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Use a peltier to chill air ?? Hi, I was thinking today, what if you sandwiched a peltier between two heatsink/fan units ? One side would produce cold air, the other hot. With a little air flow control, via ducting and housing you could blow ambient air over the chilled heatsink to produce chilled air which is vented into your box whilst ambient air is blown over the hot heatsink and vented outside your box. You'd need thermal insulation around the peltier and between the fan bases to stop them being in contact anywhere but the peltier. The peltier wouldn't have to struggle that much to freeze the cold heat sink since it isn't 'actively' producing any heat (as opposed to normal peltier solutions where you put the cold side onto the cpu core or a water block to chill heated water etc ec). Workable do you think ? Chairs Cacker
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There's a reason that aircon doesn't use peltier devices. I worked through an example to see how workable it was. I made a few assumptions here. I've not modelled the air realistically. Things like humidity make a *huge* difference to the figures, as do changes in the air temperature and all sorts of other things. Generally, this means that more cooling will be required, not less cooling! Anyhow, I assumed we'd bought a 120mm YS-TECH FD1238 fan, which puts out 125CFM worth of air. Now, these units are not great for this work, so I'll convert them. 125CFM is about the same as 0.059m3/sec (That's meters cubed per second). Air has a heat capacity of around 1.08kJ/kgK (That's kilo joules per kilogram kelvin). If you want to drop the temperature of 1kg of air by 1C, then it'll take 1.08kJ! Now, air weighs approximately 1.25kg/m3 (kilogram per meter cubed). Our fan blows 0.059m3/sec, so it moves 0.07375kg of air per second (Density of air times throughput). Not much admittedly, but it is only a 120mm fan! I've also assumed we want to drop the air temperature by 10C. We know that we have to cool 0.07375kg of air a second, as that's what the fan blows. Cooling a whole kg of air by 1C would take 1.08kJ. Cooling the same amount by 10C would take 10.8kJ. So we multiply 10.8 by 0.07375 and get 0.7965. As we were dealing with kg/sec, we end up with 0.7965kJ/sec. 1J/sec is 1W. Hence, we need 0.7965KW to cool that air. Converting that into watts, gives up 796.5W of cooling required. That's just for a 10C drop on a single 120mm fan. Your peltier will need to pump 796.5W worth of heat, which would leave your hotside heatsink trying to dispose of the best part of 1300W of heat! That's why peltier devices are not used to cool air.
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Having done all that work, I've made a small mistake. The fan actually blows 135CFM, not 125CFM, so it would require more cooling than I calculated! To fix that, pretend the fan is a YS-Tech FD1212387B, rather than a FD1212389B ![]()
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Welcome to AOA Forums, Cacker! It's a very interesting question! Those dang engineers are always dashing the hopes of theoreticians upon the rocks of hard science. Of course, theoreticians are usually engineers too.
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I will admit, I did collar Kaitian to get some figures from him. ![]()
__________________ Any views, thoughts and opinions are entirely my own. They don't necessarily represent those of my employer (BlackBerry). |
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__________________ Any views, thoughts and opinions are entirely my own. They don't necessarily represent those of my employer (BlackBerry). |
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also you need drip trays for the cold heatsink > ![]() This has been tried before, with hot heatsink poking out the top and the cold one inside, as aedan points out its not very effective at the power levels its capable of doing. TEC's are really only any good when you can cool the hotside with watercooling and have a suitable way of removing the heat. They just produce so much heat tho its a pain in the ass till you get the set up just right. Its fun playing with them tho, that first time when you turn it on and watch it ice up its impressive (if you can get the hot side cold enough), i measured -36c once with chilled water. |
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Just about what an over-volted over-clocked cpu puts out > ![]() I got 1 226w pelt and it does its job wonderfully, i even snapped the wire off and soldiered it back on and it was ok. Going back to the chilled air idea, i think the pelt will prolly die pritty quick due to thermal death as the hot side will be v hot even with a large heatsink and loud fan and the cold side may well be warmer than the air in the case! anyone had any experiance with the max temp a pelt can take? |
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just had a thought, a 226watt air cooled pelt would die quick but what about a really low power one? it might be able to get decent sub ambient temps if the hot side aint putting out too muich heat and you can cool it well enough. Anyone sandwiched a low power pelt between 2 heatsink/fans before? even if it did work its not efficient use of the pelt and the actually effect it will have on overall cpu and case temps will prolly be small. |
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I quite like the air-conditioned case idea. Use the cold side loop to chill the CPU, GPU and northbridge directly in a vapochill kind of way, but typically if you use a fridge compressor it'll end up being so vastly overrated that you'll have enough spare capacity for an air inlet chiller/filter/dehumidifier. Much healthier for components ![]() Anyone feel like building one? I don't have either the time, nor the ability to lay my hands on freon in a hurry...
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i've been wondering about using an in window air conditioner unit (the R134 coolant or whatever) dunking the "cool" radiator into a resivor and chilling some water down. not sure if it would work though: even though you have a very efficient heat transfer the capacity of the A/C unit may be too small to be effective on such a mass of water (that also has a very high specific heat compared to air) basically the compressor would have to run on such a long cycle that its life would be too short or if you ran it for shorter cycles the temp decrease wouldn't really justify the extra cost. |
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And what you think about this: http://www.swiftnets.com/products/mcx462plusT.asp It has a 226W pelt and it is very good performer, but it can be used with CPU's producing no more than 100W. And for example mine CPU @ 2500 or 2600mhz produces more than 100W. The condensation is the other problem.
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I think that you'll have a heatsink trying to dissapate about 300w of heat inside your case! Thats gonna be one warm case. (and room after a while) |
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The cooling curve Swiftec gave looks about right for a TEC. It's so unusual for a manufacturer actually to test their product properly and report realistic (even conservative) results. I must say, I liked their "crash test", too ![]() Quote:
__________________ It is by coffee alone I set my mind in motion... Last edited by Kaitain; 18th August, 2003 at 09:00 AM. |
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__________________ EPoX EP-8RDA3+ | AMD T-Bred 1800+ @ 2656 Mhz 1.875V | Thermalright SLK800U + Tt Smartfan 2 + AS 5 | 2x256MB PC3200 TwinMOS Winbond BH5 | 17" Mitsubishi Diamond Pro 750SB Black | MSI GF4 Ti4800 VTD @ 320/720 | 80 GB Maxtor DM+ 7200 r.p.m. | Plextor PlexWriter Premium Black | Plextor PX-54TA Black | Chieftec BX-02B-B-SL + Chieftec 360W PSU + 4x Tt Smartfan 2 + Tt Perfect Light – 2xUV + 1xRed | Coolermaster Aerogate 2 Black |
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