Ben Lipman wrote on Monday, July 25, 2011 - 08:13 pm: you should aim to expand the space between the duct and core as this helps build a high pressure area in front of the cooler and thus aid in getting air to flow through to a hopefully low pressure area behind it.
Divergent duct, actually has more to do with slowing the airflow so it has more time to take the heat out of the cooler and work more effectively. 
