Otto-Von-Guericke universitat Magdeburg

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ANSYS Lab. Report A thermal problem solution process in ANSYS

AHMAD GOHARI

Supervisor: Mr. Alfakheri

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ANSYS mechanical (APDL):

Introduction:

ANSYS is a general purpose finite element modeling package for numerically solving a wide variety of mechanical problems, used widely in industry to simulate the response of a physical system to structural loading, and thermal and electromagnetic effects. ANSYS uses the finite-element method to solve the underlying governing equations and the associated problem-specific boundary conditions.

ANSYS is a general purpose software, used to simulate interactions of all disciplines of physics, structural, vibration, fluid dynamics, heat transfer and electromagnetic for engineers.

So ANSYS, which enables to simulate tests or working conditions, enables to test in virtual environment before manufacturing prototypes of products. Furthermore, determining and improving weak points, computing life and foreseeing probable problems are possible by 3D simulations in virtual environment.

ANSYS software with its modular structure as seen in the table below gives an opportunity for taking only needed features. ANSYS can work integrated with other used engineering software on desktop by adding CAD and FEA connection modules.

ANSYS can import CAD data and also enables to build geometry with its "preprocessing" abilities. Similarly in the same preprocessor, finite element model (a.k.a. mesh) which is required for computation is generated. After defining loadings and carrying out analyses, results can be viewed as numerical and graphical.

ANSYS can carry out advanced engineering analyses quickly, safely and practically by its variety of contact algorithms, time based loading features and nonlinear material models.

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- Solve this problem and show the temperature gradient graphically, draw the required temperature gradient on a diagram which is showed on line A.

20c

A Tb(walls)=90c

Dimensions:1*1 h=10

T=20c 3m T=20c

Tb(walls)=90c

h=10

1m 1m 6m 20c

Heat conductivity coefficient: 10

Heat convection coefficient: 10 Bulk temperatures: 90c

Preparing Geometry (Modeling) and Meshing:

First we open Ansys application. We choose the Jobname and then location of file which we want to save our operation then press Run.

1st step: we should define our problem field. In this case choose Thermal.

The path of choosing operation field:

- Preferences> Thermal> ok

2nd step: We want to choose our element type. In this problem our Model is rectangular so we choose “ Quad 4node 55”. For rectangular models this kind of element type is better because the mesh would be 4nod meshes.

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The path of choosing element type:

- Preprocessor>element type>add-edit-delete>add>Solid> Quad nod4 55>ok>close

3rd step: Now we want to define thermal conductivity of our model.

The path of defining thermal conductivity:

Preprocessor>material property>material model>Thermal>conductivity>isotropic>KXX (Define 10 for this problem)

4th step: Now I want to create the model. There is rectangle (6*3) and there are two square holes in it.

First I create the bigger rectangle. Dimensions (6*3)

The path of creating this model is:

Preprocessor>modeling>create>area>rectangle>by two corners> (a new window would open, we should define the corner left point of rectangle and the values of width and height)

Filling out the values:

1- Wp x: 0 2- Wp y: 0 3- Width: 6 4- Height: 3

Now I want to model the small rectangles which are located on the big rectangle, we will subtract those rectangle later. We want to make holes instead of small squares.

The path of modeling is:

Preprocessor>modeling>create>area>rectangle>by two corners> (a new window would open, we should define the corner left point of rectangle and the values of width and height)

Filling out the values:

1- Wp x: 1 2- Wp y: 1 3- Width: 1 4- Height: 1

The other square:

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Preprocessor>modeling>create>area>rectangle>by two corners> (a new window would open, we should define the corner left point of rectangle and the values of width and height)

Filling out the values:

1- Wp x: 4 2- Wp y: 1 3- Width: 1 4- Height: 1

Picture no.1: Modeling

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5th step: Now I want to subtract those two small areas from the bigger rectangle.

The path is:

Preprocessor>modeling>operate>Boolean>subtract>area> (choose the bigger area)>ok> (choose the smaller areas, I mean two small squares)>ok

Picture no.2: two small squares are subtracted

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6th step: Meshing:

Ansys solve the problems with finite element method, so the model should be meshed, it means the model should become to many of small element. Now I want to mesh the model:

The path of meshing is:

Preprocessor>meshing>mesh tool>click smart size and choose the number one (it means the finite elements would be smallest automatic possible elements, the result would be more accurate with smaller mesh)>mesh>choose the area of the model>ok

Picture no.3: The model is meshed

Boundary condition and solutions:

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1st step: I want to define the boundary conditions. It contains temperatures and the convection parameter which contains (Bulk temperature and heat transfer coefficient)

I want to define the temperature of surrounding lines of rectangle.

The path is:

Solution>define loads>apply>thermal>temperature>online> (Choose the surrounding lines of big rectangle)>apply TEMP to endpoint>define the temperature 20>ok

2nd step: I want to define the condition of heat convection which is ( Heat trans. Coeff=10 , Bulk temperature= 90 centigrade)

The path is:

Solution>define loads>apply>thermal>thermal convection>online>choose the inner lines of two holes>ok> (The new window appears. Define the “Film coefficient=10” and “Bulk temperature=90”)>ok

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Picture no.4: Boundary conditions are defined

3rd Solving the problem:

Now the model and boundary conditions are ready and the model is solvable by ANSYS.

The path is:

Solution>solve>current LS>ok

4th Showing the results:

The problem is solved but the results are not appearing yet. Now I want to plot the result.

The path is:

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General postproc>plot result>contour plot>nodal solution>DOF solution>nodal temperature>ok

Picture no.5: The temperature gradient is plotted

Plot the Graph:

1st step: It’s possible to draw graphical gradient changes in ANSYS. We should define some point which shows the path of the graph. We can define the points with this command:

General postproc>path operation>define path>(by location>define the name path, for example I define it “path”)>ok>(Now a new window appear that we should define the name the point and its location(x,y,z))

The window:

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1- Path point number: 1 2- X,Y,Z location: X=3,Y=3

Define a new point:

1- Path point number: 2 2- X,Y,Z location: X=3,Y=0

ANSYS will ask for more points but we can press cancel to prevent the repetition of this window.

2nd step:

General postproc>path operation>map onto path>(define the name of path that we chose it before “path”)>ok

3rd step:

Showing the graph:

General postproc>path operation>plot path item>on graph>(choosing the name of path which here “path”)>ok

Now the graph is drawn.

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Picture no.6: themal gradient graph on line A