Available Variables for Postprocessing
FLUENT provides radiation quantities that you can use in postprocessing when your model includes the solution of radiative heat transfer. You can generate graphical plots or alphanumeric reports of the following variables/functions:
In the Radiation... category:
In the Wall Fluxes... category:
See Chapter 30 for definitions of these postprocessing variables. Note that in addition, incident radiation, transmitted, reflected and absorbed radiation flux are also available on a per-band basis for the non-gray DO model.
| The sign convention on the radiative heat flux: heat flux from the wall surface is a positive quantity.
| It is possible to export heat flux data on wall zones (including radiation) to a generic file that you can examine or use in an external program. See Section
13.2.4 for details.
Reporting Radiative Heat Transfer Through Boundaries
You can use the Flux Reports panel to compute the radiative heat transfer through each boundary of the domain, or to sum the radiative heat transfer through all boundaries.
See Section 29.2 for details about generating flux reports.
Overall Heat Balances When Using the DTRM
The DTRM yields a global heat balance and a balance of radiant heat fluxes only in the limit of a sufficient number of rays. In any given calculation, therefore, if the number of rays is insufficient you may find that the radiant fluxes do not obey a strict balance. Such imbalances are the inevitable consequence of the discrete ray tracing procedure and can be minimized by selecting a larger number of rays from each wall boundary.
Displaying Rays and Clusters for the DTRM
When you use the DTRM, FLUENT allows you to display surface or volume clusters, as well as the rays that emanate from a particular surface cluster. You can use the DTRM Graphics panel (Figure 13.3.28) for all of these displays.
Display DTRM Graphics...
To view clusters, select Cluster under Display Type and then select either Surface or Volume under Cluster Type.
To display all of the surface or volume clusters, select the Display All Clusters option under Cluster Selection and click the Display button.
To display only the cluster (surface or volume) nearest to a specified point, deselect the Display All Clusters option and specify the coordinates under Nearest Point. You may also use the mouse to choose the nearest point. Click on the Select Point With Mouse button and then right-click on a point in the graphics window.
To display the rays emanating from the surface cluster nearest to the specified point, select Ray under Display Type. Set the appropriate values for Theta and Phi Divisions under Ray Parameters (see Section 13.3.11 for details), and then click on the Display button. Figure 13.3.29 shows a ray plot for a simple 2D geometry.
Including the Grid in the Display
For some problems, especially complex 3D geometries, you may want to include portions of the grid in your ray or cluster display as spatial reference points. For example, you may want to show the location of an inlet and an outlet along with displaying the rays. This is accomplished by turning on the Draw Grid option in the DTRM Graphics panel. The Grid Display panel will appear automatically when you turn on the Draw Grid option, and you can set the grid display parameters there. When you click on Display in the DTRM Graphics panel, the grid display, as defined in the Grid Display panel, will be included in the ray or cluster display.
Reporting Radiation in the S2S Model
When you use the S2S model, FLUENT allows you to view the values of the view factor and radiation emitted from one zone to any other zone. You can use the S2S Information panel (Figure 13.3.30) to generate a report of these values in the console window or as a separate file.
Report S2S Information...
The steps for generating the report are as follows:
The following is an example of how the data is presented:
S2S Information From wall1 to: Viewfactor Incident Radiation wall1 0.0000 0.0000 wall2 0.2929 171387.7813 wall3 0.2929 155305.7969 wall4 0.4142 29055.9023 From wall2 to: Viewfactor Incident Radiation wall1 0.2929 306451.9688 wall2 0.0000 0.0000 wall3 0.4142 214195.0938 wall4 0.2929 19153.2715
Note that the header listed above ( S2S Information) is not displayed in the console window.