Fouling factor in boiler design

Normally fouling factor in steam side remains very less say 0.001 h.m2.℃/Kcal and gas side remains around 0.06 h.m2.℃/Kcal

The fouling factor is the reciprocal of the heat transfer coefficient of the layer formed due to the fouling. The fouling factor is denoted by the symbol Rf. Therefore as per the definition, it is given by, Rf=1/h where h is the heat transfer co-efficient.