Fluid Convection


What Does Fluid Convection Do?

If you have previously run a fluid flow analysis on one or more parts of this model, you can have the velocity profiles use in the thermal analysis. A few guidelines that must be followed when using this option are:

  1. The geometry of the part that was analyzed as a fluid flow model must be identical in the heat transfer model. The processor is going to match up the velocity values at the coordinates.

  2. You must assign a specific heat value and a mass density value for the fluid part.

  3. It is recommended that you create a fine mesh near the edges of the fluid where it will interact with the solid.

The basic process to perform a fluid convection analysis is to first create and mesh an assembly containing both the solid and fluid parts making sure that the meshes are matched at the interfaces of the parts. Next, save the model as a new filename and delete (or deactivate) the solid parts. Now perform a fluid flow analysis on the fluid. Go back to the original file and set it up as a heat transfer analysis. The parts that represent the solids only require a thermal conductivity as a material property (for steady state heat transfer). The part that represents the fluid requires a thermal conductivity, mass density and specific heat values. The equation that will be used to solve for the temperatures is:

Where

r = Mass density of the fluid

Cp = Specific Heat of fluid

u, v, and w = Fluid velocity in the x, y, and z directions

T = Temperature

k = Thermal conductivity

QH = Internal heat generation

Applying a Fluid Convection:

Note

Fluid Convection cannot be applied when the model includes smart bonding. If a fluid convection load is required, the meshes should match between the parts in order to have the parts be bonded, and disable the smart bonding option (uncheck "Analysis: Parameters: Contact: Enable smart bonded/welded contact").

  1. After you switch analysis types to the thermal analysis, right click in the display area while nothing is selected. Choose the "Fluid Convection..." command.

  2. Click in the "Velocity Data" column of the spreadsheet for the first row. A standard "open window" dialog will appear. Navigate to the folder where the fluid velocity results are located and pick the file.

  3. Click in the "Enabled" column if necessary to set it to "Yes", indicating that the selected results will be applied to the specified part.

  4. Pick the part in the "1st Part" drop-down box to fill the "Part" column in the spreadsheet.

  5. If you want the thermal analysis to take into account the heat generated by friction created by the viscous flow, click in the "Viscous Heat" column to change the value to "Yes". Note that the viscous heating should only be used if turbulence is included in the analysis.

  6. If turbulence was included in the fluid flow analysis for the selected load case, click in the "Turbulence" column to change the value to "Yes". Otherwise, set it to "No".

  7. Select the load case (which corresponds to a time step) from the fluid flow analysis from which the velocity profile will be used in the "Load case" drop-down box.

If velocity results exist in multiple files, or if additional parts are required, click the "Add Row" button. Then repeat the above steps for the new row.

 

Tip

The inlet temperature of the fluid must be specified. Either use the "Applied Temperature" or a "Convection" load on the faces of the fluid.