EVAPORATING EXTENDED MENISCUS IN A V-SHAPED CHANNEL

A mathematical model of the evaporating extended meniscus in a V-shaped channel was developed to investigate the effect of wedge half-angle and vapor mass transfer on meniscus morphology, fluid flow, and heat transfer. The liquid was unsaturated, flowed down the wedge due to gravity, and evaporated into atmospheric air. The average Nusselt number was found to decrease as the wedge half-angle increased, primarily because of an increase in the average wall-interface temperature difference. The mean curvature changed from zero at the interline to a constant, at a distance approximately three times the adsorbed layer thickness from the wall. The capillary pressure calculated from first principles was nearly twice as large as that determined from a semicircular approximation of the mean curvature. We believe that this was partially due to the presence of the van der Waals attraction near the wall. Downstream from the inlet, both thermocapillary convection and pressure recovery in the liquid caused the interline to move downward toward the wedge apex and then upward away from the apex until the piezometric pressure gradient was equal to zero. The locus of liquid dry out points were estimated based on axial locations where the piezometric pressure gradient was equal to zero; this represented a point of zero flow in the channel. As expected, the points where dry out occurred, moved closer to the inlet as the surface mass flux was increased.