Ying-Xin Wang
The Isermann Department of Chemical Engineering, Rensselaer Polytechnic Institute,
Troy, NY 12180-3590
Joel L. Plawsky
The Isermann Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, USA
Peter C. Wayner, Jr.
The Isermann Department of Chemical Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180-3590
Sinopsis
The optimum use of interfacial free energy gradients to control fluid flow in small regions naturally leads to simpler passive heat transfer systems. In this context, "passive" refers to the natural pressure field for fluid flow due to changes in the intermolecular force field resulting from an imposed nonisothermal temperature field. Although the particular Constrained Vapor Bubble, CVB, discussed can be viewed as a large version of a wickless heat pipe, it is a much more general heat transfer concept. Herein, it is an ideal system for the optical study of microscale transport processes in droplet condensation due to interfacial phenomena. This paper concerns the movement of a single condensed ethanol sessile drop into a concave liquid film. The intermolecular force is found to be much larger than the gravitational force and dominates condensate removal. A dimensionless force balance for viscous shear stress demonstrates the effect of changes in the contact angle and curvature. A dimensionless difference in free energy is identified as the cause of spontaneous condensate removal.