Thermal and flow characterization in nanochannels with tunable surface wettability: A comprehensive molecular dynamics study

The understanding of the convective heat transfer process for fluid flows through nanochannels becomes imperative due to the wide application of the micro/nanochannel cooling technology. In this work, thermal and flow characteristics in nanochannels with tunable surface wettability are investigated systematically using the molecular dynamics method. First, different temperature and velocity distributions in the entrance region and the fully developed region are observed in nanochannels at different surface wettabilities. The Kapitza resistance and boundary layer effect at the entrance induce the distinct temperature jump and velocity slip, which further determine the Nusselt number variation. Second, owing to the strengthening of the atom momentum exchange and wall shearing, the enhancement of the surface wettability boosts the convective heat transfer capacity and pressure drop in nanochannels. Meanwhile, we discover that a quasi-solid fluid layer appears near the wall when the wall-fluid interaction strength is strong enough and acts as a phonon bridge between the solid walls and the fluid to enhance the thermal energy transmission effectively. Finally, we evaluate the thermal and flow characteristics in nanochannels with tunable surface wettability comprehensively by the Colburn factorjand friction factorfand find out the optimum surface wettability range in nanochannels, corresponding to chi = 1.00-1.75.