Laser Spectroscopy thermal management

A company that built very specialist laser spectroscopy gas measurement systems for the oil and gas industry was required to meet a particularly high permanent operating temperature of 65 Celsius to receive the accreditation required for a multi-million dollar new market. The problem was, because the system was laser based it required relatively high currents and exact temperature stabilisation to maintain the laser at the correct frequencies. Therefore, prior to my involvement, the system when exposed to an ambient temperature of 65+ Celsius had an internal operating temperature in excess of 115 degrees Celsius. This, of course is not acceptable and the unit regularly failed within minutes, often catastrophically.

Because the system is certified there was very specific criteria involved when reducing the temperature:

  • the internal volume of the case can not be increased
  • cooling can only be passive
  • cooling cannot increase the outer volume
  • cooling cannot use external liquids
  • Cooling cannot be active

As one can see this is an interesting task to complete. However, the solution was relatively simple. A prototype was built that involved copper strands to see how effective the transfer of the heat:

This proved to be effective and dropped the temperature by 20 degrees. Next step was to refine it. So heat pipes where used (as can be seen in the image below), and the final temperature reached was 81 degrees at an ambient of 65, or an almost 40 degree temperature drop

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