New boundary conditions for the evaporating thin-film model in a rectangular micro channel

The augmented Young–Laplace equation has been validated for modeling evaporating thin-films in the literature. However, physical conflicts still exist when it is used with the traditional rules to model the entire meniscus. New boundary conditions are developed for this model. The new conditions ensure that the center of the intrinsic meniscus is on the axis of the micro channel. The calculations indicate that the meniscus radius of the intrinsic region increases with the superheating of the heater wall. This implies a reduction of the capillary suction and a reduction of the critical heat flux for the whole micro channel. A polar disjoining pressure model is used and compared with the non-polar model. A narrow, but high heat flux, sub-region is also found at the thinner end of the intrinsic region. By considering the new boundary conditions and this sub-region, the thin-film region can be integrated smoothly with the bulk liquid region.