After being in service for a period of six months, a heat exchanger transforms 10% less heat than it does what new. Determine the effective fouling factor in terms of its clean overall heat transfer coefficient. It may be presumed that the heat exchanger operates between the same temperature differentials and that there is no change in the effective surface area due to scale build up

Correct Answer: 0.11/ U CLEAN
Q CLEAN/Q DIRTY = U CLEAN/U DIRTY.