Lets Talk Radiators Because there is some BAD information out (just replaced mine)

[FLUXING]

Is there any engineering proof of this? ANY coating adds a layer to go through for heat exchange unless the paint has a better heat coefficient than the metal...

Believe it or not, black radiates heat better than bare metal, I' m talking about a thin layer of black and not a 1/2" tick coat of paint.

Just look at the heat exchangers installed on electronic boards, if they are painted, they would ne black.

LEVY

[DCUK Martin]

Wow, lots of misinformation going on here. Not pointing the finger, just saying people have gained PhD's on the subject of heat transfer and it's complex. My knowledge is 30 hours of formal teaching across three years of a mechanical engineering degree and I only scratched the surface of the subject!

Heat is transferred from a body by one of three ways: Radiation, conduction and convection.

Conduction is the movement of heat energy through a solid - eg from the coolant within the radiator to the fins on the outside. Some metals are better than others and copper is excellent as not only does it conduct very well, it has a very low specific heat capacity, meaning it doesn't take much energy to heat up nor does it store much.

Now lets look at convection. This can be "free" or "forced" and involves heat being dissipated to a surrounding fluid (in this case, air and indeed in the case of the coolant flowing from engine to radiator).

Free convection is what the radiators in your house rely on. Heat doesn't rise, but hotter air is less dense than colder air and so it rises relative to the surrounding air and in your home, this creates slow currents of moving air around the room.

...but this is not good enough for a car engine which has to dissipate an awful lot of heat energy, so it relies on forced convection. This is where air is blown over the body to allow it to convect heat away at a considerably higher rate - either by the car moving forward, or the fans drawing air through the radiator.

Radiation - part of the electromagnetic spectrum in wavelengths longer than visible red light, aka infra red - is the heat you feel when the sun shines on your back. It's also what you'd feel if you held your hand about 6" away from the car's radiator when there's no air flow.

It is absolutely the case that matt black is a more efficient colour for radiating heat - google "black body heat transfer" if you really want to go to sleep early, but the bottom line is that most of the heat being dissipated by a radiator is by forced convection to the air flowing through it

So where does this leave the double/triple row radiator debate?

Someone said it earlier: the more surface area in contact with the fluid the better. Well yes, but only if the surface area of the cooling fins then amplify it sufficiently. In other words: The overall radiator surface area, the internal surface area as seen by the coolant and the speed of coolant flow through the individual tubes all play a part in a not-at-all-simple function to define the optimum configuration, but I'm happy that all other things being equal (eg not comparing copper with brass) a triple row core will dissipate heat more effectively than a twin row core, but it won't be 50% more effective.

[David T]

Martin, you mixed up 2 things, the # of rows of tubes and wither or not to paint and what color. If 3 rows gives you more TOTAL surface area (on the air side AND the water side) then 3 rows is better. In most cases 2 big rows will beat 3 smaller rows (assuming the same overall dimensions).

On the subject of paint, you are correct, if you want to improve the ability of the heat exchanger to radiate heat, black is a better color. Since, as you point out, the overwhelming majority of the heat is exchanged by convection, NOT radiation, the color has little to do with improving heat exchange. The paint's main purpose is to prevent corrosion. On a copper radiator you are probably better off not painting it. This way you are not adding another layer that the heat has to conduct through. In all cases the thinner the coating of paint the better. I have seen old time radiator shops that used to dip the rads. It winds up plugging some of the space between the rows, blocking air. Not good. Just about everyone sprays them now.
David Teitelbaum

[Bitsyncmaster]

So does each row reverse the direction of coolant flow? I think the point is to get longer distance.

[DCUK Martin]

Actually David, I was very careful in what I wrote: the ability of the radiator to dissipate heat is a function of the internal surface area, the external surface area and *the speed of flow*. By going from single to twin row, you're reducing the cross section area but increasing the surface area (area being proportional to diameter squared). This will increase flow speed. This only really applies to the twin row rads whose depth is the same as oem. The triple row units are usually deeper and again *all other things being equal* must therefore be more effective.



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[David T]

The differences you are referring to are measurable but inconsequential in the "real world". You are entering the realm of marketing claims and they are always exaggerated.
David Teitelbaum

Actually David, I was very careful in what I wrote: the ability of the radiator to dissipate heat is a function of the internal surface area, the external surface area and *the speed of flow*. By going from single to twin row, you're reducing the cross section area but increasing the surface area (area being proportional to diameter squared). This will increase flow speed. This only really applies to the twin row rads whose depth is the same as oem. The triple row units are usually deeper and again *all other things being equal* must therefore be more effective.



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[tommyrich]

I think one of the earliest points was Brass vs Aluminum. There is a good article that explains the evolution of the modern radiator (for the layman)

http://www.stockcarproducts.com/rad2.htm

It expains that even thought copper/brass is a better conductor than aluminimum, they are soldered together creating another, less conductive interface. Aluminum radiators can be made with larger diameter tubes (aluminum is stronger than brass) and better tube-to-fin contact.
Tom

[DMCMW Dave]

It expains that even thought copper/brass is a better conductor than aluminimum, they are soldered together creating another, less conductive interface. Aluminum radiators can be made with larger diameter tubes (aluminum is stronger than brass) and better tube-to-fin contact.
Tom

And aluminum is much cheaper and lighter, both very important to car manufacturers.

[DCUK Martin]

The differences you are referring to are measurable but inconsequential in the "real world". You are entering the realm of marketing claims and they are always exaggerated.

No David I'm talking basic physics. I've never even seen an advertisement for a radiator making claims that "3 rows are better than 2" but all other things being equal, it will be unless the flow is disproportionately compromised.

It just won't be 50% better.

[Bitsyncmaster]

New:
Aluminum, 2 core, 1.875" total core thickness, 27 fins, uncoated with bottles polished for even less absorption, core is also about 2" wider left to right than original.

Preliminary tests are good. Pushing the engine hard with AC on MAX I dont even think I've hit 200F yet. Hoping tomorrow will be really hot out so I can test it more in Florida heat.

Since your new one is longer, what did you need to change to install it?