Ultimate cooling?

[peterb]

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I don't see why its such a HUGE deal for everyone... this is the only website I have asked about TEC where everyone shuns it. Maybe that's because the others are all extreme enthusiasts so TEC is pretty normal to them where as at hexus air cooling is favoured with a few people water cooling.

===snip====

Eityher you haven't read the previous posts properly - or you don't understand the concepts of thermal management and heat transfer...

The CPU generates heat which in a normal set up, pases to a heat sink. If that heat sink was in a vacuum, it would soon reach the same temperature as the CPU. However we use absorb the heat and remove it either by convextion of forced cooling, so that the hot air is blown to the outside of the case, and cold air drawn in.

With water cooling, the heatsink is cooled by water, which has a greater specific heat capacity than air (it can absorb more heat without increasing its temperature). The hot (or warm) water is pumped to the outside of the case where it is cooled by air - the point being that there is a heat flow from hotter to cooler, eirther in one stage (air) or two stages - water and air.

A Peltier device is a semiconductor device. If it connected to a powersupply in frre space, one side will get hot, the other one cold - in other words a temperature difference, and this is what some car coolboxes use, and some of those little beer can fridges. If you look at those car cool boxes, there is a big heatsink on the outside which dissapates the heat the the peltier device is effectively pumping out (in fact you can think of it as a heat pump) The heat energy out will be the sum of the heat energy absorbed (on the cold side) plus a bit because it isn't 100% efficient. If the peltier decvice was put in a closed (insulted) box and power applied, eventually the two sides would get to the same temperature (or the device would destroy itself) because there is nowhere for the heat to go.

Peltier devices are quite thin - so if you fitted it to the top of the CPU (a small area) then the hot side of the device is still going to be in the case, and you still need something to remove the heat from it, otherwise it will lose efficiency or destryoy itself. You can remove that with a heatsink - fan cooled - or a water block - water cooled.

Alternatively, you could use a conventional heatsink, and remove the fan and put a peltier device on that. It will still be putting the heat into the case, so it has to be removed with the case fanss, otherwise the heatsink will start absorbing the heat back from the air round it, and the temperatures will just rise. The only way you could do it would be if the hot side of the peltier device was mounted on the side of the case, the CPU bonded directly to the cold side while plugged into the mobo. This would use the case as the heatsink (ultimateky still air cooled) but would require a completely bespoke case, and would pose problems connecting othe bits to the mobo.

I hope that explains why Peltier devices are not quite as good as you might have thought. Ultimately the CPU is propducing heat - and that heat has to be removed to the outside of the case - removing it just from the CPU is not enough.

[Noxvayl]

This is much better... constructive reasoning and not random this is better than that with the reasons vaguely laid out. Thank you for the posts

Eityher you haven't read the previous posts properly - or you don't understand the concepts of thermal management and heat transfer...

The CPU generates heat which in a normal set up, pases to a heat sink. If that heat sink was in a vacuum, it would soon reach the same temperature as the CPU. However we use absorb the heat and remove it either by convextion of forced cooling, so that the hot air is blown to the outside of the case, and cold air drawn in.

With water cooling, the heatsink is cooled by water, which has a greater specific heat capacity than air (it can absorb more heat without increasing its temperature). The hot (or warm) water is pumped to the outside of the case where it is cooled by air - the point being that there is a heat flow from hotter to cooler, eirther in one stage (air) or two stages - water and air.

A Peltier device is a semiconductor device. If it connected to a powersupply in frre space, one side will get hot, the other one cold - in other words a temperature difference, and this is what some car coolboxes use, and some of those little beer can fridges. If you look at those car cool boxes, there is a big heatsink on the outside which dissapates the heat the the peltier device is effectively pumping out (in fact you can think of it as a heat pump) The heat energy out will be the sum of the heat energy absorbed (on the cold side) plus a bit because it isn't 100% efficient. If the peltier decvice was put in a closed (insulted) box and power applied, eventually the two sides would get to the same temperature (or the device would destroy itself) because there is nowhere for the heat to go.

Peltier devices are quite thin - so if you fitted it to the top of the CPU (a small area) then the hot side of the device is still going to be in the case, and you still need something to remove the heat from it, otherwise it will lose efficiency or destryoy itself. You can remove that with a heatsink - fan cooled - or a water block - water cooled.

Alternatively, you could use a conventional heatsink, and remove the fan and put a peltier device on that. It will still be putting the heat into the case, so it has to be removed with the case fanss, otherwise the heatsink will start absorbing the heat back from the air round it, and the temperatures will just rise. The only way you could do it would be if the hot side of the peltier device was mounted on the side of the case, the CPU bonded directly to the cold side while plugged into the mobo. This would use the case as the heatsink (ultimateky still air cooled) but would require a completely bespoke case, and would pose problems connecting othe bits to the mobo.

I hope that explains why Peltier devices are not quite as good as you might have thought. Ultimately the CPU is propducing heat - and that heat has to be removed to the outside of the case - removing it just from the CPU is not enough.

I completely understand that...

I will be using my existing cooling to cool the peltier... So my TRUE will dissipate any heat given off by the peltier and with the fans I have that heat will then be taken out the case in the air and the ambient temperature won't be effected too much if it is even noticable. The peltier will only add an extra 30W of heat into the case as my current CPU produces 110W of heat which my TRUE easily dissipates. I think my TRUE would easily be able to handle an extra 50+W since the heatsink doesn't even get warm when at full load(the heatsink remains cold when at full load).

I don't see a peltier adding so much heat to the case that it will cause a problem. It would be more like adding a more powerful CPU; replacing my E6550 with a QX9775. The QX9775 will add more heat to the case but it won't add so much heat to the case that it will cause problems.

I don't know if you think I am looking to cool my PC to sub zero temps or what but I expect with the 140W peltier that my CPU temp would end up between 5-15C. While the heatsink would be dissipating 55C which is not too much higher than what it is currently doing but the result on the opposite end(CPU end) is a significant reduction from my current 40C at load.

A recent conversation with a person who is currently using a peltier leads me to believe that a normal heatsink is easily able to handle the temperatures produced on the hot side of the peltier, this is why I do not believe your claims of the peltier overheating the inside of my case. This person has shown me picture evidence of the parameters I explained above from a 140W peltier(55C on the hot side and -20C on the cold side, obviously my CPU will bring the cold side temp above zero seeing though it does produce a decent amount of heat). Now while I do take this with a grain of salt I did say before I will test the peltier myself before using it to make sure my heatsink can handle it. It costs £5 for the peltier and then maybe 1h testing to see if it works the way I anticipate, not that big a deal if I find it too daunting or if in fact it is not suitable for what I have in mind.

I do not see any problem with the peltier that I am not able to deal with. Heat shouldn't be an issue as I have explained above and time installing+effort is not a problem for me.

[peterb]

No problem - well, if you do go ahead, please post back the results (good or bad - if they are good, it will be of interest, if it doesn't work as well as you hope, that is of interest too - negative results are just as useful - and I promise not to say "I told you so" if it doesn't work! )

[moogle]

let us know how much more power it uses

[Noxvayl]

I just need to wait until next month until I can spare £5 for the peltier... oh and my previous energy meter isn't working. I had it plugged into a socket when we had a power failure and somewhere between the power tripping and coming back on the meter stopped displaying a reading

But I hope to be able to borrow one from my uncle(he is an electrician) again, going to be odd explaining what happened to the last one I "borrowed"...

[Webby]

It will not be an extra 50W it will be an extra 140W don't forget you need to remove the energy you are putting into the peltier as well. Either way you will still need more cooling in the shape of faster fans to cool it all so it will not make your computer any quieter.

[Noxvayl]

It will not be an extra 50W it will be an extra 140W don't forget you need to remove the energy you are putting into the peltier as well. Either way you will still need more cooling in the shape of faster fans to cool it all so it will not make your computer any quieter.

Are you forgetting that the peltier has a cold side? Only if you add a hot plate would it be CPU temp + hot plate temp = temp produced. The peltiers cold side absorbs the heat given off by the CPU therefore that heat is not effecting the system any more and you are left with the heat produced by the peltier only...

And I am not getting a peltier to make my PC quiet... I never said I was looking into peltiers for a quiet cooling solution.

[Webby]

Ok so are you saying that you CPU outputs for example 100W and your TEC consumes 140W but you think you will only need to cool 140W? What happened to the other 100W? Energy doesn't just vanish.