness, outperforms both purely superhydrophilic and superhydrophobic GNPs coatings. The base GNPs coating achieves an impressive 143% increase in the Nusselt number and reduces the surface temperature by up to 25°C. However, the enhanced boiling performance with the base GNPs comes at the expense of increased pumping power, analogous to the use of inserts in channel flow. The improved heat transfer is coupled with higher flow resistance and energy consumption, leading to a performance evaluation criterion value well below unity. This study provides interesting insights into the application of GNPs in subcooled flow boiling in microchannels to improve the efficiency of electronics cooling.