Painting Intercooler Black - Better heat dissipation?

[river]

Hi,

Yeah, I tend to think the minimal advantage in changing the colour to improve heat transfer efficiency would give you very little benefit in the real world application - unless, as stated, every last miniscule of effficiency is necessary for racing or other such requirements.

Before painting the IC, I'd be looking at getting other gains such as improving the air flow through the IC, and anything else, which could provide bigger net gains in performance.

As far as colours go, in regards to heat absorbtion.... black heats up more quickly and dissipates its heat more readily, white heats up less quickly and dissipates its heat more slowly.

seeyuzz
river

[TERRA Operative]

Correct ducting to the intercooler will have a FAR greater benefit than the colour of the fins.

Many people get it the wrong way around, making a funnel that leads to the cooler, where in fact you want an inverted funnel arrangement, so the air will slow down through the core and extract the heat correctly.

\........../
.|||||||||||||.....Not this (air in from the top)

/.......\
||||||||||||.....This is good.

A good rule of thumb is an opening of around 25% of the total surface area of the cooler. Any more and the cooler acts as a dam and the air just goes around.

On paper it equates to 15%-20% increase in performance versus no duct, real world is more along the lines of 5%-8%.


Thickness is another consideration. The second half of any core only does a quarter of the work, due to the core warming the air as it passes. Thick cores tend to have higher resistance to the passage of air too.



basically there are a lot of things that will give you greater gains before painting the core...

[brett_celicacoupe]

\........../
.|||||||||||||.....Not this (air in from the top)

/.......\
||||||||||||.....This is good.

the top one will create a larger pressure difference across the cooler, meaning more air will flow through it and so should transfer more energy.

i cant see how the bottom one would be better. your basically saying that the air moving slower is better

[Sigmeister]

Just to add to this, annodizing doesn't really like heat...so to speak. Depending on the colour.

My uncle used to be an annodiser and he used to do a lot of stuff for me. Whenever I'd ask for an engine part to be done, he was always weary.

He was right, anything that got hot or was in a high temp area, would tend to lose it's colour\finish. In saying that, black was quite resilient but would lose it's deepness and kind of go matte. Gold, red and blue seemed to just turn to poo, the colour would really fade and quite quick as well.

[oldcorollas]

thats just the organic dyes and stuff....
you seal the pores in boiling water, but prolonged heat may kil the dye...

the oxide on the other hand... alumina is used to protect superalloys at 1200C, so the oxide itself has no problem with heat.. the aluminium will melt far before the oxide has issues

[Jt_70R]

brett, the slower moving air has more time to actually remove the heat from the other medium.

completely removing a thermostat a coolant system can have similar detrimental effects, because the water simply passes through too quickly and doesnt have enough time in the rad to transfer its heat.

[brett_celicacoupe]

why dont you have an opening to the intercooler the size of a 5c piece then? the air will be going very slow then


until the entire exposed outer surface in contact with atmosphere is at the temperature of the ambient air, EVERY increase in air flow through the intercooler will result in an increase of energy removed from the air discharged from the turbo. theoretically though you can never reach this point (newtons law of cooling).

[oldcorollas]

what happens if you paint an air/water intercooler black?

i liked your first post better


arguably, radiated heat transfer has fark all effect in a contact heat transfer system... much better to maximise surface area (tree like internal heat sinks?) then to paint with anything..

for air to air, how much heat do you guys reckon is put out by radiation when an IC is... 60C, 100C, 150C? compared to convection


must be sfa really... esp if you WANT the IC to have the far end at room temp....

sure you can feel heat being radiated from say, a hot cup of tea, but not from very far away... and if you blow a fan onto it, then i bet you can7t feel any radiated heat at all..

[af300e]

Why not, run a nice piece of flexi pipe from the turbo to the A/C box intake and then into the engine intake? Just drive with A/C on full blast. It's an A/C-IC (copyrighted )

Someone will think this is a good idea..............

Watch for the "How do I plumb my A/C into me engine intake?" thread

[TERRA Operative]

An intercooler will only flow as much air as can pass through the gaps between the channels and turbulators.
You can't expect to take a funnel with twice the inlet area of the core and force twice the ambient air through the core. With that type of duct, the air will pile up in front of the core and simply go around. Your flow through the core will not increase.

A 5c hole is a little undersized for 25% of most intercoolers.....

Many cars these days use this idea for their radiators. Ever notice how small the front dams have become on modern cars compared to radiator size, yet their cooling performance is still adequate for higher performance engines?

The EF Falcon, which had a ducted radiator design, had a cooling efficiency greater than earlier models with a smaller intake.

[TERRA Operative]

Why not, run a nice piece of flexi pipe from the turbo to the A/C box intake and then into the engine intake? Just drive with A/C on full blast. It's an A/C-IC (copyrighted )

Someone will think this is a good idea..............

Watch for the "How do I plumb my A/C into me engine intake?" thread

Too late...

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

[YLD-16L]

When I was looking into radiators I found a great site that had tested a whole heap of methods of alterting airflow through a radiator and improving the low pressure area in the engine bay. It had thermal images of the radiator as it was tested for each method and the one that worked best was as Terra pointed out, smaller inlet area than the heat exchanger surface area.

Biggest gains were made by reducing alternate air pathways at the front of the bay that bypassed the heat exchanger and by reducing the pressure on the engine bay side of the heat exchanger.

[o_man_ra23]

It doesn't look silver?? It is the radiator part of a WTA which is colour effected when talking about thermal efficiency, as there is not much surface area on the intercooler section.

Personally I would coat my IC for hiding purposes, but since I will have a bare aluminium radiator, and a bare aluminium A/C condenser, so that would make a black IC stick out like dog's nuts.

With relation to velocity of air cooling, it is true to a point that slower air will help. To this end, Pylon racing R/C planes have a very small air intake closely coweled past the cooling head fins of the motor, out a much larger rear opening to most efficiently cool their 300kph ultra leaned out engines. I don't know the practical limits of this slowing effect, and I guess more research into the optimal flow rate vs core thickness and heat differential would have to be undertaken to work out what velocity of air you want. You would then need to work out what speeds you will be working the car the hardest at (ie for highway other than NT, it is 110kph, race track may be >200kph) and work out what ratio of opening to core size you want from there. I dare say that anything you do on the street will either be efficient without a coweling, or be illegal (or be in the NT's open limits roads)

Just my $0.022 (GST inc.)

[takai]

FWIW i did this experiment a few years back. Had a new IC off eBay which i was going to use on a car. Hooked one end up to a hair drier, with the other venting to atmosphere 4m away. Temp probe on the inlet and outlet.

First run raw (well AluOx) and the second run black, ran each for 3hrs and measured temps every 5s.
Used the differential between the entry and exit temps as the measurement so as to try to eliminate the difference in heat for the hair drier.

A simple t-test showed no significant difference (p > 0.6) between the unpainted and black cores, with the unpainted core being a poofteenth hotter.
A one-way ANOVA gave the same results, but showed that there was a significant correlation between input temps and output temps (DUH).

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.

Conclusion: In measurable terms, at realistic temperatures, it doesnt matter. Sure it might if you are designing re-entry panels for the Space Shuttle, but for a car IC, no difference



Oh yeah, on the other hand, anodizing doesnt take nicely to hot temperatures. My temp sensor adaptor (inline radiator one) is anodized black and after a few months of operation has stripped the colour off the back of it (engine side). Thats with water temps around 85deg.

Edit2: i should dig up my notes and setup a new test rig so i can write it up in IEEE journal format and see if i can get a publication out of it.

[takai]

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.