title: Condensation on Highly Superheated Surfaces: Unstable Thin Films in a Wickless Heat Pipe.
abstract: A wickless heat pipe was operated on the International Space Station to provide a better understanding of how the microgravity environment might alter the physical and interfacial forces driving evaporation and condensation. Traditional heat pipes are divided into three zones: evaporation at the heated end, condensation at the cooled end, and intermediate or adiabatic in between. The microgravity experiments reported herein show that the situation may be dramatically more complicated. Beyond a threshold heat input, there was a transition from evaporation at the heated end to large-scale condensation, even as surface temperatures exceeded the boiling point by 160 K. The hotter the surface, the more vapor was condensed onto it. The condensation process at the heated end is initiated by thickness and temperature disturbances in the thin liquid film that wet the solid surface. Those disturbances effectively leave the vapor "superheated" in that region. Condensation is amplified and sustained by the high Marangoni stresses that exist near the heater and that drive liquid to cooler regions of the device.
authors.affiliation: The Howard P. Isermann Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, USA.
authors.forename: Akshay
authors.initials: A
authors.lastname: Kundan
authors.affiliation: The Howard P. Isermann Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, USA.
authors.forename: Thao T T
authors.initials: TT
authors.lastname: Nguyen
authors.affiliation: The Howard P. Isermann Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, USA.
authors.forename: Joel L
authors.initials: JL
authors.lastname: Plawsky
authors.affiliation: The Howard P. Isermann Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, USA.
authors.forename: Peter C
authors.initials: PC
authors.lastname: Wayner
authors.affiliation: NASA Glenn Research Center Cleveland, Ohio 44135, USA.
authors.forename: David F
authors.initials: DF
authors.lastname: Chao
authors.affiliation: NASA Glenn Research Center Cleveland, Ohio 44135, USA.
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Sicker