Building my Radiator
09-18-2010, 08:16 PM
#16
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Thermal Conductivity - k - W/m.K of our radiator cores.
At 125 degrees C the thermal condictivity of materials for our radiators in question are:
Aluminium = 255
Brass = 109
Copper = 400
Conductive Heat Transfer
Heat transfer takes place as conduction if there is a temperature gradient in a solid or fluid
Conduction will take place if there exist a temperature gradient in a solid (or stationary fluid) medium.
Energy is transferred from more energetic to less energetic molecules when neighboring molecules collide. Conductive heat flow occur in direction of the decreasing temperature since higher temperature are associated with higher molecular energy.
Fourier's Law express conductive heat transfer as:
q = k A dT / s (1)
where
A = heat transfer area (m2, ft2)
k = thermal conductivity of the material (W/m.K or W/m oC, Btu/(hr oF ft2/ft))
dT = temperature difference across the material (K or oC, oF)
s = material thickness (m, ft)
From the above it can be seen that aluminum if a better heat transfer medium than brass, however, copper is the best.
I have an aluminium cored radiator fitted, but I have two spare brass or bronze units and I note that the brass/bronze radiators are nearly twice the thickness of the aluminium unit with more finned tubes fitted. I would suggest this is because of the thermal condictivity differential of the core materials to achieve the same cooling capacity.
Some may find this interesting.
Tails 1990 928S4 Auto
At 125 degrees C the thermal condictivity of materials for our radiators in question are:
Aluminium = 255
Brass = 109
Copper = 400
Conductive Heat Transfer
Heat transfer takes place as conduction if there is a temperature gradient in a solid or fluid
Conduction will take place if there exist a temperature gradient in a solid (or stationary fluid) medium.
Energy is transferred from more energetic to less energetic molecules when neighboring molecules collide. Conductive heat flow occur in direction of the decreasing temperature since higher temperature are associated with higher molecular energy.
Fourier's Law express conductive heat transfer as:
q = k A dT / s (1)
where
A = heat transfer area (m2, ft2)
k = thermal conductivity of the material (W/m.K or W/m oC, Btu/(hr oF ft2/ft))
dT = temperature difference across the material (K or oC, oF)
s = material thickness (m, ft)
From the above it can be seen that aluminum if a better heat transfer medium than brass, however, copper is the best.
I have an aluminium cored radiator fitted, but I have two spare brass or bronze units and I note that the brass/bronze radiators are nearly twice the thickness of the aluminium unit with more finned tubes fitted. I would suggest this is because of the thermal condictivity differential of the core materials to achieve the same cooling capacity.
Some may find this interesting.
Tails 1990 928S4 Auto
09-19-2010, 02:05 PM
#17
I used to work in a Radiator shop years ago. The fin portion of the radiator is made of copper. Tubes are brass. You can get the cores buit to custom specs if you wish. They can buld a core with a more dense fin count for a higher heat transfer area and you can get different sizes of tubes as well. It is possible to get a core with only one row of tubes to as high as six or eight rows of tubes. The end tanks are generally brass with brass fittings soldered to them.
http://www.youtube.com/watch?v=ayQWX...eature=related
http://www.youtube.com/watch?v=ayQWX...eature=related
Last edited by G Man; 09-19-2010 at 02:22 PM.
09-19-2010, 03:45 PM
#18
Rennlist Member
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Generally speaking, cooling performance increases with more rows until you get to three or four, then performance actually starts to fall off.
The fifth row becomes a non-cooling bypass, as the air that it sees is already heated by the first four rows...
The fifth row becomes a non-cooling bypass, as the air that it sees is already heated by the first four rows...
09-24-2010, 08:34 PM
#19
Rennlist Member
Thread Starter
My radiator is on its way to me. We ended up with 3 rows of tubes 5/8" and they are dimpled for premium cooling, 2 1/4" core, brass tanks and a steel frame. They also used my oil coolers. I'm sure it will be heavy so I will lose a few lbs to make up for it. He under estimated the price so I gave him $600.00 instead of the $550.00 quoted. He assures me it will be a cooling machine and it will not look as good as the aluminum. The other plus will be IT CAN BE REPAIRED IF NEEDED.
Thomas
Thomas
09-24-2010, 09:21 PM
#20
Rennlist Member
I'm seem to recall that Mark A. had a used copper rad sitting on the shelf many Sharktoberfests ago. Is it still there gathering dust? Might be interesting to see how it was designed.
09-24-2010, 09:30 PM
#21
So....would there be much of a market for a copper/brass replacement radiator for the 928? I am still in contact with the shop I used to work at. I could chat with the owner about producing these if there was enough interest. Sounds like Thomas got what he wanted with his.
09-24-2010, 10:51 PM
#23
Rennlist Member
Thread Starter
Thomas
09-24-2010, 10:53 PM
#24
Rennlist Member
Thread Starter
So....would there be much of a market for a copper/brass replacement radiator for the 928? I am still in contact with the shop I used to work at. I could chat with the owner about producing these if there was enough interest. Sounds like Thomas got what he wanted with his.
09-25-2010, 11:57 PM
#26
Rennlist Member
Thread Starter
So....would there be much of a market for a copper/brass replacement radiator for the 928? I am still in contact with the shop I used to work at. I could chat with the owner about producing these if there was enough interest. Sounds like Thomas got what he wanted with his.
I actually like the all black front now. Trans and engine oil are going to run cooler also.
Thomas
