Workshop 7:Thermal Steady State

Analysis of a Composite Slab

University of Puerto Rico at Mayagüez Department of Mechanical Engineering

Modified by (2008): Dr. Vijay K. GoyalAssociate Professor, Department of Mechanical EngineeringUniversity of Puerto Rico at Mayagüez

Thanks to UPRM students enrolled in INME 4058 sections 2006-08

Scope

The purpose of this workshop is to demonstrate ANSYS capabilities in solving thermal problems. For this we will solve the steady state temperature field of a composite slab with a hole using the following prescribed geometry and boundary conditions:

Geometry and Boundary Conditions

Starting ANSYS

From your desktop:

Click on: START > All Programs >

ANSYS >

ANSYS Product Launcher.

Here we will set our Working Directory and the Graphics Manager

Working Directory

This is the

10.0 ANSYS

Product Launcher

main window. Select the Working

Directory and type

the name of work

shop on Job Name.

Click the button:

Customization/Preferences.

On the item of Use custom

memory settings type 128

on Total Workspace (MB):

and type 64 on

Database (MB):

Then click the Run

bottom.

Graphics Setup

* This setup applies to computers running under 512 MB of RAM* This setup applies to computers running under 512 MB of RAM

This is ANSYS’s Graphical User Interface window.

ANSYS GUI Overview

GUI Filtering

In order to maximize your workspace to meet your needs. Let’s filter out the GUI (Graphical User Interphase). Click on Preferences > Choose on GUI Filtering:

Thermal > OK.

GUI Filtering

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Element Definition

For ANSYS to properly analyze the problem, we must choose well the appropriate element. We will choose Element Type Quad 4node 55:

Element Definition

Element Type:

1. On Main Menu window, click Preprocessor > Element Type > Add/Edit/Delete

2. Click Add… on The Element Types Window

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Element Definition

3. On the Library of Element Type window select Quad 4node 55 > click OK > click Close on the Element Type window

plane55 will produce either quadrilateral or triangular elements for thermal analysis

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Material Properties

Now lets assign the thermal conductivity (k) for the two materials of this problem: Material 1 – KXX = 20 Material 2 – KXX = 50

Material Properties

1. On the Main Menu Window select Preprocessor > Material Props > Material Model.

2. On the Material Model Behavior window select Material Model Number 1 > Thermal > Conductivity > Isotropic

3. On the Conductivity for Material Number 1 enter 20 for Thermal Conductivity KXX > click OK

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Material Properties

4. To add a second material: Click on the tab: Material > New Model > Define Material ID insert 2.

Material Properties

Click on: Thermal > Conductivity > Isotropic > then on KXX insert the thermal conductivity of the second material (KXX = 50) > OK and close the Material window.

Geometry

The strategy to produce the geometry is to create two rectangles (material 1 & 2) and remove a hole from the material 1

Geometry

1. To create first rectangle, on the Main Menu Window select Preprocessor > Modeling > Create > Areas > Rectangle > By 2 Corners

2. On the Rectangle by 2 corners window enter WP X = 0 > WP Y = 0 > Width = 0.05 > Height = 0.05 > Click Apply

Note that all dimensions were converted to meters

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Geometry

3. To create the second rectangle repeat the process 2, using the following values:

WP X = .05

WP Y = 0

Width = .1

Height = .05

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Geometry

4. To create the circle, on the Main Menu Window select Preprocessor > Modeling > Create > Areas > Circle > Solid Circle

5. On the Solid Circular Area Window enter WP X = .025 > WP Y = .025 > Radius = .01 > Click OK

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Geometry

6. To create the hole select Preprocessor > Modeling > Operate > Booleans > Subtract > Areas

7. Click on the left rectangle > Click Ok on the Subtract Areas window

8. Click on the circle > Click OK again on the Subtract Areas window

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Geometry

9. To join the two rectangles, select Preprocessing > Modeling > Operate > Booleans > Glue > Area

10. On the Glue Areas window select Pick All \ OK

Now ANSYS know that the two rectangles are in contact, and make one big composite slab.

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Meshing

To make the finite element analysis we must first divide the object into small elements, this is called meshing.

Meshing

1. On the Main Menu window, select Preprocessor > Meshing > Mesh Tool

2. On the Mesh Tool window Click on Smart Size > Select 5 > Select Mesh: Areas > Click on Set under Element Attributes

3. On the Meshing Attributes Window select Element Type number: 1 Plane 55 > Material number: 1 > click OK > Mesh > Click on the left rectangle

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Meshing

4. A screen like this will appear.

To view the two rectangles again go to Plot \ Areas

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Meshing

5. Repeat steps 1 through 3 selecting Material Number: 2 on the Meshing Attributes Window and Clicking on the right rectangle after selecting Mesh.

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Meshing

6. To see the mesh go to PlotCtrls \ Numbering

7. On the Plot Numbering Controls Window got to Elem/Attrib numbering \ select Material numbers \ Click OK

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This should give you a color plot showing the areas and elements. Each element contains a number which refers to the material numbers we just set for each piece. The different material types are also denoted by the different colors.

Boundary Conditions

Now we will apply the given boundary conditions for each side of the slab. Left Wall @ T = 200 Right Wall @ T = 50 Lower Wall is adiabatic Upper Wall has a h = 150 @ T = 25 Hole has a flux of q = 100

Boundary Conditions (Temperature)

1. On ANSYS Main Menu Window select Preprocessing > Loads > Define Loads > Apply > Thermal > Temperatures > On Nodes

2. On the Apply TEMP on Nodes window Click on Box and draw a box around the left edge of the model to pick these nodes.

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Boundary Conditions (Temperature)

3. On the New Apply TEMP on Nodes window select DOFs to be constrained: Temp \ Apply as: Constant value \ Load Temp Value: 200

4. Repeat above procedure to apply the temperature boundary condition on the right boundary with a temperature of 50.

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Boundary Conditions (HT Coefficient)

1. On ANSYS Main Menu Window select Preprocessing > Loads > Define Loads > Apply > Thermal > Convection > On Nodes

2. On the Apply CONV on Nodes window Click on Box and draw a box around the top edge of the model to pick the nodes along the top edge.

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Boundary Conditions (HT Coefficient)

3. On the New Apply CONV on Nodes window select VALI Film coefficient\ enter h of 150 \ VAL2I Bulk Temperature \ 25 \ Click OK

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Boundary Conditions (Heat Flux)

1. On ANSYS Main Menu Window select Preprocessing > Loads > Define Loads > Apply > Thermal > Heat Flux > On Nodes

2. On the Apply HFLUX on Nodes window Click on Circle and draw a circle that catches the nodes around the hole.

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Boundary Conditions (Heat Flux)

3. On the New Apply HFLUX on Nodes window select VALUE Load HFLUX value\ enter 100 \ Click OK

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Note: All geometry boundaries are adiabatic by default in ANSYS. So if you wish to apply symmetry or zero heat flux boundary conditions at any face of your model you have to do nothing to that face. We do not do any thing to the bottom edge of our model because it is an adiabatic surface by default.

Display Settings

4. To see the boundary conditions on the model go to PlotCtrls \ Symbols

5. On Symbols windows go to Surface Load Symbols\ select Convect FilmCoef \ Show pres and convect as \ select Arrows \ Click OK

6. Repeat step 5 selecting Heat Flux instead of Convect FilmCoef

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FEM Solution

We are ready to start with the finite element analysis and obtain the temperature distribution across the slab.

FEM Solution

1. On ANSYS Main Menu window select Solution > Solve > Current LS

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Temperature Distribution

1. On ANSYS Main Menu Window select General Postproc > Plot Results > Vector Plot > Predefined

2. On the Vector Plot of Predefined Vectors window Click OK

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