for a long while now, I have been thinking about anodized black intercoolers. Please don't think me crazy here, we all (decently informed)know that a dark color transfers heat better. I have been thinking that anodizing the actual intercooler aluminum would yield a couple of percent increase in efficiency. also you don't have a layer of paint (insulator) to make things worse. I am actually going to try this myself, I however want some opinions. I also think that this would be a cool way to make a FMIC look sleepe-rish.
One of the reasons I wonder about this is because if you go with too big an intercooler, you get pressure drop. if you do this and it works(technically speaking) then you could increase the efficiency without sacrificing boost pressure.
Any thoughts and/or experience and knowledge would be thoroughly apreciated.

Note: this is an Idea I have only thought to use with FMIC and stock mount FD intercoolers. And I am a formaly trained mechanic, just new to race tech.
oh, and I did search for those who will say to.

dpf22

 

for some odd reason, I was logged in as another person, but I actually wrote and started this. just so people know

dpf22

 

I'm not so sure dark colors transfer heat better. But then again I may not be one of the well informed people. At any rate, I would assume that if this were the hot setup the factory Audi LMP cars would have used such an intercooler.

http://community.webshots.com/script...ecurity=CXFwtg

 

hmm, this is just me thinking out loud, but if the sun where to be on the anodized black intercooler, wouldnt you get heat soak really bad?

 

I thought the material of something that our eyes perceive as black typically retains more heat due to it's nature of absorbing more photonic energy compared to other materials which we see as different colors. The goal is to transfer, not retain - so I cannot see how anodized black would help at all.

 

I see that I am not impressing anyone. ok, here is what I know.
Dark colors TRANSFER heat better. therefore, a dark intercooler (obviously they are not exposed to the sun) would work good at speed.(technically) many people should notice that a lot of factory radiators and condensers are painted black. this is to facilitate heat transfer, although I don't like paint because it is a layer of insulator. Mabe I am just pissing into the wind here, but I think that this Idea has a valid point to be made(though I have no Idea why it hasn't been used in racecars which is why I ask for input from lots of sources). I am liking the responses though so far.

Keep'em coming

dpf22

 

As far as my limited understanding of thermal conductivity, there is no variable for color in any of the formulae.

Black radiators is something of an industry standard, and I don't think it has anything to do with thermal conductivity efficiency.

Most of the import rads are natural (aluminum) finish.


-Ted

 

You could experiment with this stuff and report your results back to us:

http://techlinecoatings.com/introduc...rmaldispersant

 

ah I see I got a tech guru's attention.
hey ted, from what I learned about it(and I could very well be wrong here) black has a better transfer efficiency than other colors. I also know that it tends to retain heat, but that is mostly when in a stationary non-ventilated situation. this is obvious if you touch a black car that has been sitting in something like las vegas sun all day, it damn near burns your hand like touching a stove. but what that is, is actually heat transfer from the paint to your hand via.... I think the term is convection (process of heat transfer through direct contact)
like I said, I have been thinking a lot about this. if you have any thoughts or disagree, please feel free. I am open to a lot of suggestions. and I plan to experiment with this Idea as soon as possible. I will actuall post results here if I can get reliable readings on AIT
Thanks for the input

dpf22

 

Pressure drop is bad on SMALL intercoolers that restrict flow. A big intercooler is likely to flow better and thus have lower pressure drop (which is the difference in pressure before and after the IC). A big intercooler does have more volume, which slows boost response a bit, but that isn't pressure drop.

-Max

 

Uh, do you have references?
Some of the other things you mentioned are pretty twisted.
Where are you getting this stuff from?

You're talking about "black body radiation", but it has nothing to do with high temps transfer to your hand in the desert.

Yes, darker colors absorb "radiation" (i.e. electro-magnetic waves, visible "light").  This is why darker (paint on) cars get hotter sitting in the sun.

Easy experiement to see if your theory is true...
Get one of those laser temp surface thermometers.
Heat white car (torch) up to same temp as black car - verify with laser thermometer, touch with your hands.
Do they feel differently?
Does the darker surface feel hotter? (Hmm, maybe that's not a good idea to ask that.)

No, convection is the term that describes the cyclical rotation of airflow due to temperature change going from hot to cold and back to hot again.

See "convection oven"


I think you're thinking too much.
If there is any change due to color change, it would be almost insignificant.

Black body radiation is applied more towards visible or near visible electro-magnetic waves being absorbed by a dark enigma body (black holes, etc.).  I don't this is applicable to the dark body emitting or transferring energy (i.e. temperature) away from it.

We were talking about intercoolers, right?


-Ted

 

Thanx for that bit of info. I got my values screwed up, I will remember that

 

Okay Ted, looks like you have gone and proven that this will not work, but that is why I started this thread, to see if this would work feesably or not. unfortunately I don't yet have the opportunity to test this(I will). I have been curious about this. Very nice Ted you made me think harder

 

Yeah, we just had a pointless yet fun heat transfer discussion! Why pointless? Because in the scheme of things, energy emitted via radiation from an intercooler is insignificant. There are 4 modes of heat transfer: radiation, conduction, natural convection, and forced convection. You have hot air rushing internally through the intercooler and cool air rushing through the intercooler externally, i.e. forced convection. There is conduction involved transferring heat from the internal fins to the external, but I assume you aren't looking to make the intercooler out of an alternate material.

 

Thanx for the refresher!
It's been almost 10 years since I've delved into this stuff seriously...


-Ted

 

thats right, I was assuming anodized aluminum with the same construction as a normal one

 

oh, and its not pointless if someone learns something

that would be me if you didn't know
and thanx for joining this discussion

 

well, you did mention something about an FMIC, and usually those things see the sun all the time....

 

this one isnt directly in the sun, but you can see that any time before 10am or after 2pm the sun is going to be able to hit it (oh, and this is the only pic i could find with an FMIC, so dont mind the silvia being on an RX7 forum.....)

 

No worries, however, aren't the intercoolers such as an FMIC on an FC more receded into the bumper?
Just a thought, I could be wrong. I have never seen one up close enough to tell myself.
I don't mind the picture at all, actually its a nice car. like the FC rx7,I have a liking for the s13 silvia and 180sx (240sx in U.S.)

 

Okay, my read on things.

Assuming no change in the thermal properties than the color, a black anodized brick will dump more heat than a natural aluminum one. Black things have a better emissivity than lighter colored things... this means that they both take in heat from radiation more quickly (as we all know) and dump it more quickly. A perfect "blackbody" object will have an emissivity of 1, while a perfect reflector would be 0. So, to pull examples out of my thermodynamics text, a black painted thing might have an emissivity of 0.98 while a piece of polished gold would be around 0.02.

I can even point to a perfect real life example of this, the SR-71 Blackbird. Titanium is, of course, not black normally; they're painted that way. Kelly Johnson, the project head, originally objected to the idea of adding 70 pounds to the thing by painting it black, but at the temperatures it's operating at, painting it black allowed a *SIGNIFIGANT* amount of heat to be gotten rid of.

So. Black helps with radiation. The problem is, for an IC, which direction will radiation be going? Well, that's a problem. There's this big hot engine in there somewhere which puts out a lot of heat, and the sun and... well, there's no sure thing that heat will be going *out* of the IC through radiation. The SR-71 was very very hot, and surrounded by nice, cold, sort-of-air, so it could dump a *LOT* of heat through radiation. ICs are not all that hot, and could well be surrounded by things hotter than them; best case minimal heat transfer and worst case it would be taking *IN* heat from the surroundings.

But what about forced convection?

Well... emissivity isn't explicitly mentioned in most forced convection equations. OTOH, convection is, by several sources I came across, the least well understood method of heat transfer. It would seem to me that there'd be some relationship but it may be relatively minimal.

http://www.aavidthermalloy.com/produ.../anodize.shtml

There's mentionabout benefit of anodizing in heat sinks; they say it gets to be relatively minimal in forced convection applications. That's the best evidence I can find there.



So, to summarize, it would help radiation, but that may well do a lot more harm then good. It might (emphasis on might) help convection, but if so by fairly minimal amounts. As people would suggest, empirical evidence (what big-budget race teams do) would suggest that there's no advantage to black anodizing intercoolers.

 

For the intercooler to be taking in heat from it's surroundings the car would have to be shut off and just sitting there. Heat only flows towards an equilibrium as i'm sure you know.

One other thing you didn't really stress is that the blackbird is moving very fast through the air. Faster moving air cools significantly better than slower moving air. Why is this?

A higher velocity (of any fluid) yeilds a higher heat transfer coeffcient. The hear transfer coeffcient is a function of the velocity, Geometry, Type of fluid, and the Type of convection. The difference from attempting to creat a black body emmiter will be more apparant on the blackbird because the air around it is traveling at significantly higher velocities and i think it's safe to assume that the velocity profile on the blackbird is light years better than the velocity profile of an RX7 with a large front mount intercooler.

I'm probably rambling and I should get back to work. but this is a great discussion and this debate has played out many times in my head.

later, M

 

True, heat does flow towards equilibrium. But in the engine compartment you have a lot of stuff emitting heat... I was just positing the thought that all the heat being radiated from the engine / turbos / etc would be greater than the temperature of the IC. Especially given the reputation for FDs having *REALLY* high underhood temperatures.

I'm not sure if that would actually be the case, not having numbers for typical IC and underhood temperatures, but I think that it's possible.

This is getting offtopic but... no, I didn't stress that at *ALL* because convection doesn't work with airflow at supersonic velocities. This is intuitively obvious from looking at the leading edges... which are heating up because of *aerodynamic heating*. Now, sure there's subsonic flow over the parts of the airframe that are behind the bow wave, but there's not a lot of surface area meeting this subsonic airflow (compared to a radiator) and at 90k feet, air is not dense enough to take in much heat per volume. So convection cooling is relatively minimal.

To solve the heat issue, it's cooled by circulating fuel throughout the airframe to use as coolant to remove heat from the leading edges. The top of the aircraft has a lot of surface area... and is essentially facing space... so you have a lot of potential for radiant cooling there. Thus, the body of the aircraft is a lot cooler, as is the fuel. And heck, after the fuel has taken in heat from cooling the airframe, you can just *BURN* the stuff!

 

Thank you kenku, that was very good information. and also for M's. I really enjoy learning more about how to make things better on cars. and this helped me a lot, I think I may end up trying this scenario even though it might be miniscule in difference(good or bad) I am interested in what will happen to the IAT(intake air temp) I will do this even if I have to buy another intercooler to replace it if things don't go right.
I think having a small high velocity fan on the intercooler pulling air through would help a lot whether it is anodized or not.


dpf22

 

Ive often thought about a titanium intercooler with aluminum fins. The titanium would allow the walls of the intercooler to be much, much thinner, thus allowing heat transfer to occur more rapidly, thus increasing intercooler efficiency. Would also save tremendously on the weight of a large intercooler. But thats just me...I love titanium.

Putting things into laymans terms, the reason a darker colored object seems to "feel" hotter than than an equal, lighter colored object (after heatsoak, or sunshine) is because it is radiating its heat outward faster. The downside is that it also absorbs heat faster.
As mentioned before, this would only be a problem at very low speeds or stops. But with with some heat sheilding, you could eliminate most of the heatsoak factor.

I definitely wouldn't anodize my manifolds black, but an intercooler might work out well.

This would be an interesting test for someone to do....maybe me