RE: Source for cooling? (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Fri, 19 Oct 2007 23:07:20 -0700
From: Dave Halliday <dh@xxxxxxxxxxxxxx>
To: 'Tesla list' <tesla@xxxxxxxxxx>
Subject: RE: Source for cooling? (fwd)

Two nits:

Scott -- Nick mentioned that this was a Peltier Fridge.
This is the correct description of what you are looking to explain.

http://en.wikipedia.org/wiki/Thermoelectric_cooling

Nick -- Unfortunately, these are only about 5% to 10% efficient and they
will only support a gradient of about 40 degrees.  A Rankine compressor
(standard refrigerator) is about 50% to 60% efficient.  If you need to cool
anything more than 20-30 watts, you need to look at something other than
Peltier junctions. 

Read the first part of this PDF:

http://www.tinaja.com/glib/hack68.pdf

And this entire PDF (for general info)

http://www.tinaja.com/glib/ratholes.pdf



Dave


> -----Original Message-----
> From: Tesla list [mailto:tesla@xxxxxxxxxx] 
> Sent: Friday, October 19, 2007 11:50 AM
> To: tesla@xxxxxxxxxx
> Subject: RE: Source for cooling? (fwd)
> 
> 
> ---------- Forwarded message ----------
> Date: Fri, 19 Oct 2007 12:24:16 -0400
> From: Scott Bogard <teslas-intern@xxxxxxxxxxx>
> To: Tesla list <tesla@xxxxxxxxxx>
> Subject: RE: Source for cooling? (fwd)
> 
> 
> Hi Nick,
>      The reason your freezer does not have a compressor is that it
> operates by a thermocouple, two dissimilar pieces of metal 
> laid side by
> side, with an electric current passed through them.  Somehow 
> this cools
> the fridge, as one heats up faster than the other (and the 
> hot one gets
> cooled by a fan, which draws heat from the other piece of 
> metal and the
> fridge, I am unsure of the exact details).  As for the fans, 
> make sure you
> figure out how much power they need, they may be electronically
> controlled, and supplying them with a non regulated power 
> source may be
> bad for them (or it may not, I am no expert).  I personally use small
> squirrel cage fans for everything I want cooled, similar to those in
> microwaves.  Good luck.
> 
> Scott Bogard.
> 
> > Date: Fri, 19 Oct 2007 08:57:17 -0600
> > From: tesla@xxxxxxxxxx
> > To: tesla@xxxxxxxxxx
> > Subject: Source for cooling? (fwd)
> > 
> > 
> > ---------- Forwarded message ----------
> > Date: Thu, 18 Oct 2007 21:22:34 -0400
> > From: Nick Andrews <nicothefabulous@xxxxxxxxxxx>
> > To: tesla@xxxxxxxxxx
> > Subject: Source for cooling?
> > 
> > I got a dorm-size fridge, Avanti brand off of the local 
> freecycle group for free.  It was purchased but quit working 
> after a few months by a local office.  They cut the cord and 
> got their money back, and I got the fridge.  I spliced a cord 
> on to check it out and guess what?  It has no compressor, but 
> it does have a 4" fan central in the back inside which runs 
> air over an aluminum heat sink.  Peltier-fridge!  
> > 
> > I opened the back, and there is a PWM power supply (SMPS) 
> to run the interior fan and two fans at the bottom of a 
> bigger heat sink on the back of the unit.  Bad design has the 
> fans blowing the air up through the heat sink and onto the 
> power supply.  It has an interior light.  I need to look for 
> a sticker to see how much power it uses...
> > 
> > The point is, though, that these may be a source of 
> good-size Peltier junctions for possible use of cooling IGBTs 
> or other semiconductors.
> > 
> > Nick A 
> > 
> > 
> 
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