Effect of surface wettability on carbon nanotube water-based nanofluid droplet impingement heat transfer

Recent studies into droplet impingement heat transfer have demonstrated that it has great potential for providing high heat flux cooling in areas such as thermal management of electronics. The wettability of the surface affects the flow dynamics of the impingement process and the resulting heat transfer. In this study, the effect of surface wettability on carbon nanotube water-based nanofluid droplet impingement heat transfer has been studied and compared with water. Superhydrophobic or hydrophilic coatings are applied on one face of monocrystalline silicon wafers (the drop impinges on this face) while the other face is painted matt black to permit infrared thermography. The silicon wafer is preheated to 40 C and a single droplet impinges normally on the top facing coated surface of the monocrystalline silicon wafer. The inverse heat conduction problem has been solved using the measured black face temperature. For both the water and nanofluid droplets, the convective heat transfer coefficient reduces with the decrease in surface wettability. It is found that the nanofluid produce a significantly higher convective heat transfer coefficient during droplet impingement than water, with the enhancement increasing with increasing wettability.