Heat pipe theory and applications

1
Heat pipe theory and applications

• Contents
• Heat Pipe and its special features
• Operation limits
• Applications
• Summary

2
Heat pipe and its special features

• Basic principles
• It is two-phase heat transfer device and it
  can transfer heat from one place to another very
  effectively.
  
• In the container, this is only one kind of
  fluid in two phases liquid and vapor.
  
• This type of heat pipe is called
  thermosphon.
  
• It has two components
• - the working fluid, used to transfer heat
  from
  
• heating side (evaporator) to cooling side
  
  
• (condenser).
• - the container, used to seal the fluid
  inside.
  
• The liquid vaporizes in the heating zone
  and moves
  
• upward and then condenses in the cooling
  zone. The
  
• liquid moves downward by gravity force. The
  process
  
• repeats continually.
• What happen if the heat input region is above
• the heat output region?

3
The heat pipe

• The principle of heat pipe

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Heat pipe and its special features

• The general heat pipe has three components
• - the working fluid
• - the container, and
• - the wick structure to provide capillary
  pump effect to transfer the liquid
  
• phase of the working fluid from the
  condenser to evaporator of the heat
  
• pipe. The wick contents many small pores
  which are through pores. By
  
• using the capillary tube principle, the
  liquid can be sucked higher,
  
• depending the diameter of the tube

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Heat pipe and its special features

• Very high heat conductivity--a good heat
  spreader
  
• Heat input rate 20W, D
  11.5mm L 500mm

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6

• Heat pipe heat sink

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Heat pipe and its special features

• Reliableno moving parts
• Flexibleit can be made in different forms
• Light weight and high efficiency
• It does require external power to move the
  working fluid
  
• Noiseless operation

8
2 Operation limits of heat pipe

• Capillary limit
• Pressure balance of the working fluid,

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System level applications

• Cooling notebook computers

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System level applications

• Uniform temperature of the system