Mech-HT 13.0 L05 SteadyState

7/23/2019 Mech-HT 13.0 L05 SteadyState

1/18

Customer Training Material

ec ure

Stead -State

Heat Transfer

Heat Transfer

L5-1ANSYS, Inc. Proprietary

2010 ANSYS, Inc. All rights reserved.Release 13.0

December 2010


2/18

ANSYS Mechanical Heat Transfer

Customer Training MaterialChapter Contents

Steady State Heat Transfer:

A. Steady State Theory

B. Model Setu

C. Steady State ExampleD. Multiple Step Solutions

. ,



December 2010


3/18


Customer Training MaterialA. Steady State Theory

When the flow of heat does not vary with time, heat transfer is

referred to as steady-state.

Since the flow of heat does not var with time the tem erature of

the system and the thermal loads on the system also do not varywith time.

From the First Law of Thermod namics the stead -state heat

balance can be expressed simply as:

- =



December 2010


4/18


Customer Training Material. . . Steady State Theory

For steady-state heat transfer, the differential equation expressing thermal

equilibrium is:

0...

=+

+

+

qT

kT

kT

k zzyyxx

The corresponding finite element equation expressing equilibrium is:

=



December 2010


5/18


Customer Training MaterialB. Model Setup

General Notes on Thermal Loads and Boundary Conditions:

In Mechanical, model boundaries that have no applied loads are

Symmetry boundary conditions are imposed by letting theboundaries be adiabatic (exception is symmetry models using

, .

Reaction heat flow rates are available at fixed temperature DOFs,

convective boundaries and radiation regions.



December 2010


6/18


Customer Training Material. . . Model Setup

Analysis Settings:

Step Controls: control multiple steps

as wells as auto time stepping.

Nonlinear Controls: specifyconvergence criteria and control line

search solver option.

Output Control: controls content and

frequency with which results are

saved.

Analysis Data Management: general

options controlling file management

and solver units.



December 2010


7/18


Customer Training MaterialC. Steady State Example

This example presents a walk through

for a steady state analysis.

The model represents and electrical coil

composed of an iron core surrounded by

a copper coil separated by a plastic

insulator. The assembly rests on a steel

mounting plate.

We assume the coil is in operation for

sufficient time to reach a steady state.

Boundary Conditions:

The iron core generates heat at 0.001

W/mm^3.

The copper coil is experiencing forcedconvective heat loss at a rate of 0.1

W/mm^2 in a 30 C ambient environment.



December 2010

and assumed to be at a fixed 25 C.


8/18


Customer Training Material. . . Steady State Example

After specifying a Steady State Thermal analysis type, selecting the

desired geometry and adding or creating the necessary materials in

Workbench, we begin the model setup in Mechanical.

The materials are assigned in the details of each part as shown here:



December 2010


9/18



After evaluating the default mesh, several mesh controls are added to

modify element size and shape:

Note, the DesignModeler geometry was assembled as a multi-body part,

thus the mesh is continuous across parts which means no contact is

necessary.

Multi-body Part MeshDetail Showing Shared

Nodes



December 2010

RMB and Generate Mesh to

Evaluate Any Changes


10/18



The boundary conditions detailed earlier are applied to the

appropriate regions of the model:

Highlighting the Steady-State Thermal (A5) branch allows all BCs to be

displayed on a common plot.

Since the model is steady state and linear we will leave the Analysis



December 2010

ett ngs n t e r e au t con gurat on an so ve t e mo e .


11/18



When the solution is finished its good practice to

check the validity of the solution before proceeding:

By inspecting the core details we can see that the

cores volume is 44698 mm^3.

Since the heat generation load is 0.001 W/mm^3, we

can calculate the heat generation as 44.698 W.

e s ea y s a e assump on means a e

temperature and convection boundary conditions must

equal the heat input.

and dropping both boundary conditions onto the

Solution branch.

An RMB to Evaluate All Results will update the

reaction probes.



December 2010


12/18



By summing the probe results we find good

agreement:

Hgen - Rtemp - Rconv = 0

44.698 10.532 34.165 = 0.001

Having verified an energy balance we can

proceed to postprocess other results.



December 2010


13/18



Results Can BeScoped to Individual

Parts to Refine the

Solution Display for

Each

Directional Results, Heat

Temperature Plot for

All Bodies Gives a

Good Overview of the

Distribution

Flux Here, Can Be Displayed

as Vectors to Enhance the

Interpretation of Heat Flow

Throughout theAssembly



December 2010


14/18



In addition to the default results, user defined results can be

requested. These results may be combined in expressions as well.

Worksheet View for

Solution Branch

Shows User Results

Available

User Defined Result Definitions:

TEMP = temperature. ENERGY (kinetic) = N/A .

TF = thermal flux.

ENERGY (Potential) = thermal heat dissipation

energy.

TERR = thermal error energy.

HEAT = heat flow.



December 2010

VOLUME = displays the volume of all elements

attached to scoped region.

N command).


15/18


Customer Training MaterialD. Multiple Step Solutions

Multiple steady state solutions can be setup and solved sequentially

from the Analysis Settings:

The graph and table display solution points.

By changing the Current Step Number each step is configured

independently.

Note this is not a transient analysis.



December 2010


16/18


Customer Training Material. . . Multiple Step Solutions

Loads can be varied for each solution bychoosing the Current Step Number.

Example, temperature load:

ga n e grap an a e sp ay e npu

variation. Loads will ramp from the previous step:

Note: for linear anal ses sin le solution there is nodifference between ramped or step applied loads.



December 2010


17/18


Customer Training Material. . . Multiple Step Solutions

The Analysis Settings

can be set up for multiple

steps rather than one at a

time.

Worksheet view allows

review of all settings in a

sin le a e.



December 2010


18/18

Customer Training Material

or s op

Solenoid

Heat Transfer



December 2010

Mech-HT 13.0 L05 SteadyState

Documents

Transcript of Mech-HT 13.0 L05 SteadyState