New Peltiers

OniExpress

Limp Gawd
Joined
Feb 11, 2009
Messages
179
Hi folks. So I've recently aquired three 600 watt peltiers, and now I'm looking for the most functional equipment to use them with. My ideal goal is a rack-mount oil immersion setup; motherboard trays will be aranged from side to side vertically, with space equivalent to three 4U bays slid in from the top. Right now I don't have call for that kind of space, so instead I'd like to set up a smaller immersion for a single atx system.

I've been researching this project off-and-on for quite a few years, but I've still not seen a consensus about a few questions. For starters, I'm not sure if I would get a better distribution of chilled oil from immersed radiators/coldplates or from simply pumping the whole mass of the fluid out through the peltiers. Using a radiator seems to me like it would eliminate the most hotspots (fluid dynamics being what they are, I can't think of an easy way to distribute the chilled oil across a large tank), and it would also seem to be the more convenient option. I just don't recall ever seeing it done that way before.

My preferred option at the moment is to sandwich the peltier between two heatsinks; one pumping the cold side out through the immersed radiator and the other side going to a large reservoir to dissipate heat. Ammong other problems, I've only found one coldplate (on eBay, no less) that seems to fit the bill (copper with copper pipe wound through it) for against the peltier itself.

Alright, enough rambling. That's enough for a first thread; I'll wait to see if I get any feedback. >_>
 

Arcygenical

Fully [H]
Joined
Jun 10, 2005
Messages
25,068
Don't rely on unassisted onvection within the fluid.

I would get a 1/2" copper tube (that's equal to the width of your tank), solder one end shut (use a copper cap) then drill about 10 small holes in it facing upwards. Place the tube at the bottom-middle of the tank.

Cold coolant would be pumped into this "manifold" and it would exit the holes, and with convection, rise to the top of the tank. Hotter coolant would be collected at the top, and pushed through a heat exchanger using an oil pump.

Note, you know your system will be drawing ~2.2kw with three of those peltiers chilling the fluid, correct?
 

OniExpress

Limp Gawd
Joined
Feb 11, 2009
Messages
179
Yeah, I know it's a power sucking monstrosity of a cooling system.

I was planning on a sealed radiator on the interior with a set of fans mounted to "blow" the oil up across the board.
 

OniExpress

Limp Gawd
Joined
Feb 11, 2009
Messages
179
OK, so now I have more time to elaborate.

My current concept is to use two copper blocks with copper pipe to sandwich the peltiers. Then I'd use a 3x120 radiator inside the oil tank with three fans (LED ones, as an asside; to be able to tell when the peltiers are running) and some sort of radiator on the outside (possibly passive, but more than likely with fans due to necessity from the heat).

As for the wattage, I'm planning on having each peltier and one fan running off of a seperate 700+ psu. This way I can run all three to bring the tank down to temperature and then possibly a lower level to "idle" at a desired temperature. Partially as a power saving measure, and partially because I don't know how low all three running 100% will bottom out with the system; getting it too cold would cause a lot of condensation/frosting issues on the outside.
 

Arcygenical

Fully [H]
Joined
Jun 10, 2005
Messages
25,068
"copper blocks to sandwich the peltiers" is a good idea, if you want to keep the peltiers outside of the tank, and pipe the cold fluid (I would assume alcohol, with a hard, soldered line to the radiator) into the actual tank for circulation.

You'll want large blocks, with very long channels milled into it. And insulation is an absolute must, to the nth degree.

What are you planning to use as coolant in the tank? The radiator assembly would get very, very cold, even your low viscosity oils would gel up moving through a radiator whose surface temp is far in the negatives.
 

flak-spammer

Limp Gawd
Joined
Aug 24, 2007
Messages
262
I hope you aren't going to try and cool the hotside of the peltier with an air heatsink. If you do I'll warn you since I've worked with a few lower wattage ones, you'll need a massive heatsink, my 136.8w pelt running at 12v was pumping out so much heat that the SI-128 SEs heatpipes couldn't move it fast enough. So don't bother with that kind of wattage trying to use an air heatsink water is your only option.
 

Arcygenical

Fully [H]
Joined
Jun 10, 2005
Messages
25,068
I hope you aren't going to try and cool the hotside of the peltier with an air heatsink. If you do I'll warn you since I've worked with a few lower wattage ones, you'll need a massive heatsink, my 136.8w pelt running at 12v was pumping out so much heat that the SI-128 SEs heatpipes couldn't move it fast enough. So don't bother with that kind of wattage trying to use an air heatsink water is your only option.

He said a passive radiator, although I agree, one would need an absolutely massive passive radiator to cool ~2000w of peltiers.

Like, you could route it inline with your furnace's exhaust, and use it to heat your house, exclusively, in the winter.
 

OniExpress

Limp Gawd
Joined
Feb 11, 2009
Messages
179
Like, you could route it inline with your furnace's exhaust, and use it to heat your house, exclusively, in the winter.

That's not exactly a negative around here this time of the year. :p

If I can figure out how to use SketchUp a little more competently, I'll have some designs later on.
 

BrainEater

[H]ard|Gawd
Joined
Jul 21, 2004
Messages
1,087
He said a passive radiator, although I agree, one would need an absolutely massive passive radiator to cool ~2000w of peltiers.

It's only 2000 watts in a no load condition.....With a heatload ,it's more like 3 or 4 thousand watts.

I fully agree that a passive system isn't gonna cut it.

Each heatsink ( for each peltier ) will need to sink 1200 watts...to do this passively will require very large and heavy heatsinks......like 15 lbs of heavy....

http://www.surplussales.com/Heatsinks/HeatSink1.html ... see # 3 .

These heatsinks are expensive too.Hundreds of dollars.Much cheaper to watercool IMO...

:D
 

flak-spammer

Limp Gawd
Joined
Aug 24, 2007
Messages
262
Even with really good heatsinks you'd still end up with a 20-60 degree delta, making them useless. With water you might even have some troubles.
 

OniExpress

Limp Gawd
Joined
Feb 11, 2009
Messages
179
Not entirely sure yet.

I've had construction started on one of the cooling water reservoirs already. Basically it's a plastic coated drum, with a radiator running through the interior. It's a bit overkill, but these guys are going to be pumping out a lot of heat (understatement). Eventually I might connect the drums up to a water line so that it can periodically be flushed with fresh, colder water.

I'll get pics up when a drum is finished, but the metalshop primarily works for a few local companies and can't always get to them at the rate I'm paying.
 
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