Thermal Nonequilibrium and Viscous Dissipation in the Thermal Entrance Region of a Darcy Flow With Streamwise Periodic Boundary Conditions

2011 ◽  
Vol 133 (7) ◽  
Author(s):  
A. Barletta ◽  
E. Rossi di Schio ◽  
L. Selmi

The thermal entrance region in a plane-parallel channel filled by a fluid saturated porous medium is investigated with reference to steady forced convection and to a thermal boundary condition given by a wall temperature longitudinally varying with a sinusoidal law. The effect of viscous dissipation in the fluid is taken into account, and a two-temperature model is employed in order to evaluate separately the local fluid and solid matrix temperatures. The asymptotic temperature distributions are determined analytically. The governing equations in the thermal entrance region are solved numerically by a finite element method and by the method of lines.

Author(s):  
Eugenia Rossi di Schio ◽  
Antonio Barletta

The present paper studies the thermal entrance region in a concentric annular duct filled by a fluid saturated porous metallic foam, with reference to steady forced convection and to a thermal boundary condition given by a wall temperature longitudinally varying with a sinusoidal law. The effect of viscous dissipation in the fluid is taken into account, and a two-temperature model is employed in order to evaluate separately the local fluid and solid matrix temperatures. The governing equations in the thermal entrance region are solved numerically by the method of lines. The Nusselt numer and its mean value in an axial period is evaluated, with reference both to the inner and the outer boundary.


Author(s):  
Eugenia Rossi di Schio

The Darcy-Graetz problem for a channel filled by a nanofluid saturated porous medium is studied. The flow is assumed to be fully developed, and a boundary temperature linearly varying with the longitudinal coordinate in the thermal entrance region is prescribed. A study of the thermal behaviour of the nanofluid is performed by solving numerically the fully–elliptic coupled equations. For the model of the nanofluid, both thermophoresis and Brownian diffusion are taken into account. The governing equations have been solved separately for the fully developed region and for the thermal entrance region. With reference to the fully developed region the solution has been obtained analytically, while for the thermal entrance region it has been obtained numerically, by a Galerkin finite element method implemented through the software package Comsol Multiphysics (© Comsol, Inc.). The analysis shows that for physically interesting values of the Péclet number the concentration field depends very weakly on the temperature distribution. Indeed, the homogeneous model could be employed effectively, since the effects of thermophoresis and Brownian diffusion are negligible.


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