Author Topic: A look at Peltier cooling  (Read 109097 times)

0 Members and 1 Guest are viewing this topic.

taylorp035

  • Hero Member
  • *****
  • Posts: 1204
  • Country: us
  • Stressed spelled backwards is Desserts
Re: A look at Peltier cooling
« Reply #33 on: February 17, 2011, 05:24:14 PM »
I have recently bought a 134 w chip and played with it for a few days.  As for your efficiency, I thought it was closer to 10%, which is much less than a refrigeration pump.

For my supermileage car, we are buying a ~240 w chip to make a cooled seat.  We plan on running it at half power for better efficiency.  I have read that going past 75% of the power rating is pointless for cooling things down, unless you have a massive heat sink.  Our chip will be hooked up to a water block and a aluminum heat sink + a 100cfm box fan.

Once you turn the chip off, they heat up to the hot side temp real fast.  Trying the generate power is almost impossible.  My max was about 2v at 1 amp for a few seconds using some big pieces of aluminum on both sides.


Madscientist267

  • Hero Member
  • *****
  • Posts: 1181
  • Country: us
  • Uh oh. Now what have I done?
Re: A look at Peltier cooling
« Reply #34 on: February 17, 2011, 06:08:31 PM »
Quote
less than a refrigeration pump

I have my reservations about this for sure. Chicken or Egg is in play here, so to speak.

My only light in the tunnel at this point is the idea that they can hold a reasonable facsimile of temperature difference at very low power levels.

That's probably the key point in all of this; Peltiers can be throttled, compressors cannot.

It's going to come down to average power consumption. So let's play with some math real quick...

These numbers aren't really directly comparable, because they are taken from two rather different sized implements, but the concepts are there...

The compressor on the Lowes box draws just shy of 2 amps (RLA) at 120V. That's 240W.

If it runs for 6 minutes out of every hour, that's 24wH of power used just countering the leakage in the insulation.

Take the 10 Peltiers, and run them continuously, however throttled way back.

If they can maintain the temperature in the chamber for less than 24W, it's plausible to do something like this.

If they can maintain it for less than 12, its completely viable.

The Coleman can do it with 9W. It's also all of maybe 2 cubic feet.

Problem is, a bigger chamber means more surface area, and all else being equal, means more thermal leakage, which means more power to keep the heat where it needs to be.

Not sure if it scales linearly (probably not, my luck it's more likely a square...?), but even if it is linear, 5 cubic feet would translate into 2.5x the power required to keep that same balance.

Works out to 22.5W, which is still less power than the compressor.

Also, with Peltier, not contending with motor start surges.

Steve
The size of the project matters not.
How much magic smoke it contains does !

zap

  • Hero Member
  • *****
  • Posts: 1107
  • There's an app for that
Re: A look at Peltier cooling
« Reply #35 on: February 17, 2011, 07:10:52 PM »

Problem is, a bigger chamber means more surface area, and all else being equal, means more thermal leakage, which means more power to keep the heat where it needs to be.

Not sure if it scales linearly (probably not, my luck it's more likely a square...?), but even if it is linear, 5 cubic feet would translate into 2.5x the power required to keep that same balance.

I've been following this post from the start because I've always wanted to play w/a peltier, the one thing that doesn't seem to have been mentioned, much, is the insulation... orrrrr... did I miss a big chunk?  :-\

Seth7

  • Newbie
  • *
  • Posts: 30
Re: A look at Peltier cooling
« Reply #36 on: February 17, 2011, 07:14:16 PM »
Me too .. i bought 50 @ 100W peltier's 7 years ago .... and i have a 80lb heatsink from a 900Mhz CDMA amp .....
building a PicMicro to PWM dosent seem too hard ....

Mike KC7NOA

Madscientist267

  • Hero Member
  • *****
  • Posts: 1181
  • Country: us
  • Uh oh. Now what have I done?
Re: A look at Peltier cooling
« Reply #37 on: February 17, 2011, 08:30:37 PM »
Zap -

The concept of insulation has gone all over the place on this one. Passive, active, back to passive, and now homebrew...  ;D

This is where I'm at for the moment on this...

From the post with the heatsink dimension specs:

Quote
Also, considering using some 'aerogel' based insulation to give it that final space-age touch (the 'SpaceLoft' blanket, near the bottom):

http://www.buyaerogel.com/

Anybody have any experience with this stuff? Claims to be a couple times more insulating than styrofoam... and only a minor irritant to various body parts.

It resembles something between felt and wool...

Not using that for the very first tests however. Decided I'm going to cheap out until I get an idea of whether to continue funding the project.

Going to build a surrogate door out of cardboard, fiberglass insulation, and duct tape to see if the principles are worth chasing.

At least that way if it bombs on me and all I end up with is a bunch of Peltiers and a freezer, I still have just that. A working freezer.

If the preliminary tests work as expected, I'll move on to pseudo-destruction of the real door and go for the good insulation.



Seth -

Quote
building a PicMicro to PWM dosent seem too hard

Just don't forget that raw PWM doesn't work as one would expect with a Peltier module. The power input needs to be as smooth as possible, ideally a pure DC 'waveform'.

HEAVY filtering is in order here to maximize efficiency.

PWM taking an all-to-nothing approach causes multiple problems with Peltiers;

1 - When in 'all' state, the module is running full throttle at it's least efficient operating point

2 - When in 'nothing' state, the module is not providing any cooling whatsoever, and the residual heat from the hot side will tend to head back toward the cool side, defeating the purpose of running it to start with

3 - PWM can be stressful on thermocoupled joints such as in a Peltier module, due to the repeated heating/cooling cycles happening several thousand times a second, eventually leading to module failure.

A buck converter is likely the best solution, again, heavily filtered.

Steve
« Last Edit: February 17, 2011, 08:33:58 PM by Madscientist267 »
The size of the project matters not.
How much magic smoke it contains does !

Madscientist267

  • Hero Member
  • *****
  • Posts: 1181
  • Country: us
  • Uh oh. Now what have I done?
Re: A look at Peltier cooling
« Reply #38 on: February 17, 2011, 08:44:30 PM »
By the way, the Coleman is now in 'coasting' mode, running at 5V, using 9 watts.

I have the data from the full power cool down, just need to plot it on paper.

I'll put it up after I have a few days of data collected from the coasting...

Steve
The size of the project matters not.
How much magic smoke it contains does !

DanG

  • Hero Member
  • *****
  • Posts: 1122
  • Country: us
  • 35 miles east of Lake Okeechobee
Re: A look at Peltier cooling
« Reply #39 on: February 17, 2011, 10:11:23 PM »
Umn - in a dual-source unit the peltiers can never be shut off, I guess you're ready for 24/7/365 DC amps.

Environment heat freon eventually will have to deal with unless energized, even (baffled, shrouded, gated) it will be shining more heat than the original insulation design.

Madscientist267

  • Hero Member
  • *****
  • Posts: 1181
  • Country: us
  • Uh oh. Now what have I done?
Re: A look at Peltier cooling
« Reply #40 on: February 17, 2011, 10:32:21 PM »
Quote
Umn - in a dual-source unit the peltiers can never be shut off, I guess you're ready for 24/7/365 DC amps.

Correct; as long as this continuous drain is less than the averaged consumption that the compressor would use to perform the same work by cycling, it's Peltier for the win.


Quote
Environment heat freon eventually will have to deal with unless energized, even (baffled, shrouded, gated) it will be shining more heat than the original insulation design.

On this, you lost me just a bit. Elaborate? :)

Do you mean as in heat leaking in from the outside via the freon plumbing, acting like heat pipes?

I had considered that, not entirely clear on how to get around it. Chalked it up as one of the losses I was just going to have to accept as part of the design...  ???

Steve
The size of the project matters not.
How much magic smoke it contains does !

zap

  • Hero Member
  • *****
  • Posts: 1107
  • There's an app for that
Re: A look at Peltier cooling
« Reply #41 on: February 17, 2011, 11:30:59 PM »
I don't understand why the peltier can't be shut off ???

Do I need to increase my fish oil intake?

Madscientist267

  • Hero Member
  • *****
  • Posts: 1181
  • Country: us
  • Uh oh. Now what have I done?
Re: A look at Peltier cooling
« Reply #42 on: February 18, 2011, 12:20:44 AM »
It's a two part problem that only really has one solution: Trickling.

First, a Peltier that is turned off isn't too much less of a heat conductor than if it were just replaced with an aluminum block of similar dimensions. The heat from the outside readily leaks back through to the cold side from the hot side.

Second, because they are so inefficient, they generate more heat than they move, so the excess heat found on the hot side will quickly find its way back to the cold side, in addition to whatever is leaking from the ambient air on the hot side.

The result is you will actually put more heat in the fridge than you were taking out.

The only way around this is to keep them powered up, but throttled back so that they are not allowing the reverse heat creep.

In this design, however, I'm taking it a step further and adding just a touch more juice to keep what is leaking through the box insulation pumped to the outside.

Steve
The size of the project matters not.
How much magic smoke it contains does !

zap

  • Hero Member
  • *****
  • Posts: 1107
  • There's an app for that
Re: A look at Peltier cooling
« Reply #43 on: February 18, 2011, 12:39:09 AM »
OK... so why not make the module movable?
Imagine a CD/DVD tray holding the module on top of the lid.  The module slides out from over it's "hole" when not working and a "plug" of insulation is pulled into it's place.  I would think a stock CD/DVD tray could handle that and it could be automated to work with a thermostat.
Since the module is outside the chest it could then be powered off without harm?

Madscientist267

  • Hero Member
  • *****
  • Posts: 1181
  • Country: us
  • Uh oh. Now what have I done?
Re: A look at Peltier cooling
« Reply #44 on: February 18, 2011, 12:59:09 AM »
The logistics in that would be a nightmare... :(

The biggie that comes to mind right off the top of my head is the heatsink grease.

If using mechanical means to isolate the two worlds were employed, it would be more feasible to either insulate the cold side sink from the chamber, or remove the entire assembly and plug the hole.

Either way, separating and pairing the module on demand is pretty much out of the question. It would be like taking your CPU out of your computer whenever you're not using it.

Steve
The size of the project matters not.
How much magic smoke it contains does !

zap

  • Hero Member
  • *****
  • Posts: 1107
  • There's an app for that
Re: A look at Peltier cooling
« Reply #45 on: February 18, 2011, 01:42:27 AM »
If using mechanical means to isolate the two worlds were employed, it would be more feasible to either insulate the cold side sink from the chamber, or remove the entire assembly and plug the hole.
That's exactly what I was talking about.  Forget separating the assembly.
Have the whole thing sitting up far enough so you can slide a piece of insulation under the whole thing?  A CD/DVD tray could do that more easily.

I can draw a pic if ya want.


Madscientist267

  • Hero Member
  • *****
  • Posts: 1181
  • Country: us
  • Uh oh. Now what have I done?
Re: A look at Peltier cooling
« Reply #46 on: February 18, 2011, 09:38:59 AM »
Hmm... Yeah, I think I can see the basic concept you're getting at. I just don't know if it would be worth all the trouble.

Another side effect of powering down the Peltiers when off-cycle comes from the idea that they aren't exactly quick about 'setting up'.

It takes a little bit to get the temp of the cold side heatsink down after initial power application. So, for whatever length of time it takes to get the sink down below the temp of the cooled chamber, it will be depositing heat into the chamber until the point of thermal equilibrium (and subsequently reversal) is reached.

This might take a good percentage of the energy that would have otherwise just have been used in maintaining the differential.

Thermodynamics is a ^#$@&, I know. LOL

I'm piecing the big picture together as I go, and so far, it's falling into place why Peltier is not more commonplace as a heat pump.

I'm pursuing it really only for a few reasons. One, and this is big, no moving parts to wear out. Two, no noise. Third, power conversion losses would be less (thinking in terms of comparing running a compressor from an inverter vs directly driving the Peltiers).

Problem is, it's already a very close call, if it even is possible to do the job with less energy than a compressor uses. But that's what I'm here to try and find out. :)

One of the first things I intend on doing when I receive the modules is taking one of them, and temporarily mounting the hot side on a heatsink, and leaving the other side exposed.

I'll get (at least) two useful pieces of info out of this:

First, I'm going to find out what the absolute bare minimum power requirements are to get various temperature differences, then plot the results. There will be a knee somewhere in the curve, and that is roughly the butter zone for the most efficient active cooling.

The other, is to find out where the lowest possible power input begins to have an effect. I have a theory that I haven't really been able to confirm just yet; Once they begin to pump heat, they seem to resist heat flow better from the opposite direction. In other words, they may be able to provide active insulation (at least for themselves) from the outside temperature with even less power than what it takes to just maintain the temperature. If I am correct, and the relationship is non-linear, small changes of a few degrees in temperature on the outside would not readily propagate to the inside through the module. With passive insulation, there is strictly a linear relationship between temperature difference and rate of transfer.

The effect of this would be that even though they may end up being less than useful for active cooling (or even maintenance), if they can provide active insulation for the entire box for much less power than I am even seeing for maintenance, this is still very much so doable. They would need to be spread out, so we've gone full circle on that again as well...

I apologize for the 'bipolar/circular' tendency of this entire thread. Lots of variables, lots of thinking on paper, and lots of theory. I fear the zig-zagging won't stop until I can physically try some of my thoughts in real application.  :-\

Steve
The size of the project matters not.
How much magic smoke it contains does !

Bruce S

  • Administrator
  • Super Hero Member Plus
  • *****
  • Posts: 5370
  • Country: us
  • USA
Re: A look at Peltier cooling
« Reply #47 on: February 18, 2011, 09:42:05 AM »
Steve.
The no big surge start-up is one thing I really do like about these.
Even if they turn out not to be so efficient, being able to start one up without a large invertor is very worth while and appealing.

Cheers;
Bruce S
   
A kind word often goes unsaid BUT never goes unheard

zap

  • Hero Member
  • *****
  • Posts: 1107
  • There's an app for that
Re: A look at Peltier cooling
« Reply #48 on: February 18, 2011, 10:21:50 AM »
I apologize for the 'bipolar/circular' tendency of this entire thread. Lots of variables, lots of thinking on paper, and lots of theory. I fear the zig-zagging won't stop until I can physically try some of my thoughts in real application.  :-\

Steve

None needed.
It's an interesting post... and... I'll :-X now.

dnix71

  • SuperHero Member
  • ******
  • Posts: 2513
Re: A look at Peltier cooling
« Reply #49 on: February 18, 2011, 04:46:59 PM »
Zap maybe not moving the peltier assembly out of the way, but rather just sliding an insulated cover over the assembly would be easier. Mylar with some foam for a shield. Maybe like a roll up door.


zap

  • Hero Member
  • *****
  • Posts: 1107
  • There's an app for that
Re: A look at Peltier cooling
« Reply #50 on: February 18, 2011, 05:37:25 PM »
Yup... that's what I was saying up there a ways.

I think the peltier should be on the top.  Seems to me the cold would naturally fall into the cooler.



You could ignore the drive mechanism if need be and make the sliding part also be the on/off switch.

dnix71

  • SuperHero Member
  • ******
  • Posts: 2513
Re: A look at Peltier cooling
« Reply #51 on: February 18, 2011, 09:02:16 PM »
The drive mechanism could be simply a spring loaded solenoid. When energized, it pulls back the insulation. Cut the power and the spring closes it. The spring doesn't have to be large and it doesn't have to snap shut, just gently pull shut.

Madscientist267

  • Hero Member
  • *****
  • Posts: 1181
  • Country: us
  • Uh oh. Now what have I done?
Re: A look at Peltier cooling
« Reply #52 on: February 19, 2011, 01:41:01 AM »
What effect will this have from heat shock when the Peltier warms up... You then have to drop the temps again.

I don't think they're efficient enough to ever completely cut off. "Cheaper ta keeper". :)

Cycling a heatsink down to temp can take minutes. :(

Steve
 
The size of the project matters not.
How much magic smoke it contains does !

DamonHD

  • Administrator
  • Super Hero Member Plus
  • *****
  • Posts: 4125
  • Country: gb
    • Earth Notes
Re: A look at Peltier cooling
« Reply #53 on: February 19, 2011, 06:25:57 AM »
I think the sliding flap is Maxwell's demon!  B^>

Rgds

Damon
Podcast: https://www.earth.org.uk/SECTION_podcast.html

@DamonHD@mastodon.social

Madscientist267

  • Hero Member
  • *****
  • Posts: 1181
  • Country: us
  • Uh oh. Now what have I done?
Re: A look at Peltier cooling
« Reply #54 on: February 19, 2011, 09:52:40 PM »
Got the sinks yesterday BTW!

Was easy, too... no digging. They had been stacking them all, some with fans still on them.

I'll be returning the fans (due to a glitch in communication and understanding of what was what on my part), but the sinks are mine! All 30 of 'em!



The heatsinks laid out before cleaning and de-fanning.





Detailed shot of one of them, with an old pack of smokes for size comparison.





All cleaned up (even ran them through the dishwasher). This is the rough configuration physically that they will be in.

Main difference is that I will probably use two rows on the cold side instead of three to make up for the inherent heat generation.

Still not entirely clear how I'm going to go about holding them all together and in place, although I'm thinking something like thermal epoxy on each sink to something like a 0.25 inch slab of aluminum plate for each side. The Peltiers would then be sandwiched between the two slabs with standard heatsink grease.

Or something like that.

At least it didn't cost me a thousand bucks!  ::)

Steve
The size of the project matters not.
How much magic smoke it contains does !

zap

  • Hero Member
  • *****
  • Posts: 1107
  • There's an app for that
Re: A look at Peltier cooling
« Reply #55 on: February 19, 2011, 11:35:12 PM »
Still not entirely clear how I'm going to go about holding them all together and in place, although I'm thinking something like thermal epoxy on each sink to something like a 0.25 inch slab of aluminum plate for each side. The Peltiers would then be sandwiched between the two slabs with standard heatsink grease.

Or something like that.


Folks have been using JB Weld for many years for such things... the metal in it tends to conduct heat very well.

I think the sliding flap is Maxwell's demon!  B^>

Rgds

Damon

The design I posted is my intellectual property and mine alone... if Maxwell doesn't like it, Maxwell can sue me ;)
« Last Edit: February 19, 2011, 11:39:58 PM by zap »

Madscientist267

  • Hero Member
  • *****
  • Posts: 1181
  • Country: us
  • Uh oh. Now what have I done?
Re: A look at Peltier cooling
« Reply #56 on: February 20, 2011, 03:24:20 PM »
Freezer got here today as well. Had to pull some strings - they were trying to deliver it next Saturday.

I don't think so.

Here it is with the heatsinks 'mocked up' on a board sitting on top of the unit...



Looks like with a little careful spacing and substrate management, I'll be able to cover the entire top. :)

Steve
The size of the project matters not.
How much magic smoke it contains does !

taylorp035

  • Hero Member
  • *****
  • Posts: 1204
  • Country: us
  • Stressed spelled backwards is Desserts
Re: A look at Peltier cooling
« Reply #57 on: March 07, 2011, 07:26:54 PM »
I have been messing around with these last few days and there are so many variables that I just decided to make a spreadsheet that does it for me.  If you guys want to make a fridge, the biggest bang for your buck comes in the form of a bigger fan or bigger heat sink.  Getting the lowest C / W rating will let you lower your input power to the chip. 

I'm in the same situation right now, as I am trying to make a cooled seat, but I have some serious limits to how much power I can use.  At 25w of cooling, I can achieve a temp drop of 22.4 C at 300W input and 200 CFM on my 2"x5" heat sink.  But at 300w, my battery will die in 5 min.  Most likely I will end up with a 23 min run time w/ 2 batteries and a 9.5C temp drop.  I will have to update once I get the whole system working.

DanG

  • Hero Member
  • *****
  • Posts: 1122
  • Country: us
  • 35 miles east of Lake Okeechobee
Re: A look at Peltier cooling
« Reply #58 on: March 08, 2011, 09:00:34 AM »
Umnn - you have moving air already, and the auxiliary fan.. maybe you can go a little more basic..

Evaporating a gram of water at 106°F in one minute absorbs 569 calories or 2.25646442627 BTU or 39.65 watts heat energy.

The same amount ice to evaporated vapor carries away 720 calories per gram or 2.8552801176 BTU or 50.17 watts heat energy.

An average sensible heat for a human standing might be 4 BTU per minute, with brisk activity that is 6 BTU.

If you can keep wicking from acting as an insulator then having just enough water holding vs. surface area might give ten minutes of coolth. The old dip seat in water, shake twice and ride trick.

taylorp035

  • Hero Member
  • *****
  • Posts: 1204
  • Country: us
  • Stressed spelled backwards is Desserts
Re: A look at Peltier cooling
« Reply #59 on: March 08, 2011, 09:24:16 AM »
We could spray water on the heat sink, in which the water should evaporate fairly quickly.  Our idea will work, but we probably bought TEC's that were too large (Qc = 248 and 134w). 

Here is the set up right now:







Things that majorly change the performance include where we put the fan and the power input.  Our fan is only 100 CFM, so we plan on buying a 250 CFM soon. According to my calculations, that will drop the temperature at least 10C.  The water pump pushes 2 GPM and the water block is 3" x 3" for scale.  The water pipes are 3/8" I.D, 1/2" O.D.

« Last Edit: March 08, 2011, 09:40:22 AM by taylorp035 »

taylorp035

  • Hero Member
  • *****
  • Posts: 1204
  • Country: us
  • Stressed spelled backwards is Desserts
Re: A look at Peltier cooling
« Reply #60 on: March 11, 2011, 12:09:18 PM »
After messing around with the set up, we managed to get the temp down to 54 F.  Interestingly, we were shipped the wrong fan, which has an output of 2W instead of 6W, hence there is no way that the fan was putting out 100 CFM.  So we boosted the voltage on the fan to 21v and made a new shroud to direct the air.  To get the lowest temperature, we ran our TEC at 8A and 9v, so the heat sink wouldn't get too hot and the overall temp drop would be lower.  Yesterday I found a delta fan that puts out 252 CFM.  After watching a bunch of videos of it in action, I have no doubt that the performance of it will be up to the task of removing the heat.


taylorp035

  • Hero Member
  • *****
  • Posts: 1204
  • Country: us
  • Stressed spelled backwards is Desserts
Re: A look at Peltier cooling
« Reply #61 on: March 16, 2011, 09:24:50 PM »
I got my new uber 252 CFM 120mm box fan, and I got the temp down to 50.77 F @ 12A and ~12.5v (total system power = fan + TEC + pump).  Then then hooked up the 40' of tubing and made myself a "cooled office chair".  It turned out to be very effective.  More of this will be posted hopefully in its own thread when more progress + time is allowed for (things are moving very fast  ;D ).

Madscientist267

  • Hero Member
  • *****
  • Posts: 1181
  • Country: us
  • Uh oh. Now what have I done?
Re: A look at Peltier cooling
« Reply #62 on: March 17, 2011, 07:01:55 PM »
coolth... hmm... a highly technical term... ;D

I want to add that stacking the modules may provide more heat flow at a lower power input, just based on what I've seen so far. More bang for the buck.

I'm considering the concept myself, although I have to weigh all the variables because I am looking at running them anywhere from a trickle to full power, and stacked modules will cause the 'cold side' module to overheat because they are the same size. This wouldn't be a problem at lower power levels but at full throttle it is liable to let the smoke out.

I would think that the following combination would be the most efficient:

1 - Run two modules stacked at reduced power. You would of course need to experiment and make a curve for power input vs heat flow to find the butter zone. Maybe even individually adjust them and/or try two different capacity modules (the smaller on the cold side).

2 - Trickle water onto a wick material at the heatsink. The wick would extend out of the heatsink fins somewhat to provide better surface area.

3 - Allow free air that was ducted from the outside to flow over the heatsink and wick (that odd named duct comes to mind, cant think of the name right off the top of my head).

4 - Tweak the flow rate of the cooling water for minimum heat difference between the sides of the Peltier, yet provides adequate cooling to the entire surface of the seat (under load!)

By doing this, you'd eliminate the fan, further saving on power, and your modules would be running at an optimal power level.

Shouldn't be hard, you said you already have two different modules, just slap a piece of 1/4" aluminum between them to optimize heat transfer, and give it a shot. I'd be willing to bet you can get the same cooling for significantly less power. Maybe 30% or so?

FWIW

Steve
The size of the project matters not.
How much magic smoke it contains does !

taylorp035

  • Hero Member
  • *****
  • Posts: 1204
  • Country: us
  • Stressed spelled backwards is Desserts
Re: A look at Peltier cooling
« Reply #63 on: March 18, 2011, 11:37:33 AM »
I found this website to be very helpful.  They have PDF's on the performance of the chips, so you can calculate things before you spend any money.  This is where I bought all of my stuff (the water block, heatsink, and TEC).
http://www.customthermoelectric.com/

I'm not sure that running the water pump at a slower speed will help you.  The C/W of the water block goes down as you increase the flow rate.  In my setup, I am loosing about 4C through the water block @ 2 gpm.

As for stacking the chips, they have a few setups like this, where the max delta T is around 80 C instead of 60C.  Under real operating conditions with a load, the delta T is generally much lower (20-30 C).  The graphs that they have demonstrate this very well.

I'm not sure how well the evaporative cooling will work, but I can say that increasing the fan speed will make your quest for colder temperatures much easier.  If you could have a stream of running water over the heatsink (slow flow rate), you could get colder temperatures much easier than using a fan (probably less power consumption too.  Maybe you could have a 10 gallon container of water that acts like a reservoir, and as long as the temperature stays below 80 ish degrees F, things should work well.  Reaching 40 F with fans and heatsinks would be very challenging, especially if you want more than 5w of cooling.  My cooled seat cools at about 25-50w.


Bruce S

  • Administrator
  • Super Hero Member Plus
  • *****
  • Posts: 5370
  • Country: us
  • USA
Re: A look at Peltier cooling
« Reply #64 on: March 18, 2011, 11:55:01 AM »
For Madscientits267's freezer setup the water-bath of even wick method may be the better way to go since water is able to wick away heat better than a mere fan.
On Taylorp035's vehicle and the need to keep weight at a minimum, I believe the fan to be the better route, unless its leads to added battery weight to keep up with the demand.

I'm following both posts and both are moving along with great info.
I have a 1CF beer fridge that has a traditional cooling system that gave up its last pump.
I plan on using this to work with the 4 4x4inch TECs I have been saving for just this something  :D

Thanks you guys for all the information and on-going tests!
Bruce S
A kind word often goes unsaid BUT never goes unheard

taylorp035

  • Hero Member
  • *****
  • Posts: 1204
  • Country: us
  • Stressed spelled backwards is Desserts
Re: A look at Peltier cooling
« Reply #65 on: March 18, 2011, 11:58:50 AM »
No problem.  Its a lot of fun  ;D

Power drain will be around 150w, or about 11 min run time on 1 battery.  Each extra battery will add 3/4 lb or so.  Also, having water being sprayed around all of our electronics is probably a bad idea.

More progress will be made tonight.