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Peltier

Herschel Peeler

Feb 21, 2016
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Just like your Fridge or Freezer, Insulation is VERY IMPORTANT.

And Peltier Modules are Very Low Efficiency, compared to compressor types of refrigeration.
I would recommend at LEAST 1 or 2 inches of Styrofoam over ALL Exterior Surfaces.

Try it your way and you will find it Does Not work very good.
You Might get 5 degrees lower.

And If you fan does Not keep the Hot Side COOL, than the Cold side will Get WARMER

No argument on the efficiency. A marketable product is not the objective. Just curiosity of duplicating a system I saw in the works before. It was a kilowatt size RF generator for an aircraft application previously cooled by CO2. It had a high failure rate. The next generation used a Peltier junction in a liquid. It felt like liquid silicone but I didn't get a chance to ask about it at the time. Failure problems solved. It must be more effective than air cooling, even if it is cO2. or something.
 

Chemelec

Jul 12, 2016
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I DOUBT it would work using Peltier Modules.
Unless you used quite a few of them, Possibly Double Stacked ones, to get a Greater Temperature Difference.

Or some HIGH CURRENT ONES.

Here are Some I have.

Peltier.JPG Greater Temperature Difference.
 

Herschel Peeler

Feb 21, 2016
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I DOUBT it would work using Peltier Modules.
Unless you used quite a few of them, Possibly Double Stacked ones, to get a Greater Temperature Difference.

Or some HIGH CURRENT ONES.

Here are Some I have.

View attachment 28057 Greater Temperature Difference.

Mine is a more complete assembly with heat sinks on both sides. Why do you think cooling a liquid would be different from cooling air? Air doesn't transfer heat as good as, say, antifreeze. All that changes is the medium being cooled.
 

BobK

Jan 5, 2010
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The point of liquid cooling is to move the heat away from the device so that it can be dissipated somewhere else, presumably where there is more space for a heat sink. Your Peltier device just moves it again. You still have the same heat to get rid of, plus the extra heat created by operating the Peltier cooler.

Bob
 

Herschel Peeler

Feb 21, 2016
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The point of liquid cooling is to move the heat away from the device so that it can be dissipated somewhere else, presumably where there is more space for a heat sink. Your Peltier device just moves it again. You still have the same heat to get rid of, plus the extra heat created by operating the Peltier cooler.

Bob

True.. The only thing I am changing is medium. Air just sucks at transferring heat. It takes a lot of space and movement to be effective.
 

BobK

Jan 5, 2010
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But you still have to remove the heat from the liquid.

Bob
 

davenn

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Air just sucks at transferring heat. It takes a lot of space and movement to be effective.

but you are still going to have to use moving air to cool the peltier, huh
you mite as well cut out the peltier and cool the liquid directly with forced air ... as in a vehicle radiator style system
 

Herschel Peeler

Feb 21, 2016
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But you still have to remove the heat from the liquid.

Bob

The junction removes the heat from the liquid. An external fan on the hot side removes that heat. The objective is to keep the electronics board cooler than with just forced air.
 

Herschel Peeler

Feb 21, 2016
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but you are still going to have to use moving air to cool the peltier, huh
you mite as well cut out the peltier and cool the liquid directly with forced air ... as in a vehicle radiator style system

Yes, an external fan cools the junction. The objective is to keep the electronics board cooler. I am expecting the liquid to be more effective than forced air. "Vehicle radiator" type I suspect will not get as cold as the Peltier junction.
 

BobK

Jan 5, 2010
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Davenn is right, all the Peltier is doing is adding heat that you must remove because it is not 100% efficient. The hot side of the Peltier produces more heat than the cool side removes. So cooling the liquid directly is more efficient.

Bob
 

davenn

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The objective is to keep the electronics board cooler
yes we all understand that

I am expecting the liquid to be more effective than forced air. "Vehicle radiator" type I suspect will not get as cold as the Peltier junction.

I think you seriously overestimate the effectiveness of a peltier device for such an application

with any type of cooling that you are looking at .... water/Freon, radiator and fan cooling etc, the objective is not to freeze the system
but rather to keep the electronics well below max operating temp.


Dave
 

BobK

Jan 5, 2010
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Why don't you tell us what it is you are trying to do? The temperature you need to keep the device at, and the ambient air temperature, for starters.

Bob
 

Herschel Peeler

Feb 21, 2016
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yes we all understand that



I think you seriously overestimate the effectiveness of a peltier device for such an application

with any type of cooling that you are looking at .... water/Freon, radiator and fan cooling etc, the objective is not to freeze the system
but rather to keep the electronics well below max operating temp.


Dave

This could very well be the case. I could very well be overestimating the Peltier.
 

Herschel Peeler

Feb 21, 2016
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Why don't you tell us what it is you are trying to do? The temperature you need to keep the device at, and the ambient air temperature, for starters.

I have no goal in mind. I have the stuff to do it and time on my hands.
 

hevans1944

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Jun 21, 2012
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Interfacing the "cold" side of a Peltier heat pump to a heat-transfer liquid, and then circulating the liquid to the electronics to be cooled is an excellent idea. One way to do this is to seal the "cold" face of the heat pump flush in a hole cut in the wall of an insulated liquid heat-transfer fluid reservoir. For maximum heat transfer from the liquid to the heat pump face, the liquid should be sprayed onto the "cool" heat pump face under pressure through nozzles. The cooled liquid is collected and circulated to the electronics boards in a cooling chamber that is also insulated. Plumbing from the cooled reservoir to the cooling chamber should be insulated.

It won't make much difference if the spray bar is operating in air or submerged in liquid heat-transfer fluid, but the components to be cooled should be fully immersed in the cooled liquid and the warmed liquid collected by the circulating pump for delivery back to the spray bar head.

The heat-transfer fluid can be any liquid that is electrically non-conductive and that remains liquid when heated to the maximum temperature expected of the electronics being cooled. This could be de-ionized or distilled water, with or without antifreeze, kerosene, or (my favorite) 3M Fluorinert. IMO silicone oils and refined mineral oil are not very good heat-transfer liquids, but use whatever works.

Back in the day, we used R13 as the heat-transfer liquid because it remains liquid over a wide temperature range at atmospheric pressure and is a good dielectric... the thing we were cooling was at a negative 20 kV potential with respect to earth ground. Unfortunately, R13 is a "greenhouse" gas when accidentally released into the atmosphere, so it is not only very expensive but increasingly hard to procure since it can no longer be manufactured in the United States or imported. All stock sold today comes from R13 that has been recovered from commercial refrigeration systems... about $2000 for 100 Lbs the last time I purchased any. Fluorinert isn't cheap, but it is at least available.

Heat must be removed from the "hot" side of the Peltier heat pump and transferred to something, usually ambient air forced with a fan to flow over a finned heat-sink. If space is at a premium, the "hot" side of the heat pump can also be water-cooled, but you still have to remove the heat from the water and exhaust the heat somewhere.

The Peltier heat-pump is just one component of a sophisticated immersion cooling system. While it may be more reliable than mechanical refrigeration, it is way more inefficient. OTOH, if all you want to do is move a few watts of heat away from your over-clocked CPU, maybe a Peltier heat pump can help with that. I think a conventional finned heat-sink and fan works just fine for that, but some folks like to push the envelope of their electronics. One thing for sure: Peltier heat-pumps are fun to play with!
 

Karthik rajagopal

May 9, 2016
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1 http://www.marlow.com/resources/general-faq/6-how-do-thermoelectric-coolers-tecs-work.html
very simply a peltier moves heat from one place to another using semiconductors

2 uses are for cooling and heating (its odd but yes heating) and if you make one side hot and other cold it could theoretically generate power too... but not efficiently. peltiers can be found inside computers on the cpu (not standard but it is fun to do) to help cool it. this is the most widely used peltier, however there are peltier fridges, air cons etc

3 to connect a peltier up connect it like a motor. one wire black-, 1 wire red +. if you hook these up the other way around then the hot and cold sides will reverse. this can be beneficial if you want to make a cup holder, keep some drinks cold, other warm

now having said all of this peltiers are currently a great idea for non-mechanical/moving parts cooling. unfortunately they suck amps like fish suck water.....

ok lastly a peltier works on 2 key aspects... number 1 if they get too cold or hot they no worky
2 the best thing to look at is a temperature difference. what I mean from this is that lets say 30 degrees is the temp dif(TD) that means the cold side will only ever be 30 degrees colder than the hot side. so if you don't take away the heat (heat sink, water, fan(not so effective without heatsink) then the hot side will slowly get hotter when this happens the cold side gets hotter too.... so then you actually start warming it.
2a having said this if you want a 60 degree TD the easiest way is to plug a heat sink on the hot side of one, the plug the cold side to the hot side of another..... this will give you colder temps... but more amps
Thank you so much for your reply.
 

Sunnysky

Jul 15, 2016
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Peltier devices can be used for RF, medical imaging , radar transmitters etc, where massive cooling and low thermal resistance is critical.

They can also be used to cool semiconductors in expensive production testers that maintain a temperature of 25'C when tested, regardless of D.U.T. power dissipation.

Although Liquid cooled CPU's are popular, the advantage with Peltier devices is overclocked CPU"s can be frozen with large Peltier devices.
See attached for Direct -Air, Air-Air, Liquid-Air types. avail at Digikey
http://cdn.lairdtech.com/home/brandworld/files/ETS-BRO-Thermoelectric-Assemblies.pdf
e.g.
Power - Cooling 207W
Current 8.1A Voltage 24V http://www.digikey.com/product-deta...utions/DL-210-24-00-00-00/926-1091-ND/2269653

I wonder if someone wants to brew coffee while chilling a beer at the same time.
 
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