Heat Sink Design and Optimization

Presented to Dr. Dereje Agonafer

By

ThermaFlow

August 11, 2016

Outline• Introduction• Testing & Simulation• Results• Conclusion

2Erik Jacobs

Introduction• Background• Average Power Usage Effectiveness (PUE)

• Average PUE of 2.9 for U.S. servers in 2013• Power required for cooling is a major concern• Research on how to improve heat sink

performance

• Motivation• Improve heat sink thermal efficiency• Decrease PCH operating temperature

3Erik Jacobs

4Erik Jacobs

PCH Location

Figure 1.2: Extruded Fin Heat Sink Figure 1.3: Inline Circular Pin Heat sink

Figure 1.1: Winterfell 2OU Hybrid Cooling Server

Procedure1. Develop server model2. Incorporate model into ANSYS Icepak3. Experimental testing4. Perform Computational Fluid Dynamics (CFD) simulation5. Compare simulation & experimental results

5Erik Jacobs

Previous work• Solid model built in Solidworks, imported to Icepak• Parameter-based testing• CFD simulations with conformal meshing

6Erik Jacobs

Figure 1.4: Solid model of server Figure 1.5: Area surrounding PCH (Hard drive not shown)

PCH Location

Outline• Introduction

• Testing & Simulation• Results• Conclusion

7Adam McAvene

Experimental testing• Test was run on the Winterfell 2OU hybrid cooling server

8

External radiator fan and bread board

Server Power Supply

Winterfell 2OU Hybrid Cooled Server

Sample Heat sinks and TIM Injector Figure 2.1: Experimental

Test SetupAdam McAvene

Icepak Model

9

Figure 2.2: Isometric View of CAD-constructed CFD model

Figure 2.3: Isometric View of Icepak-native CFD model

Adam McAvene

Meshing

10

• Non-conformal meshing implemented• Reduce “mesh bleeding”• Refine specific object without affecting other areas

• Significantly reduced testing time

Figure 2.4: Example of Conformal mesh of thin objects

Figure 2.5: Example of Non-conformal mesh of thin objectsAdam McAvene

Heat Sink Designs

11

Figure 2.6: Elliptical Pin Heat Sink

Figure 2.8: Hexagonal Pin Heat Sink

Figure 2.7: Square Pin Heat Sink

Figure 2.9: Cross-Cut Fin Heat SinkAdam McAvene

• Manufactured by Alpha Novatech• Proprietary

“Micro-Forging” Process• Al-6063 (Thermal

Conductivity: 209 W/m-K)

Miniature Partitions• 55 x 8 x 1 and 19 x 8 x 1 mm^3• Redirect airflow leaving the heat sink

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Figure 2.10: Square Pin Heat Sink With Mini Partitions

PCH Located Underneath Heat Sink

Binh Tran

13Binh Tran

Without Mini Partitions

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• Flow leaves from gaps between square pins• Air does not travel (and convect) through entire length of heat sink

Figure 2.11: Cross-Sections of Heat Sink/PCH Temperature Without Partitions

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With Mini Partitions • Flow exit regions become much smaller• Increased convection near exit regions

Figure 2.12: Cross-Sections of Heat Sink/PCH Temperature With PartitionsBinh Tran

Vapor Chamber• Heat Spreader• Increase conduction in heat sink base

15Patil, UTA 2015Figure 2.13: Vapor Chamber Icepak ModelBinh Tran

1616

Figure 2.14: Heat Sink/ PCH assembly with standard base

Figure 2.15: Heat Sink / PCH assembly with vapor chamber base 16

Outline• Introduction• Testing & Simulation

•Results• Conclusion

17Ryan Hart

18

Simulation Results vs. Experiment Results

• Mean PCH Temperature (100% CPU Utilization)• Simulation: 61.86 ± 1.47• Experimental : 61.83

• Worst case % Error: 2.4%

Idle

40%60%

80%100%

MEM

+ CPU

50

52

54

56

58

60

62

64

66

68

70

55.0

4

60.1

3 61.8

7

62.0

1

61.8

3 64.0

5PCH

CPU Utilization %

Mea

n PC

H T

empe

ratu

re (°

C)

Figure 3.1: Extruded Fin Experimental results for different power utilizationsRyan Hart

Baseline Test Results

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• Cross-Cut fin lowest temperature for base heat sinks

• Extruded fin, elliptical, and circular pins have roughly same range of temperature

Figure 3.2: Maximum PCH Temperature for Heat Sinks without Modifications

Ryan Hart

Mini Partition Test Results

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• Lowers cross-cut fin, elliptical and square pin temperatures• High reduction in square pin

PCH temperature• Negligible or

detrimental effect on hexagonal and circular pin fins• Possible interference with

flow mixing

Figure 3.3: Maximum PCH Temperature for Heat Sinks Mini PartitionsRyan Hart

Vapor Chamber Test Results

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• Lower PCH temperatures on all designs• Heat spreading increases

potential convection• Higher temperature

drop in cross-cut, extruded fin and circular pin heat sinks

• greater effect for denser heat sinks

Figure 3.4: Maximum PCH Temperature for Heat Sinks with Vapor Chamber basesRyan Hart

Partitions + Vapor Chamber

22Figure 3.5: Maximum PCH Temperature for Heat

Sinks with both Mini Partitions and Vapor ChambersRyan Hart

Outline• Introduction• Testing & Simulation• Results

•Conclusion

23Damone Norwood

Final Design

24Damone Norwood

• Cross-Cut Fin• Thermal Improvement• No Modification- 2°C

• 2.9% Temp. decrease• VC + Mini Partition - 4.3°C

• 6.2% Temp. decrease

Figure 3.6: Final Heat sink Design

Summary • Modeled server in Icepak• Implemented non-conformal meshing• Experimental Testing to validate CFD model within 5% error• Developed final design & server improvements• PCH temperature reduction of 6%

25Damone Norwood

Discussion

26

Questions?

Works Cited

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[9] Patil, Dhanraj Arun. “CFD Modeling and Parametric Study of Vapor Chambers as Heat Spreaders for High-Power Electronic Devices” Master’s Dissertation, Department of Mechanical Engineering, University of Texas at Arlington, Arlington, TX, 2015

Further Work• Additional Physical Model Testing• Recirculating Flow • Ducting and Vapor Chamber

• Further Design Considerations

• Quantify power savings from cooling• Both (internal fan and coolant)

26Damone NorwoodFigure 3.3: Winterfell 2OU Hybrid Cooling

Server Rack