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International Heat Transfer Conference 15

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

Versatile Models for Condensation of Fluids with Widely Varying Properties from the Micro to Macroscale

Srinivas Garimella
Sustainable Thermal Systems Laboratory, The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA

Brian M. Fronk
School of Mechanical, Industrial and Manufacturing Engineering Oregon State University Corvallis, OR 97331

Jeffrey A. Milkie
Georgia Institute of Technology

Brendon L. Keinath
Georgia Institute of Technology

DOI: 10.1615/IHTC15.cds.010516
pages 592-604


KEY WORDS: Condensation, two-phase/multiphase flow, heat exchanger

Abstract

Over the past several years, a considerable amount of data on heat transfer and pressure drop during condensation of a variety of fluids in channels with hydraulic diameters in the 0.1 mm – 15 mm range has been collected by the authors. These data have been obtained in circular and non-circular channels for a range of pure synthetic, hydrocarbon, and other natural refrigerants (e.g., R-134a, R-245fa, n-pentane, carbon dioxide, ammonia), and azeotropic mixtures (R-404A, R-410A). In addition, these data span reduced pressures from 0.03 < Pr < 0.9, essentially spanning the entire vapor-liquid dome, over a range of mass fluxes from 50 < G < 800 kg/m2-s. Across such a wide range of fluid properties (differing by an order of magnitude), operating conditions and channel geometries, the forces governing the transfer of heat, mass and momentum vary considerably. The probabilities of gravity, shear and surface tension driven flow mechanisms, void fractions and phase distributions, and other phenomena change significantly across this wide parameter range, significantly affecting the local transport phenomena. This paper represents an attempt to develop unified models that are able to predict condensation heat transfer for this vast range of fluids, operating conditions, and geometries while accounting for the varying flow mechanisms and transitions. Such a generally applicable model for predicting heat transfer in condensing flows is critical for the realization of highly efficient, compact thermal energy systems.

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