you actually need a wye diverting valve. Page 399 of the mcmaster catalog.Quote:
Originally Posted by Clue69Less
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you actually need a wye diverting valve. Page 399 of the mcmaster catalog.Quote:
Originally Posted by Clue69Less
I'll stick with my simple ball valve. It has 1/4" BPT and no restrictions when open. And it was cheap - 9 bucks. Sort of like McMaster-Carr 4093T23 but 1/4 BPT.Quote:
Originally Posted by ArtosDracon
I think I see what you mean, you're going to use a plastic wye and just shut off flow to the chiller with it in parallel to your main loop? You are going to use a second ball valve to shut off flow to the radiator right? If not they're just going to fight each other at ambient and the radiator is likely to have a lot more capacity than the TECs.Quote:
Originally Posted by Clue69Less
That would be soo cool to make a smaller version of that that could be controlled by a sensor that would shut off when it is within 2-3c of ambient temp, and back on when it goes above that. Would be ideal for overclocking and eliminate the need for insulating the tubes/motherboard since it would throttle back or shutoff when it goes to idle or low use (where the TEC would be cooling at a greater rate then heat is getting dumped into the water, which would let it go sub ambient and create condensation)
sounds like you guys are wanting to make a coolit system
yeah, but, one that actually works.... :rofl:Quote:
Originally Posted by littleowl
no such thing!!!! :shakes: you guys need to read on heat pipes because they can only carry so much heat no matter how cool you try and make them. That is the downside!Quote:
Originally Posted by ArtosDracon
Who mentioned heat-pipes?Quote:
Originally Posted by littleowl
Yep. I know it's wasteful to even mess with TECs but this way they will only run when I am playing with the OC. Under normal circumstances, I doubt that I'll run the CPU OC high enough to need the TECs.Quote:
Originally Posted by ArtosDracon
Within limits, the CoolIt is OK. But I don't want to just have manageable temps at stock clock. I admit I've only glanced the CoolIt reviews for a number of reasons but I'd like to be able to run down around 0C and maybe get a little more OC headroom. I'll be particularly interested in playing around with it around winter time when the heat belching forth from the TECs can be put to good use. I used to fly scientific missions with 1KW of TECs venting onto the back of my seat. That's difficult to appreciate when the ambient temp of the plane is over 50C.Quote:
Originally Posted by ArtosDracon
OH my you have a lot to learn about tec if you think a coolit is ok! LOL
I'm VERY familiar with how heatpipes work but, what does that have to do with CoolIT stuff, everything I've seen of theirs is either direct die tec or a water chiller.Quote:
Originally Posted by littleowl
reading this morning I think I confused the 2 threads your talking in. :rofl: It has been a long week.
I thought you might have been refering to the post with quad 6mm and quad 10mm heatpipes. Thats a funny thread.Quote:
Originally Posted by littleowl
yeah that it is! I don't think it will work at all! but that is my opinion
Quote:
Originally Posted by littleowl
Go back and read what I said:
"Within limits, the CoolIt is OK. But I don't want to just have manageable temps at stock clock."
I've worked with 1.5KW TEC setups in scientific applications where detector temperatures needed to be held constant within a fraction of a degree, so I'd say I've learned plenty about TEC. This PC TEC stuff is fun and games by comparison.
LoL Guys NOL gets the package tomorrow.
And he will do the tests. So wish him luck.
Quote:
Originally Posted by Clue69Less
you have any pic's of that setup? sounds very interesting...
I like that idea of using the two way ball valve, that could be sweet
I'm still working on the case mod so the TEC parts are sitting for now. I'll start a thread when I get going on it again.Quote:
Originally Posted by systemviper
oh I missed that part about within limits. :ROTF:Quote:
Originally Posted by Clue69Less
well we are talking about duo and quad chips and there is no use for coolit products unless your only going to run stock.
boy it is about time Naekuh!! :p:Quote:
Originally Posted by NaeKuh
Those are exactly the limits I was thinking of.Quote:
Originally Posted by littleowl
Package arrived @ Nols :D
Now i need him to respond on the status of the parts. The last time i sent out a ups shipment, they broke a leg off my RD-30 GRRRRR.
Nice DIY, at least you guys went ahead with the concept, one of few. Congrats, will now show us its plus and minus points better :up:
I have to admit, theory doesn't favor the setup design for providing efficient cooling though. Don't really want to get in detail right here, looks like plenty has been mentioned already and it was only for practical experimentation, in which case... everything absurd to genius goes. :D
I'm going to be building on a sub-ambient thermal concept myself by December, but it doesn't feature TEC units at all.
Status of parts?
Okay in the box; triple 120mm swiftech rad, 6 yate loons, the beautiful peltier assembly, meanwell, some wierd thin 80mm ish fan, a copper topped apogee, a laing d5 and I think thats it. Will be trying a few possible configurations, and most importantly will attach a ton of thermocouples and look like I'm doing something hard and technical.
Can't wait for pictures and results!Quote:
Originally Posted by n00b 0f l337
those water-blocks are quite epic :ROTF: :up:
some day one of you guys involved has to try out 8 air-cooled peltiers. with 8 50W @ 12V peltiers + a 150W heatsource you'd have an average of (50 + 150/8)=68W output per peltier, which a $5.99 heatsink from newegg should easily handle.
with 40mm square peltiers + 60mm width k7 heatsinks you could do this x 2:
Lets go nol we are all waiting!
Quote:
Originally Posted by hollo
I worked with big TEC system that was air cooled. It had a home-made huge Al heat sink and a bunch of high rpm 12cm fans. It could heat up the airplane on a cold morning and totally wilt you on a hot day. I didn't ever want to hear "TEC" again after doing a misison in Mexico during a heat wave.
Quote:
Originally Posted by n00b 0f l337
Man I need to work on that "Look like I'm doing something hard and technical" thing...:)
Thanks for doing the testing..:up:
Used one hand to scratch your head and the other one on your balls.Quote:
Originally Posted by Martinm210
Got a Q, what size bolts to attach the yates to the rad?
1" bolts will do but i suspect 1.125"Quote:
Originally Posted by n00b 0f l337
edit also 6/32 threading mcr-320 right?
MCR-320 is indeed 6/32.
K 6/32 :)
Oh, i want one... i mean i NEED ONE!!!
any testing progress?
Haven't had time, I'm sorry, hooked up fans, and have been searching for my tubing, started taping on temperature probes though.
looking forward to some results :D:D:D this thing looks like a beast. Very cleanly done too.
I'll send you some spare cheapy 1/2-3/4 if tubing is the only issue! I'm sure naekuh has some laying around too!
This thread is kinda withering on the vine. Is there a backup band that can play during the intermission?
:rofl:Quote:
Originally Posted by Clue69Less
I think someone just needs to go and kick NOL in the butt to get him moving!! LOLQuote:
Originally Posted by Clue69Less
Hey didnt get any time last week! Finals today and tomorrow. All thermocouples are attached though! And I've plumbed her. Gotta add some distilled water and do some quick wiring.
lets go then! :DQuote:
Originally Posted by n00b 0f l337
Haha come on wait for tomorrow ;)
I wish Ihad better tube, this homedepot crap sucks lol.
oh yeah it does!!! it would be much better if you had some nice tygon or masterkleer
How many feet do you need? I've got some spare 1/2 by 3/4 tygon.Quote:
Originally Posted by littleowl
I am good with it but nol needs it.
Check out my project here.Quote:
Originally Posted by hollo
10 basic air heatsinks on 10 40mm peltiers (rated as 137w). The idea is to run each peltier at no more than 5v (from the 5v line of my existing PSU, so no extra PSU required). Not aiming for ultra cold temperatures, but a little boost without using too much power. Also, I'm trying to do it as cheaply as possible.
The work in the link above is more like a prototype as I have made so many compromises. However, as a proof of concept it will show me if Im wasting my time or not.
ALso, its painfully slow progress though as I cant do any work on it whilst at university which is where I am almost all of the time. I have made some progress from the end of that thread, ill have to put some more pictures up soon.
I'm anxious to see how this performs! I'd go with a separate power supply.
Quote:
Originally Posted by Scarlet Infidel
That is still an option. My testing seems promising with regards to using the same PSU for system and chiller, but testing and maths are not the same as trying it for real.Quote:
Originally Posted by Clue69Less
I don't want to thread-jack. Feel free to post on the thread on the other forum, ill probably start a thread on this forum too soon.
And here I thought you were the back up band???Quote:
Originally Posted by Scarlet Infidel
j/k
Gotta get some distilled water, doing some wiring.
Well i gave that air thing a thought. However this is what i know about TEC's.
The colder you keep the hotside the cooler the cold side will be.
Martin made these blocks so they kick buttin being free flowing. He also glass beaded the interior, so theres quite a bit of surface area on both the hotside and cold side.
Needless to say, i dont think martin will ever make another pair. He died making mine.
What i intend on doing with this unit. At this point i made the size and gauged the performance and footprint. This unit is almost definitely going on an external box. The hotside will probably be cooled off a 480GTX. :D
I may drop in another meanwell, and upgrade the TEC's thats if my poor breaker can handle that amperage.
Very true, though I don't think you can assume that water is automatically going to make the hot side cooler than heatsinks.Quote:
Originally Posted by NaeKuh
In the way you have yours set up, I think water is the right way. You have few, relatively high powered peltiers and are using a beefy water cooling radiator.
However, for discussion sake, consider my lower powered project with 10 peltiers and which is designed to be very quiet. Each peltier will be cooling approx 20 watts of heat and adding at least 10 of their own. Lets say 35 watts of heat on the hot side per peltier to be conservative.
Lets say the very cheap basic heat sinks I'm using have a c/w of 0.4. This is based on 2 14cm yate loons. Then the hot side would be approximately 14 degrees above ambient.
Now, if i water cooled them, I would have the thermal resistance of the hot side water block and the thermal resistance of the radiator. A PA120.2 is what I'm making mine to compete against (in terms of size/number of fans) but ill use the figures of a PA120.3 as that would make more sense to use in a chiller.
As my project is going for quiet and cheap id go for yate loons at 7v. But for this ill use the 12v figures. So I would estimate the hot side c/w is approximately 0.035. This has to cope with 350w giving a a hot side temp of 12.25 above ambient. But then we have to take into account the extra pump which may well be 18w (for a DDC) bringing the hot side temp to about 13c above ambient. This is why I'm toying with the 6w DB-1 - especially on the peltier cold side.
So really, for me, using air cooling gives about the same results as water but is smaller, cheaper, less power hungry and quieter. Of course you are using a different type of chiller with different goals and I think you are right to use water, I just wanted to illustrate a point.
NB all figures are wildly approximate and use all sorts of assumptions (such as that both schemes have the same resistance from the TIM).
well here you run into the problem i ran into.
Did you factor the fact that it can take 350W of energy to change 1C in h2o?
Flip that ;)Quote:
Each peltier will be cooling approx 20 watts of heat and adding at least 10 of their own.
That doesn't actually make any sense. 350W for how long to change what volume of water?Quote:
Originally Posted by NaeKuh
Edit: are you saying a system like mine is likely to use 350w to get water only 1c better than normal water cooling?
That's not what I'm saying at all. In the example above is was taking 100-150w to keep the water cooling a 200w load at 3-5c below ambient compared to straight water being 5-10c above ambient with the same size and noise constraints.
The above was just comparing how you cool the hot side of a chiller in my specific circumstances, not talking about the merits of a chiller on the whole which I believe can be done effectively and efficiently.
Are you saying that as a pessimist (or a realist from experience) or because that's how you think peltiers work? I don't want to suggest you don't know what you are talking about when you probably do, but for the benefit of those that don't know:Quote:
Originally Posted by n00b 0f l337
When you lower the voltage across a peltier element from its maximum you increase its coefficient of performance. So at low voltages you can pump more energy across the peltier than it consumes itself.
However doing this also has the affect of lowering the heat differential maintained across the element.
The following is in ideal conditions of no load on the cold side (not possible) but the theory is sound:
So my peltiers at the full 15.2v can move 89w of heat (for 0 dT) for 137w power usage. this is a COP of 0.65. Here the max dT would be 67 degrees with no load on the cold side.
If I run them at a third of that (~5v) then the power draw is 13w but the element can pump up to about 40w at a dT of 0 which is a COP of 3. Here with no load the dT is more like 30c.
Once you add in load on the cold side it changes all the figures, but the principle remains the same.
No peltier element will always use more then they move. If you drop a 137W usage peltier from 15.2V to 5; You reduce from 9amps to 3amps rougly. That now means 15W consumption. Now your going to be closer to around 14-15W movement, however I've never seen a peltier that will begin moving more then they consume.
Quote:
Originally Posted by n00b 0f l337
A couple of years ago, my boss had me measure efficiency curves for a wide range of TECs. The results were dismal. I ran them over their functional range in terms of voltage and hot side temp. We had excellent lab facilities so the heat flow measurements were solid. All of the advertised efficiencies were totally bogus. Some measured as low as 10%, the good ones around 50% at their best - so basically agreeing with your numbers above. At high load, 40% is good.
Im sorry i should of finished it.Quote:
Originally Posted by Scarlet Infidel
It takes 350W @ water traveling 1.5gpm for it to change 1C.
So it takes a signficant amount of wattage to pull this thing off. :T
Gah more pics!
I've been lurking for a few months and i like this project the best!
And I was worried id steal focus in this thread...
Still don't agree with what you are saying here, there are too many other variables.Quote:
Originally Posted by NaeKuh
Its concerns me that you seem to have done proper testing that shows such poor results.Quote:
Originally Posted by Clue69Less
What do you do as a job?
Despite all this, I still think it is possible. Cathar had a good attempt at it a few years back and I've seen a few other had limited success.Quote:
Originally Posted by n00b 0f l337
I recently set up a small, very crude, testing setup I had one of these peltiers ata little over 8w cooled by a basic heat sink. On the other side I had a poor water block and a pump rated at 27w but that i measured to draw more like 20w.
I know not all 20w of the pumps heat went into the water, but people generally reckon 60-90% will, and when I put the pump alone in a small loop with a reservoir the temp rose at a rate to suggest it was dumping around 16w.
After all this the water leveled off at 1-2c under ambient. Now, I may well have missed something and all you concerns worry me, but how can I have managed results like this in such a poorly optimised test platform?
I don't claim to know the technical details about TEC's, but my experience with them has shown that compressor-based chilling is just more efficient.
TEC's and their inefficiency seems to be a common thought 'round the 'net:
http://www.coolchips.gi/technology/ccalc.shtml
Pelt Basics:Quote:
For comparison purposes, a typical thermoelectric (Peltier) cooler has a Carnot efficiency of about 5-8%. A typical domestic refrigerator compressor has a maximum Carnot efficiency of about 45%.
http://www.overclockers.com/tips45/
http://en.wikipedia.org/wiki/Thermoelectric_cooling
How you got those results, I don't know. Due to the Laws of Thermodynamics, I do know that 8 watts of heat movement + 12-18 watts of heat source != more than 19 watts of heat movement total.Quote:
Thermoelectric junctions are generally only around 5–10% as efficient as the ideal refrigerator (Carnot cycle), compared with 40–60% achieved by conventional compression cycle systems (reverse Rankine systems like a compressor). Due to the relatively low efficiency, thermoelectric cooling is generally only used in environments where the solid state nature (no moving parts, maintenance-free) outweighs pure efficiency.
Either the temperature measurement was off, the TEC was improperly rated, or there was something else helping cool the water.
With all due respect
is something that greatly annoys me, it holds back innovation with little real reason. Those efficiency figures are all true, when you run a peltier at its full ratings. If you use its characteristics carefully you can get some good results.Quote:
Originally Posted by THE JEW (RaVeN)
Jorlen has just showed a system where 63w of power to the peltiers have given him sub ambient water temperatures with a 100w load.Quote:
Originally Posted by Cathar;
Ive seen it for myself, Ive run the maths which supports it. Its not witchcraft, you just have to be open minded.
Jeez 63w moving 100w?
You gotta link me to something that shows us how to do that.
I'm still having trouble understanding how he got to move 100w of heat with 63 w pelts.Quote:
Originally Posted by Scarlet Infidel
Okay havent gotten a huge amount of time, and away this weekend, but for some reason I've got a leak in a barb. Must not have put it in all the way or something, draining loop, pulling out barb, and adding some teflon tape.
Further research shows I had forgotten about COP :(Quote:
Originally Posted by Liquid.
However, the linked thread with a near $1000 cost on cheaply attained parts doesn't exactly help TEC's case ;)
If we're all going to go on a COP/efficiency binge, perhaps we should start designing systems ahead of time with a given TEC and heatsink/waterblock. Using the previously linked software below, one could potentially make a decent cooler at a decent cost:
http://www.kryotherm.ru/soft.zip
http://www.kryotherm.ru/?tid=84
I don't think it would be as good/bang for buck as phase, but it would be an interesting project.
Sorry for off topic--looking forward to NoL tinkering :)
Replace the bolded link with thisQuote:
Originally Posted by THE JEW (RaVeN)
http://www.kryotherm.ru/dir2attz/soft.exe ;)
I'm building mine much more cheaply, only time will tell how good it is though.Quote:
Originally Posted by THE JEW (RaVeN)
also keep in mind, you are not cooling the water, you are removing heat from the water in a steady state system.Quote:
Originally Posted by NaeKuh
At any reasonable water cooling flow rates, the temperature of the water throughout the entire loop can be considered constant if you've had your system on long enough to reach steady state. Your calculations should not even take into account the temperature change of the water as it moves through individual components on the loop. The pelts will only be removing heat from the cold side that the processor and whatever else you have in the loop creates, and not changing the temperature of the water.. Thus your pelts only have to be rated to be able to handle the heat generated by the components.
The only time the specific heat of the water really enters into any of the modeling that really needs to be done here is during start up if you wanted to calculate the time it would take to reach steady state.
I'm trained as a chemist. In grad school, I spent my first two years building interfaces and writing software for computer control of instrumention. Yes, that was a long time ago. In my first real job, I got involved in thermal analysis and helped modernize calorimeters. Fast forward over twenty years and I was building mass spectrometers for measuring airborne pollutants when my boss found out that I'd worked in thermal analysis. So he gave me a pet project of his where he'd been trying to cool a detector cell with TECs. The problem was that the aircraft did not have "air conditioning" until it got up to ~14,000' and because of that, the cooling of the hot side of the TECs was a problem at startup and also when dropping low to do altitude profiles. The detector needed very stable temps. I finally bought a small industrial air conditioner to cool the hot side and the only down side to that was jealousy from other teams on the airplane.Quote:
Originally Posted by Scarlet Infidel
I have similar experience - but I was maintaining constant temperature for sensors on oil rigs. The gear could end up on a north sea platform in the dead of winter, or in Africa in high summer. We needed to maintain 25C plus or minus 2 degrees for the electronics package to assure the stability of readings.Quote:
Originally Posted by Clue69Less
One thing for sure - in a TEC setup, you will not see better than 40% efficiency and probably a lot less. For high efficiency cooling of water, I believe the best way is to just use standard air conditioning or refrigerator components.
The advantage TECs provide is the ability to provide tight temp control, and also to provide cooling with a small physical size and better packaging options. Going way sub-ambient is not an option with water and messy with phase change, but fairly easy to do with TECs - attached is a shot of a cooler I helped my nephew build which delivered air at around 5C to a 100W heat load with hot side air cooling. But it used nearly 300W to do it, so the air cooler had to unload around 400W. The Blue Orb is the cold side - it provided air at 5C to a Vanessa cooler on the CPU and generally cooled the air in the whole case. The hot side has a giant Melcor sink which has .08 C/W with 120CFM. Not shown is the drip pan <G>. An interesting project, but for the small improvement in temp at the CPU, done a whole lot quieter and with a tenth the power using a small phase change unit and WC...
Word.Quote:
Originally Posted by Uncle Jimbo
Interesting stuff, but its obvious from the offset that's a really inefficient way of using Peltier elements, unless I've badly misunderstood. It would be nice to know a few more details about that project and how you have implement peltiers in the past.Quote:
Originally Posted by Uncle Jimbo
well i would actually have to agree with you on this statement.Quote:
Originally Posted by Scarlet Infidel
Because water is a better medium for transfer on the cold side. Also this is what i felt on the hotside. Im trying to milk the entire unit for efficiency. By watercooling the hotside, the cold side gets cooler, and i can use less voltage to get desired results. no?
Yeah, that's correct and a very sensible way of getting the most out of your chiller.
I wouldn't recommend trying to air cool the hotside. The reasons I'm air cooling my hot side is:
Lower cost,
lower noise (that's not likely but still possible),
smaller size,
to be different,
to prove that it can be done,
because my heatload is spread over a large area,
and because I don't think it will be much worse than water cooling if done carefully.
I have designed pelt based control systems going back more than 20 years. Typically these have an instrument package in a sealed NEMA enclosure, and the pelt cools if load is too hot, heats if load is too cool. These are typically on 48VDC systems so we use 2 24V pelts in series with SCR chopper control. Those systems ran in ambient as low as -40C and as high as 50C.Quote:
Originally Posted by Scarlet Infidel
The efficiency of the TEC improves with hot side temp, with best efficiency around 50C hot side, so air cooling the hot side is actually more efficient. For example, the curves on a CP1-12730, a big 62mm TEC, show 240 Qc W with 5C differential and the hot side at 50C - but only 190 Qc W at 25C for the same volts and amps. Since what you want is to take cold side below ambient, you want closer to 30C differential with the hot side at 50C. With a 16V supply and 30A, that TEC will move about 140W. It will use 480W getting there, so your heatsink needs to be able to dissipate 620W which is big.
the cooling effect you get is determined by the surface area of your heat exchanger (you have lots of that!) and the rate at which the water goes through. To change the temperature of 1 gram of water 1 degree C requires 4.18 Joule (watt-second). At 0C, a gallon of water is about 8.33 Lbs or about 3.77 kg - 3770 grams. For a 1GP/M flow, 1/60th of that goes by in a second, so 63 grams go by each second. Cooling that by 1C requires about 260W. Ideally, the TEC above would drop the water temperature by about .5C - assuming the heat exchanger transfers the energy. Higher flow rates will do less transfer.
In comparison, the guts from a standard wall mount water cooler will cool 1 GPM by .5C using about 200W. so it is more than twice as efficient, but not nearly as pretty!
In answer to your question, the setup I pictured used the same CP1-12730, but operated at 12V and 22A. This is a more efficient area of the operating curve, as I move 100W with only 260W input. If you plan on using 2 TECs, you might find this to be a good choice - it powers from a standard PSU. for about 500W input you move 200W, which would get you close to a 1C drop at 1 GPM. The heat dissipated would be about 350W for each of the 2 units. The big Melcor sink would give a 25C rise with that load.
The attached CP1-12730 curves can be used to tell pretty much what this TEC will do - there are similar curves for most commercial TEC units.
very nice points.. in a distant future I will try to do the same :) ( no money ATM)Quote:
Originally Posted by Scarlet Infidel
I will be using about 20 x 40w undervolted and air cooled..I am still looking for a big and effective HS for the hot side..would love to run it fanless if possible. the only thing that is going to be a real killer is a decent psu
@uncle jimbo: you could have said 1 calorie instead of 4.18 joule :P.. make it simple for us :P.. nice info
The cold side will not get much colder because it is effectively in a water bath. But you are right, the TEC will move more heat for the same voltage with a lower differential, and water cooling the hot side will reduce the differential. However, TECs have a negative coefficient of heat - so they draw more current when the hot side is cooler. Using the curve from my previous post, and assuming a 12V supply, we can see that lowering the differential from say 30C to 10C will give a 30% increase in Qc W (100W to 150W). But lowering the hot side from 50C to 30C will reduce the effective resistance of the TEC from about .55 Ohm to around .4 Ohm, so instead of supplying 22A, we now need 30A.Quote:
Originally Posted by NaeKuh
So with the hot side at 50C, you supply 264W to move 100W, or 2.64W in per watt moved. With the hot side at 30C, you supply 360W to move 150W, or 2.4W in per watt moved. That buys you a slight increase in efficiency and moves more heat. But doing 2 TECs with air and a 50C hot side moves 200W for a 520W cost, again at 2.6 W per w moved. For a 9% increase in efficiency, you need to create a whole additional cooling system for the hot side WC.
Or if, as you state, you reduce the voltage, you could go to 10V which puts the amps at 25, and you are moving 100W with 250W in. That's about where you started, except you added the complexity of WC on the hot side, and you need a 10V supply, which is not off the shelf. And now you are at 2.5W in per watt moved, so it is only 5% more efficient.
The other issue you would face is that with a small differential, you will swing the amps a lot depending on heat load. That puts a big demand on the PSU... with a 25C or 30C differential, the amp swings are much lower for a change in load.
I like to design these to use an off the shelf $40 PC supply and not a $200 lab supply. OC work is expensive enough without going too exotic. Getting a supply that can deliver 30A at 12V continuous is a lot harder and more expensive than one that will do 22-25.
Not trying to be arcane - you have to put the 4.18 in somewhere to get to watts... too bad, it's handy to have 1 cal = 1 degree.Quote:
Originally Posted by Duh
BTW you might do better to use bigger pelts even if you want to undervolt - they are really just more elements per package anyway. Per my previous post, the best efficiency is with the hot side hot - draws less amps to get to the same point on the curve. If you put 2 of the TECs I was discussing in series across 12V, you will probably get about 11A draw and move about 35W per unit. That gets to 1.9W in per watt moved, which is about as good as it gets for TECs. I have never tried running a unit that low and the curves don't go down there, so it is something you would need to test. BTW just work around 12V as a design center and you'll find cheap PSUs that can do the job. Also a smaller number of bigger TECs makes finding heat sinks easier. With only 100W or so per unit, you could go fanless with a standard CPU sink I think.
Unfortunately I am using ten TEC1-12709 elements. I can easily find graphs for TEC1-12708 and 12710 but not for mine. This caused me to look in more depth at the equations that are used to make the graphs. I prefer this to using graphs because its gives me more control and more accurate numbers.Quote:
Originally Posted by Uncle Jimbo
You seem to know a fair deal about thermodynamics and peltiers so it still concerns me that you don't think you can get a peltier to move more heat that it consumes. I have seen it happen with my own test setup.
The only thing that I can think of, is that either you are used to using peltiers from a different perspective or that I've messed up somewhere. With all your examples you always seem to be using the peltiers at quite high towards their maximum voltage.
I and others have found that about 1/3 of the maximum voltage and below is where they really become useful. Have you ever used peltiers in this kind of range? If so, how did you feel they performed?
If I look at the curves for the TEC-12730 which seems to be similar to the element you mentioned.Quote:
Originally Posted by Uncle Jimbo
For a 35w heat load with a dT of 15c it will draw 6A at 4v. So 24W power consumption to move 35W of heat. Why does this seem so far off what you said?
The answer, Im fairly certain, lies in the fact that in yours the dT will be much higher. Perhaps around 40C from that graph (excuse any mistakes, I really don't like these graphs)?
On an aside, does anyone have a guide to using the Kyrotherm software? I think ls7corvette is pretty familiar with it. A link to a guide or "dummies" manual might help us all start calcing out some info.Quote:
Originally Posted by Liquid.
Maybe I should just pick up one of my mech friend's thermal books.
I've never used pelts down in the bottom of their operating range, and I am usually looking for a larger delta T (30C or so), so I don't have any direct experience with the operating range you are discussing. You have definitely caught my attention though.Quote:
Originally Posted by Scarlet Infidel
Many valuable innovations came from people who 'didn't know any better' than to try something that a more experienced person would dismiss as unworkable. Experience is a two edged sword - the things you know can filter your thinking and blind you to what you don't know. The whole point of doing this 'out of the mainstream' work is to break that view of how things work, and come at it from a fresh perspective.
Like many semiconductors, pelts develop internal EMF which affects the effective series resistance, and without published data, the only way to determine that is by experiment. Just to get an idea of the base operating levels at zero delta T and low voltage, I took a CP1-12730 ((which is supposed to have the same performance as the TEC 12730) and put it between two Melcor HX5-301 sinks ( http://www.melcor.com/bonded.html ) which have .07 C/W at 102 CFM and .13 in free air, so they should effectively keep the differential at zero for these low wattages. I then applied 3.3V and 5V with a series resistor of .1 Ohm to measure the current accurately.
I found that your estimates are close for amps draw - 3.3V drew 3.5A, and 5V drew 4.6A. The pelt actually drew a little less current than your estimate.
The next question is how much heat is moved. To do that I will put a gallon of water initially at 25C in an insulated container, and put the cold side in it, while maintaining the hot side at 25C in air. The drop in water temp over time will give us the heat transfer. But that will have to wait for another day...
Glad you can see some merit in what I'm saying and are even willing to give it a try.
I would almost be offended by your statement about people "who 'didn't know any better' " except I entirely agree. It can be a pain when 9/10 of those people are not suggesting anything sensible and you start to just dismiss them.
However, I would like to point out that I didn't stumble on the idea of running lower voltages out of chance, I did a whole load of reading and computer simulations first.
I'm looking forward to your results. I did a similar experiment with a water loop on the cold side to measure how quickly the water temp dropped. However mine was not as controlled as Id have liked and I had the added variable of the pumps heat load.
no offense meant at all - the 'experienced' people are often the first to dismiss a potentially good idea. I was only saying that many - maybe a majority - of innovative ideas come from people who are not 'experts'. For example almost all of the great discoveries of the 19th century were done by people who were not 'experts' but just had an interest in the problem, and the energy to go after a solution.Quote:
Originally Posted by Scarlet Infidel
I will test your low voltage approach and give you some feedback, but can't do it for a few weeks as I am traveling...
No problem, enjoy yourself.
Just one small suggestion. You have done an excellent job there. With so many peltiers you would have had no option other than to go for a heat exchange system using water on both sides. I am using two 68w peltiers with an air cooled system on the hot peltier side.
You will get some heat transfer between the hot and cold side with the clamping stainless steel bolts. My advice would be to go for slightly smaller diameter bolts and use transistor insulating mounts (plastic) to insulate the two sides. You could eliminate the heat transfer almost entirely.
These are the type of insulators I am referring to.
http://s263.photobucket.com/albums/i...e01/screws.jpg
You could also use nylon bolts and nuts.
Just one more piece of advice. Don't run the peltiers without the pump running.
That waterblock will freeze very quickly, as there is only a small volume of water. Remember ice expands and can easily damage your cold waterblock.
You should keep the cold side water volume in the system to a minium. That way it will be more efficient.
If you keep good airflow inside your computer case, condensation will not be a problem.
You could run the water through say a 120 mm radiator and fan and use it to cool the air inside the whole case. That way everything is cooled down.
Nylon and plastic are OK as long as everything stays cold, but not if the pelt ever gets hot - the nylon will not hold torque. Fiber washers and stainless steel bolts are a better choice - the SS does not transfer much heat. I use 3mm SS. Take care to apply torque evenly and not too much - the pelt can crack if one side is tightened before the others. A neoprene gasket will help to keep radiant transfer between hot and cold side down. But if the temp differential is small, loss from those factors is not really a factor.Quote:
Originally Posted by desone
Good point about freezing the block - if you are using a remotely controllable PS (like a converted ATX PS) you can switch the TEC supply on when the pump runs, and it is fairly easy to also shut it off if the cold side temp gets below a safe level.Quote:
Originally Posted by desone
You see im the oposite.Quote:
Originally Posted by Uncle Jimbo
When i got something in my head that i want, i go out and get whats needed.
The only thing im regretting right now is that i didnt grab the 600W meanwell like nol told me to. Now looks like i might need to grab another 320W meanwell.
Okey anyhow from my understanding and thank you jimbo, you've been an valuable resource to me in the past 2 threads, you think i should keep the hotside on air?
Let me rephrase this question after you know some background.
1. i have more excess h2o crap then air crap. So if i was to go out and get sinks, i would need to buy everything from ground up. The blocks are custom by Martin, so i would need to send out a block to a millist, and have him mill me a counter top where i can sink my screws in. Ummm... sounds like too much work.
2. The pump i designated for this system is still unknown. Most likely a DDC-3.2 for the cold side. The hotside i already picked up the DB-1. Since the loop was to be small to begin with, if your saying i want the hotside at a higher delta, i could always connect it to an MCR220. Kinda lost on this. But if your saying i want to keep a 50C on the hotside, then i figure MCR220 with a heat load of around 300-400W will probably make my coolants ~ 35-40C on a small radiator like that.
Blah, if i need to go out and get the sinks, man... No comment. :\
Okay sorry for lack of pics but camera trouble. So far though, I'm not seeing any benefit at all from the Tec chiller when in parallel. (As in, liquid pumped through hot side then rad on one half of a loop then hopping into resevoir, and other side going pump through cold side to load tester and back). And I'm not even applying load to the load tester yet. Cool side gains 1-2C, hot side gains 3-5C, and I'm sure that will get worse with a load.
yeah i could of told you that.Quote:
Originally Posted by n00b 0f l337
I seriously give the MCR320 new respect after this project.
Nol, run it straight like it originally should of been designed as.
Yep thats up next :)
I think you should use what you have around if you can. I have a 600W meanwell that I use for testing 24V stuff. But if you are planning on running 12V (i.e. 16V TEC), a regular ATX PSU does a fine job for a lot less money.Quote:
Originally Posted by NaeKuh
You can use WC on the hot side - you will lose a little efficiency but you will get more out of the TEC.
I'll look over the previous posts again and see if I can give you some advice on layout and design. Do you already have the TECs you want to use? That would help...