Peltier/TEC questions

[joemac]

I have recently noticed an increase in question about Tec’s such as what Tec should I use what block, power supply, pump etc. One thing that stands out in my mind is the lack of target temperatures. I don’t see any one saying well I want to achieve x temperature with x processor (maybe I have not looked hard enough) its more like what should I use to cool x processor? It only makes sense to me that a target temperature be defined when these questions are asked. I just want to bring this up in its own thread so it does not seem like I am flaming anyone.

[j813]

formulas on calculating please
I'm a basic newbie on computation whether TEC or plain ol h2o cooling. heck even on total h2o system design
I dont even understand terms like C/W, etc. :shrug:
Thanks!

[Brians256]

There are formulas for TECs. You need to know:

1) TEC model
2) input voltage on the TEC
3) hot side temperature (how well can you cool the backside of the TEC)
4) wattage of heat input on the cold side

In fact, go to melcor's website. They used to have a free program to design a system!

Now, the kicker is that it is hard for us watercoolers to know 3 or 4. The hotside temperature really depends upon how good your cooling system is. The wattage of heat input depends upon a value that the CPU manufacturers don't give out and it doesn't include the parasitic heat input caused by leakage (where heat moves in from the motherboard and surrounding environment to a cold CPU).

If you know the C/W of your waterblock and system, it is easy to know the backside temp of the TEC. I know very few estimates of C/W that are accurate, mostly because people's system's are never exactly the same (is your tubing length etc... the same as the reviewers that do system-styled reviews?). Maybe you can use something like 0.2 C/W for your system as an estimate with one degree of precision (yours may be 0.13 or 0.27 but make some good guess). Then use the wattage of your target TEC to calculate the backside temp.

If you perfectly insulate the CPU and TEC, you can assume that only CPU heat is a factor. Work from that as a maximum coldness you could ever reach.

Finally, you could just try it based upon the best suggestions from this forum because it is just too hard to really calculate the actual numbers that go into the design program.

[Butcher]

CPU manufacturers give out heat values for their CPUs, check the data sheet for your CPU.

[Brians256]

Originally Posted by Butcher

CPU manufacturers give out heat values for their CPUs, check the data sheet for your CPU.

Yes, but it also depends upon how good the insulation is, what the coolant temp is, etc...

[jaydee]

Originally Posted by joemac

I have recently noticed an increase in question about Tec’s such as what Tec should I use what block, power supply, pump etc. One thing that stands out in my mind is the lack of target temperatures. I don’t see any one saying well I want to achieve x temperature with x processor (maybe I have not looked hard enough) its more like what should I use to cool x processor? It only makes sense to me that a target temperature be defined when these questions are asked. I just want to bring this up in its own thread so it does not seem like I am flaming anyone.

Target temp? I don't see why. IMO it is as low as you can get it is the concept. Same as overclocking. As high as you can get it. To set targets is limiting your potential IMO.

[Bertz_maru]

Target temp? I don't see why. IMO it is as low as you can get it is the concept. Same as overclocking. As high as you can get it. To set targets is limiting your potential IMO.

^^ yeh.. i agree..

[bigben2k]

Yeah but you can also configure a TEC not to frost up... (more work: more fun! ).

[jaydee]

Originally Posted by bigben2k

Yeah but you can also configure a TEC not to frost up... (more work: more fun! ).

But why? If it isn't frosting up then there isn't enough cooling going on to justify using one eh?

[iggiebee]

IMO, also it is necessary to consider the difference between the Designer and the User; two different species.

While the designer, engineer or creator would be very interested in specifics as to how something works or is made, the end user is simply not interested in those facts, as an example, no one needs to know how a telephone or computer works in order to use one proficiently.