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

Subject: [DPRG] Re: [TCRG] More power dissipation thoughts.
From: Kipton Moravec kip at kdream.com
Date: Wed Oct 10 11:31:13 CDT 2001

I missed the original message on this.

But I thought in general  the units for heat sinks are not cubic inches but
square inches of surface area.  When you do fins you count both sides of the
surface and edges that come into contact with the air. That is the surface
area you transfer heat to the air with.  In general the metal thickness just
helps transfer the heat through the heat sink, (which is not a bad thing).

Kip

----- Original Message -----
>From: "Gary Croll" <gary.croll at ucr.edu>
To: "Dallas Personal Robotics Group" <dprglist at dprg.org>
Sent: Wednesday, October 10, 2001 10:24 AM
Subject: [DPRG] Re: [TCRG] More power dissipation thoughts.


>
> >Chuck,
>
>       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...
> >
> >--Chuck
> >
>
> Gary Croll
> University of CA.
> Distance Learning
> 909.787.3041
> fax 787.7282
> vid 787.8813
>
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