26 de nov de 2010

Palestra do Prof. Timothy A. Shedd da University of Wisconsin-Madison sobre Escoamentos Bifásicos

Prof. Timothy A. Shedd,

Associate Professor of Mechanical Engineering

University of Wisconsin-Madison


Two-Phase Internal Flow: Toward a Theory of Everything

Two-phase flow and heat transfer is still an area of intense research and great uncertainty. Even severely restricting ourselves to just annular, internal two-phase flow does not significantly improve our chances of accurately predicting either pressure gradients or heat transfer coefficients for an arbitrary tube geometry or fluid. This paper summarizes a series of investigations that aim to identify the fundamental governing physics of internal two-phase flow: a Theory of Everything. The techniques developed to do so have been varied, and many will be presented. At the macro-scale, simultaneous visualization and measurement of pressure gradient and heat transfer coefficients have led to interesting observations about the relationship between flow regimes and these fundamental macro-scale behaviors. The important and often neglected impact of entrainment (both liquid into vapor and vapor into liquid) will be discussed as well. Since the macro-scale behaviors are governed, for the most part, by behaviors at the micro-scale, a number of techniques have been developed to study this near-wall behavior in quantitative detail. In particular, dye-assisted Planar Laser Induced Fluorescence has provided the first accurate portrayals of the gas-liquid interface annular flow and micro-scale multiphase Particle Image Velocimetry has been used to obtain the velocity within the liquid film of annular flow from within microns of the wall to velocities within the waves 500 microns or more from the wall. Statistical analyses of these data point toward a general approach for modeling wall shear in two-phase concurrent internal flow. Additional work is leading toward a similarly fundamental approach to heat transfer models, though the analysis presented is still in preliminary stages. In summary, while still a fair distance from a Theory of Everything, this work provides insights and examples of how it may be achieved through careful research, analysis and, most importantly, productive collaboration.

Local: Sala de seminários do LETEF - SEM

Data e horário: 13/12/2010 (segunda-feira) 10 horas da manhã

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