Bewy said

Radiators:easy
'Alum on the other hand is much stronger so the tubes can be twice as wide. At first glance this might not appear to be such an advantage...The water flow characteristics of a four row copper core are pretty much the same as a two row alum alum core. However, when we consider the heat transfer area the alum tubes EASILY wins to the tune of up to a 20% gain. The fins, which transfer heat to the air passing through the rad, only contact the flat sides of the tube. The rounded ends of the tubes have no finning, so there is no heat transfer of any significance from this area. Thus with only half the number of tube ends, the alum rad will give up more heat to the fins.'

From the Bosch Automotive Handbook, 9th Edition 1500+ pages.
' The cores of the coolant radiators in modern passenger cars are almost exclusively made of alum. ....There are two assembly variants: brazed & mechanically joined.
For HIGH PERFORMANCE engines, the best solution is the brazed flat tube & corrugated fin rad.'

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