In scaling experiments, the formation of fouling layers on heat transfer surfaces usually proceeds in a non-uniform manner. The result is a non-uniform layer, and hence a varying thermal resistance over the area covered with scale. Consequently, a non-uniform heat flux distribution results over the heat transfer surface. To evaluate the changes in the heat flow distribution resulting from a non-uniform scale layer, numerical calculations have been performed using a case where CaSO4 scales form on a heated copper plate subjected to a shear flow. The calculated heat flux is used to calculate fouling resistances from measured temperatures. The results of the numerical calculations confirm that a non-uniform heat flux distribution occurs over the surface when the plate is partially covered with scale. Further, it is seen that the heat flux, the surface temperature, and the driving force all decrease with increase in scale accumulation.