The ultimate pelier setup

[captain]

I would like to know the ultimate peltier setup.

What will work best. 2 220watt peltiers side by side or 2 172watt side by side on a 172watt peltier.

I have read on the forum that putting
2 172watt peltiers side by side on a 172watt pelier not be effective. Why is that?????
The 2 172watts peltiers will cool the single one. Is that not effetcive since you are REALLY cooling the hot side. i know that it will produce a LOT of heat but if we don't look at that it shopuld be an effective setup

[Mr Evil]

It all comes down to this equation:

DT/DTmax = 1 - (Q / Qmax)

This shows that the amount of cooling in oC is proportional to the amount of heat that must be removed.

With your suggested setup of two Peltiers on top of one Peltier, the bottom one will give little cooling because it must remove a lot of heat relativ to its rating. The second two Peltiers will not only hav eto remove the heat from the CPU, but also the power consumed by the first Peltier, which in the case of a 172W device operated at full power could be as much as 270W. This means that the second two Peltiers will also be operating close to their limit and so they will give very little cooling.

In the other case, with just the two more powerful Peltiers, they will be operating well below their limit, so you should get a DT closer to DTmax, which is more than the not-much + not-much in the other case.

[Butcher]

On a 100W cpu with a 0.05C/W water block on it and ambient of 25C, you'd get these results:

220W: Tcold = 6.2C Thot = 43.3C dT = 37.1C
2x220W: Tcold = 4.1C Thot = 56.6C dT = 52.5C
1x172W: Tcold = 11.7C Thot = 40.1C dT = 28.4C
2x172W: Tcold = 2.0C Thot = 50.2C dT = 48.2C
1x172W/2x172W: Tcold = 23.7C Tmid = 52.2C Thot = 60.4C dT = 36.7C
1x172W/2x220W: Tcold = 17.1C Tmid = 45.5C Thot = 66.8C dT = 49.7C

These assume dTmax of 68C for all TECs, 15V TECs run at 13V, 24V TECs run at 21V. These numbers are theoretical, in reality they'd be a bit different.
Note none of these setups will actually burn out the TECs but the stacking really doesn't work well, the top two just can't cope with the heat load.
The best dT is from 2x220W TECs, so if your water cooling system can better 0.05C/W (which is damn good), you would be better with dual blocks. Otherwise a single 220 is the best.

[GigaFrog]

Where can we get the Rth of different water blocks?

and a software than can make the calculations above?

[ 12-05-2001: Message edited by: GigaFrog ]

[Butcher]

Rh isn;t based on waterblock alone but on the entire cooling setup; wb, rad, tubing, pump, height from pump to highest point, etc. etc.

[Mr Evil]

Rth is not usually quoted for any CPU coolers of any kind (unfortunately), so you have to work it out from the data given in reviews.

I have written a program that can do the above calculations, including calculations of Rth. It doesn't support using Peltiers in series, though as I don't expect anyone to actually use such a configuration. Get it here: http://www.cheese83.freeserve.co.uk/comp/software.htm

[ 12-06-2001: Message edited by: Mr Evil ]