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Using FEHT
Keith A. Woodbury
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Introduction
• FEHT– Is a simple finite element conduction heat
transfer analysis program– Use of this program entails the same basic
steps necessary to solve heat transfer problems with commercial software
– Is restricted to 2-D problems with less than 1000 nodes
– Can solve steady or unsteady (transient) problems
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Overview
• Numerical heat transfer analysis requires the following steps– Define geometry– Define mesh for computation– Assign properties– Define boundary conditions (and initial
conditions, if necessary)– Solve for the temperatures– Perform any desired post-processing
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Overview (cont)
• We’ll illustrate use of the program via an example -
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Open FEHT
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Define Geometry
• First set the grid to something convenient for drawing your 2-D geometry
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Define Geometry
• Then draw the outline of your object
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Define Geometry
• “Draw -> Outline…” tips– The crosshair cursor does not snap to the grid– Holding the “shift” key while drawing
constrains the motion to straight lines– To make a corner you can click and continue
to the next point
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Define Mesh• When an outline is complete, the outline
blinks, and the “Draw->Element Lines…” option is activated
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Define Mesh
• “Draw->Element Lines…” tips– Elements must be triangular– Element lines can only connect at nodes (you
can’t join an element line to the middle of another element line!)
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Define Mesh
• Keep going…
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Define Mesh
• It can be tedious with a lot of nodes
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Specify Properties• Click on one of the elements (NOT and edge or
node) – the entire outline will begin blinking• Now go to “Specify->Material Properties” on the
menu (or right click on the object)
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Specify Properties
• You can choose from a library of materials or select “not specified” and enter your own data
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Apply Boundary Conditions
• Either– Use the pointer to drag a box around a region
of the boundary, or– Click on a segment of the boundary
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Apply Boundary Conditions
• The selected portion(s) of the boundary will blink
• Choose “Specify->Boundary Conditions” or right click
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Specify Boundary Conditions
• Fill in the boundary condition information
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Apply Boundary Conditions
• At any time, “Run->Check” will tell the status of your model
• After all boundaries have been assigned conditions, “Run->Calculate”
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Solve for Temperatures
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Post-Processing
• “View->Temperatures” shows the computed nodal temperatures
• “View->Temperature Contours” makes a color map of the solution
• “View->Temperature Gradients” visualizes the heat flow directions
• “View->Tabular Output” gives a table of the solution that can be cut/pasted