Event
Seminar | Evap., Dynamics & Crisis Phenomena in Thin Liquid Films Sheared by Gas in Narrow Channel
Monday, September 29, 2014
2:00 p.m.
DeWalt Seminar Room, 2164 Martin Hall
Amir Riaz
ariaz@umd.edu
http://www.enme.umd.edu/events/seminars
Mechanical Engineering Seminar
Evaporation, Dynamics and Crisis Phenomena in Thin Liquid Films Sheared by Gas in a Narrow Channel
Speaker: Oleg Kabov, Ph.D.
Professor
National Research Tomsk Polytechnic University
Tomsk, Russia
Abstract:
Thin liquid films driven by a forced gas/vapor flow (stratified or annular flows), i.e. shear-driven liquid films are a promising candidate for the thermal management of advanced semiconductor devices in earth and space applications. Two-sided three-dimensional non-stationary mathematical model was developed. For a deformable gas-liquid interface convection heat transfer in the liquid and the gas phases as well as temperature dependence of surface tension and liquid viscosity are taken into account. The problem has been reduced to five governing equations for the film thickness, temperature fields in the gas and liquid, vapor concentration in the gas phase and gas pressure. Systematic numerical investigations of evaporation and evolution of free interface deformations at wide-ranging variation of gas and liquid Reynolds numbers have been performed. It is shown that the minimum film thickness takes place near the end of the heater, deformation of the film as a bump takes place at the front edge of the heater, and two lateral waves are formed near the lateral sides of the heater. Phase shift schlieren technique, high-speed visualization and infrared thermography have been used in experimental investigations. Experiments with water and FC-72 in flat channels (height 1.2-2 mm) have been conducted. Pure nitrogen has been used as a gas phase. Maps of flow subregimes for shear-driven film were plotted. Stratified flow exists and stable in minichannels with width of 40 mm. Critical heat flux (CHF) for a shear driven film may be up to 10 times higher than that for a falling liquid film, and reaches more than 400 W/cm2 in experiments with water. Thermocapillary effect can be considered as one of the most important reason for the crisis phenomenon for a smooth heater. The longitudinal micro-fins with the height of 0.3 and 0.5 mm may increase CHF.
Bio:
Oleg A. Kabov graduated from the Tomsk Polytechnic State University, Russia, in 1978 and received the Ph.D. degree from the Institute of Thermophysics, Siberian Branch of Russian Academy of Sciences (IT) in 1987. In 1999 he received the degree of Doctor of Sciences in Physics and Mathematics (habilitation) from the same institute. In 2007 he has been granted the diploma of Professor on thermal physics and thermal fluids science of Russian Academy of Sciences. Since 1987, he has been the Head of Laboratory of Enhancement of Heat Transfer in IT (Novosibirsk). His current research interests include: shear-driven and falling liquid films and rivulets, two-phase flows in microgravity and hypergravity, drop spreading and drop evaporation, condensation, evaporative and thermocapillary convection. From 1997 till 2012 he was in a research staff of the Universite Libre de Bruxelles and has been managing the "Two-Phase Systems Group" of the Microgravity Research Center of ULB. He was involved as a coordinator and researcher in the several experiments performed under microgravity conditions (Parabolic Flights, Sounding Rockets, International Space Station). Experiments in 10 parabolic flights campaigns of the European Space Agency have been performed. He has authored and coauthored 271 papers in referred journals and conference proceedings, 7 patents, has delivered 59 keynotes, plenary, and invited lectures at technical conferences and institutions. Since 2009 he is involved in close cooperation with Center of Smart Interfaces of Technische Universität Darmstadt as a Fellow. He is a member of National Committee on Heat and Mass Transfer of Russian Academy of Sciences. Since 2009 he is a member of the Editorial Board of the Journal of Microgravity Science and Technology. In 2006 Professors Kabov and Legros initiated the permanent yearly Workshop on Two-Phase Systems for Ground and Space Applications. Since 2013 he is serving as Editor-in-Chief of the Journal “Interfacial Phenomena and Heat Transfer” published by Begell House.
