Heat and mass transfer of water flow in graphene nanochannels: effect of pressure and interfacial interaction.

The low-resistance transport of water within graphene nanochannels makes it promising for electronic cooling applications. However, how the water pressure and the water-graphene interaction strength affect the flow field and the thermal transfer, including velocity slip, friction coefficient, Nusselt number, temperature slip, interfacial thermal resistance, and variation of physical properties, is still not clearly understood. In this paper, we employ molecular dynamics (MD) simulations to investigate qualitatively the heat transfer of water flow in graphene nanochannels. Our results reveal that the water peak density near the wall increases approximately linearly with water pressure and water-graphene interaction strength. The water peak density near the water-graphene interface is a key factor in regulating interfacial flow and heat transfer characteristics. Under constant inlet temperature, the relationship between velocity slip length and peak density follows a consistent power function, simply modifying the pressure or the interaction strength doesn't bring a specific effect. The Nusselt number and interfacial thermal resistance are not solely dependent on water peak density; at the same water peak density, increasing interaction strength results in lower interfacial thermal resistance compared to increasing pressure. Increasing pressure improves both interfacial heat transfer and internal heat transfer of water. Furthermore, the convection heat transfer coefficient increases approximately linearly with flow resistance when pressure and interaction strength vary moderately. Finally, we notice that pressure and interaction strength hardly affect the variation range of viscosity and thermal conductivity at a channel height of 10-12 nm. These qualitative insights could lead to the development of more efficient cooling systems for electronic devices.