It has to be black unless you want it to run hot.
What sort of radiator place gives back a radiator without paint? Sounds a bit dodgy to me!
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| Author: | mini-dunger [ Tue Dec 25, 2007 2:44 pm ] |
| Post subject: | Radiator |
HI all, I had my radiator cut up and cleaned the otherday. its bare brass and it needs a coat of paint. Does it have to be black? as long as its heat proof paint? thanks |
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| Author: | Morris 1100 [ Tue Dec 25, 2007 5:17 pm ] |
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It has to be black unless you want it to run hot. What sort of radiator place gives back a radiator without paint? Sounds a bit dodgy to me!
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| Author: | Kennomini [ Tue Dec 25, 2007 5:31 pm ] |
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Why do they have to be black? Same with most mechanical parts, doesn't black attract heat so in theory white would be better suited correct  ?
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| Author: | Morris 1100 [ Tue Dec 25, 2007 5:51 pm ] |
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Kennomini wrote: Why do they have to be black? Wrong, black will transfer heat better than any other colour.
Same with most mechanical parts, doesn't black attract heat so in theory white would be better suited correct ?Experiment: Get two bottles and a thermometer. Paint one bottle white and paint the other one black. Fill both bottles with water and see which one cools quicker. I bet it is the black one. |
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| Author: | slinkey inc [ Tue Dec 25, 2007 6:17 pm ] |
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Paint the radiator black, but leave the top parr brass and polish it up before each Mini show. Looks awesome, and in my case, made no noticable difference to the engine temperature. |
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| Author: | Mokesta [ Tue Dec 25, 2007 8:41 pm ] |
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You want a thin coat. A thick coat of acrylic paint will insulate and reduce the ability to transfer heat. As said above, black is best for radiant heat transfer. Colour has no impact on convective heat transfer. |
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| Author: | drmini in aust [ Tue Dec 25, 2007 8:42 pm ] |
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Morris 1100 wrote: Kennomini wrote: Why do they have to be black? Wrong, black will transfer heat better than any other colour. Same with most mechanical parts, doesn't black attract heat so in theory white would be better suited correct ?Experiment: Get two bottles and a thermometer. Paint one bottle white and paint the other one black. Fill both bottles with water and see which one cools quicker. I bet it is the black one. The same/similar reason that solar hot water collectors are always black. Black absorbs or radiates heat better. |
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| Author: | mini-dunger [ Tue Dec 25, 2007 11:10 pm ] |
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isnt it the air flow/circulation around the radiator that disapates (sp) heat? If anything wouldnt a layer of paint regardless of colour increase the surface area of the radiator? this would be beneficial wouldnt it? So does this mean that a bare brass radiator would cause my engine to run hotter than one that was painted black? If a bare brass radiator does not overheat I should be able to paint it a colour similar to brass and have no problems as long as the paint I use has insulation propertys that are equal to that of the original colour? It came back from the radiator shop bare because I told them to. I was going to bling it up but they squirted silver solder all over the thing. It looks like crap so I will have to paint it.. |
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| Author: | mini-dunger [ Tue Dec 25, 2007 11:19 pm ] |
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i just read this article. http://www.newton.dep.anl.gov/askasci/e ... g99320.htm Since my radiator is under my bonnet where its dark i dont think it matters? its a weird one. |
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| Author: | drmini in aust [ Wed Dec 26, 2007 6:11 am ] |
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It's only the 2 tanks that are brass- the rest is copper- that's where the heat is dissipated. Bling the top tank if you want... it won't make any difference. 
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| Author: | smac [ Wed Dec 26, 2007 7:46 am ] |
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ooooo I really hope some of the resident pencil-heads look in on this topic because there is a LOT of debate about it, event amongst the 'experts'. Car radiators dump heat by two methods: conduction and radiation. Two problems here: by their intense fin design heat radiated by the fins is aimed straight at the opposing fins....which tend to absorb it...ie counter productive. But all is not lost 'cause we have conduction as well. However we tend to blast cold air through our radiators as fast as possible....big mistake as the the air needs to sit next to the fin in order for heat to be transferred by conduction. Can't have the air stationary though as the air will eventually reach the temperature of the fin and therefore transfer stops....so there will be an ideal air speed for heat transfer by conduction....but I see very little work going into determining what it is. Although very hard to test in a 'real life' practical example, you will find that a slower air (fan) speed of a certain rate will cool a car more effectively than a super powered jet stream. Anyway...where am I going....o yeah - so radiator design is crap. We are trying to transfer heat by two methods....but this also means we are dealing with multiple wavelengths, the best solutions for which may interfere. As stated in one of the links above, for the radiated heat which is in the infra-red spectrum most colours don't matter, as they are 'transparent'. So what's the answer? No idea! However if I had to jump either way I'd be inclined to say that because (in general) car coolant systems and radiators are really inefficient, I reckon you won't get a measurable difference due to radiator colour...there may be a technical advantage of one or another, but will it be measurable (and therefore actually matter)? I need a nap.... EDIT: d'oh...missed a point. As mentioned above, although we use paint for colour (or lack thereof in the case of black) we can't discount the effect of the material (the paint content). This will impact the heat transfer process as well (reduce it is my bet). So another thing to throw into the mix: is the gain (if any) of adding black paint more than the loss due to poorer conduction? |
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| Author: | drmini in aust [ Wed Dec 26, 2007 8:02 am ] |
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Well use some nice chinese `lead based' paint then..   (joking...)
The black paint coating is very thin, by necessity- otherwise it's counterproductive as you say. |
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| Author: | Mokesta [ Wed Dec 26, 2007 10:08 am ] |
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Oh dear... We seem to have a few too many people whose entire physics knowledge has been learnt from Neil Crompton. Or maybe Fast Fours. Please read J.P. Holman - Heat Transfer. M |
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| Author: | drmini in aust [ Wed Dec 26, 2007 10:16 am ] |
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Mokesta wrote: Oh dear... We seem to have a few too many people whose entire physics knowledge has been learnt from Neil Crompton. Or maybe Fast Fours.
Please read J.P. Holman - Heat Transfer. M precis please. 
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| Author: | mini-dunger [ Wed Dec 26, 2007 11:24 am ] |
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Mokesta wrote: Oh dear... We seem to have a few too many people whose entire physics knowledge has been learnt from Neil Crompton. Or maybe Fast Fours.
Please read J.P. Holman - Heat Transfer. M me is not really a thinking man, can you give me the gyst? |
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