External Forced cooling

In some applications, a device with forced cooling is subjected to appreciable external cooling effects. A fan inside the device provides component cooling, but a high-speed (incompressible) flow around the device convects heat from the exterior of the enclosure. In the other forced-cooling applications, this effect is either neglected or simulated with a film coefficient boundary condition. In this application, the heat transfer from the exterior of the enclosure is modeled with an air volume that surrounds the device.

Applications

Modeling Strategy

A volume surrounding the device must be constructed. In some cases the surrounding volume is a physical structure, such as a wind tunnel. In other cases, the device is in either a very large room or an open environment:

The device can either be sealed or vented. If sealed, air within the device is separated from the surrounding volume. If vented, air in the surrounding volume passes around as well as through the device.

Materials

Boundary Conditions

Note: Do not specify flow conditions directly on the device.

Heat transfer boundary conditions should always be applied if the objective is to learn the temperature distribution. (These can be omitted if the objective is to assess only the flow.)

Note: In most cases, a temperature should not be specified on the device.

Mesh

A basic guideline for a high-quality analysis model is that the mesh distribution be sufficient to resolve the flow and temperature gradients efficiently. In regions where the flow circulates or experiences large gradients (such as in wakes, vortices, and separation regions), a finer mesh is required.

For most models, use Automatic Sizing to define the mesh distribution. It may be necessary to locally refine the mesh on geometric features that are highly detailed. For more information about Mesh Autosizing and model preparation...

In some cases, it may be necessary to adjust the Minimum Refinement Length to reduce their effect on the overall mesh count.

To locally refine the mesh in high-gradient flow regions:

Running

On the Physics tab of the Solve dialog:

Autodesk Simulation CFD stops the solution either when the specified number of iterations have elapsed or when the solution is converged, whichever comes first. To ensure the analysis is not stopped before converging, set the Iterations to Run to 500. Most analyses converge within 200-300 iterations so 500 should provide an adequate margin.

Results Extraction

Flow Distribution

Component Temperatures

For more general information, use the extensive collection of results visualization tools to extract flow and thermal results.

Things to Avoid