Workshop 5

Fin Tube Heat Exchanger

WS 5-1ANSYS, Inc. Proprietary© 2009 ANSYS, Inc. All rights reserved.

August 2009Inventory #002667

ANSYS Mechanical Heat Transfer

Workshop 5 - Fin Tube Heat Exchanger

Training ManualProblem Description

• An aluminum section of fin and tube heat exchanger is to beanalyzed. Since the model represents an axially symmetric s tructure,a 90 section will be modeled.

• The tube carries a hot fluid while the exterior surfaces expe rience aconvective condition.

• It has been determined that the fluid causes a wall temperatu re of 200C at the entrance and 150 C wall temperature at the exit. We wil l usea function load to apply this temperature

WS 5-2ANSYS, Inc. Proprietary© 2009 ANSYS, Inc. All rights reserved.

August 2009Inventory #002667

a function load to apply this temperature

Workshop 5 - Fin Tube Heat Exchanger

Training ManualUnits Setup

• Open Workbench and specify the unit system (Metric, kg, mm, s, ºC, mA, N, mV).

• Choose to “Display Values in Project Units”.

WS 5-3ANSYS, Inc. Proprietary© 2009 ANSYS, Inc. All rights reserved.

August 2009Inventory #002667

Workshop 5 - Fin Tube Heat Exchanger

Training ManualModel Setup

1. From the Workbench project page toolbox, select a Steady State Thermal analysis system.

WS 5-4ANSYS, Inc. Proprietary© 2009 ANSYS, Inc. All rights reserved.

August 2009Inventory #002667

2. Right click the Geometry cell and import geometry “Fin_Tube_WS5.x_t”.

3. Double click the Engineering Data cell.

Workshop 5 - Fin Tube Heat Exchanger

Training ManualModel Setup

4. Highlight the General Materials library and add “Aluminum Alloy” to the current project.

WS 5-5ANSYS, Inc. Proprietary© 2009 ANSYS, Inc. All rights reserved.

August 2009Inventory #002667

5. Double click the Model cell to open the Mechanical application.

Workshop 5 - Fin Tube Heat Exchanger

Training ManualPreprocessing

6. Expand the Model branch and highlight the part “FinTube”.

7. In the details change the material assignment to “Aluminum Alloy”.

WS 5-6ANSYS, Inc. Proprietary© 2009 ANSYS, Inc. All rights reserved.

August 2009Inventory #002667

• A check in engineering data will confirm the aluminum’s thermal conductivity property is temperature dependent.

Workshop 5 - Fin Tube Heat Exchanger

Training ManualPreprocessing

8. Highlight the mesh branch.

9. Select the 2 symmetry faces, RMB > Insert > Sizing.

WS 5-7ANSYS, Inc. Proprietary© 2009 ANSYS, Inc. All rights reserved.

August 2009Inventory #002667

10.Set “Element Size” to 2 mm.

11.Highlight the mesh branch, RMB > Generate Mesh.

Workshop 5 - Fin Tube Heat Exchanger

Training ManualPreprocessing

• When complete, inspect the resulting mesh.– Note, if desired you may mesh without the size contr ol for comparison.

The default mesh is quite coarse for this model.

WS 5-8ANSYS, Inc. Proprietary© 2009 ANSYS, Inc. All rights reserved.

August 2009Inventory #002667

Default MeshSize Controlled Mesh

Workshop 5 - Fin Tube Heat Exchanger

Training ManualPreprocessing

12.Highlight the “Steady State Thermal” branch.

13.Highlight the interior wall of the tube section, RMB > Insert > Temperature.

14. In the details for the temperature

WS 5-9ANSYS, Inc. Proprietary© 2009 ANSYS, Inc. All rights reserved.

August 2009Inventory #002667

14. In the details for the temperature load change the magnitude field from “Constant” to “Function.

15.Enter the function in the magnitude field:1. 200 – 0.25*y

16.Specify a range from 0 to 200

Workshop 5 - Fin Tube Heat Exchanger

Training ManualPreprocessing

• Make sure surface select mode is active.17. In the graphics window, RMB > Select All.18.Use the control key and unselect the interior, ends

and symmetry faces of the fin tube model (5 faces in all).– When finished you should have 33 faces selected.

WS 5-10ANSYS, Inc. Proprietary© 2009 ANSYS, Inc. All rights reserved.

August 2009Inventory #002667

19.RMB > Insert > Convection.

• Continued . . .

Workshop 5 - Fin Tube Heat Exchanger

Training ManualPreprocessing

20.Change the magnitude field to “Tabular” (Temperature).

21.Enter Ambient Temperature = 30 ºC22.Enter the coefficient values shown in the

convection table.

Temperature ºC H (W/mm 2*ºC)

WS 5-11ANSYS, Inc. Proprietary© 2009 ANSYS, Inc. All rights reserved.

August 2009Inventory #002667

Temperature ºC H (W/mm *ºC)

0 0.004

10 0.0054

20 0.006

40 0.0066

60 0.007

100 0.0077

Convection Coefficient h(T)

Workshop 5 - Fin Tube Heat Exchanger

Training ManualSolution

23.Solve:– Although there are temperature dependent materials and boundary

conditions, the output shows that the solution conv erges quickly (2 iterations).

24.Highlight the Temperature and Convection loads and drag and drop

WS 5-12ANSYS, Inc. Proprietary© 2009 ANSYS, Inc. All rights reserved.

August 2009Inventory #002667

24.Highlight the Temperature and Convection loads and drag and drop them into the Solution branch:– This is a shortcut to setting up reaction probes fo r boundary conditions.

25.Evaluate All Results.

• A check of reactions shows good agreement between input and output heat.

Workshop 5 - Fin Tube Heat Exchanger

Training ManualPostprocessing

26. Insert a temperature result and evaluate. Note the temperature variation along the Y direction.

WS 5-13ANSYS, Inc. Proprietary© 2009 ANSYS, Inc. All rights reserved.

August 2009Inventory #002667