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© 2011 ANSYS, Inc. August 11, 20111

Jing Heng Wen

E-Z-GO, Textron

Optimization of Heat-sink Fin Features using ANSYS


Background:Heat sinks are frequently used when heat exchange is required for electric circuits.

In cases where the heat generation is evenly distributed, the height and spacing of fins are uniform. However, when heat generation is locally concentrated, uniform fin distribution is not the most efficient design.

Tasks of Virtual Prototyping:Virtual prototyping is applied to the investigation of fin feature design in order to

reduce the cost when re-tooling is required. (1) To make sure that the new design will increase the heat transforming efficiency; (2) To reduce the weight.


Procedures:(1) Analyze original design as the baseline;(2) Investigating heat generation sources;(3) Simple method to see the possibility for weight cut; (4) Optimize Fin Space, Height following the structure/installation requirement.(5) Validation


Heat Exchange: Improve ~10-15% Material Reduction: ~10% of Heat Sink


Original Product vs. Optimized Product


Am

bien

t T=5

0C, M

ax. 1

08.9

0 C

Am

bien

t T=2

0C M

ax. 7

5.63

0 C

Step 1. Original Model (Baseline)



Total Heat Source: 88W (1) Center Wall: 12W+10W+10W+10W+18W=60W (2) Longer Side: 15W(R) +7W = 22W (3) Shorter Side: 6W (R)

The investigation of heat generation: Concentrate Distribution

Center WallWall 1, at Longer Side

Wall 2, at Shorter Side


Step 2. Heat Generating Source Investigation


Am

b T=

20C,

Max

. 77.

80 C

Test

Mod

el 1

Step 3. Simple Method (Conduct/Film) for the Possibility of Weight Cut (A)

Optimization of Heat-sink Fin Features using ANSYSTe

st M

odel

2

Increasing the height of 3 Fins +0.025M. So total adding is 0.075M

Removing 3 Fins at the end of one side, Cut fin 0.05*3=0.15M

Am

bien

t T=2

0C, M

ax. 7

5.80 C


Summary of Test Model 1, Test Model 2 and Original

The results suggests that changing the height of fin and density could reduce the weight by increasing heat transform efficient.

We know the possible method. Now, we need to know how to determine their height and space

(density) in detail. Optimization analysis by FEA is used.

Model Description LC 1, Tbulk = 50C LC 2, Tbulk = 20C

Max. T Min. T Max/Min Difference Max. T Min. T Max/Min Difference

Model 1 Original 108.9C 77.5C 31.4C 75.6 C 43.5C 32.1C

Model 2 Removed 3 side fins 111.6C 84.3C 27.3C 77.8C 49.6C 28.2C

Model 3 Removed 3 side fins 109.4C 83C 26.1C 75.8C 48.6C 27.2C

1.5 X H of 3 center Fins

Step 3 (B). Simple Method to Find the Possibility of Weight Cut



Max

. 74.

80 C u

nder

Bul

k 20

0 C


Straight Fin Baseline, Max. M=0.631kg

Max

. 107

.50 C

und

er B

ulk

500 C

Step 4. Fin Density (Space) & Height Change, Model with Straight Fin Optimization Analyzing Base Model w/Straight Fin (Step 4-1, 4-2 & 4-3)


P27(3): b7 P26(3): b6P23(4): b3

P22(4): b2P21(3): b1

P25(3): b5P24(3): b4

P20: w1

Step 4-1: Fin Density (Space) Change, Model with Straight Fin (A) (Optimization Analysis – Model with Parameters)

Eight (8) Parameters

Model


© 2011 ANSYS, Inc. August 11, 201110

4-1 (B): Fin Density (Space) Change, Model with Straight Fin(Optimization -- Response Surface Result – Local Sensitivity)


b1

b2

b5

b7

b3

b4

b6w1

Max. Temperature

Min. Temperature

© 2011 ANSYS, Inc. August 11, 201111

Max

. T v

s.. b

1an

d b6

Max

. T v

s.. b

1an

d b7

Max

. T v

s.. b

1an

d b5

Max

. T v

s.. b

1an

d b2

Optimization of Heat-sink Fin Features using ANSYS4-1 (C) : Fin Density (Space) Change, Model with Straight Fin

(Optimization Analysis Result – Sensitivity Chart)

Hold b1, see how T changes (sensitivity) following b7/b6 (Left) and b5/b2 (right)?

© 2011 ANSYS, Inc. August 11, 201112

4-1 (D): Fin Density (Space) Change, Model with Straight Fin(Goal Driven Optimization Analysis Result Summary)

Tradeoff – Max. Temperature vs. Mass

Best: 71.9 vs. 74.80C (base), M=0.631

Reduced Samples


© 2011 ANSYS, Inc. August 11, 201113

Step 4-2: Fin Height Change, Model with Straight Fin & Equal Space (A) (Optimization Analysis - Model)

P30:l1

P31:h3

P28:h2

C: 0.075m

P29:h4

Four Parameters in DesignModeler

Model

APDL Command in Mechanical (add another parameter ARG1)


© 2011 ANSYS, Inc. August 11, 201114

4-2 (B): Fin Height Change, Model with Straight Fin (Optimization – Response Surface – Local Sensitivity)

P29:h4

h4

h2

h3

l1

Mass

Max. T


Max. TemperatureMass

h3

l1

h4

h2

© 2011 ANSYS, Inc. August 11, 201115

4-2 (C): Fin Height Change of Model with Straight Fin(Optimization Analysis –Sensitivity Chart)

Max. T vs. h2 and h4

Mass vs. h2 and h4

Max. T vs. h2 and l1

Mass vs. h2 and l1 Mass vs. h2 and h3

P29:h4


Hold h2, see how T & Mass change (sensitivity) following l1 (best l1 for T, Left low), h4 (right) and h3 (center)?

Model with Parameters

© 2011 ANSYS, Inc. August 11, 201116

4-2 (D): Fin Height Change of Model with Straight Fin(Goal Driven Optimization Analysis – Set & Result)

Tradeoff – Max. Temperature vs. Mass

Best: Mass 0.590 vs. 0.631 (base) T=74.780C

Result of Optimized Model, Height Change only


© 2011 ANSYS, Inc. August 11, 201117

Step 4-3. Combining Fin Height and Space Change (A) Optimization Model with Dimension Parameters

P29: h4


+ 8+4=12 Parameters

© 2011 ANSYS, Inc. August 11, 201118

Am

bien

t T=2

0C, M

ax. T

=74.

550 C

Optimization of Heat-sink Fin Features using ANSYSO

ptim

ized

Par

amet

ers

Am

bien

t T=5

0C, M

ax. T

=107

0 C

4-3 (B). Combining Fin Height and Space Change Optimized 12 Parameters, Mass=0.576kg, T=74.550C (Base M:0.631Kg,T:74.80C)

Inacceptable gap

© 2011 ANSYS, Inc. August 11, 201119

4-3(C). Combining Fin Height and Space Change Re-adjusted 8 Parameters Toward to Market-Manufacture Acceptable Model - Optimization


Note - h3: Shipping package; l1: optimized; b7: gap limit; w1: limited; TL: defined

Parameter Table Detail of Design of Experiments

© 2011 ANSYS, Inc. August 11, 201120

Sens

itivi

ty

Max

. T &

Mas

s Tr

ade-

off

Opt

imiz

ed C

andi

date

sM

anuf

. Acc

epta

ble

-Ve

rific

atio

n

1. S

elec

ted

as r

espo

nse

poin

t

2. Acceptable /Round for Manufacture 3. Pints Verification, Mass=0.573Kg, Max. T=74.70C

Optimization of Heat-sink Fin Features using ANSYS4-3 (D). Combining Fin Height and Space Change , Goal Driven Optimization Results

b1

b2

b6b1

Mass Max. T

b5

b5

b2b6

© 2011 ANSYS, Inc. August 11, 201121

Am

bien

t T=2

0C, M

ax. T

=74.

70 C


Opt

imiz

ed /A

ccep

ted

Para

met

ers

(Edi

t in

Para

met

er S

et T

able

/Ref

resh

)

Am

bien

t T=5

0C, M

ax. T

=107

.40 C

Mod

el G

eom

etryStep 4-3(E). Combining Straight Fin Height and Space Change (Manufacture)

Results of ALL Accepted Parameters, Mass=0.579kg, T=74.7C (Base Mass=0.631,T=74.80C)

Update

© 2011 ANSYS, Inc. August 11, 201122

Model FEA Thermal Analysis LC 4 (50C) LC 5 (50C) Volume ( Fin L )

LC 1, Ta=50C, LC 2, Ta=20C, Thermal Thermal + V (Fin L) V (Fin L)

# Detail Report Max. T Min. T Max. T Min. T Stress F 11 lbf cm^3 (cm) Reduction

Model 1 Original A 108.9 C 77.5 C 75.6 C 43.5 C N/A N/A V547.82(L116.3) Base

Model 5 2400C C, enforced 108.4 C 82.7 C 75.3 C 45.3 C 14 Mpa 150 Mpa V484.44(L101.7) 11.50%(13%)

Ori

gina

l Hea

t Sin

k

Rede

sign

ed H

eat S

ink

(Spa

ce/H

eigh

t/In

stal

latio

n/Th

ick/

Prof

ile/W

ave)

Step 5: Final Model Validation (A) Summary, Optimized vs. Original (Geometry & Results)


© 2011 ANSYS, Inc. August 11, 201123

Original Model of Thermal Analysis Results

Final Model of Thermal Analysis Results (T+5%)

Step 5 (B): Final Model Validation -- Compared with Original in FEA Thermal

Am

bien

t T=5

2.50 C

, Max

. 108

.40 C

Max

-Min

=25.

80 CA

mbi

ent T

=500 C

, Max

. 108

.90 C

M

ax-M

in=3

1.40 C

Am

bien

t T=2

10 C, M

ax. 7

5.30 C

M

ax-M

in=3

00 CA

mbi

ent T

=200 C

, Max

. 75.

60 C

Max

-Min

=32.

10 C


© 2011 ANSYS, Inc. August 11, 201124

Step 5 (C). Final Model Validation -- Thermal Structure Stress Check


Static Structure Analysis

Thermal Structure Analysis

© 2011 ANSYS, Inc. August 11, 201125

Test PASS/FAIL Criteria:Test 2. Operating Temperature:

-20 0C to +60 0C. The power supply shall operate without any evidence of degradation throughout a “Normal Temperature” range of 0 0C to +40 0C. For thermal protection above +40 0C, its output will be reduced by 2.5% / 0C until reaches 50% power at 60 0C, above which it will shutdown

Test Figure 1: Current Thermal de-rating curve

Test Figure 2: Current in normal T (-20 0C to +40 0C)

Step 5 (D). Final Model Validation -- Prototype Test


Test Figure 3: Charge parts temperature distribution

All prototypes passed test successfully.

© 2011 ANSYS, Inc. August 11, 201126

RESULTS & CONCLUSION

In summary, ANSYS , a virtual prototyping tool, is used for Heat Sink Redesign:(1) The electric charge has been in mass production years and is very successful. The

finding has been submitted to and is pending in US patent office. (2) ANSYS is providing a powerful tool to help us to decide whether improvement is

accessible; (3) Optimization tool help us to determine the dimension rapidly and accurately ; (4) Saved cost and valuable time.

Without the full cooperation in R&D lab and product design team, the strong support and leadership from the management in E-Z-GO Product Engineering Department, the virtual

prototyping could not be implemented. The author is indebted to many colleagues from E-Z-GO, Textron.

ACKNOWLEDGEMENTS


jing heng wen e-z-go, textron - ansys · pdf filejing heng wen. e-z-go, textron. ... when heat...

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