Painting Intercooler Black - Better heat dissipation?

[big_zop]

Good points made towards determining the best ducting arrangement based upon the conditions. But for a street car, i think the worst case scenario would have to be stuck in traffic with little to no airflow.

Would be interesting to try and test some of these though, rather than going by what someone says. Admittedly, race tech books would give you a good starting point (if a little biased towards optimium performance rather than a compromised street affair).

Another way to test would be to use a 3D modelling program. I know that SolidWorks uses one as a member of last years FSAE team designed an intake dual stage injection and modelled the airflow distribution which also had to include the intercooler. Not sure how easy it is to learn but i will one day... And remember that a program will only give you the correct result if you enter the correct data.

[Pr0j3kt_SuPrA]

lol intresting thread. ok would the material of the core increase effcientcy? eg copper core...?

[TERRA Operative]

Ok, second post regarding cowling, and airspeeds.
If you have a liquid flowing through your heat exchanger at too high a rate it does not have enough contact with the surrounding metal in order to transfer the heat to the exchanger. This is a significant issue.

However, with air, you have a secondary issue of lamina flow, where the air around the inlet is turbulent due to the change in the lamina upon entry to the IC. Its debatable whether this can be improved or whether it is actually a good thing due to turbulent air being better for introduction into the tubes on the IC. Current consensus around here (a bunch of engienerds with nothing better to do, is that while turbulent air would be better for promoting cooling, it would probably still be better to do this from a restriction in the airflow to slow its entry into the IC or passage through the IC.

Note here that most FMICs woudl have a fairly "hard" 90deg bend before entering the IC, so this could suffice in that term.

Thats about enough for now, i have a 1330 meeting.

That's exactly what turbulators between the channels on radiators and intercoolers do. They basically ensure that there is no laminar flow in the core, thereby increasing the total air contact possible.

Although the more turbulators, the less flow. It's a trade-off between cooling performance and total flow.

Basically, you want dense turbulators if you have a large intercooler, as the lower flow is offset by the large flow capacity of the intercooler.
If you have a small core, or the core is in front of a radiator, you want an intercooler with low-density turbulators, to get as much air flow through (and to the radiator too).

Generally High-density turbulators are around 12 'fins' per inch. Low density turbulators are about 6 per inch.

Good points made towards determining the best ducting arrangement based upon the conditions. But for a street car, i think the worst case scenario would have to be stuck in traffic with little to no airflow.

With proper sealing (ie foam strip) the radiator fan will help pull air through when the car is stationary, although, the cooler will be primarily acting as a heatsink in that setup (but then, who produces boost at idle, except screw chargers..)

[oldcorollas]

Too late...

http://autospeed.com/A_110600/cms/article.html

if it has been patented, it means they aren't going to use it, and just want royalties from anyone who tries to market such a system

but it will work.. and is not such a bad way to cool a refrigerant system at the drags, instead of using dry ice all the time.. adds weight tho.

it would probably work fairly well on the street tho, where you have plenty of time before giving it stick.... but then the requirements for outrigth performance are no longer there

[Mos]

Edit: i should say here that i was measuring temps with a pair of K-type thermocouples inserted into the airstream. The ADC i was using was stripping it back to 2 decimal places, so it should be reasonably accurate. That said, i was calibrating my thermocouples off my other K-type couple enabled Fluke, so all measurements would be about as accurate as that, which the Fluke site rates as +-0.02C.

I think you'll find that's its resolution and not its accuracy - your actual measurements will be nowhere near that accurate.
http://us.fluke.com/usen/products/sp...(FlukeProducts
The Fluke 87V thermocouple is spec'ed at +-2.2 degrees or 2% whichever is greater.
I once had a Tektronix K type thermocouple and meter accuracy tested during cal and its accuracy was no better than 0.5 degree at 50 degrees and 0.6 at 100. The meter is accurate to within spec (after all it's just measuring voltage) but the accuracy of the thermocouple itself is crap.

If you have a liquid flowing through your heat exchanger at too high a rate it does not have enough contact with the surrounding metal in order to transfer the heat to the exchanger. This is a significant issue.

Can you expand on this a bit? My understanding has always been that heat/energy transfer is proportional to the temperature difference, so replacing mildly warm air with cold air is better than leaving the mildly warm air in there and letting it continue heating at a constantly decreasing rate.
In terms of removing total energy from one medium and passing it to another, the concept of slowing the cooling medium (ie ambient air) is counter intuitive.

Edit: expanding slightly, obviously you only have one chance to cool the charge air so you want to remove as much heat as possible in the single pass through the cooler, but the cooling air is not under the same restrictions and increasing the amount of cooling air can only serve to remove more heat rather than less. The restrictions on the cooling air, in my understanding, are not based on energy transfer, but on how much air it is practically possible to move past the core and through the engine bay.

In terms of an air conditioner cooling the air in a closed chamber, running the air con on its slowest setting will get the air coming out of the evaporator as cold as it can get, but it does not get entire chamber cold as quickly as possible.

I'd love to model this because the concept of slowing the coolant to increase overall energy transfer is counter intuitive to me - what am I missing?

Mos.

PS. I'm removing the crap.

[big_zop]

Can you expand on this a bit? My understanding has always been that heat/energy transfer is proportional to the temperature difference, so replacing mildly warm air with cold air is better than leaving the mildly warm air in there and letting it continue heating at a ever decreasing rate.
In terms of removing total energy from one medium and passing it to another, the concept of slowing the cooling medium (ie ambient air) is counter intuitive.

Mos.

PS. I'm removing the crap.

Energy transfer is not instantaneous, it takes time and i will put up the formula when i find it (cant remember it off the top of my head). The shorter the time period, the less the energy transfer and the less the temperature drop. Yes, if the air is cooler, the temperature difference is greater and therefore the changes are greater. I know the equation is exponential and will put it up when i find it (ie. two different temperature mediums coming to equilibrium).

I know that there will be a compromise and many references that i have read saying that a smaller duct opening is better never really provided any evidence or reasoning to prove why (well, not that i remember either).

[PlacentaJuan]

i get that bit about slower air having more time to transfer heat, but isnt it all about the VOLUME of air?

you are still going to have a higher volume of air travelling through the core if it it moving at a faster rate.

sure the air wont have collected the same amount of heat per unit volume but you will get 10x the volume at a higher velocity.

[YLD-16L]

I know that there will be a compromise and many references that i have read saying that a smaller duct opening is better never really provided any evidence or reasoning to prove why (well, not that i remember either).

I am not as educated in this field as some of you guys posting in here but my understanding was that the aim was to create a significant pressure differential across the heat exchanger in order to "pull" the air through the core as the high pressure area at the front of the heat exchanger core is often turbulent and poor at "forcing" air through the core??

The only example of the above I have had personally was with an oil cooler mounted against a radiator with approx 12mm gap between the two. The oil cooler whilst like that did very little once at the track and oil temp soared to around 120 deg C. Doing nothing more than sealing it to the radiator core with foam strip and the temps never got over ~108 deg C.

Before and after the oil cooler experienced the exact same frontal airflow but I can only assume that once sealed it was able to experience the low pressure of the engine bay on the other side of the core and hence draw more airflow and increase its cooling efficiency.

Obviously in this case more air passsing through the heat exchanger was a significant improvement but how on earth your average Joe Bloggs could determine the optimum amount of flow over a heat exchanger bar trial and error is beyond me????

[takai]

I think you'll find that's its resolution and not its accuracy - your actual measurements will be nowhere near that accurate.
http://us.fluke.com/usen/products/sp...(FlukeProducts
The Fluke 87V thermocouple is spec'ed at +-2.2 degrees or 2% whichever is greater.
I once had a Tektronix K type thermocouple and meter accuracy tested during cal and its accuracy was no better than 0.5 degree at 50 degrees and 0.6 at 100. The meter is accurate to within spec (after all it's just measuring voltage) but the accuracy of the thermocouple itself is crap.

That is true, i had a look again and the Fluke meter i have is accurate to 0.02C, but the K-type is accurate to +-1.2C. So take the readings with a grain of salt.

That said, i trust the stats a bit more, because with the design of a T-test you are able to generate a significant result by simply increasing the number of readings (n) until you achieve a significant reading. Now i was taking one reading every 10s, so thats 1080 readings over the 3hr period, easily enough to spoof a T-test. Yet the T-test still returned a null value, so i would be trusting that. Plus there was a significant correlation between input and output temps, (p<.001) [i looked up the test last night in my lab books] so the thermocouples wernt wandering much, if at all.
Furthermore since i was using the same thermocouples for the test, and the readings were the differential between the two, and the comparison the difference between black and clear coat, I believe the experimental design still holds valid, despite the possible inaccuracy of the K-type. Especially given the fact that the differential doesnt seem to be wandering at all (significant correlation).

Can you expand on this a bit? My understanding has always been that heat/energy transfer is proportional to the temperature difference, so replacing mildly warm air with cold air is better than leaving the mildly warm air in there and letting it continue heating at a constantly decreasing rate.
In terms of removing total energy from one medium and passing it to another, the concept of slowing the cooling medium (ie ambient air) is counter intuitive.

Edit: expanding slightly, obviously you only have one chance to cool the charge air so you want to remove as much heat as possible in the single pass through the cooler, but the cooling air is not under the same restrictions and increasing the amount of cooling air can only serve to remove more heat rather than less. The restrictions on the cooling air, in my understanding, are not based on energy transfer, but on how much air it is practically possible to move past the core and through the engine bay.

In terms of an air conditioner cooling the air in a closed chamber, running the air con on its slowest setting will get the air coming out of the evaporator as cold as it can get, but it does not get entire chamber cold as quickly as possible.

I'd love to model this because the concept of slowing the coolant to increase overall energy transfer is counter intuitive to me - what am I missing?

Mos.

PS. I'm removing the crap.

Maybe i didnt make myself clear enough, i wasnt talking about slowing the coolant, you want the coolant to be flowing quickly as possible (think wind chill factors) through the IC, but rather slowing the charge within the IC.
I think the example which most people will be familiar with is to take differential temperatures from the inlet and outlet of an intercooler. When i did my first F/I conversion i was told by the shop which did the IC that it was good to have both the inlet and outlet of the IC hot, or at least as hot as each other, because that showed that the IC was working. But thats somewhat counterintuitive, because as the charge air flows through the IC it would be cooled by the heat transfer to the external coolant. However if the charge air flows at too high a rate through the IC there is not a significant heat transfer to the external coolant and therefore both ends of the IC are closer in temp. Basically the differential (which i measured in my first experiment) is very low, and therefore the IC is doing diddly squat.

What YLD and Zop say is true as well though, in a lot of "performance" cars the IC is a bigger restriction than the surroundings, and therefore creates a wall of high pressure which doesnt assist in the airflow through the intercooler. Creating a higher pressure zone (differentially higher pressure) around the outside of the IC can help to force air through the IC, which has the side-effect of slightly slowing the air down in order to reduce turbulence.

[o_man_ra23]

Radiator flow is slowed so that as much cold air can pass the water to reduce it's temp. The lower the temp of the water, the greater the difference in temp between water and cylinder, and so the faster the heat is drawn out of the cylinder. If the rates of transfer were not exponential, then there would be no great benefit in slowing the coolant flow.

With a WTA, the coolant going from the heat exchanger to the IC should be colder than the fluid going from the IC to the heat exchanger. The Air should be colder on the inlet side than on the turbo side.

Sounds like sealing the IC to the radiator (by means of a non-thermally conductive foam tape or similar) will give better gains than any coatings or colour changes. Big fans will help reduce the issues of sitting at traffic lights.

Air Conditioner CAI is my idea... get your own

[amichie]

The electricity transmission industry has been using black painted heat exchangers in power transformers for years as it is simply a better black body radiator.

[takai]

Sounds like sealing the IC to the radiator (by means of a non-thermally conductive foam tape or similar) will give better gains than any coatings or colour changes. Big fans will help reduce the issues of sitting at traffic lights.

The biggest difference i noted was when the temp switch failed in the AE92 and the rad fan turned on permanently. Made the IC nice and cool.

[oldcorollas]

The electricity transmission industry has been using black painted heat exchangers in power transformers for years as it is simply a better black body radiator.

but at what temperatures?
they are cooling hot oil usually and temps are likely a bit higher than an IC will get.

other thing to not is that those exchanger are probably steel? (not sure on that) and so they NEED a coating or paint of some kind to stop rusting... may as well make it black, even if it has no effect.

as said before, Al2O3 is a GREAT black body emitter (80%?) so why cover it with a layer of polymer?

Re: radiator vs IC.. water has a SHITLOAD more heat capacity than air....

[takai]

Re: radiator vs IC.. water has a SHITLOAD more heat capacity than air....

Yes, but everyone forgets that air and water both have similar flow properties (i.e. both are liquids) and therefore they seem to treat air and water differently.

[oldcorollas]

they are both fluids, but the volumne of each fluid to have the same heat capacity is large...
water is 4.186J/gC, density 1000kg/m^3
air is about 1.005, density (80C), 1 kg/m^3 (wow, that heavy?)

so... for equal heat capacity, you need about 4200 times the amount of air as water, for the same temp change.
ie, for a 5L cooling system to drop 10 deg, you need to raise the temp of 21000L of air by 10 deg. (in reality, the temp raise of air is higher, and temp loss of water lower...)

hmm... they do act differently due to density and viscosity... ie things like turbulence, and heat transfer by conduction..
i dunno, i don7t really care either way


oh, also, i wouldn't trust a K type at low temps.. the voltages are simply not high enough. do you have any wire extensions? were they proper extension wire to negate voltage generating couplings?? was it a proper plug (ie, same as the extension wire deal?)
at high temps.. ie 500-1000, maybe you can be within a degrees or two, but low temps are shit.
there are other TC types that are more accurate in that range...
however, regardless of systematic error, the relative differences should still stand... mostly