Woodruff School of Mechanical Engineering
Condensation in Microchannels
Prof. John Rose
Queen Mary University, London UK
Friday, September 18, 2009 at 11:00:00 AM
MRDC Building, Room 4211
Dr. Srinivas Garimella
The talk will review a recent theoretical approach, based only on the Nusselt approximations for laminar film condensation, to condensation in channels having typical dimensions around 1 mm. Most importantly, transverse motion of the condensate film due to surface tension is included along with gravity and streamwise shear stress. The method is applicable to any channel section with a vertical axis of symmetry. Numerical results have been generated for various channel shapes, dimensions, fluids, vapour-to-surface temperature differences and vapour mass fluxes. It is found that, over a certain length of channel, the local mean (around the channel perimeter) heat-transfer coefficient is essentially independent of gravity and surface shear stress and depends only on surface tension. Dimensional analysis, as well as an approximate analytical treatment for the surface tension dominated region, leads a relation between the Nusselt number and a single dimensionless group analogous to that in the Nusselt theory except that the gravity term is replaced by a surface tension term. Data for 7 fluids, 5 temperature differences, 7 channel geometries and 5 channel inclinations are well correlated by a Nusselt-like equation with Nusselt number dependant on one dimensionless group involving vapour-to-surface temperature difference, surface tension and the other relevant fluid properties. If time permits a new experimental programme, aimed at obtaining data of unsurpassed accuracy will be outlined.
John Rose has been Professor of Mechanical Engineering at Queen Mary, University of London since 1985. He is a Fellow of the UK Institution of Mechanical Engineers and of the American Society of Mechanical Engineers. He is a member of the UK Heat Transfer Committee. His teaching interests are in the fields of thermodynamics, fluid mechanics and heat transfer. He was president of the UK Heat Transfer Society 2007/08. He has held sabbatical appointments at MIT, US Naval Postgraduate School and the Universities of Tokyo and Kyushu. His research interests are mainly in the field of condensation heat transfer in which he has published some 150 theoretical and experimental papers. He is presently UK editor of International Journal of Heat and Mass Transfer, International Communications in Heat and Mass Transfer and Experimental Heat Transfer
Refreshments will be served.