AdvancedTopic 96 of 105Thermodynamics & Fluids
Heat pipes
Passive devices transferring heat via evaporation and condensation.
In depth
A sealed tube with a wick and working fluid: evaporator vaporises liquid, vapour flows to condenser, capillary action returns liquid. Effective conductivity hundreds of times that of copper, isothermal and passive. Used in laptops, satellites and solar collectors.
Key points
- No moving parts
- Operating temperature range depends on fluid
- Orientation limits
ExampleA laptop CPU is cooled by a flat heat pipe leading to the fan.
Heat pipes move heat with very high effective conductivity and no moving parts, which makes them ideal for laptops, satellites and electronics cooling.
What is Heat pipes?
Passive devices transferring heat via evaporation and condensation.
Why is it important to understand heat pipes?
Heat pipes move heat with very high effective conductivity and no moving parts, which makes them ideal for laptops, satellites and electronics cooling.
How does a heat pipe work?
Liquid evaporates at the hot end, vapour travels to the cold end and condenses, and the liquid returns by capillary action or gravity.
What limits a heat pipe?
Its maximum heat transport, set by capillary limit and the working fluid properties, and it must not be operated outside its orientation or temperature range.
How is Heat pipes used in practice?
Typical applications include cooling a laptop CPU with a copper heat pipe, transferring heat from a satellite instrument to a radiator and moving heat out of a power electronics cabinet without fans.
What should I learn before Heat pipes?
Study "Boiling and condensation" first (topic 95 of 105 in Thermodynamics & Fluids). It covers the groundwork this topic builds on.
What are the key points of Heat pipes?
No moving parts. Operating temperature range depends on fluid. Orientation limits.
Can you give an example of Heat pipes?
A laptop CPU is cooled by a flat heat pipe leading to the fan.
What comes after Heat pipes?
The next topic is "Electronics cooling", which builds directly on this one.
How difficult is Heat pipes?
It is classed as Advanced in Thermodynamics & Fluids (topic 96 of 105). It is an advanced topic. It assumes you are comfortable with the intermediate topics in Thermodynamics & Fluids.