Actually for the materials, the ability to dissipate heat is easily measured
and aluminum in a similar configuration does not perform as well as brass. The
benefit of aluminum is weight savings and strength (which allows for better
designs).
One company selling aluminum radiators has published numbers for the side
tanks where a lot of the heat is reportedly dissipated.
here's a graphic that they use that highlights there extruded tank design with
more surface area out-performing all tanks.
www.flex-a-lite-blog.com/wp-content/uploads/2010/03/radiator-heat-rejection.j
pg?w=285
They go on to say:
"Heat rejection is the term for measuring the ability of a material to
transfer heat to the air. This is what a radiators job boils down to: Take
engine heat that has been transferred to the engine coolant and transfer it to
the atmosphere. Heat rejection is measured by the amount of British Thermal
Units (BTU) per hour the system can dissipate. Higher BTU/hour means more heat
transfer and better cooling.
Brass radiators came in nearly all vehicles until the 80s. A typical
original-equipment brass radiator rejects heat at a rate of about 1,500
BTU/hour. Thats pretty good, and this is why brass was chosen as the material
for radiators. In the 80s, car manufactures wanted to reduce costs and lower
vehicle weight. This led to changing the radiator design to use composite
(plastic) tanks with an aluminum core. The plastic tanks transfer about 1,000
BTU/hour; considerably less than the traditional brass construction. Next we
come to aluminum radiators. It might surprise you to learn that the typical,
smooth aftermarket aluminum radiator tanks dissipate heat at a rate of about
only 700 BTU/hour! Thats less than half the BTU of brass sidetanks!"
Anyway, the common wisdom is that core design and not material is what matters
most.
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