Cooling Tip
03-11-04, 04:14 PM
#27
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This is absolutly true. Radiators should be painted flat black for the highest radiative heat transfer rate. I have an engineering textbook on heat transfer at home that says so. A radiator painted flat black will have about a 10 or 15 % higher radiative heat transfer rate than if painted any other color. Ironically, a bright unpainted metal surface (like all those "high efficiency" polished aluminum radiators i keep seeing pictures of on all of your cars) has the lowest radiative heat transfer rate.
Paint em flat black, and you go from the worst to the best...less bling, more function.
The next mod on my car will be a Fluidyne radiator, and i will paint it flat black with radiator paint before installation.
Mike Parsons
Paint em flat black, and you go from the worst to the best...less bling, more function.
The next mod on my car will be a Fluidyne radiator, and i will paint it flat black with radiator paint before installation.
Mike Parsons
03-11-04, 04:30 PM
#28
built my own engine
i thought black radiated visible wave energy (i.e, not infrared ranges)
these are totally different spectrum wavelengths and different types of energies you guys are referring to
these are totally different spectrum wavelengths and different types of energies you guys are referring to
03-11-04, 04:34 PM
#29
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My water temps can vary by 10F simply by the ambient temps being a little different or a little bit of stop-and-go vs free-flowing traffic.
Are you telling us that your water temps dropped 10F CONSISTENTLY by simply painting the radiator black? Or are you telling us that your water temps dropped 10F after installing a new copper radiator that is painted black?
Are you telling us that your water temps dropped 10F CONSISTENTLY by simply painting the radiator black? Or are you telling us that your water temps dropped 10F after installing a new copper radiator that is painted black?
03-11-04, 05:19 PM
#30
screwed by chad hall
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please someone back this up with real scientific evidence...we dont need all of the rx7 newbies painting their IC and RAD. black for no reason...well i would like to hear more about this
03-11-04, 05:29 PM
#31
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helps radiant cooling in traffic, but not the dominant convective cooling at speed. never saw a black nascar rad, where they want to use minimum air flow duct size for minimal drag.
03-11-04, 05:44 PM
#32
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Isn't this something to do with "Black Body Radiation". I quote "In practice no material has been found to absorb all incoming radiation, but carbon in its graphite form absorbs all but about 3%. It is also a perfect emitter of radiation. At a particular temperature the black body would emit the maximum amount of energy possible for that temperature. This value is known as the black body radiation. "
It's a long, long time since I graduated, any of you younger guys help.
It's a long, long time since I graduated, any of you younger guys help.
03-11-04, 06:03 PM
#33
Blow up or win
Originally posted by ptrhahn
I wonder if doing one of those black zinc/annodized finishes would be even better than a coat of paint?
I wonder if doing one of those black zinc/annodized finishes would be even better than a coat of paint?
The best reason to use the black paint is to keep the fins from turning unsightly and to retard extenal corrosion over the life of the radiator -which is a non-issue compared with INTERIOR corrosion. Copper turns blue/black/green and aluminum white/grey. The paint does help with heat transfer, but the gains are miniscule compared to allowing more airflow through the engine room and thereby increasing the efficiency of the radiator, whether copper or aluminum.
I think painting a radiator (with hopes that it will lower temps) that is not brand spanking new would be a waste of time and money.
03-11-04, 06:08 PM
#34
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A radiator can transfer heat via conduction and radiation. I think a black radiator will radiate heat more readily than any other color. A radiator's ability to conduct heat is independent of color.
03-11-04, 06:12 PM
#35
Blow up or win
Originally posted by gdnimr0d
please someone back this up with real scientific evidence...we dont need all of the rx7 newbies painting their IC and RAD. black for no reason...well i would like to hear more about this
please someone back this up with real scientific evidence...we dont need all of the rx7 newbies painting their IC and RAD. black for no reason...well i would like to hear more about this
"Black paint will really only benefit 'radiative heat-transfer' by providing a better suface emmissivity... In automotive heat-transfer devices, the conduction & convection dominate the heat-transfer (radiative HT is essentially neglected).
Black paint will cause additional problems:
1. Acts as a small additional resistance to conductive heat-transfer ie. lowers heat-transfer performance;
2. Paint can clog the micro-louvers in the multi-louver fins, & will limit the designer's ability to create high-performance louvers... ie. lowers heat-transfer performance.
3. Paint never completely coats the centre sections of the core, leading to areas of higher corrosion potential for copper-brass radiators. (In fact unpainted copper-brass radiators last 30% longer than painted copper-brass units... interesting...)
This is where unpainted aluminium automotive heat-transfer devices are able to gain additional small performance increases...
Now, if only copper-brass radiators did not need to be coated..."
Des Aubery
(adTherm Technology - www.adtherm.com - des@adtherm.com )
He is a mechanical engineer specializing in this stuff...
Last edited by RonKMiller; 03-11-04 at 06:15 PM.
03-11-04, 07:55 PM
#37
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well from what i have herd in this post it seams to work but doesnt make sense black absorbs heat like a black car will be hotter to the touch then say a red or white car in the summer sun so why does black make a differance on a radiator
03-11-04, 08:29 PM
#38
Blow up or win
Originally posted by FD3SR1
well from what i have herd in this post it seams to work but doesnt make sense black absorbs heat like a black car will be hotter to the touch then say a red or white car in the summer sun so why does black make a differance on a radiator
well from what i have herd in this post it seams to work but doesnt make sense black absorbs heat like a black car will be hotter to the touch then say a red or white car in the summer sun so why does black make a differance on a radiator
1. Starting a sentence with "well", and not capped,
no comma. (3)
2. "i" not capped.
3. "herd", as in a group of animals, no doubt.
4. "seams", as in your pants.
5. "doesnt", why bother with a apostrophe...
6. "then" - you meant than.
7. "differance".... you did mean difference, right?
8. No period at the end of your run on sentence. (2)
9. I probably missed a few others.
I hope you enjoy your career as a "french fry technician" at the local McDonalds, since you are well on your way toward reaching your highest level of incompetency.
Not only do you get an F in English, your question is so ******* stupid in the first place (after it has been answered by a Mechanical Engineer) you deserve one of these on top:
03-11-04, 08:43 PM
#39
Blow up or win
Originally posted by salamander
A radiator can transfer heat via conduction and radiation. I think a black radiator will radiate heat more readily than any other color. A radiator's ability to conduct heat is independent of color.
A radiator can transfer heat via conduction and radiation. I think a black radiator will radiate heat more readily than any other color. A radiator's ability to conduct heat is independent of color.
Nice to run into someone on this forum that knows what they are talking about.
I would substitute "convection" for "radiation". but we are talking fine points here...WAY beyond the intellect of *most* of the forum members...
Last edited by RonKMiller; 03-11-04 at 08:46 PM.
03-12-04, 08:59 AM
#42
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Some hard facts…
The total heat transfer away from an automobile radiator is a combination of convection and radiation. When the car is moving and air is blowing across the radiator, convection is dominant, but when the car is stopped (say in traffic..) radiation plays a much larger role. Color has a negligible affect on convection, this is true. Radiation is a different story.
The ability of a surface to radiate heat is quantified by the term “emissivity”. Emissivity is the ratio of the ability of the surface in question to radiate heat to that of a theoretical “perfect radiator”, or “blackbody emitter”. It has a value of 0 (very low) to 1 (perfect emitter).
My Heat Transfer book lists the following values for emissivity:
Polished aluminum: 0.04
Anodized aluminum: 0.76
Black paint over a metallic substrate: 0.98
White paint over a metallic substrate: 0.90
So as you can see a polished aluminum surface has almost no ability to radiate heat away from it, paint that same surface black and it becomes almost a “perfect emitter”.
I don’t know for sure, but I doubt that aftermarket Al radiators are anodized, they look polished to me.
For arguments sake lets say that your radiator IS anodized, then by painting it black you increase its ability to radiate heat by 28.9 %.
If the radiator is NOT anodized, and is polished, then by painting it black you increase its ability to radiate heat by 2450%.
How many people here have overheated their FD driving 60 MPH on the freeway? How many people have overheated sitting in traffic? If you want to increase the ability of your radiator to radiate heat away while sitting in traffic by 2450%, then paint it black. I am not saying that you will increase the total efficiency of your radiator by that amount, since some convection is still taking place when the car is at a stop (radiator fans pulling air across the radiator), but only that you will increase the radiation portion by that much.
Somebody mentioned NASCAR radiators are not painted? How often have you seen one of those cars sitting in traffic on your way to work? NASCAR radiators work with constant airflow over the radiators, so painting them black/not painting them black isn’t an issue.
Car manufacturers screw up lots of things, but painting radiators black isn’t one of them.
Mike Parsons
The total heat transfer away from an automobile radiator is a combination of convection and radiation. When the car is moving and air is blowing across the radiator, convection is dominant, but when the car is stopped (say in traffic..) radiation plays a much larger role. Color has a negligible affect on convection, this is true. Radiation is a different story.
The ability of a surface to radiate heat is quantified by the term “emissivity”. Emissivity is the ratio of the ability of the surface in question to radiate heat to that of a theoretical “perfect radiator”, or “blackbody emitter”. It has a value of 0 (very low) to 1 (perfect emitter).
My Heat Transfer book lists the following values for emissivity:
Polished aluminum: 0.04
Anodized aluminum: 0.76
Black paint over a metallic substrate: 0.98
White paint over a metallic substrate: 0.90
So as you can see a polished aluminum surface has almost no ability to radiate heat away from it, paint that same surface black and it becomes almost a “perfect emitter”.
I don’t know for sure, but I doubt that aftermarket Al radiators are anodized, they look polished to me.
For arguments sake lets say that your radiator IS anodized, then by painting it black you increase its ability to radiate heat by 28.9 %.
If the radiator is NOT anodized, and is polished, then by painting it black you increase its ability to radiate heat by 2450%.
How many people here have overheated their FD driving 60 MPH on the freeway? How many people have overheated sitting in traffic? If you want to increase the ability of your radiator to radiate heat away while sitting in traffic by 2450%, then paint it black. I am not saying that you will increase the total efficiency of your radiator by that amount, since some convection is still taking place when the car is at a stop (radiator fans pulling air across the radiator), but only that you will increase the radiation portion by that much.
Somebody mentioned NASCAR radiators are not painted? How often have you seen one of those cars sitting in traffic on your way to work? NASCAR radiators work with constant airflow over the radiators, so painting them black/not painting them black isn’t an issue.
Car manufacturers screw up lots of things, but painting radiators black isn’t one of them.
Mike Parsons
03-12-04, 09:03 AM
#43
Lives on the Forum
Originally posted by Mike Nola
When the car is moving and air is blowing across the radiator, convection is dominant
When the car is moving and air is blowing across the radiator, convection is dominant
Originally posted by Mike Nola
but when the car is stopped (say in traffic..) radiation plays a much larger role.
but when the car is stopped (say in traffic..) radiation plays a much larger role.
03-12-04, 09:25 AM
#44
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Lets shove this through the bullshit filter a little.
Painting your radiator will help keep your car cool. If anything the black paint will clog your radiator fins causing less airflow.
Wake up people. This whole thread makes zero sence and is completely false information. If you believe this then I have a bridge that I can sell you.
Painting your radiator will help keep your car cool. If anything the black paint will clog your radiator fins causing less airflow.
Wake up people. This whole thread makes zero sence and is completely false information. If you believe this then I have a bridge that I can sell you.
03-12-04, 11:10 AM
#46
Blow up or win
Ahem.......once again guys - here is what an EXPERT in this field has to say. He is a Mechanical Engineer who makes his living consulting on this very issue. If you don't believe him.....
"Black paint will really only benefit 'radiative heat-transfer' by providing a better suface emmissivity... In automotive heat-transfer devices, the conduction & convection dominate the heat-transfer (radiative HT is essentially neglected).
Black paint will cause additional problems:
1. Acts as a small additional resistance to conductive heat-transfer ie. lowers heat-transfer performance;
2. Paint can clog the micro-louvers in the multi-louver fins, & will limit the designer's ability to create high-performance louvers... ie. lowers heat-transfer performance.
3. Paint never completely coats the centre sections of the core, leading to areas of higher corrosion potential for copper-brass radiators. (In fact unpainted copper-brass radiators last 30% longer than painted copper-brass units... interesting...)
This is where unpainted aluminium automotive heat-transfer devices are able to gain additional small performance increases...
Now, if only copper-brass radiators did not need to be coated..."
Des Aubery
(adTherm Technology - www.adtherm.com - des@adtherm.com )
Can we now put this thread to rest, and get on to more important subjects like which BOV makes the coolest sound?
"Black paint will really only benefit 'radiative heat-transfer' by providing a better suface emmissivity... In automotive heat-transfer devices, the conduction & convection dominate the heat-transfer (radiative HT is essentially neglected).
Black paint will cause additional problems:
1. Acts as a small additional resistance to conductive heat-transfer ie. lowers heat-transfer performance;
2. Paint can clog the micro-louvers in the multi-louver fins, & will limit the designer's ability to create high-performance louvers... ie. lowers heat-transfer performance.
3. Paint never completely coats the centre sections of the core, leading to areas of higher corrosion potential for copper-brass radiators. (In fact unpainted copper-brass radiators last 30% longer than painted copper-brass units... interesting...)
This is where unpainted aluminium automotive heat-transfer devices are able to gain additional small performance increases...
Now, if only copper-brass radiators did not need to be coated..."
Des Aubery
(adTherm Technology - www.adtherm.com - des@adtherm.com )
Can we now put this thread to rest, and get on to more important subjects like which BOV makes the coolest sound?
Last edited by RonKMiller; 03-12-04 at 11:12 AM.
03-12-04, 11:38 AM
#47
Rotary Enthusiast
Originally posted by RonKMiller
Nice to run into someone on this forum that knows what they are talking about.
Nice to run into someone on this forum that knows what they are talking about.
03-12-04, 12:17 PM
#48
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Ron, your "expert" contradicts himself. In item 3 he states "In fact unpainted copper-brass radiators last 30% longer than painted copper-brass units... interesting...", then a few lines later he states "Now, if only copper-brass radiators did not need to be coated.."
Which statement is correct?
Mike
Which statement is correct?
Mike
03-12-04, 01:59 PM
#50
Blow up or win
Originally posted by Mike Nola
Ron, your "expert" contradicts himself. In item 3 he states "In fact unpainted copper-brass radiators last 30% longer than painted copper-brass units... interesting...", then a few lines later he states "Now, if only copper-brass radiators did not need to be coated.."
Which statement is correct?
Mike
Ron, your "expert" contradicts himself. In item 3 he states "In fact unpainted copper-brass radiators last 30% longer than painted copper-brass units... interesting...", then a few lines later he states "Now, if only copper-brass radiators did not need to be coated.."
Which statement is correct?
Mike
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