Binary Fluid Mixture and Thermocapillary Effects on the Wetting Characteristics of a Heated Curved Meniscus

An investigation has been conducted into the interactions of binary fluid mixtures (pentane $[C5H12]$ coolant and decane $[C10H22]$ additive) and thermocapillary effects on a heated, evaporating meniscus formed in a vertical capillary pore system. The experimental results show that adding decane, the secondary fluid that creates the concentration gradient, actually decreases the meniscus height to a certain level, but did increase the sustainable temperature gradient for the liquid-vapor interface, so did the heat transfer rate, delaying the onset of meniscus instability. The results have demonstrated that interfacial thermocapillary stresses arising from liquid-vapor interfacial temperature gradients, which is known to degrade the ability of the liquid to wet the pore, can be counteracted by introducing naturally occurring concentration gradients associated with distillation in binary fluid mixtures. Also theoretical predictions are presented to determine the magnitudes of both the thermocapillary stresses and the distillation-driven capillary stresses, and to estimate the concentration gradients established as a result of the distillation in the heated pore.