[Amps] Fw: Tubes vs. Solid State (was) Expert Amps2K-FA:AnyOpinions?

[Paul Christensen]

Dick Frey, K4XU gave me permission to post his interesting insight (see below).  Dick is an engineer for a major semiconductor manufacturer.  Probably the chart won't make it through the mail list.  Those who want it, please reply in private.

Paul, W9AC

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Paul,



 

Vapor-phase cooling is neat. Good ol' Alpha PA70V. If we reduce the pressure to lower the boiling point of the cooling liquid (closed system - no evaporation), you utilize the same heat of vaporization, transfer a lot of heat, but at a significantly lower temperature. This is already being done with heat pipes.

 

Heat is heat. Whether we make it with tubes or transistors, we have to move it and dissipate it. The fundamental difference between tubes and transistors is their operating temperature.  Transistor are also more dense, smaller with higher W/cm³.  You need an efficient sink. Here's the chart for water:





Pumping the cooling loop pressure down to 1 psia makes the water boil at 100°F. The heat moves just as well.  Keep the condenser/radiator above the heat source so the water can return to the sink by gravity. You still have to move that heat to the ambient environment. If that is your shack, better open the window, or use a big bucket of cold water and a heat exchanger.

 

Food for thought.

 

73,

Dick

  

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Richard Frey, P.E. K4XU