CAMCOS Reports DayCAMCOS Reports DayMay 17, 2006May 17, 2006

Mathematical and Mathematical and Statistical Analysis Statistical Analysis

of Heat Pipe Designof Heat Pipe Design Sandy DeSousaSandy DeSousa Cuong DongCuong Dong

Sergio de OrnelasSergio de Ornelas Michelle FerneliusMichelle Fernelius

Marian HoferMarian Hofer Tracy HolsclawTracy Holsclaw

Adam JennisonAdam Jennison Diem MaiDiem Mai

Kim NinhKim Ninh Misako van der PoelMisako van der Poel

All heat pipes and data presented today are purely fictional. Any similarity with any heat pipe, functioning or not, is purely coincidental.

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Requirements for CoolingRequirements for Cooling

Solid metal rods lose Solid metal rods lose too much heat to the too much heat to the environmentenvironment

Cannot use a Cannot use a powered cooling powered cooling system, too much system, too much power consumption power consumption caused the problemcaused the problem

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Heat

Transfer of HeatTransfer of Heat

Heat PipeHeat Sink

Processor

Heat Added Heat Released

*Drawing is not to scale.

Evaporation Condensation

Heat Absorbed

Heat Absorbed Heat Released

Heat Released

Heat Transfer within Heat Transfer within a Heat Pipea Heat Pipe

*Drawing is not to scale.

Wick Structure

Wick Structure

Container

Container

    MEDIUMMEDIUM

  MELTING MELTING PT. (° C ) PT. (° C )

BOILING PT. AT BOILING PT. AT ATM. PRESSURE ATM. PRESSURE

(° C) (° C)

  USEFUL USEFUL RANGERANGE

(° C)(° C)

HeliumHelium

AmmoniaAmmonia

WaterWater

Silver Silver

- 271- 271

- 78- 78

00

960960

- 261- 261

- 33- 33

100100

22122212

-271 to -269-271 to -269

-60 to 100-60 to 100

30 to 20030 to 200

1800 to 2300 1800 to 2300

Created by carving out grooves on the interior Created by carving out grooves on the interior core of the Heat Pipe. core of the Heat Pipe.

Utilizes multiple wire layers to create a porous wick.

Sintering can be used.

Utilizes densely packed metal spheres.

Sintering must be used to solidify the spheres.

φφ

……

Condensation

θθ

LengthLength DiameterDiameter Bending angleBending angle FlatnessFlatness MaterialMaterial

ӨӨ

Ө

TermTerm P-valueP-value

ConstantConstant 0.0000.000

PowderSizePowderSize 0.0000.000

WickThicknessWickThickness 0.4670.467

LiquidChargeLiquidCharge 0.0000.000

PowderSize*WickThicknessPowderSize*WickThickness 0.0000.000

PowderSize*LiquidChargePowderSize*LiquidCharge 0.0000.000

WickThickness*LiquidChargeWickThickness*LiquidCharge 0.0210.021

PowderSize*WickThickness*LiquidChargePowderSize*WickThickness*LiquidCharge 0.0050.005

Individual 95% CIs For Mean Individual 95% CIs For Mean HP Mean --+---------+---------+---------+-----HP Mean --+---------+---------+---------+----- 5 1.01 (-*-)5 1.01 (-*-) 13 1.06 (-*-)13 1.06 (-*-) 17 1.09 (-*-)17 1.09 (-*-) 9 1.12 (-*-)9 1.12 (-*-) 19 1.22 (-*-)19 1.22 (-*-) 15 1.40 (-*-)15 1.40 (-*-) 11 1.61 (-*-)11 1.61 (-*-) 7 1.62 (-*-)7 1.62 (-*-) --+---------+---------+---------+-------+---------+---------+---------+----- 1.00 1.20 1.40 1.601.00 1.20 1.40 1.60

The minimum occurs at:

Powder size = 77.2

Wick thickness = 0.65

Liquid charge = 138

Ө = 0.5988

Response SurfaceResponse Surface

39% Improvement

θ

Does variability in the manufacturing process Does variability in the manufacturing process

affect our analysis?affect our analysis? There are 3 heat pipes of “identical” constructionThere are 3 heat pipes of “identical” construction

θ

Term P-valueTreatment 0.016Heat Pipe (nested within Treatment) 0.039

170 mm

Evaporator 65 mm

Adiabatic

30 mm Condenser 75 mm

Wick thickness .75 mm

Copper thickness .25 mm

Axis

p(T) is the saturated vapor pressure at T.p(T) is the saturated vapor pressure at T. Viscosity and density of vapor change with Viscosity and density of vapor change with

temperature.temperature.

No slipu = 0

Axis

Viscosity of water change with temperature.Viscosity of water change with temperature. K (permeability of wick structure) depends of the K (permeability of wick structure) depends of the

porosity and size of sphere.porosity and size of sphere.

Slip condition

Axis

Heat flux Forced ConvectionNatural

convection

θθ

θθ

θθ

θθ

θθ

θθ

Hypothesis: Heat pipe with varying copper thickness might be better.