Heat pipe technology originally used for space applications has been applied it to laptop computer cooling. It is an ideal, cost effective solution. Its light weight (generally less than 40 grams), small, compact profile, and its passive operation, allow it to meet the demanding requirements of laptops.
For an 8 watt CPU with an environmental temperature no greater than 40°C it provides a 6.25°C/watt thermal resistance, allowing the processor to run at full speed under any environmental condition by keeping the case temperature at 90°C or less.
Figure 2: Heat Sink Inside a Laptop |
One end of the heat pipe is attached to the processor with a thin, clip-on mounting plate. The other is attached to the heat sink, in this case, a specially designed keyboard RF shield. This approach uses existing parts to minimize weight and complexity. The heat pipe could also be attached to other physical components suitable as a heat sink to dissipate heat. (See photo of inside of laptop computer).
Because there are no moving parts, there is no maintenance and nothing to break. Some are concerned about the possibility of the fluid leaking from the heat pipe into the electronics. The amount of fluid in a heat pipe of this diameter is less than 1cc. In a properly designed heat pipe, the water is totally contained within the capillary wick structure and is at less than 1 atmosphere of pressure. If the integrity of the heat pipe vessel were ever compromised, air would leak into the heat pipe instead of the water leaking out. Then the fluid would slowly vaporize as it reaches its atmospheric boiling point. A heat pipe’s MTTF is estimated to be over 100,000 hours of use.
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