HEAT PIPES…

PRESENTED BYSYAM S NAIRS5 MECHANICALCPTC

Introduction

• A heat pipe is a device that efficiently transports thermal energy from its one point to the other.

• It utilizes the latent heat of the vaporized working fluid instead of the sensible heat.

• As a result, the effective thermal conductivity may be several orders of magnitudes higher than that of the good solid conductors.

Heat

Transfer of Heat

Heat PipeHeat Sink

Processor

Heat Added Heat Released

*Drawing is not to scale.

Basic Components of a Heat pipe

Evaporation Condensation

Heat Absorbed

Heat Absorbed Heat Released

Heat Released

Heat Transfer within a Heat Pipe

Wick Structure

Wick Structure

Container

Container

Component of heat pipe1.Container

• Metal Tubing, usually copper or aluminum.

• Provides a medium with high thermal conductivity.

• Shape of tubing can be bent or flattened.

2.Working Fluid

• Pure liquids such as helium, water and liquid silver

• Impure solutions cause deposits on the interior of the heat pipe reducing its overall performance.

• The type of liquid depends on the temperature range of the application.

  MEDIUM

 MELTING PT. (° C )

BOILING PT. AT ATM. PRESSURE

(° C)

 USEFUL RANGE

(° C)

Helium

Ammonia

Water

Silver

- 271

- 78

0

960

- 261

- 33

100

2212

-271 to -269

-60 to 100

30 to 200

1800 to 2300

Examples of Working Fluid

3.The wicking structureAxial Groove Wick

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

Screen Mesh Wick

Utilizes multiple wire layers to create a porous wick.

Sintering can be used.

Sintered Powder Wick

Utilizes densely packed metal spheres.

Sintering must be used to solidify the spheres.

Purpose of the Wick

• Transports working fluid from the Condenser to the Evaporator.

• Provides liquid flow even against gravity.

How the Wick Works

• Liquid flows in a wick due to capillary action.

• Intermolecular forces between the wick and the fluid are stronger than the forces within the fluid.

• A resultant increase in surface tension occurs.

Ideal Thermodynamic Cycle

• 1-2 Heat applied to evaporator through external sources vaporizes working fluid to a saturated(2’) or superheated (2) vapor.

• 2-3 Vapor pressure drives vapor through adiabatic section to condenser.

• 3-4 Vapor condenses, releasing heat to a heat sink.• 4-1 Capillary pressure created by menisci in wick pumps condensed fluid into evaporator section.

• Process starts over.

Heat Pipe Applications• Electronics cooling- small high performance

components cause high heat fluxes and high heat dissipation demands. Used to cool transistors and high density semiconductors.

• Aerospace- cool satellite solar array, as well as shuttle leading edge during reentry.

• Heat exchangers- power industries use heat pipe heat exchangers as air heaters on boilers.

• Other applications- production tools, medicine and human body temperature control, engines and automotive industry.

LAPTOP HEAT PIPE SOLUTION

Heat pipes used in processor

HEAT PIPE IN CPU

Camera

Types of Heat Pipes• Thermosyphon- gravity assisted wickless heat pipe.

Gravity is used to force the condensate back into the evaporator. Therefore, condenser must be above the evaporator in a gravity field.

• Leading edge- placed in the leading edge of hypersonic vehicles to cool high heat fluxes near the wing leading edge.

• Rotating and revolving- condensate returned to the evaporator through centrifugal force. No capillary wicks required. Used to cool turbine components and armatures for electric motors.

• Cryogenic- low temperature heat pipe. Used to cool optical instruments in space.

Advantages Of Heat Pipes

• Last a very long time.• Completely noiseless.• Requires no mechanical or electrical

input.• Provide lower operating costs.• Are virtually maintenance free.• Are environmentally safe.

Disadvantages

• High cost.• Requires that the air streams must be

relatively clean and may require filtration.• Requires that the two air streams be adjacent

to each other,

CONCLUSION• Heat pipe is a thermal super conductor under

certain heat transfer condition they can transfer the heat energy 100 times more than available best conductive materials, because of negligible temp. Gradient exist in heat pipe.

• The heat pipe has compactness, light weight, reversible in operation and high thermal flux handling capability makes heat pipe to use new modern era and in many wide variet application to overcome critical heat dissipation problem.

References

• www.heatpipe.com.• www.cheresources.com.• www.indek.com• www.wikipedia.org

THANK YOU…