Heat Transfer by Free Convection

Model ID: 122

This example describes a fluid flow problem with heat transfer in the fluid. An array of heating tubes is submerged in a vessel with fluid flow entering at the bottom.

This is a multiphysics model that involves more than one kind of physics. The incompressible Navier-Stokes equations from fluid dynamics work together with a heat transfer equation, which means that the Laminar Flow interface is used for laminar single-phase fluid flow and the Heat Transfer interface for heat transfer.

In this model, the equations are coupled in both directions. First you add free convection to the fluid flow with the Boussinesq approximation. This approximation ignores variations in density with temperature, except that the variations give rise to a buoyancy force lifting the fluid. This force enters the F term in the incompressible Navier-Stokes equations.

At the same time, the heat equation must account for the velocity field. The velocity field from the Laminar Flow appears automatically as a predefined option in the model input for the velocity field that determines the convective heat transfer.

This model was built using the following:

COMSOL Multiphysics