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Quieter Microwave

Passive Magnetron Cooling
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Microwaves have three moving parts, two of which are quiet, the third of which is loud. The quiet parts are the turntable and the rotating antenna. The noisy part is the fan that cools the magnetron.

What if, instead of using a fan, the magnetron was passively cooled, using a heat pipe?

Or perhaps, two heat pipes... A cylindrical heat pipe would move heat upwards from the magnetron to the top surface of the appliance, and would be thermally coupled to a flat heat pipe (such as are used in some laptop computers) that would spread heat horizontally across the top surface of the outside of the appliance.

goldbb, Oct 19 2009

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       Of course, a cheaper way to get a quieter (though not quite silent) microwave would be to have a fan, as usual, but make it's speed variable.   

       A PID controller could control the speed of the fan, in response to a thermometer connected to the magnetron.
goldbb, Oct 19 2009
  

       The way it's done in large radar systems is to immerse the magnetron in transformer oil, which is electrically inert and has excellent specific heat compared to air.   

       An oil-cooled thermo-syphon or pump-assisted microwave oven could be made very quiet, but would be heavier, probably bulkier, more expensive to manufacture and probably more difficult and expensive to service.
8th of 7, Oct 19 2009
  

       sp: quite=quiet in the first sentence.
WcW, Oct 20 2009
  

       I am surprised that the bulk of the noise from a microwave is from the fan but I will take that at face value. There has been significant progress made in affordable low-noise fans in the computer sector which can probably be transferred to the microwave problem. The heat tube solution sounds good, but may still require some active convection to help ensure air circulation and cooling. w.r.t. the disposal of the heat, it seems sensible to pump it inside the microwave chamber if there is sufficient differential, and switch to an external outlet only when required. Alternatively, is there a good reason why we can't design magnetrons to operate at much higher temperatures and dispense with cooling entirely?
vincevincevince, Oct 20 2009
  

       //design magnetrons to operate at much higher temperatures// Yes the higher temperature could be vented into the interior of the oven to speed the cooking process.
pocmloc, Oct 20 2009
  
      
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