2015 05 21-22 EDM workshop board - Thermal management

WORKSHOP #2

Thermal Management Tools and Hints:

HEAT PIPES

by Vincent Fetzer

FAE

Thermal management tools and hints workhop

SummaryI. Definitions: heat transfer & heat pipe

II. Heat pipe concrete applications: cooling modules

III. Cooling modules: examples of applications

IV. Heat pipe: physical functioning

IV.1 - Thermal conductivity

IV.2 - Phase transition: latent heat of vaporization & condensationSynthesis

V. ExperimentsFull copper bar versus holed heat pipeHoled heat pipe versus functioning heat pipeWick structure observation

Workshop #2 - Thermal Management Tools and Hints: HEAT PIPES - Vincent Fetzer FAE

I . Definitions: heat transfer & heat pipe

In the process of reaching thermodynamic equilibrium, heat is transferred from the warmer object / zone (A) to the cooler object / zone (B).

At thermodynamic equilibrium, heat transfert is zero (TA = TB).

A heat pipe is a heat-transfer closed device which contains a liquid able to transport the heat from a hot spot (A) to drain it away (B).

More specifically, a heat pipe it’s a closed metal channel which contains a heat-carrying liquid:

- from the1rst heat pipe extremity: the heat source (A),

- to the 2nd heat pipe extremity: heat dissipater (B).

Workshop #2 - Thermal Management Tools and Hints: HEAT PIPES - Vincent Fetzer FAE - p 1

TATB

warmerzone

coolerzone

heat transfert (Q)BA

graphicprocessorA2 A1

mainboard processor

blower

Bheatsink

Q1

Q2

surroundingmedium:

air

II . Heat pipe concrete applications:cooling modules

In practice, a heat pipe is a sealed tube in contact with the "devices" which allow heat transfer between:

- heat source A, the hot spot side which needs to be coolede.g. a PC microprocessor or a LED (at its Tcase when running) is strongly placed against a heat exchanging plate where the heat pipe is crimped to get the best thermal conductivity,

- heat dissipater B, passive heat exchangere.g. an aluminum heat sink cools / dissipates heat by natural or forced convection in the surrounding medium (i.e. without or with fan).

This ensemble is called cooling module.

example: notebook computer cooling module

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Q total = Q1 + Q2

III . Cooling modules: examples of applications

Workshop #2 - Thermal Management Tools and Hints: HEAT PIPES - Vincent Fetzer FAE - p 3

notebookcomputers

data servers

VGA cards

LED lighting

audioamplifiers

Workshop #2 - Thermal Management Tools and Hints: HEAT PIPES - Vincent Fetzer FAE - p 4

SA

TBTA

SB

IV . Heat pipe: physical functioning

IV.2 - Phase transition: latent heat of vaporization & condensation

Boiling liquids behaviourexamples: - pot of boiling water - lighter refilling

Condensing gas behaviourexamples: - steam on the mirror - morning dew

of the bathroom

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Workshop #2 - Thermal Management Tools and Hints: HEAT PIPES - Vincent Fetzer FAE - p 6

gas

liquid

IV . Heat pipe: physical functioning

Synthesis:

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Wick typestructures:

Capillary action:

V. Experiments

Using resistances (U = R x I) and FLUKE Thermo-camera:

V.1 Full copper bar versus holed heat pipe

V.2 Holed heat pipe versus functioning heat pipe

Using LEICA microscope:

V.3 Wick structure observation

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Thank you.

Workshop #2 - Thermal Management Tools and Hints: HEAT PIPES - Vincent Fetzer FAE - p 9