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924guy · Posted: Fri May 07, 2004 8:09 am Post subject: alternative to Intercooler?

just an idea thats been bouncing around the back of my head for awhile..ive no idea if its even remotely realistic, acurate, or actionable, but here it is..

Ive been loosely studying cooling semi conductors (very loosely) , like the ones they put in the portable coolers you can plug into the car to keep your drinks cold... the units themselves are very small, and require a heatsink and fan.. but the guts are fairly tiny.. heres an example: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=4660&item=3813825352&rd=1 .

Now, the thought occured to me that "if" one were to cut a 931 charge tube in half, remove a few inches or the runner and splice in an aluminum box with one or more of these units bonded to it (cold side) , with the heatsink and fan external to it, isnt it possible to dramatically reduce the intake air temp? Since thats my understanding of the pupose of an IC, i thought just maybe with a bit of work one could refridgerate (in effect) the charge tube and at least equal the effects of a top mount ic in much smaller package..and much more cheaply. and if this is so, the only other problem would be a potential for excessive water build (ice) inside the tube.. however the temp is controlled by the voltage and is should be easy to ensure it doesnt drop below freezing via a rheostat or potentometer.

is this idea so off the wall it could actually work? or am i missing a pressure variable that wouldnt be achieved that a conventional ic covers, or cant be compensated for in this manner?

if its ridiculous , i wont be offended.. but i figured id throw it out there and see what gets thrown back..
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78 924
82 931 SE "smokey"
99' VehiCross
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Paul · Posted: Fri May 07, 2004 10:55 am Post subject:

I'm guessing the amount of heat we could transfer using those thermocouples would be almost nothing. We need to remove major BTUs.

924guy · Posted: Sat May 08, 2004 12:54 am Post subject:

good point... ill have to do some tests and take intake air temp readings and compare them against a theoretical heat soak ability.. but along the same lines im almost thinking that even simply "refridgerating" an ic could allow a vast reduction in the size of the ic yet equal the results of a much larger unit..its all in the effectiveness of the heat transfer.. wouldnt it be cool to be able to splice in a small electrically cooled IC unit thats not much larger that the current runner and achieve the same as say, a front mounted ic?
my first thought was that it wouldve been tried and experimented with already if it could be done, and maybe it has.. but perhaps its worth a further look in into..
at some point i think i can bench test such a project using a portable heater (to approximate the intake air temp from a turbo) a few temp sensors and a runner with a refridgerated ic spliced in.. ill have to take some stock data and crunch some numbers first, find the time, spare runner and a place to play...just thoughts at this point though....
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Eric
78 924
82 931 SE "smokey"
99' VehiCross
Y2K Honda Insight
http://www.cardomain.com/id/924Guy
Performance by Pasha

-nick · Joined: 16 Nov 2002 Posts: 2699 Location: Cambridge, MA

An old turbo drag car trick was to pack the air-water IC (if so equiped) with dry ice! Of course, this is for one 1/4 mile at a time

I bet Paul's probably right. The amount of BTU's needed to soak up requires some serious refrigeration.

-nick

MunkPuppy · Posted: Sat May 08, 2004 3:22 am Post subject:

well now you've got me thinking... which can be dangerous after getting a graveyard shift at the manufacturing plant where I work

I had a huge thing typed out, but I think I can sum it up...

You'll need lots of surface area to effectively cool the intake air, and a good way to cool the hot side of the peltiers. I would think that a homemade water-cooling setup using a heater core from a very small vehicle would work fine to cool the multiple peltiers needed. IMHO, I think that tapping a cooling line from the engine's cooling system may be too hot for this purpose.

The aluminum box idea is a start, but as with any cooling solution, surface area is key for effective thermal transfer. Maybe some kind of grid or a cluster of copper or aluminum tubing inside the intake would help things a little? It could create enough airflow restriction to cancel out the benefits of the colder air charge. I don't know, as I haven't tried it, nor have I the faintest clue on how to calculate it. I hate math anyways.

And, I don't really think you'd need to worry about condensation, as the air most definately doesn't sit still long enough for moisture to stick to something, and the heat of the incoming air would probably evaporate any condensation.

A little moisture in your air/fuel mix is good anyways

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Smoothie · Posted: Sat May 08, 2004 3:29 am Post subject:

I'm a bit pessimistic on the idea also and have to place my guess with the "too much BTU's" scenario.

If you want to play with the idea though - a quick test might be:
Place the cooling element inside a 2"-3" tube.
Drill holes, one just before and one just after the cooler, sized to allow insertion of the end of a thermometer.
Shoot your hair drier through and measure temps before and after the cooler.

Your hair drier probably won't even get hot enough to consider this a real good test though, since air temp output from turbos (non-intercooled) tends to be in the 250*F to 350*F range.
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"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

IanJ · Posted: Sat May 08, 2004 5:35 am Post subject:

What you want is one of these.....

From http://www.thelegacycontinues.co.uk/CRYOINTSPRAYER.HTM

There is some debate on the subaru forums as to the benefits of this. Some people are worried about metal fatigue of the turbo/intercooler parts due to the amount of cooling difference it provides. Others think it may make the air too cold and too dense and actually sap power.

Me......I know nothing!

Ian
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kye · Posted: Mon May 10, 2004 1:01 pm Post subject:

very interesting idea.. shame on me for not thinking of it - gee, i'm only switching my computer to water cooling, so why would I think of it?!

I did a scout around on the net, and got anything from 1000W/kg/degree to 0.0484W/Kg/degree, so progressing beyond this point is a little silly. hard data required!

would you make the chamber out of aluminium? how easy/hard is that to work with? do you weld it or what?
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it's funny, but when they said "Anything is Possible", that's exactly what they meant....

924guy · Posted: Tue May 11, 2004 12:40 am Post subject:

the cryo sprayer is almost ridiculously easy to build..paintball co2 tank from walymart for $20 , and some fittings and tubing.. im thinking an electronic sprinkler valve(rainbird type, look up "potato cannons" to see how this works) could be tied into a boost pressure switch to turn it on only when under boost, even at a certain boost pressure given the right sensor...

the only issue i can think of is carting around a bottle of co2 all the time.. co2 is best kept in its liquid state, which can be accomplished by pressure and/or temperature. the pressures can exceed 1400psi or more.. the tanks are required to have blow off valve for just that reason. the lines would act as expansion chambers to convert the liquid to gas, or a chamber can be added for that purpose. But a co2 tank sitting in the sun, or even in a car trunk will blow out once the temp gets high enough, and thats a bad thing ..so the tanks would need to be kept cool (under about 80 F , all the time. ) not really a safe option for those of us in warm climates without a cooling system for the tank, which makes it not very practical for everyday use.

as far as the cooler plates go, im thinking they might be best applied to chill a top mount ic rather than replace it, electronically achieving the same as the cryo sprayer described above.. safer than co2 and maybe increase the cooling effieciency of a small ic ..dont know.. but if its possbile to make a small ic as effiecient as a large front mount, youd get allot of bang for the buck...and the install would be so much easier... the heat transfer rate is the obsticle obviously, i still want to play with the idea though...these things have coime a long way ...
_________________
Eric
78 924
82 931 SE "smokey"
99' VehiCross
Y2K Honda Insight
http://www.cardomain.com/id/924Guy
Performance by Pasha

numbbers · Posted: Wed May 12, 2004 10:53 am Post subject:

If you use a heater core, would you want to mount the heater core so that the air flows through the tubes with the fins in the water bath, or with the air flowing through the fins, and the water just circulating through the tubes?
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1980 924 Turbo

Smoothie · Posted: Thu May 13, 2004 1:30 am Post subject:

The usual arrangement would be to have the water/(coolant) flowing through the tubes and the air flowing over the fins. The other-way-'round would just be impractical and restrict the air flow too much.
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"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

speedsta2003 · Joined: 12 Nov 2002 Posts: 302 Location: Lincoln, Nebraska

nothing better than a good ol' front mount IC and a good spray of nitrous on it.
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kye · Posted: Thu May 13, 2004 5:30 pm Post subject:

ok, I was waiting for someone to pop in and do the physics/maths, but no-one did, so i'll have a go at it.. it seems like 100 years since I did these calculations, but i'll have a go and you guys can play 'spot the maths error'!

Specific Heat of Air: 0.25 cal/g or Kcal/Kg (from http://www.howe.k12.ok.us/~jimaskew/pheat.htm)
Density of air: approximately 1.22 Kg/m3

1m3 = 1,000,000cc and 1000cc = 1L
therefore air is 1.22g/L.

1 cal is approx 4.2J and a Watt is 1J/s
0.25cal/g is 0.305J/L, which is 0.305W/s/L

so, what's the flow rate of the air at that point?
and what's the temperatures the air (and thus the tubing) will be at?

assuming that the peltiers will be able to cool the air fast enough they will also need to be able to stand the temperatures they'd have to work in.
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it's funny, but when they said "Anything is Possible", that's exactly what they meant....

kye · Posted: Thu May 13, 2004 7:01 pm Post subject:

this place http://www.eureca.de/english/index.html has peltiers that can take up to 250C (on their hottest side I think) but most conventional ones appear to peg out about 150..

a search also reveals that people have tried this idea and it didn't work.
http://www.autospeed.com/cms/A_2088/article.html summarised an idea about using a peltier to cool the water sprayed on the intercooler as not viable. they talk about the heat of the turbo being too much for the peltiers to be cooled by the electrical system.

also, we've got to get rid of the heat on the hot side of the peltier (which is the heat of the thing you're cooling + the energy taken up by the peltier, which is up to 200W in the bigger ones), so for that we should be using fans, or free air movement. if we're doing that, we may as well just use fans or air movement to cool the turbo itself, as the turbo is going to be hot enough above ambient for it to still be efficiently cooled with ambient temp air.

can anyone see a problem with my logic? i'd love this to work!

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it's funny, but when they said "Anything is Possible", that's exactly what they meant....

kye · Posted: Thu May 13, 2004 7:04 pm Post subject:

this thread somewhere else talks about it too, and they conclude something similar.

_________________
it's funny, but when they said "Anything is Possible", that's exactly what they meant....