Porous Baffle Interface

Physically, a porous baffle represents a porous membrane through which fluid may pass and experience a pressure drop. Conductive heat transfer is modeled in the impermeable portion of the baffle.

Perforated plates

Thin filters

Wire screens

Gauze

The baffle has infinitesimal thickness.

If the porous baffle is thought of as a perforated surface, then the ratio of the area of the holes to the area of the surface, is called the porosity,

The viscous shear stress is computed as a linear combination of the shear stress in the fluid and the shear stress at the wall. The porosity,

, provides the linear weighting.

For conjugate heat transfer, the porous baffle offers a finite thermal resistance. Just as in the baffle interface, conduction is modeled as a one-dimensional process and thermal inertia is neglected. A thermal resistance per unit area,

, for conjugate heat transfer may be specified. The relation between the heat flux across the contact interface,

, and the temperature difference,

, is given by Eqn. 2, and the thermal resistance may be estimated by Eqn. 1.

The total heat transfer across the porous baffle is computed as a linear combination of the heat transfer due to convection and diffusion in the fluid and the conduction though the baffle. The porosity,

, provides the linear weighting factor.

The pressure drop,

, is specified as follows:

where

is the superficial velocity normal to the surface,

and

are user-specified coefficients, and

is the fluid density at the interface.

It is assumed that the direction of the flow is unchanged as it passes through the baffle.