transient thermal analysis of power electronics

Chapter 45: Transient Thermal Analysis of Power Electronics

45 Transient Thermal Analysis of Power Electronics

Summary 856

Introduction 857

Modeling Details 857

Solution Highlights 857

Results 860

Modeling Tips 864

Pre- and Postprocess with SimXpert 865

Input File(s) 919

Video 919

MD Demonstration Problems

CHAPTER 45856

SummaryTitle Chapter 45: Transient Thermal Analysis of Power Electronics

Features Transient thermal analysis using CHEXA elements

Geometry

Material properties

Analysis characteristics Nonlinear transient thermal analysis

Boundary conditions All material is initially at 25oC then a heat flux is applied on top surface of the copper chip for 10 seconds.

Element type 8-node CHEXA

FE results Temperature contours at t = 10 seconds.

Copper

Aluminum

Y

XZ

10 X 10 X 8

1.295 X 1.295 X 0.2

Units: mm, g, sec, C

Flux 1.4907 W/mm2

(0 to 10 seconds)

kCu 0.386W mm K– = kAl 0.204W mm K– =

CpCu 0.383J g K– = CpAl 0.896J g K– =

857CHAPTER 45

Transient Thermal Analysis of Power Electronics

IntroductionThis problem demonstrates the transient thermal capability of SOL 400 in solving a short duration heating on a chip through a copper tab attached to an aluminum backing.

Modeling Details

Figure 45-1 Chip Analysis (Nastran Test File: chip1.dat)

In many applications, the power dissipation inside integrated circuits is transient in nature. The device maybe turned on for 10 seconds or less. The above model (Figure 45-1) consists of D2pak copper tab mounted on the aluminum heat sink. Due to the symmetry, only a quarter of the model is meshed.

Solution HighlightsThe following are highlights of the Nastran input file necessary to model this problem:

$! NASTRAN Control SectionNASTRAN SYSTEM(316)=19$! File Management Section$! Executive Control SectionSOL 400CENDECHO = SORT$! Case Control SectionIC = 13SUBCASE 1$! Subcase name : NewLoadcase$LBCSET SUBCASE1 DefaultLbcSet THERMAL(SORT1,PRINT)=ALL FLUX(PRINT)=ALL ANALYSIS = HTRAN SPC = 15

Copper

Aluminum

Y

XZ

10 X 10 X 8

1.295 X 1.295 X 0.2

Units: mm, g, sec, C

Flux 1.4907 W/mm2

(0 to 10 seconds)


CHAPTER 45858

DLOAD = 16 NLSTEP = 1BEGIN BULK$! Bulk Data Pre SectionPARAM* SIGMA 1.7140E-9PARAM POST 1$! Bulk Data Model SectionPARAM PRGPST NO MAT4 1 0.386 0.383 0.00895 CuMAT4 2 0.204 0.896 0.00271 AlPSOLID 1 1 PSOLID_1PSOLID 2 2 PSOLID_2

$ CHBDYG Surface ElementsCHEXA 126 1 17 18 1 19 179 181+ + 147 183CHEXA 127 1 179 181 147 183 180 182+ + 148 184CHEXA 128 1 18 20 2 1 181 185+ + 149 147CHEXA 129 1 181 185 149 147 182 186+ + 150 148$ Loads for Load Case : tranTABLED1 1 LINEAR LINEAR + + 0.0 1. 10. 1. 10.1 0.0 100. 0.0+ + ENDT$!TLOAD1 1 2 1QBDY3 2 1.5 0 2176CHBDYG 2176 AREA4 148 150 158 156$ Dynamic Load Table : flux_timeTABLED1 1 0. 1. 10. 1. 10.2 0. 20. 0. 100. 0. ENDT$ Default Initial TemperatureTEMPD 13 25.DLOAD 16 1. 1. 1NLSTEP 1 12. + + GENERAL -10 0 5 + + FIXED 600 5 + + HEAT UPW 0.01 0.01 0.01ITER 2 + + 10 2 0.2

The transient thermal analysis is indicated by ANALY=HTRAN. The IC option in the case control section points to the initial temperature of the model. In this case, The IC=1 points to the TEMPD in the bulk data section, and the initial

temperature is set at 25 oC. The DLOAD bulk data in the case control either points to the DLOAD in the bulk data with same ID.

Furthermore, the DLOAD in the bulk data section can then point to the multiple load set ID that refers to either TLOAD1, which called a time dependent table TABLED1 or TLOAD2 which has built in function such as unit step, sine, or cosine functions.

859CHAPTER 45


TABLED1 1 LINEAR LINEAR + + 0.0 1. 10. 1. 10.1 0.0 100. 0.0+ + ENDTTLOAD1 1 2 1QBDY3 2 1.5 0 2176CHBDYG 2176 AREA4 148 150 158 156DLOAD 16 1. 1. 1

Field 3 on the TLOAD1 record has an integer value of 2 which points to a transient heat load of QBDY3 with this same set ID. In the field 6 of the TLAOD1 is the ID of time-dependent table of this heat flux. We see that the heat load is 1.0 from time equals to 0 to 10 seconds and, at 10.2 seconds, we shut this heat load back to zero.

Solution ProcedureThe nonlinear procedure used is defined through the NLSTEP entry:

NLSTEP 1 12. + + GENERAL -10 0 5 + + FIXED 600 5 + + HEAT UPW 0.01 0.01 0.01ITER 2 + + 10 2 0.2

We are running a total 600 time steps with equal steps of 0.02 seconds and output the temperature at every 5th step. This means that the temperature will then be output at 0.1, 0.2, and 0.3 seconds, respectively. Also we can use the Method called FIXED and the convergence is set on the error on temperature (U) with 0.01 as the error tolerance. Grid point 195 is the fastest responding in the copper tab; it is also used in subsequent graphs to illustrate how fast the chip heats up and cools down.

Figure 45-2 Early Temperature History of Grid Point 195


CHAPTER 45860

Results

Figure 45-3 Temperature Contours at 5 Seconds

Figure 45-4 Temperature History Past 10 Seconds

Suppose that the user decided to add a fan to increase the cooling on top. To simulate this, we will apply convection boundary condition on the top surface where the convection coefficient is a function of time and the ambient

temperature is also at 25oC. We can then compare this run against the previous run that has no convection. Convection

is applied as a heat transfer coefficient of . The temperature contours at 5 seconds are shown in Figure 45-5.

H 0.02W mm2

C– =

861CHAPTER 45


Figure 45-5 Temperature Contours at 5 Seconds

Another comparison between the two models is shown in Figure 45-6, where the influence of the cooling is very obvious with the entire model returning to the initial conditions after about 20 seconds.

Figure 45-6 Temperature Histories With and Without Cooling

By applying the convection on the top surface, the temperature of the chip is now cooled from 40.3 to 33.2oC. In this run we have a total of three time dependent boundary conditions. The DLOAD in the bulk data section (Nastran test file Chip_spcd1.dat) points to multiple TLOAD1 options as shown in the table below.

Boundary Conditions TLOAD1 ID SPCD/DAREA

Grid (enforced temperature as a function of time) TABLED1 (ID)

H(time) 2 5 2556 2

Heat flux(time) 1 3 1

Tambient(time) 6 8 2555 3


CHAPTER 45862

The SPCD is used only on enforced temperature as a function of time.

TLOAD1 1 3 1TLOAD1 2 5 1 3TLOAD1 6 8 1 2

TABLED1 1 LINEAR LINEAR + + 0.0 1. 10. 1. 10.1 1. 100. 1.+ + ENDTTABLED1 2 LINEAR LINEAR + + -10. 0.02 0.0 0.02 5. 0.02 10. 0.02+ + 20. 0.02 ENDTTABLED1 3 LINEAR LINEAR + + 0.0 1. 100. 1. ENDT$!PCONV 4 3 0 0.0MAT4 3 1.SPOINT 2555SPCD 5 2555 25.SPC1 4 2555TEMP 21 2555 25.$!SPOINT 2556SPCD 8 2556 1.0SPC1 7 2556TEMP 21 2556 0.02QBDY3 3 1.5 0 2176CHBDYG 2176 AREA4 148 150 158 156

TEMPD 21 25.SPCADD 23 4 7DLOAD 24 1. 1. 1 1. 2 1. 6NLSTEP 1 12. + + GENERAL -10 0 5 + + FIXED 600 5 + + HEAT UPW 0.01 0.01 0.01ITER 2 + + 10 2 0.2

SPOINT 2555 indicates the ambient temperature for the convection, while SPOINT 2556 represents the variation of convection coefficient with time.

863CHAPTER 45


Specifies a free convection boundary condition for heat transfer analysis through connection to a surface element (CHBDYi entry).

Format:

Example:

$ Convection to Ambient of Load Set : htimePCONV 4 3 0 0.0MAT4 3 1.SPOINT 2555SPCD 5 2555 25.SPC1 4 2555TEMP 21 2555 25.

SPOINT 2556SPCD 8 2556 1.0SPC1 7 2556TEMP 21 2556 0.02

CONV 2201 4 2556 2555CHBDYG 2201 AREA4 17 18 37 73

CONV Heat Boundary Element Free Convection Entry

1 2 3 4 5 6 7 8 9 10

CONV EID PCONID FLMND CNTRLND TA1 TA2 TA3 TA4

TA5 TA6 TA7 TA8

1 2 3 4 5 6 7 8 9 10

CONV 2 101 3 201 301

Field Contents Type Default

EID CHBDYG, CHBDYE, or CHBDYP surface element identification number.

I > 0

PCONID Convection property identification number of a PCONV entry.

I > 0

FLMND Point for film convection fluid property temperature.

I > 0 0

CNTRLND Control point for free convection boundary condition.

I > 0 0

TAi Ambient points used for convection. I > 0 for TA1I > 0 for TA2 through TA8

TA1 for TA2 through TA8


CHAPTER 45864

The SPOINT 2556 is on the field 5 (CNTRLND) on the CONV, and the SPOINT 2555 is on the field 6 (TA1). The field 6 on the MAT4 option is the convection coefficient times the tabeld1 ID 2 where this a function of time. At time equal to zero, the value is equal to 0.02, and time equal to 10 seconds, the value is 0.03.

For SPOINT 2556, we used SPCD and SPC1 to specify enforced temperature as a function of time. The value of 1.0 that specified on the field 5 on the SPCD bulk data entry actually is a scale multiplier to the TABLED1 ID 2 that it refers to.

The ambient temperature is constant at 25oC, but we could make it time dependent as well. It is important that for any enforced temperature as a function of time or any use of a control node in RADBC or CONV bulk data entries, that a value of 1 is specified on field 5 on the TLOAD1 or TLOAD2 entry to indicate that this refers to the SPCD.

Modeling TipsThe transient thermal analysis involved a lot more data compared to a steady state thermal analysis since every time step requires a temperature distribution. It is sensible to monitor those nodes that handle the time-dependent boundary conditions. In this case, the convection coefficient as a function of time is applied to SPOINT 2556 which, when plotted as a graph in SimX, should behave as described by the input. The other point of interest is where the heat load is applied.

Adaptive time stepping facilitates capturing transient thermal behavior more precisely than uniform stepping, because the length of each time step changes based upon changes in temperature. To invoke adaptive time stepping requires the nonlinear procedure defined through the NLSTEP entry:

NLSTEP,6,12.0,GENERAL,10,1,10,ADAPT,0.001,1.0E-5,0.5,HEAT,U,1.0E-6,1.0E-6,1.0E-6,AUTO

and a backward Euler thermal operator with the NDAMP parameter:

PARAM,NDAMP,0.5

This will run for a total time period of 12 seconds with an initial time step of 12/1000. The minimum time step is 12*1e-5; the convergence is set to U and is at 1e-6. The allowable range of the NDAMP parameter is -2.414 to 0.414, and any NDAMP value that violates this range is reset to the closest allowable value. Here it triggers the backward Euler operator. (NDAMP = 0 would be the Crank-Nicholson operator). The adaptive time stepping would avoid the small oscillation seen in Figure 45-4 since the backward Euler operator is both stable and immune to oscillations. The input files nug_45c.dat and nug_45d.dat use this operator.

http://www.mscsoftware.com/doc/nastran/mdug/input_files/ch045/nug_45c.dat

http://www.mscsoftware.com/doc/nastran/mdug/input_files/ch045/nug_45d.dat

865CHAPTER 45


Pre- and Postprocess with SimXpert

Run SimXpert with Structures Workspace

a. For the Default Workspace, select Structures

a


CHAPTER 45866

Specify the Model Units

a. Tools: Options

b. Observe the User Options Window

c. Select Units Manager

d. For Basic Units, specify the model units

e. Length = mm; Mass = g; Time = s; Temperature = celsius, Force = N

f. Click OK

a b

c e

d

867CHAPTER 45


Create a Surface with a 45° Angle

a. Create two straight curves

b. Geometry tab: Curve/Curve

c. For X,Y,Z Coordinate, enter 1.295, 0, 0; click OK

d. For X, Y, X Coordinate enter 1.295, 1.295, 0; click OK

e. Click Apply

f. For X,Y,Z Coordinate, enter 10, 0, 0; click OK (not shown)

g. For X,Y,Z Coordinate, enter 10, 10, 0; click OK (not shown)

f. Click Apply

e

b

c d

f


CHAPTER 45868

Create a Surface with a 45° Angle (continued)

a. Create two straight curves

b. Geometry tab: Surface/Filler

c. For Curves screen, select 2 curves

d. Click OK

b

c

d

c

869CHAPTER 45


Mesh the Surface

a. Create mesh seeds on the four curves of the surface

b. Meshing tab: Automesh/Seed

c. For Curves screen, select the shortest curve and the opposite curve

d. Select Number of Elements, enter 5; click OK

e. Do this for the lower-right curve, using One Way Bias

f. Select Number of Elements and L2/L1

g. For Number of Elements, enter 10

h. For L2/L1, enter 5; click OK

i. Do this for the last curve, using One Way Bias (not shown)

j. Select Number of Elements and L2/L1 (not shown)

k. For Number of Elements, enter 10

l. For L2/L1, enter 0.2; click OK (1/5) (not shown)

b c

d

e

fg

h

c

f

i


CHAPTER 45870

Mesh the Surface (continued)

a. Create mesh seeds on the four curves of the surface

b. Meshing tab: Automesh/Surface

c. For Surfaces to mesh screen, select the surface

d. For Mesh type, select Quad Dominant

e. For Mesh method, select Mapped

f. Click OK

b

c

de

f

c

871CHAPTER 45


Reflect the Part

a. Reflect (mirror) the Part (surface and its mesh)

b. Tools: Transform/Reflect

c. To define a plane to reflect about, create a node at the origin (0,0,0) and one above it (0,0,10)

d. Nodes/Elements tab: Create/Node

e. For X,Y,Z Coordinate, enter 0,0,0; click OK

f. For X,Y,Z Coordinate, enter 0,0,10; click OK (not shown)

g. Click OK

d

e

g


CHAPTER 45872

Reflect the Part (continued)


b. Tools: Transform/Reflect

c. For Plane, select Any Plane

d. Select Make Copy

e. Select Nodes

f. Select the node at the origin

g. Select the node at the tip of the surface (interior angle is 45°)

h. Select the node that is above the origin

dc

e

b

f

g

h

873CHAPTER 45


Reflect the Part (continued)


b. From Reflect - Any Plane pick panel, select Parts

c. Screen select the Part

d. Click Done; then click Exit

d

b c


CHAPTER 45874

Create a Square Surface to be Congruent at Lower-left

a. Create a square surface at the lower-left corner of the Part

b. Geometry tab: Curve/Curve

c. For Entities screen, select the node at the origin and the node to its right

d. Click OK

b

c c

d

875CHAPTER 45


Create a Square Surface to be Congruent at Lower-left (continued)


b. Geometry tab: Surface/Filler

c. For Curves screen, select the curve just created and the curve just above it

d. Click OK

b

c c

d


CHAPTER 45876

Mesh the Square Surface at Lower-left


b. Meshing tab: Automesh/Surface

c. For Surfaces to mesh screen, select the square surface just created

d. Click OK

b

c

d

c

877CHAPTER 45


Connect the Adjacent Elements (continued)

a. Connect the adjacent elements using equivalence

b. Nodes/Elements tab: Modify/Equivalence

c. Set geometry to wireframe (not shown)

d. Tools: Identify to display the node labels (not shown)

e. For Entities screen, select all the nodes

f. For Merging tolerance, enter 0.05

g. Click OK

b

e

f

e

g


CHAPTER 45878

Connect the Adjacent Elements (continued)

a. Connect the adjacent elements using equivalence

b. Click OK

c. View: Clear Labels (not shown)

d. Tools: Identify (not shown)

e. For Identify Entities pick panel, select Nodes (not shown)

f. Click All (not shown)

g. Click Exit (not shown)

h. Observe only one node label

i. View: Clear Labels (not shown)

b h

879CHAPTER 45


Sweep 2-D Elements to Create 3-D Elements

a. Create 3-D elements by sweeping the 2-D elements

b. Meshing tab: FEM based/Normal

c. For Shell Elements screen, select all the elements

d. For Distances, enter -8

e. For Layers, enter 8

f. Click OK

c

b

c

f

ed


CHAPTER 45880

Sweep 2-D Elements to Create 3-D Elements (continued)


b. Model Views: Isometric View

c. Observe the 3-D elements

b c

881CHAPTER 45


Create 3-D Elements for Applying Heat Flux

a. Create 2-D elements at the location where they are needed

b. View > Entity Display Filter: Show/Hide 3D FE

c. Tools: Transform/Translate (not shown)

d. For Translate XYZ, enter 0, 0, 8

e. Select Make Copy

f. Select Elements

g. Model Views: Top

h. Screen select the 2-D elements for the square surface

i. Select Done

j. Model Views: Isometric View

b

d

e

f

g

h

i

j


CHAPTER 45882

Create 3-D Elements for Applying Heat Flux (continued)


b. Observe the new 2-D mesh that is to be sued to create the 3-D elements for the application region for

the heat flux

c. Rotate model as needed

b

883CHAPTER 45



a. Create 2-D elements at the location where they are needed

b. Meshing tab: FEM based/Normal

c. For the Shell Elements screen, select the 2-D elements that were just created

d. For Distances, enter -0.2

e. For Layers, enter 2

f. Click OK

g. Model Views: Isometric View (not shown)

h. Render:FE Shades with Edges (not shown)

b

f

ed

c c


CHAPTER 45884



b. Observe the 3-D meshes

b

885CHAPTER 45


Delete All 2-D Elements

a. Eliminate all 2-D Elements for the model

b. Edit: Delete

c. From the Delete pick panel, select Elements

d. Select Advanced

e. From the Extended Pick Dialog, select CQUAD4

f. Select the entire model

g. Click Done

h. In the Delete window, click Yes

i. Click Exit

b

c

i

h

g

ed

f


CHAPTER 45886

Connect All 3-D Elements

a. By using equivalence, all 3-D elements can be connected

b. Modes/Elements: Modify/Equivalence

c. For Entities screen, select the entire model

d. For Merging tolerance, enter 0.5

e. Click OK

f. Click OK

b

c

e

d

f

887CHAPTER 45


Material Properties

a. Design material properties for Copper and Aluminum

b. Materials and Properties tab: Material/Isotropic

c. For Name, enter Copper

d. For Young’s Modulus, enter 210

e. For Poisson’s Ratio, enter 0.28

f. For Thermal Conductivity, enter 0.386

g. For Specific Heat, enter 0.383

h. For Thermal Density, enter 0.00895

i. Click OK

i

c

e

d

fgh

b


CHAPTER 45888

Material Properties (continued)

a. Design material properties for Copper and Aluminum

b. Materials and Properties tab: Material/Isotropic

c. For Name, enter Aluminum

d. For Young’s Modulus, enter 210

e. For Poisson’s Ratio, enter 0.28

f. For Thermal Conductivity, enter 0.204

g. For Specific Heat, enter 0.896

h. For Thermal Density, enter 0.00271

i. Click OK

i

c

ed

fgh

b

889CHAPTER 45


Element Properties

a. Define element properties for Copper and Aluminum parts of the model

b. Materials and Properties tab: 3D Properties/Solid

c. For Name, enter SOLID_Copper

d. For Entities screen, select the solid elements that are to represent the Copper

e. under Material on the Model Browser tree, select Copper

f. Click OK

c

ed

f

b

d

e


CHAPTER 45890

Element Properties (continued)

a. Define element properties for Copper and Aluminum parts of the model

b. Materials and Properties tab: 3D Properties/Solid

c. For Name, enter SOLID_Aluminum

d. For Entities screen, select the solid elements that are to represent the Aluminum

e. Under Material on the Model Browser tree, select Aluminum

f. Click OK

c

ed

f

b

d

e

891CHAPTER 45


Define Time Dependent Heat Flux on Copper Chip

a. To define the time dependent heat flux that is to be normal to the Copper chip, first define the time

dependent function for the heat flux

b. Fields/Tables tab: Tables/NastranBDF/Tabled1

c. For Name, enter TABLE_1

d. For X and Y values, enter the values shown below

e. Click OK

c

e

d

b


CHAPTER 45892

Define Time Dependent Heat Flux on Copper Chip (continued)

a. Define the time dependent heat flux that is to be normal to the Copper chip

b. LBCs tab: Heat Transfer/Normal Flux

c. For Name, enter Normal_Flux_Copper_Chip

d. For Entities screen, select the nodes at the top of the chip

e. For Heat Flux, enter 1.4907

f. Under Flux vs Time scaling function on the Model Browser tree, select TABLE_1

g. Click OK

c

g

d

b

def

893CHAPTER 45


Define Time Dependent Heat Flux on Copper Chip (continued)

a. Define the time dependent heat flux that is to be normal to the Copper chip

b. Observe the model with the applied heat flux

b


CHAPTER 45894

Create a SimXpert Analysis File

a. Create a SimXpert analysis file for performing an MD Nastran analysis

b. Right click on FileSet, and select Create new Nastran job

c. For Job Name, enter a title

d. For Solution Type, select SOL400

e. For Solver Input File, select the path

f. Unselect Create Default Layout

g. Click OK

b

g

fe

d

c

895CHAPTER 45


Create a SimXpert Analysis File (continued)


b. Right click on Load Cases and select Create Loadcase

c. For Name (title), enter NewLoadcase

d. For Analysis Type, select Nonlinear Transient Heat Trans

e. Click OK

b

e

d

c


CHAPTER 45896



b. Right click on Loads/Boundaries and select Select Lbc Set

c. For Selected Lbc Set, enter DefaultLbcSet; click OK

d. Under LBC Set in the Model Browser, double click on DefaultLbcSet to observe the lbcs

that are assigned

e. Click Cancel

b

d

c

e

897CHAPTER 45




b. Under Simulations, transient analy power... in the Model Browser, double click on Solver Control

c. Select Solution 400 Nonlinear Parameters

d. For Default Init Temperature, enter 25; click Apply

e. Select Output File Properties

f. For Test Output, select Print

g. Click Apply

h. Click Close

2009 MSC.Software Corporationb

e

d

c

f

g

h


CHAPTER 45898



b. Under Simulations, transient_analy_power... NewLoadcase in the Model Browser, double click on

Loadcase Control

c. Select Subcase Transient Heat Transfer Parameters

d. For Initial Time Step, enter 0.02

e. For Number of Time Steps, enter 600

f. Click on Temperature Error

g. For Temperature Tol., select 0.01

h. Click Apply (not shown)

i. Click Close (not shown)

.

.

b

f

dc

g

e

899CHAPTER 45



a. Create a SimXpert analysis fole for performing an MD Nastran analysis

b. Under Simulations, transient_analy_power...,Load Cases, NewLoadcase in the Model Browser,

right click on Output Requests

c. Select Nodal Output Requests

d. Select Create Temperature Output Request

e. Click on Suppress Print

f. For Sorting., select By Frequency/Time

g. Click OK

b

f

d

c

g

e


CHAPTER 45900

Run a SimXpert Analysis

a. Perform a SimXpert thermal analysis

b. Under Simulations in the Model Browser, right click on transient analy power elect

c. Select Run

b

c

901CHAPTER 45


Attach the SimXpert Analysis Results File

a. Attach the SimXpert result file

b. Click on Attach Results

c. For File path, select the results file transient_analy_power_elect.xdb

d. Click OK

b

c

d


CHAPTER 45902

Display a Chart of Temperature Results

a. Display the thermal results for all the times

b. Results tab: Results/Chart

c. For Results Cases., select the results for all the times

d. For Results Type, select Temperatures

e. For Target Type, select Nodes

f. Pick Filters: Accumulate Mode

b

c

d e

f

903CHAPTER 45


Display a Chart of Temperature Results (continued)


b. Select two nodes; e.g., Node 1522 and Node 67

c. For Independent axis., select Time

d. Click Add Curves

bc

d

b

b


CHAPTER 45904



b. Observe the temperature results

b

905CHAPTER 45


Define Free Convection off Heat Storage Body

a. Define free convection off top of model

b. LBCs tab: Heat Transfer/Free Convection

c. For Name, enter Free Convection_Al_Body

d. For Ambient Temperature, enter 25

e. To make picking easier, hide the lbc Normal Flux_Copper_Chip (not shown)

f. For Entities screen, select the nodes at the top of the Aluminum body. Make sure to select

the node at the corner

g. DO NOT CLICK OK

. c

d

b

f

f f


CHAPTER 45906

Define Free Convection off Heat Storage Body (continued)


b. Change the picking to Pick Filters: Accumulate Mode

c. Change to different view using Model Views: Front (not shown)

d. For Entities screen, select the remaining nodes at the top of the Aluminum body

e. Click on Advanced

f. For Convection coefficient, enter 0.02

g. Click OK

e

b

dd

f

g

907CHAPTER 45


Define Free Convection off Heat Storage Body (continued)


b. Observe the model with its free convection markers

b


CHAPTER 45908

Create a SimXpert Analysis File


b. Under FileSet in the Model Browser, right click on Create new Nastran job

c. For Job Name, enter a new title

d. For Solution Type, select SOL400

e. For Solver Input File, select the path

f. Unselect Create Default Layout

g. Click OK

b

g

fe

d

c

909CHAPTER 45




b. Right click on Load Cases, and select Create Loadcase

c. For Name (Title), enter NewLoadcase

d. For Analysis Type, select Nonlinear Transient Heat Trans

e. Click OK

b

e

d

c


CHAPTER 45910



b. Right click on Loads/Boundaries, and select Select Lbc Set

c. For Selected Lbc Set, enter DefaultLbcSet

d. Double click on DefaultLbcSet to observe the lbcs that are assigned

e. Click Cancel

.

b

e

d

c f

911CHAPTER 45




b. Double click on Solver Control

c. Select Solution 400 Nonlinear Parameters

d. For Default Init Temperature, enter 25;click Apply

f. Select Output File Properties

g. For Text Output, select Print; click Apply

h. Click Close

b

f

d

c

g

h


CHAPTER 45912



b. Double click on Loadcase Control

c. Select Subcase Transient Heat Transfer Parameters

d. For Initial Time Step, enter 0.02

e. For Number of Time Steps, enter 600

f. Click on Temperature Error

g. For Temperature Tol., enter 0.0.1; click Apply

h. Click Close (not shown)

b

f

dc

g

e

913CHAPTER 45




b. Right click on Output Requests

c. Select Nodal Output Requests

d. Select Create Temperature Output Request

e. Click on Suppress Print

f. For Sorting, select By Frequency/Time

g. Click OK

b

f

d

c

g

e


CHAPTER 45914

Run a SimXpert Analysis

a. Perform a SimXpert thermal analysis

b. Right click on tran_analy_with_free_conv

c. Select Run

b

c

915CHAPTER 45


Attach the SimXpert Analysis Results File

a. Attach the SimXpert result file

b. Click on Attach Results

c. For File path, select results file tran_analy_with_free)conv.xdb

d. Click OK

b

c

d


CHAPTER 45916



b. Results tab: Results/Chart

c. For Result Cases, Select the results for all the times

d. For Result Type, select Temperatures

e. For Target type, select Nodes

f. Pick Filters: Accumulate Mode

b

c

d e

f

917CHAPTER 45




b. Select two nodes; e.g., Node 1522 and Node 67

c. For Independent axis, select Time

d. Click Add Curves

bc

d

b

b


CHAPTER 45918



b. Observe the temperature results

b

919CHAPTER 45


Input File(s)

VideoClick on the image or caption below to view a streaming video of this problem; it lasts approximately 30 minutes and explains how the steps are performed.

Figure 45-7 Video of the Above Steps

File Description

nug_45a.dat MD Nastran transient thermal input file - fixed step without cooling

nug_45b.dat MD Nastran transient thermal input file - fixed step with cooling

Ch_45a.SimXpert SimXpert data corresponding to nug_45a.bdf

nug_45c.dat MD Nastran test deck using adaptive approach for heating only

nug_45d.dat MD Nastran test deck using adaptive approach for heating with convection cooling

http://www.mscsoftware.com/doc/nastran/mdug/input_files/ch045/nug_45a.dat

http://www.mscsoftware.com/doc/nastran/mdug/input_files/ch045/nug_45b.dat

http://www.mscsoftware.com/doc/nastran/mdug/input_files/ch045/Ch_45a.SimXpert

http://www.mscsoftware.com/doc/nastran/mdug/input_files/ch045/nug_45d.dat

http://www.mscsoftware.com/training_videos/mdug/ch045/2010/ch045.swf

http://www.mscsoftware.com/training_videos/mdug/ch045/2010/ch045.swf

http://www.mscsoftware.com/doc/nastran/mdug/input_files/ch045/nug_45c.dat

transient thermal analysis of power electronics

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