Surface Wettability and Boiling Heat Transfer Enhancement in Microchannels Using Graphene Nanoplatelet and Multi-Walled Carbon Nanotube Coatings

The pivotal role microchannels play in the thermal management of electronic components has, in recent decades, prompted extensive research into methods for enhancing their heat transfer performance. Among these methods, surface wettability modification was found to be highly effective owing to its significant influence on boiling dynamics and heat transfer mechanisms. In this study, we modified surface wettability using a nanocomposite coating composed of graphene nano plate (GNPs) and multi-walled carbon nanotubes (MWCNT) and then examined how the modification affected the transfer of boiling heat in microchannels. The resultant heat transfer coefficients for hydrophilic and hydrophilic composite (GNPs+MWCNT) microchannels were, respectively, 42.8% and 33.95% higher compared with that of the uncoated surface. These results verify that hydrophilic GNP-based coating significantly improves boiling heat transfer performance. It was observed that a minor increase in contact angle, from 73.142° to 75.73°, resulted in a noticeable decrease in thermal performance. This is attributed to diminished liquid film stability, reduced nucleation site activity, and weakened capillary-driven liquid replenishment. These findings underscore the crucial role of optimized surface wettability in maintaining efficient microchannel boiling. At high mass flux, the GNPS microchannels exhibited maximum pressure drop values, with a pressure drop ratio as high as 36% compared to 29% for the GNPs+MWCNT composite samples. Nevertheless, when a composite hydrophilic–hydrophobic coating was deposited through electrodeposition, the enhancement in heat transfer was less significant. This was probably due to decreased surface uniformity, diminished liquid film stability, and the disruption of effective nucleation behavior, all associated with the slight increase in surface contact angle. The obtained results can be used as guidance for designing advanced cooling surfaces in high-performance microelectronic and energy systems, where precise control of surface characteristics is critical.