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[DPRG] Re: [TCRG] More power dissipation thoughts.

Subject: [DPRG] Re: [TCRG] More power dissipation thoughts.
From: Gary Croll gary.croll at ucr.edu
Date: Wed Oct 10 10:24:57 CDT 2001


      I remember years ago, (15-20), very high power audio amplifiers 
having sealed heat exchangers attached to the heatsinks and routed to the 
back panel. Possible they were called heat pipes. These were hollow copper 
tubes of different sizes with venturis and a coolant liquid of some kind.

I believe they worked similar to a gas refrigerator on an RV. These 
refrigerators are sealed systems with no moving parts and they use a small 
gas flame or a nichrome heat coil to heat the ammonia "refrigerant" and 
cause it to move through the system. Through a system of venturis, the 
ammonia expands and contracts transferring heat away from the inside of the 
refrigerator. They work extremely well and actually get colder than 
"conventional " home refrigerators.

If you could find some of the older amplifiers that had their heat pipes in 
place, it might be an alternate method to cool your project. I know 
Technics was one of the companies that used them.

>Hmmm, that seems to be a pretty intense sink. Using "natural convection" 
>on the Wakefield chart that means the sink needs a volume of approximately 
>800 cu in. That would be a 29" x 29" heat sink with 1" tall fins. With a 
>500'/minute fan blowing on it that drops down to 150 cu inch or a 12" 
>square sink. Perhaps I should contact Pratt & Whitney for my fans :-)
>What I don't know is how much water can help this. If I let the working 
>temperature soar to 100 dC on the sink then it helps a bit.
>Should be interesting to see once I get the bars back from the machinist...

Gary Croll
University of CA.
Distance Learning
fax 787.7282
vid 787.8813

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