This is a tip from AutoSpeed Magazine. www.autospeed.com

Thought it was interesting.

Black Beauty Radiator

You want as much heat from the core to be transmitted to the air as possible. Black surfaces dissipate heat much better (and absorb it too - it's a two-way process) than bare aluminium or copper surfaces. In fact, a perfectly black surface will get rid off 1.4 times as much heat as an unpolished aluminium surface, and 1.5 times as much heat as an oxidised copper surface. With radiators made from these two materials, it makes sense to make sure that the radiator stays as black as possible. A can of matt black spray paint will work wonders.

 

Awww mine is purty aluminum coler.

 

Mine was too until I read that article.

 

very interesting im gonna check mine today

 

Thanks for the tip Jime!

 

i have a black one

 

Top of mine is black lol

 

Whatever color factory is is what mine is

 

i got a black wone

 

Mine is black, don't think I've ever seen anyting but a black radiator in any car I've owned.

 

Its the fins we are talking about not the tank on top. All 4 Max's I have had are bare aluminum.

 

yeah mine is bare alum

 

My condensor is black but the radiator is bare.

 

all black.

 

Jime- have you noticed a change??

 

Thats pretty cool! Good find Jime!

-Nick

 

My radiator is sitting in the corner of the shop, may not be installed until spring. So it was pretty easy to give it a shot of flat black.

 

Just replaced my radiator a few weeks ago with an all-black one.

 

That doesn't make any sense. So somehow the color of the radiator can change the thermal properties? Don't think so. When you paint it (any color), you're adding another barrier for the heat to pass through. A painted radiator will hold more heat inside it than a non-painted one. The one advantage might be that it will keep an aluminum rad from corroding, where the corrosion would cause a greater thermal barrier. In theory, the best material for dissipating heat would be non-oxidized copper. Aluminum is more that half as light, so it can have more and deeper fins to make up for it's inherent heat dissapation disadvantage.

The only way there's any science around this claim is in regard to black absorbing sunlight. Besides that, paint color will make no difference whatsoever to a radiator.

This should be next to the electric supercharger in the world of marketing hype.

 

If you have any scientific data to support your claim I would very much like to hear them.

I knew there would be at least one skeptic that didn't understand how radiation is effected by color. There are a lot of scientific formulae and experiments I could quote but I will keep it simple and quote "Howstuffworks" about why a refrigerator coil is painted black.

Why is the back of a refrigerator painted black?

It could simply be that black paint is cheaper... But I believe that the external coils on the back of refrigerators are painted black for the following reason: There is a rule in nature that says "a color that is better at absorbing heat is also better at radiating heat." Here is how Encyclopedia Britannica puts it:

...The rate at which a body radiates (or absorbs) thermal radiation depends upon the nature of the surface as well. Objects that are good emitters are also good absorbers (Kirchhoff's radiation law). A blackened surface is an excellent emitter as well as an excellent absorber. If the same surface is silvered, it becomes a poor emitter and a poor absorber.

Since black is a good heat-absorbing color, it is also a good heat-radiating color. One of the things the external coils do is radiate heat, so they are painted black to help that process.

You will get very warm standing next to a hot black wood stove. You will
get very warm standing next to a hot white wood stove too. But white stoves
are difficult to keep clean.

 

I was reading up on thermal radiation, and came up with this:

"Thermal radiation is defined as electromagnetic radiation in the wavelength range of 0.1 to 100 microns (which encompasses the visible light regime), and arises as a result of a temperature difference between 2 bodies.

No medium need exist between the two bodies for heat transfer to take place (as is needed by conduction and convection). Rather, the intermediaries are photons which travel at the speed of light. " from http://www.efunda.com/formulae/heat_...erview_rad.cfm

That leads me back to my point of this heat transfer property working with light, but not with conduction as in a radiator.

With wood stoves, they are black because cast-iron is nearly black. If painted black, it keeps the stove from rusting and doesn't show if the paint is chipped. Any colored wood stove would be enameled.

If I'm way off base, please let me know.

 

Maybe I'm totally wrong, but I have to agree with 98maximagle... I just don't see how a black radiator would dissipate heat better than any other color, being as it is under the hood and away from direct sunlight. Not saying you're wrong, Jime, but it doesn't seem rational to me.

 

Perhaps one possible application of this could be that black cars could have a higher under-hood temperature than white cars? Thermal Radiation from Sun goes onto black car hood>thermal radiation is converted into heat energy>metal on hood gets hotter.

 

I can almost guarantee that black/darker colored are many degrees higher under the hood, as well as pretty much any other section of the car compared to white/lighter colored cars. Although white/lighter cars do not absorb as much heat as black/darker cars, based on previous comments, their supposed ability to dissipate heat is much more inferior than the darker colors - even so, lighter cars keep cooler, correct?

 

Black will absorb more Thermal radiation (light waves) and convert it into heat energy. This will warm the metal under the black paint.

White will reflect much more of the Thermal Radiation, so it will convert much less light into heat energy.

The amount of energy each one absorbs is equal to the amount it will radiate.

 

So now we agree. Black objects radiate heat better than lighter colors.

 

yes, just take into account black leather. I have tan leather, and it doesn't get too hot in the summer, but i sat in a maxima with black leather, and even though the AC was on for a good while, the leather was still very hot to the touch, this kind of discouraged me from going the black route

I have a black radiator, i havent seen a maxima without one.

 

Jime

We are on the same page if we're talking about light and it's relationship to dark colors and heat

(this was fun, it made me do some research!)

 

Finally someone who makes sense...
this ranks right up there with ..."+20HP!!! addon chip!!!"

 

http://www.honda-tech.com/zerothread...ostid=18374187
http://www.coolingzone.com/Guest/New..._Mar_2003.html

 

I couldn't find the article.

I'm not saying their theory is wrong (it's right - matte black tends to have the highest radiative properties), but there is often a little more to the story.

1) Your car has a thermoswitch that turns the fans off/on to regulate the coolant temperature. Unless your car has trouble keeping these temps under control, the only benefit of a more efficient radiator is quicker response to changes in coolant temperature - and I don't consider that too important unless you're drag racing a turbocharged Maxima or running dyno runs without fans (which anyone who's used a dyno knows is a stupid idea).

2) Air flow is arguably much more effective at improving radiator efficiency. Pick the stones and bugs out of your radiator, and straighten the fins. Make sure all ducting is sealed well to ensure incoming air has no choice but to be driven through the radiator fins.

3) Adding a layer of paint may have a detrimental effect on conductive heat transfer. While the radiative absorption may improve, the conduction from the air to the aluminum may go down a little due to the paint acting as an insulator. Plus, because a radiator is constructed with tight fins, it could be quite hard to get the paint to cover all conducting surfaces, and the likely result is that you will get a lot of too much paint and too little paint. To really improve conduction, remove the radiator and use a de-gunking solvent to clean out the water passages, then flush the snot out of it. Buildup (called fouling) is not good.

4) Radiative cooling is only useful when the surrounding surfaces are cooler. Since the bumper fascia, cooling fan assembly, etc generally don't absorb much heat, the whole radiative effect is probably not too significant anyway.

So while the theory is not without merit, a Maxima radiator is simply not worth painting black.

Dave

 

Thats great because infra-red light is invisible and thermal. That is the heat (light) that is being radiated in your car radiator.

So all your research is true but it also applies in the absence of visible light, just because you can't see it doesn't mean its not light.

So your statement "Black will absorb more Thermal radiation (light waves) and convert it into heat energy. This will warm the metal under the black paint.

White will reflect much more of the Thermal Radiation, so it will convert much less light into heat energy.

The amount of energy each one absorbs is equal to the amount it will radiate."

Its all true but it also applies in the absence of visible light.

 

So does that mean that any heat from the engine or heat inside the radiator is the same as infrared light?

 

We are talking about heat being radiated by the radiator, not what the heat inside the engine is.

Heat inside the radiator or engine is heat inside the radiator or engine. It is transmitted to the outside by three different methods, conduction, convection and radiation. What we are currently discussing is radiation.

Now try the question again so I know what you are asking.

 

I think the paint would just would hinder the release of the heat since it's acting as an insulator like has already been mentioned.

 

Thinking is not good we want scientific data. Hearsay is not admissible.

 

So on the topic of radiation. The radiator will recieve infrared photons from hot components in the car (engine). It will also give off infrared photons, and we're saying that black will absorb and radiate more infrared radiation. As an example, mainly to express more clearly what i'm trying to say:
White radiator: 10 units IR recieved, 12 units IR radiated (net -2)
Black radiator: 20 units IR recieved, 25 units IR radiated (net -5)

I'm just assigning an arbitrary unit to IR, but I think expresses the point. I'm assuming there is a net loss of heat from the radiator, due to the hot liquid inside to hold more energy than the energy recieved through the air from the engine. This would coincide with your original point regarding color.

However, most of the heat transfer through a radiator is done through conduction (liquid>metal fins>air). By adding paint, you are adding another boundary for the heat to cross through. Unless the paint is a better conductor of heat than aluminum, then conduction efficiency would be lower.

So for black paint to lower the temperature, heat units of IR (as BTUs?) transmitted from the radiator would have to exceed BTUs blocked by the paint via conduction

But painting could have another advantage, which would be to limit corrosion to the outside of the radiator. I have little doubt that corroded aluminum is not a great conductor.

To combine the science we have come up with, I think a black anodized aluminum radiator would transfer heat the best and would also have the best longevity. The aluminum plating would have nearly the same thermal properties as the underlying radiator and would cause little interference in conduction.

 

Infrared light is only one of the ways that the heated body gives off energy. In steel, it will also give off visible light if you get it hot enough (red hot, yellow hot, white hot). Aluminum doesn't give off visible light until it's melted.

The other major way a heated body gives off energy is by directly heating whatever is in contact with it. They call this conductive heat transfer. In a radiator, the hot water conducts heat to the aluminum radiator, and the radiator conducts heat to the air flowing by.

Convection is the 3rd way heat is spread - except convective transfer is really just conduction into a fluid. In convection, there is either a natural or forced flow bringing fresh, cool fluid to the hot surface, speeding up the heat transfer compared to a non-flowing body.

Dave