Heat Pipes Applications & Working Fluid

  • Heat pipes are excellent for transfer of high levels of heat output from confined areas.
  • Once transferred from a confined area, heat can be effectively dissipated through a larger passive or active heat sink.
  • Typical applications:
    > Laptop Computers
    > High-performance processors (CPU, GPU)
    > Aerospace; spacecraft temperature equalization, component cooling
    > Constrained geometries
    > Low maintenance/high reliability applications
    > No moving parts, extreme lifetimes
    > Noise-sensitive environments where heat can be dissipated to a larger, remote heat sink
    > Stagnation regions where airflow is poor
    > Limited electrical consumption
    > Example: Passive solution to conserve battery power

How to select a working fluid?

> High surface tension – generates high capillary force and resists entrainment.
> High Vapor pressure – reduces vapor velocity.
> High latent heat – transfers more heat with less fluid.
> High thermal conductivity – lower ΔT and reduces nucleate boiling at the wick/wall interface.
> Low vapor viscosity – increase fluid flow capacity.
Working Fluid
Relative Figure of Merit [80°C] Useful Range [°C] Wick/Vessel Material Life [hrs]
Ammonia
0.45 -60~100 AL
SS304
36000
Freon113
86 -10~100 CU
AL
SS304
25000
Acetone
300 0~120 CU
AL
SS304
50000
Methanol
450 10~120 CU
AL
SS304
Less than 50000
Ethanol
340 0~120 CU
SS304
24000
Water
4000 30~250 CU 750000