Combined effects of wall slip and nanofluid on interfacial transport from a thin-film evaporating meniscus in a microfluidic channel

摘要

An improved comprehensive semi-analytical model is devised and postulated to unveil the underlying physics of thin-film evaporating dynamics in a microfluidic channel using Al(2)O(3)water nanofluid as working liquid with/without porous coating layer of nanoparticles. The model uses the mass transport equation based on the kinetic theory and the Young-Laplace equation for pressure differential and incorporates the slip boundary condition on the wall of the channel. It reveals that the wall slip is a crucial parameter that increases the cumulative heat transfer with decreased thickness of the thin-film evaporating meniscus. Furthermore, mainly three volume fractions 0.5%, 1%, and 2% has been considered in the present work and it is observed that nanofluid plays an important role in the increment of heat flux which is about 31% with the volume fraction of 2% and 25 nm diameter particles when only enhanced thermophysical properties are considered without slip. However, it exaggerates the results by 29% when porous coating layer of nanoparticles is neglected. It is also noticed that a porous coating layer deposited by the nanoparticles can even reduce the heat transfer phenomenon. Moreover, for a given combination of nanoparticle diameter and volume fraction, increase in the thermal resistance may reach up to an extent that even increased thermal conductivity cannot counteract it and hence, the heat transfer obtained using nanofluid can be worse than the heat transfer obtained using the base liquid water alone.