226W Peltier on Radeon 8500..how cold?

[dxiw]

Before I do CPU pelteir cooling I want to watercool a 226W peltier on my ATI Radeon 8500 to get some experience with pelts..and I figured a videocard would be easier to seal that a mobo.....anyways...how cold would this 226W pelt get my gpu that emits like what 30-50W of heat? also because it has a delta of 68C it means it won't cool more than hotside-68C right? so maybe since the gpu is only 30-50W I should use a 156W with a delta of 65C? woudn't it get me to the same place....? Would stacked 156W or 226W work better? I want to get my gpu to like -30 or below...as cold as possible....-50 would be nice...

[strokeside]

GPU at 30W, a 226W pelt would give you -35 degrees Celcius.
GPU at 50W, a 226W pelt would give you -30 degrees Celcius.

Now the thing is that you must run the pelt at it's rated voltage to get the whole 226W. I have a 220W pelt, rated for 14.4V, but i run it from a PSU of 12V, therefore making it only a 183W pelt.
Make sure you account for this under-usage when planning what pelt to get. So the above temps would be warmer due to the lower effectiveness of the pelt at 12V, assuming you are using a 12V PSU.

[dxiw]

i really want to get the gpu to like -50 to -80 ideally around -70C. It emits 40W..could you share the forumla i need to get temps..also...if i do 3 or 4 stacked 226W pelts then maybe I can get to -50 to -80

[phiber]

umm why so cold?

[dxiw]

I want to be the same as ln2 and do a high volt mod max out the volts......try to get core to 350.

[Ct. Strangelove]

whoa, dude read up a little more on pelts. One 226w is WAY overkill. I use a 120w on a P4 1.7 and its at 13F. Stacking pelts just doesnot work. good luck

[Silver]

Should work well in collecting water during a water shortage. You really understand the condensation problems you will incur at those temps?

[dxiw]

won't the condensation freeze around the chip?

I want to soak the whole video card in siliconegel and wrap the gpu areain neoprene


I really want a 350 core

[phiber]

umm....you shouldnt need too low temps to get 350 core....but damn yo......your gonna have a free cold water supply atleast. . . .you gonna need to cover that thing w/ six layers of neoprene...and it will STILL condensate...

[nfsga]

You're also going to have so spend a buttload of money, and figure out how to hook up more psu's.

[kevin_bouchard]

one thing to keep in mind is that the lower temp a chip runs the less resistant the wires in it are, therefore a lower voltage would do the same as a higher one at higher temps, my cpu(i know its not the same as a gpu but to give you an ideal) is a duron 800 and the voltage is around 1.6v and could overclock to 1ghz with 1.8(lowest stable voltage) then when i built my refrigderation system i was able to cool my cpu at -10c full load and overclocked it to 1.1ghz and a voltage of 1.6v :eek:, so just imagine the effects of -70c. Just start with the default voltage and go up in small steps.

[TLKfatman]

if u really want to get it that low i know of 2 ways cheap way would b to use a freezer but run it with 504R that could give u close to the temps u r looking for or just go all out and use liquid nitragen at -412 F cost u about 400$ a day or liquid O2 lil wormer but less cost:)

[johnnyw]

have you considered using a water chiller as the neslab c-65?

[R.Rabbit]

yah just get a cheap water cooling setup for your vid card and put the radiator a tub of alcohal in your freezer, then use a tec if you still want it even colder

[Starfoxer]

where are you gonna find a block that will dissipate the TEC heat (around 180W) and then the GPU heat, (another 50W) ???

those things could maybe handle 100W at the most, but 230+.....i dunno :rolleyes:

[ssjwizard]

you would need a full sized water block for something like that. it would be cheeper and easier to get a phase cooler to do temps like that you could use a realy nice small compressor to get temps like that for only 50ish Watts of heat.

[Since87]

Originally posted by Ct. Strangelove
Stacking pelts just doesnot work.

Nonsense. Most OC'ers don't know how to do it in order to get any benefit.

I created a spreadsheet that will calculate the effect of a single pelt or 2 stacked pelts. It is based on data extracted from this paper. (http://www.tetech.com/publications/pubs/IECEC1980RJB.pdf) I derived equations that match the curves shown in this document fairly well.

I've attached a zip file that contains two spreadsheets.

peltstack1.xls shows the operating characteristics for a single 226 Watt pelt powered with 12V. (Bogus values are put into the locations related to the second pelt to eliminate it's effect.)

peltstack2.xls shows the operating characteristics for a stack of two pelts. The one closest to the GPU is running on 5V, and the one closest to the waterblock is running on 12V. (The actual best results are with the first pelt running at 6.4V and the second pelt running at 14.3V, but the gain is only 3 degrees. 5V and 12V are a lot more practical. This is also going to depend a lot on the quality of the water cooling system.)

These calculations show a 5.65 degree C improvement for the stacked pelts when using 5V and 12V. Is that significant or not? Depends on how hardcore you are about your cooling.

The key is to use a large heat capacity (Qmax) pelt for both pelts. The one closer to the GPU operates in a low voltage high efficiency state. The one closer to the waterblock operates in a high heat transfer / low efficiency state.

These calculations are based on ideal situations. No one will actually get these numbers. Getting dT's within 90% of these will be doing extremely well. One of the main problems is the heat that conducts back through the pelt clamping screws. I don't know how badly leaked heat effects these equations and so I haven't figured it in. I hope to get some data on this soon and update this spreadsheet.

These are very general purpose spreadsheets with the following adjustable factors:

GPU/CPU power consumption.
Qmax (Primary and Secondary Pelts)
dTmax (Primary and Secondary Pelts)
Vmax (Primary and Secondary Pelts)
Imax ((Primary and Secondary Pelts)
Pelt operating voltage (Primary and Secondary Pelts)
Ambient Temperature
C/W of the water cooling system.

If anyone sees mistakes in these spreadsheets or has suggestions for improvements let me know.

[Edit: I just realized that where the spreadsheet says GPU Temperature it should say Coldplate Temperature. GPU/CPU temperature will be higher than that temperature.]

[johnnyw]

Hey a good resource to find out chillers is labx.com, has someone looked for some in them?