Radiator paint - how thick?
Radiator paint - how thick?
(OP)
Painting a raditaor a darker colour like matte black is known to increase the rate of heat transfer from it. My question is how thick does the paint need to be before it begins to act as an insulating component?





RE: Radiator paint - how thick?
Back in the late 30's when NACA was investigating painted finned cylinders for air-cooled aircraft engines, they found that with black enamel the best results came from coatings .002" thick, and by .005" thick the performance was about the same as unpainted cylinders. I don't remember the magnitude of the improvement, but it wasn't much.
Of course, that's a different situation and probably doesn't apply at all to yours, but it may be a good starting point.
Regards
RE: Radiator paint - how thick?
RE: Radiator paint - how thick?
I'd think that Al alloys need more salt protection than Cu.
RE: Radiator paint - how thick?
RE: Radiator paint - how thick?
conduction, convections and radiation
Painting something black only inproves the radiation portion of the equation, In order for black in improve performance it needs to shine on to some thing else, inside the core of the radiator it is shining on the fin next to it not doing much good, so I would expect only a tiny improvement if any.
Meanwhile the paint is acting as an insulator for the convection portion.
Hydrae
RE: Radiator paint - how thick?
Black only works if the surrounding objects are cooler than the radiator core. If it is completely surrounded by equally hot metal surfaces, it will lose nothing through the mechanism of radiation.
The heat loss mechanism will be almost all through conduction into the moving air stream, and black is worth zip.
Corrosion protection is another matter entirely. Something like brown zinc chromate metal primer may be better, but it wold look absolutely ghastly.
RE: Radiator paint - how thick?
interesting observation about the Cu fins being attacked but not the brass tubes--or at least the tubes aren't attacked as badly. But in general, pure Cu is more corrosion resistant than the brass alloys--the more Zn, the worse the corrosion.
Of course there are many other factors.
RE: Radiator paint - how thick?
The car is an MBG (hardly the pinnacle of technology!)and the radiator in question is the standard brass unit fitted to it at the factory.
The question came about and simply put those discussing it (including yours truly )had not even the vaguest idea.
Cheers , Pete.