Keeping It Cool: Fans, Insulation, Peltier Cooling Modul

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WildBoar
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Keeping It Cool: Fans, Insulation, Peltier Cooling Modul

Post by WildBoar » Fri Jul 12, 2002 1:22 pm

I'm going to construct a metal box out
18 or 20 gauge steel or aluminum.
Dimensions will be roughly 26" long,
6" wide, and 6" depth (or height).<p>I'm faced with a really difficult problem.
Normally, if the parts you put in the box get
hot you can exhaust the heat or bring cool air
into the box from the outside, because the
outside temperature is much lower than the
inside temperature.<p>The problem I've got is that the box will be
in a much larger chassis (or box) that will
reach temperatures of 125 degrees centigrade,
(approx. 260 degrees fahrenheit)! I've got
to keep temperatures inside the box 50% lower
than the temperature outside. Somewhere in
the 60-to-70 centigrade range.<p>There are expensive high tech insulating
materials available. For instance, a company
called Quality Heat Shield sells a 3/8 inch
thick matting with an amazing "R" value of 18.3.
It's temperature range is 40 degrees fahrenheit
below zero to 700 above! A few layers of this
stuff would certainly reduce heat penetration
drastically. But, like I said, it is expensive.<p>The only other alternative I can think of is
active cooling, or using thermoelectric (peltier)
cooling modules. Maybe cutting a hole at both
ends of the rectangular box and attaching a
module with a fan on the cold side (blowing
into the box), and a heat sink on the outside
might do the job.<p>I've never experimented with thermo-
electric modules before, so I really
don't know if the heat reduction I'm
aiming for would be achieved.<p>I'm almost afraid to ask, but does anyone
have any thoughts on the subject?<p>Wildboar<p>[ July 12, 2002: Message edited by: WildBoar ]</p>

billdar
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Re: Keeping It Cool: Fans, Insulation, Peltier Cooling Modul

Post by billdar » Fri Jul 12, 2002 2:02 pm

A guy I went to school with made a liquid cooling heatsink with a peltier device. It was to keep a chip steady at a certain temp regardless of power consumption.<p>If I remember correctly, he use a small microcontroller hooked to both a relay (for the pump) and a couple temp sensors (one on the heatsink and the other on the hot side of the peltier device). The whole set up was kinda big, but he was able to keep a stable temp withing 3 degree C.<p>And if this guy could get it working, any of you all could too. The only problem I remember him having was supplying steady current to the peltier device. I don't know if that was a function of the device, or his temp control specifications.

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MrAl
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Re: Keeping It Cool: Fans, Insulation, Peltier Cooling Modul

Post by MrAl » Fri Jul 12, 2002 2:41 pm

Hello there Wild,<p>It will be very hard to cool something inside
of a hot environment like that, but if you
could pipe the heat out of the larger box too,
you would be way ahead of the game.<p>Is there any way that you can get the heat out
of the larger box, like say, with duct work and
a fan to pull in cool air and vent it via a
second duct?
By this i mean adding duct work from the small
box through the larger box and out into the
ambient that surrounds the larger box.
This would also include water cooling via
small pipes and a pump, but the main point
being that the heat in the smaller box is brought
out into the ambient, not into the interior of the
larger box.<p>If you try to conduct the heat out of the small box
and out into the larger box interior, you will
end up raising the temperature inside the larger
box which might just keep getting higher and higher.<p>What kind of wattage are you looking at inside
the smaller box: 1 watt, 10 watt, 100watt, etc?<p>--Al<p>[ July 12, 2002: Message edited by: MrAl ]</p>
LEDs vs Bulbs, LEDs are winning.

WildBoar
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Re: Keeping It Cool: Fans, Insulation, Peltier Cooling Modul

Post by WildBoar » Sat Jul 13, 2002 6:13 am

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by MrAl:
Hello there Wild,<p>It will be very hard to cool something inside
of a hot environment like that, but if you
could pipe the heat out of the larger box too,
you would be way ahead of the game.<p>Is there any way that you can get the heat out
of the larger box, like say, with duct work and
a fan to pull in cool air and vent it via a
second duct?
By this i mean adding duct work from the small
box through the larger box and out into the
ambient that surrounds the larger box.
This would also include water cooling via
small pipes and a pump, but the main point
being that the heat in the smaller box is brought
out into the ambient, not into the interior of the
larger box.<p>If you try to conduct the heat out of the small box
and out into the larger box interior, you will
end up raising the temperature inside the larger
box which might just keep getting higher and higher.<p>What kind of wattage are you looking at inside
the smaller box: 1 watt, 10 watt, 100watt, etc?<p>--Al<p>[ July 12, 2002: Message edited by: MrAl ]
<hr></blockquote><p>*************************************************<p>Hi MrAl,<p>You're absolutely correct about dumping the
heated air out into the wild blue yonder via
ducting. Of course, that's the most logical
way to keep the heat down inside the smaller
box.<p>All I've got to do now is figure out the size
and shape of the ducts, how to channel it
around all the various obstacles along the way,
etc.<p>Like a famous campaign worker for Mr. Clinton
once said, "it's ducting, stupid", or was it
the economy, I can't really remember!<p>All kidding aside, ducting the heated air out
and away makes the most sense.<p>Thank you, MrAl.<p>WildBoar

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Chris Smith
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Re: Keeping It Cool: Fans, Insulation, Peltier Cooling Modul

Post by Chris Smith » Sat Jul 13, 2002 11:17 am

The main reason Al is correct is that the Peltier only has a limited heat difference, from the cold to hot side, and in your case the hot side of the Peltier wouldn't be able to loose heat, because the second box would be hotter than the Peltier hot side it self, thus no heat loss but a gain instead. Yes, pipe it out to the ambient air via air flow, or liquids. If money isn't an object, they make small coolers that are miniature refrigerators or you could find a old AC or refrigerator and use that.

Gary
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Re: Keeping It Cool: Fans, Insulation, Peltier Cooling Modul

Post by Gary » Sun Jul 14, 2002 12:40 am

I'd like to mention that a COMBINATION of insulation and heat transfer is needed.<p>As an architect, I know a bit about heat transfer and insulation. I've even been thinking of a solid state solar water heater using Peltier junctions, but found that they weren't that efficient, and that they don't work well at higher temperatures, like 150 degrees F or more.<p>The trick is to<p>1. limit the heat generated by the electronics in the inner box, if that is measurable.<p>2. limit heat transfer from the outer box to the inner box through insulation and breaking metal to metal contact between units.<p>3. find a method to remove the inevitable heat gain in the inside box through ducts, water or freon flow, peltier junction, heatsinks etc.

Gary
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Re: Keeping It Cool: Fans, Insulation, Peltier Cooling Modul

Post by Gary » Sun Jul 14, 2002 12:55 am

4. make the box as small as possible. the less surface area the better. You might even consider a short cylinder as a box to further limit surface area. You might even be able to use pipe insulation, although the R value is not great.

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Chris Smith
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Re: Keeping It Cool: Fans, Insulation, Peltier Cooling Modul

Post by Chris Smith » Mon Jul 15, 2002 11:26 pm

Gary,...<p> you can actually stack peltiers and almost achieve Absolute Zero. But like you say, lots of energy is needed. <p>Each one takes the heat out and adds a minus number to that of ?? - 50 ?? Degrees?<p>You can go until you get to almost zero.
[minus 450+] <p>About 60 of them? <p>But insulation is always a plus, to stop migration in or out of the heat.

keymaker
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Re: Keeping It Cool: Fans, Insulation, Peltier Cooling Modul

Post by keymaker » Sun Jul 21, 2002 3:42 am

I've seen on overclocking sites back a few months ago how to use water cooling<p>
Couldn't you pump the water to a radiator outside, where it'd be cooled?<p> <p> I don't understand what you're doing and I don't claim to know what I'm talking about but it sounds like it'd work

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Re: Keeping It Cool: Fans, Insulation, Peltier Cooling Modul

Post by forrestgump » Sun Jul 21, 2002 6:51 pm

Here is a link to a water cooler designed for cooling computer chips and harddrives.<p>http://www.tomshardware.com/howto/02q3/ ... index.html<p> Very nice kit. I think it sells for about $300-$400 but you can mount the heatsink right to a chip! It runs on 12v DC
Good luck <p>Mark

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