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Study of Heat Transfer Process using Heat Pipes

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In the present study the temperature distribution and the energy transfer from the electronics of a home appliance to an air-cooled heat sink via heat pipes is studied. The main objective of the research work is to ensure that the operation of electronic instruments is maintained under suitable working conditions. SINDA/FLUINT®, comprehensive software based on lumped parameter methods, specially focused in heat transfer and fluid flow modelling in complex systems, is used to create a model representing the cooling of an electronic board by transferring the dissipated energy to a heat sink via heat pipes.
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Authors: Joaquín Capablo, Nelson Garcia-Polanco, John Doyle [email protected] / joaquin [email protected] 2 nd September 2013, Imperial College, London, UK STUDY OF HEAT TRANSFER PROCESS FROM A CIRCUIT BOARD USING HEAT PIPES
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Page 1: Study of Heat Transfer Process using Heat Pipes

Authors: Joaquín Capablo, Nelson Garcia-Polanco, John Doyle

[email protected] / [email protected]

2nd September 2013, Imperial College, London, UK

STUDY OF HEAT TRANSFER PROCESS FROM A CIRCUIT BOARD

USING HEAT PIPES

Page 2: Study of Heat Transfer Process using Heat Pipes

INDEX1. Project Introduction2. Studied System with SINDA/FLUINT3. Results4. Parametrical Analysis5. Conclusions

213th UK Heat Transfer Conference, September 2-3, 2013, London – UK

Page 3: Study of Heat Transfer Process using Heat Pipes

13th UK Heat Transfer Conference, September 2-3, 2013, London – UK 3

1. INTRODUCTION

GREEN KITCHEN PROJECT: Innovative households can help reduce national energy consumption, not only by improving their energy efficiency, but also by reducing and reusing the waste produced in terms of heat and water. Marie Curie Action(Industry-Academia Partnerships and Pathways)

Page 4: Study of Heat Transfer Process using Heat Pipes

Heat Pipes applications

413th UK Heat Transfer Conference, September 2-3, 2013, London – UK

Efficient transport of concentrated heat

From the space to your kitchen…

Page 5: Study of Heat Transfer Process using Heat Pipes

Heat Pipes comparison

513th UK Heat Transfer Conference, September 2-3, 2013, London – UK

Effective thermal conductivity of heat pipe with that of solid copper and solid aluminum rods

Page 6: Study of Heat Transfer Process using Heat Pipes

Heat Pipes

• Advantages:-Very high thermal conductivity

-Accurate temperature control

-Accurate geometric control

Peterson (1994)

613th UK Heat Transfer Conference, September 2-3, 2013, London – UK

Page 7: Study of Heat Transfer Process using Heat Pipes

Studied system

713th UK Heat Transfer Conference, September 2-3, 2013, London – UK

1 2 3 4 Heat Generating Elements

Coin

Heat Pipes

Heat Spreader

Air Cooled Heat Sink

Heat Flow

Air Flow

Page 8: Study of Heat Transfer Process using Heat Pipes

SINDA/FLUINT® (www.crtech.com)

• Software for analysis, design, simulation, and optimization of systems involving heat transfer and fluid flow:– Aerospace– Energy– Electronics– Automotive– Aircraft– HVAC– Petrochemical industries

• NASA-standard analyzer for thermal control systems: 813th UK Heat Transfer Conference, September 2-3, 2013, London – UK

2. STUDIED SYSTEM WITH SINDA/FLUINT

Page 9: Study of Heat Transfer Process using Heat Pipes

Basic Overview of SINDA/FLUINT

• MAIN SIMULATORS:

– SINDA: Network-style (circuit analogy) thermal simulator• Nodes : Temperature points• Conductors : Heat Flow Routes

– FLUINT: Fluid network capabilities• Lumps : Thermodynamic points • Paths : Fluid Flow Passages• Ties : Heat Flow between Solid and Fluid

Q

T,C

FR,A

P,T,V

UA

R

913th UK Heat Transfer Conference, September 2-3, 2013, London – UK

Page 10: Study of Heat Transfer Process using Heat Pipes

Basic Overview of SINDA/FLUINT

• GRAPHICAL INTERFACE:THERMAL DESKTOP

– Geometric CAD-based style• Surfaces and solid parts are geometrically modeled. • Data exchange with CAD and structural software.• Good performance for analysis requiring radiation calculations, contact

conductances, heat pipes, TEC devices…

– Specific module: FloCAD• Fluid Flow Analyzer• Generation of Flow Networks • Calculation of Heat Transfer Factors

1013th UK Heat Transfer Conference, September 2-3, 2013, London – UK

Page 11: Study of Heat Transfer Process using Heat Pipes

Basic Overview of SINDA/FLUINT

• Thermo-Electric Analogy

• Energy Balance to each Node:

T2-T1= Rt*Q

CS*(dT/dt)=∑QS+QSL+Qext

QS-L

QRadiationQConvection

QConduction

Qext

T2 T1

Rt

Q

V2-V1= Re*IV2 V1

I

Re

1113th UK Heat Transfer Conference, September 2-3, 2013, London – UK

Page 12: Study of Heat Transfer Process using Heat Pipes

Basic Overview of SINDA/FLUINT

• Mass Balance to each Lump

• Energy Balance to each Lump

(dEi/dt)=∑QL+QSL

QS-L

QL1QL2

dM/dt= ∑MRLMRL1MRL2

1213th UK Heat Transfer Conference, September 2-3, 2013, London – UK

Page 13: Study of Heat Transfer Process using Heat Pipes

Pre-processing

Fortran Logic Spreadsheet Relationships

Compiling

Post-processing

PLOTS

-Control ParametersError Tolerance, Units,…

-Output ProceduresWhat? When?

-Concurrent LogicInitialization, Customizing

-Network DescriptionNodes, Conductors, Lumps…

-User DataArrays, Spreadsheet

-Operation SequenceSteady-State, Transient, Parametric Sweep

• Basic Flow Data

DATA

OUTPUTS

1313th UK Heat Transfer Conference, September 2-3, 2013, London – UK

Basic Overview of SINDA/FLUINT

Page 14: Study of Heat Transfer Process using Heat Pipes

A Network-based Method to model a Heat Pipe

14

Modeling Heat Pipes with SINDA/FLUINT

13th UK Heat Transfer Conference, September 2-3, 2013, London – UK

• Constant Conductance Heat Pipes (CCHPs): – Used in the aerospace industry for about three decades for supporting

system-level design analysis.

• Extensions possible for modeling:– CCHPs with Non-Condensible Gas (NCG).

– Variable Conductance Heat Pipes (VCHPs) with NCG reservoirs.

– Planar or Counter-Flow Thermo-Syphons.

• Other methods for modeling:– Loop Thermo-Syphons (LTSs).

– Loop Heat Pipes (LHPs).

Page 15: Study of Heat Transfer Process using Heat Pipes

Common Misconceptions when modeling a Heat Pipe

1513th UK Heat Transfer Conference, September 2-3, 2013, London – UK

• Full two-phase thermo-hydraulic modeling is required: – It represents a computational overkill in almost all cases

• Heat pipes can be represented by solid bars of high thermal conductivity:– It does not simulate a heat pipes’s length-independent resistance

– It cannot account for difference in film coefficients between vaporization and condensation

– It does not provide information on power-length product QLeff

Modeling Heat Pipes with SINDA/FLUINT

Page 16: Study of Heat Transfer Process using Heat Pipes

1613th UK Heat Transfer Conference, September 2-3, 2013, London – UK

Typical System-Level Approach

• Network-style conductor fan approach:– All walls nodes are attached directly via linear

conductances/resistances to a single vapor node.

– The wall nodes represent the liquid/vapor interface along each axial segment of length.

Modeling Heat Pipes with SINDA/FLUINT

Page 17: Study of Heat Transfer Process using Heat Pipes

Heat transfer from a circuit board using heat pipes

17

STUDIED SYSTEM

13th UK Heat Transfer Conference, September 2-3, 2013, London – UK

Heat Sources Max. Power: 330 WCoin: -3 mm thickness

-CopperHeat Spreader: - 20 mm thickness

-AluminumHeat pipes: -2 Heat Pipes

-Diameter: 10 mm-Constant conductance (CCHP)-Negligible non-condensable gas (NCG)-Vaporization Coef.: 8.640 W/m2K-Condensation Coef.: 132.640 W/m2K

Heat Sink: -4 Channels-

Aluminum-Air flow:

0.05 m3/s

Q1=10 W

Q2=20 W

Q3=250 W

Q4=50 W

Page 18: Study of Heat Transfer Process using Heat Pipes

• Heat Pipes Grid Refinement: 10 – 320 nodes

Effect of geometric discretization

1813th UK Heat Transfer Conference, September 2-3, 2013, London – UK

Temperature of Element 3

vs.

Heat pipes nodes number

3

198,0

198,1

198,2

198,3

198,4

198,5

198,6

198,7

198,8

198,9

199,0

0 50 100 150 200 250 300 350

T(�C

)

Nodes number

Page 19: Study of Heat Transfer Process using Heat Pipes

Heat transfer from a circuit board using heat pipes

1913th UK Heat Transfer Conference, September 2-3, 2013, London – UK

STUDIED SYSTEM

Page 20: Study of Heat Transfer Process using Heat Pipes

• Transient analysis:

Results: Evolution of the temperature

20

40

60

80

100

120

140

160

180

200

0 10.000 20.000 30.000 40.000 50.000

T(�C

)

t(s)

2013th UK Heat Transfer Conference, September 2-3, 2013, London – UK

Circuit Board hottest point: -Element 3

Page 21: Study of Heat Transfer Process using Heat Pipes

• Analyzed Parameters (in steady state):– Heat pipes exchange coefficients:

• Vaporization coefficient

• Condensation coefficient

– Heat load:• Variation of the heat generated by the heat sources.

– Heat pipes configuration• Variation of the length of the heat pipes

Parametric study

2113th UK Heat Transfer Conference, September 2-3, 2013, London – UK

Page 22: Study of Heat Transfer Process using Heat Pipes

• Heat Pipes exchange coefficients

Parametric study (I-II)

190

192

194

196

198

200

5.000 6.000 7.000 8.000 9.000 10.000

T(�C

)

VapCoeff (W/m2K)

2213th UK Heat Transfer Conference, September 2-3, 2013, London – UK

190

192

194

196

198

200

100.000 110.000 120.000 130.000 140.000 150.000

T(�C

)

CondCoeff (W/m2K)

Condensation Coefficient : 132.640 W/m2KVaporization Coefficient: 8.640 W/m2K

Page 23: Study of Heat Transfer Process using Heat Pipes

150

160

170

180

190

200

250 270 290 310 330

T(�C

)

Heat Load (W)

• Heat Load

Parametric study (III)

2313th UK Heat Transfer Conference, September 2-3, 2013, London – UK

Variation of the Heat Generated by the Heat Sources

Page 24: Study of Heat Transfer Process using Heat Pipes

• Heat Pipes Configuration

Parametric study (IV)

2413th UK Heat Transfer Conference, September 2-3, 2013, London – UK

197,0

197,5

198,0

198,5

199,0

199,5

200,0

0,00 0,20 0,40 0,60 0,80 1,00

T(�C

)

Heat Pipes Length Variation

ΔL/L=7.5%

Page 25: Study of Heat Transfer Process using Heat Pipes

• Temperature distribution and energy transfer from a circuit board using heat pipes

• Transient Analysis of the studied system

• Parametric Study:– Vaporization Coefficient

– Condensation Coefficient

– Heat Generated by the Heat Sources

– Heat Pipes Configuration

Conclusions

2513th UK Heat Transfer Conference, September 2-3, 2013, London – UK


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