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From: John Popelish
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X-Mailer: Mozilla 4.7 [en] (Win98; U)
Subject: Re: Question about linear derating factor for MOSFETs
References: <firstname.lastname@example.org> <3DCF50E9.CF58D143@rica.net> <3DCF5916.50B32FE1@rica.net>
Date: Mon, 11 Nov 2002 14:41:33 GMT
NNTP-Posting-Date: Mon, 11 Nov 2002 09:41:33 EST
Phil Allison wrote:
> "John Popelish" wrote in message
> > Phil Allison wrote:
> > >
> > > "John Popelish" wrote in message
> > > news:3DCF50E9.CF58D143@rica.net...
> > >
> > > >
> > > > Perhaps you could submerge the device in alcohol or freon in a large
> > > > chamber with all the air evacuated, so that all the space was filled
> > > > with saturated vapor. This can act as a heat sink over the whole
> > > > surface of the device with a thermal conductivity a few hundred times
> > > > higher than solid copper.
> > >
> > > ** I was pondering a source of chilled liquid mercury ( abound 0
> > > degrees C ) flowing across the undersurface in a laminar high velocity
> > > stream (like a solder flow bath) and then fed to a resevoir of solid
> > > What da ya reckon - a cool idea ?
> > >
> > Phase change is much better at carrying heat away than liquid flow.
> ** But the phase change has to be happening at no more than 25 to 50
> degrees on the device surface for that to work - right ? The liquid would
> have to be constantly replaced as it evaporates too so the whole device
> surface was wetted.
Right on all counts. The reduced pressure brings the boiling point
down to ambient temperature, and the vapor transport carries the
thermal energy almost instantly to all parts of the container that are
exposed to the vapor. This method of cooling is, in essence, putting
a device inside a heat pipe that is also the sink surface. There can
be something like .1 degree temperature difference between the surface
of the device and the far reaches of the container inside surface.
The dew on the surface of the container must drain back to the device
being cooled, by gravity.
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