I know just enough to keep Brian and a couple of other guys stirred up ! LOL
MY impression is that as an example ... if you have air at temperature ' A' and ' B' is half way.... then you need the same amount of air 'C' ( plus whatever is needed to make up for the less than perfect heat transfer of the type metal in the tubes ) passing across the cooling part....
Which in itself can be a lot of air... meaning a drain electrically to run the fan....