ansys composite wall

7/28/2019 Ansys Composite Wall

1/14

Thermal #2: Heat flux analysis of a composite modular wallIntroduction: In this example you will determine the heat flux through the composite modular wallshown in the figure.Physical Problem: A composite wall is widely used in cold places to insulate buildings from the coldoutside surroundings. It typically consists of insulating material packed inside a wall. The insulating materialis usually in two layers and is staggered. In this problem we will model a section of such a wall and

determine the heat flux through the wall. This gives an estimate of the amount of heat that needs to besupplied to maintain the room temperature.Problem Description:

The outer material of the composite wall is steel with thermal conductivity of 20 W/m KThe insulating material has a thermal conductivity of 0.1 W/m K.Units: Use S.I. units ONLYGeometry: See figure.Boundary Conditions: The bulk temperature on the left of the wall is 220K, and the Film Coefficient is200 W/m2K. On the right side the bulk temperature is 300K, and the Film Coefficient is 20 W/m2K.Objective:

To determine the heat flux through the given length of the wall.To plot the temperature distribution.To generate the vector plot of the heat flux.

You are required to hand in print outs for the above.Figure:

IMPORTANT: Convert all dimensions and forces into SI units.STARTING ANSYS


2/14

Click onANSYS 6.1 in the programs menu.Select Interactive.The following menu that comes up. Enter the working directory. All your files will be stored in thisdirectory. Also enter 64 for Total Workspace and 32 for Database.Click on Run.

MODELING THE STRUCTUREGo to the ANSYS Utility Menu.

ClickWorkplane>WP Settings.The following window comes up:


3/14

Check the Cartesian and Grid Only buttonsEnter the values shown in the figure above.Go to the ANSYS Main Menu and clickPreprocessor>Modeling>Create>Area>Rectangle>By 2Corners.The following window comes up:


4/14

Now we will pick the end points of the rectangles.

First make the outer rectangle of dimensions 5.25 cm X 6.75 cm, i.e. 42 units by 54 units on thegrid.Similarly make the other rectangles.Click on Preprocessor>Modeling>Operate>Booleans>Overlap>Areas. For each separateinsulation area, first select the steel area, then select the particular insulation area.If you cannot see the complete workplane then go to Utility Menu>PlotCntrls>Pan Zoom

Rotate and zoom out to see the entire The model should look like the one below:


5/14

MATERIAL PROPERTIES

We need to define material properties separately for steel, and the insulation material.Go to the ANSYS Main Menu and clickPreprocessor>Material Props>Material Models. In thewindow that comes up choose Thermal>Conductivity>Isotropic.Enter 1 for the Material Property Number and click OK. The following window comes up:


6/14

Fill in 20 for Thermal conductivity. Click OK.Now the material 1 has the properties defined in the above table. This represents the material

properties for steel. ClickMaterial>New Model in the Define Material Behavior Window to defineproperties for material 2. Repeat the above steps to create material properties for the insulation(k=0.1 W/m K).

ELEMENT PROPERTIESSELECTING ELEMENT TYPE:ClickPreprocessor>Element Type>Add/Edit/Delete... In the 'Element Types' window that opensclick onAdd... The following window opens:

Type 1 in the Element type reference number.Click on Thermal Solid and select Quad 8node 77. Click OK. Close the 'Element types' window.So now we have selected Element type 1 to be a thermal solid 8node element. The component willnow be modeled with thermal solid 8node elements. This finishes the selection of element type.

MESHING:DIVIDING THE WALL INTO ELEMENTS:Go to Preprocessor>Meshing>Size Controls>Manual Size>Lines>All Lines. In the menu that

comes up type 0.0025 in the field for 'Element edge length':


7/14

Click on OK. Now when you mesh the figure ANSYS will automatically create a mesh, whose elementshave an edge length of 0.0025m along the lines you selected.First we will mesh the steel area. Go to Preprocessor>Meshing>Mesh Attributes>Default

Attributes. Make sure the window indicates "Material Ref.#1". This function tells Ansys which

material is being used while you perform meshing functions. The window is shown below:

Now go to Preprocessor>Meshing>Mesh>Areas>Free. Pick the steel area and click OK.Repeat the same process for the insulation areas. Make sure you use the correct material number(number 2) for the insulation areas. Also since the steel and the insulation areas overlap make sure

you pick the right area. If you choose the wrong area, use Preprocessor>Meshing>Clear to undo


8/14

the previous mesh and then repeat the previous steps. The meshed area will look like this:

BOUNDARY CONDITIONS AND CONSTRAINTSGo to Preprocessor>Loads>Define Loads>Apply>Thermal>Convection>On Lines. Pick theleft line along the outer boundary. Click OK. The following window comes up:


9/14

Enter 200 for "Film Coefficient" and 220 for "Bulk Temperature" and click OK.Repeat the above for the right side of the wall. (VALI=20, VAL2I=300)Now the Modeling of the problem is done.

SOLUTIONGo to ANSYS Main Menu>Solution>Analysis Type>New Analysis.Select Steady State and click on OK.Go to Solution>Solve>Current LS.An error window may appear. Click OK on that window and ignore it.Wait for ANSYS to solve the problem.Click on OK and close the 'Information' window.

POST-PROCESSINGListing the results.Go to ANSYS Main Menu and click on General Postprocessing>List Results>Nodal Solution.The following window will come up:


10/14

Select DOF solution and Temperature. Click on OK. The nodal displacements will be listed asfollows:

The maximum value of temperature is given at the end of the above tableMODIFICATION

You can also plot the temperature distribution for this steady state case.Go to General Postprocessing>Plot Results>Contour Plot>Nodal Solution. The followingwindow will come up:


11/14

Select DOF solution and temperature to be plotted and click OK. The output will be like this:


12/14

For the vector plot go to Main Menu>General Postprocessing>Plot Results>Vector

Plot>Predefined. The following window comes up:


13/14

Select Flux & Gradient and Thermal flux ad click OK.The plot looks like the following picture. Notice that the maximum heat flux occurs along the steelmaterial that is horizontal and closer to the right wall.


14/14

ansys composite wall

Documents