Post Rad Chiller Concept

[NaeKuh]

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.

well i would actually have to agree with you on this statement.

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?

[Uncle Jimbo]

well i would actually have to agree with you on this statement.

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?

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.

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.

[NaeKuh]

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.

You see im the oposite.

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. :\

[Uncle Jimbo]

You see im the oposite.

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. :\

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.

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...

[NaeKuh]

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.

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...

There 90W TEC's if my memory serves me. And theres 5 of them.

The block is uber free flowing. Placed right along with DD MPC Universal.

Nol is doing all the testing needed. :T Thats why he has it. After he figures out the best way to use it, thats how i will adopt it.

[Uncle Jimbo]

There 90W TEC's if my memory serves me. And theres 5 of them.

The block is uber free flowing. Placed right along with DD MPC Universal.

Nol is doing all the testing needed. :T Thats why he has it. After he figures out the best way to use it, thats how i will adopt it.

Well I stand corrected on getting more heat transfer than heat in. I took a small foam cooler case and mounted the TEC (a 12730) between 2 melcor sinks in the top so that the cold side sink was in the water almost to the TEC, and the hot side was in air. I used a 110CFM fan on the hot side, giving me .06C/W thermal resistance. With 1 gallon of water initially at 25C and room ambient at 25C, I applied 5.1V from a 500W Ultra supply. Current draw settled at 5.8A after a few minutes. That represents 29.6 watts in.

After 15 minutes, the hot side measured inside the sink by the TEC was 30.1C, and the water was at 22.7C. So pulling 2.3C out of a gallon of water in 15 minutes, with a differential of about 7 degrees. That represents about 40W transfer. The total hot side load of about 70W squares with the 5.1 rise pretty well, so I believe the numbers.

That is a single 62mm TEC, and with a different mounting arrangement I could probably get 4 of them under that Melcor sink, but the hot side would get a lot hotter with a 280W load. The TEC would be more efficient at the higher temp but also working across a bigger differential.

Just to see where it would go, I put 12.2V across the TEC and ran the same test. Current stabilized at 22A for a total heat in of about 270W. After 10 minutes, the hot side was at 50C, and the cold side just under 20C, representing about 130W transfer across a 30C differential.

That leads me to believe that 4 of these, run at 5V, would cool a 1GPM flow by .5C and require 120W to do it. That is clearly in the same league as phase change cooling for efficiency.

I'd like to try the same thing with WC on the hot side to see what it would do with a lower differential - my guess is it would move over 50W but use more current, so it might not be as efficient.

[Scarlet Infidel]

Well I stand corrected on getting more heat transfer than heat in...

Glad to see the theory working in practice. Thanks for trying that out, I hope that as more people see this effect and start believing it the more people will come up with innovative ways to exploit it.

I'm still itching to finish my chiller, but I'm so indescribably busy that there's no way I can spare a weekend to return home to do it.

Edit: also, I must try to spend a little time working on my peltier calculator program, it seemed to be giving startlingly accurate results with a few tests I ran.

[NaeKuh]

That leads me to believe that 4 of these, run at 5V, would cool a 1GPM flow by .5C and require 120W to do it. That is clearly in the same league as phase change cooling for efficiency.

I'd like to try the same thing with WC on the hot side to see what it would do with a lower differential - my guess is it would move over 50W but use more current, so it might not be as efficient.

I have 5 90W TEC's and nol is saying he's having a hard time pulling the heat off the hotside. :\

What you described above was also my theory, use them downvolted nicely, and try to pull the most efficiency out of it. :T