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Mixed Convection in a Rectangular
Enclosure with Temperature-Dependent
Viscosity and Viscous Dissipation
A. Gómez López, B. Estela García Rojas, R.O. Vargas Aguilar
and L.A. Martínez-Suástegui
Abstract
The problem of laminar opposing mixed convection inside a two-dimen-
sional rectangular enclosure with asymmetrical heating is studied numerically using
the vorticity-stream function formulation of the Navier-Stokes and energy equa-
tions. The model considers viscous dissipation and viscosity is assumed to vary with
temperature according to an exponential relation, while other fluid properties are
considered constant. Numerical experiments have been performed for fixed values
of the geometrical parameters, Reynolds number of
Re
=
20, Prandtl number of
=
,
060, a range of Richardson numbers from 0 to 10, and Brinkman numbers
ranging between 0 to 40. Streamlines, temperature contours, maximum fluid tem-
perature and average Nusselt number at both walls are obtained. The results show
that combined viscous dissipation and variable fluid viscosity can be important in
the overall flow and heat transfer characteristics.
Pr
3
1 Introduction
Mixed convection studies in rectangular enclosures are important in many industrial
applications for the design of compact heat exchangers, solar collectors, cooling
of electronic equipment and other thermal devices. A comprehensive review of this
subject can be found in Aung (
1987
). However, most efforts have focused on studying
the effect of combined forced and free convection for different channel geometries,
boundary and operating conditions based on the hypothesis that the effect of viscous
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