Fouling is a source of great discussion and the topic of many publications.  You will find a good discussion in “Process Heat Transfer” by Hewitt, Shires & Bott (Begell House Publishers,  1994) as well as in a publication entitled “Heat Exchanger Fouling – Mitigation & Cleaning Technologies” by Hans Muller-Steinhagen (Institute of Chemical Engineers U.K. , 2000).