A semi-empirical correlation for crystallization fouling on heat exchange surfaces

Crystallization fouling experiments are reported in this paper. In general the results show four distinct time regions: a region where the fouling thermal resistance is zero, a region where the fouling thermal resistance is negative, a region where the fouling resistance increases steadily and a region where the fouling thermal resistance remains constant. Each of these regions can be matched with different development phases in the crystallization fouling process: nucleation phase (regions 1 and 2), growth phase and asymptotic phase. Overall the fouling curves exhibit an S-curve, characteristic of the logistic curve. A new correlation based on the solution of the logistic equation is formulated. The correlation parameters are evaluated and related to the crystallization parameters. The results of this work can find application in predicting the evolution of the fouling scale layer in heat exchangers that are in operation. The predictions can assist heat exchanger operators to plan cleaning schedules.