By matching the theoretical pressure loss of a finned-tube heat exchanger with the pressure rise over a fan through an idealized fan characteristic, the velocities and flow rates are determined for different amounts of fouling on the surfaces. Using a typical correlation for the fin-side convective heat transfer coefficient, the variation of the coefficient with fouling is then predicted. The results of the calculations show that as the blockage of the flow through fouling progresses, the heat transfer coefficient increases above that in the clean condition, reaches a maximum value, and then finally decreases in value. Variations of up to 11% have been predicted for the particular geometry considered in this study.