THEORETICAL-ANALYSIS OF THE THERMAL-RESISTANCE OF NONUNIFORM FOULING ON CROSS-FLOW HEAT-EXCHANGER TUBES

A theoretical analysis of steady-state heat conduction through homogen ous fouling on the external surface of tubes in cross-flow has been ma de. Modelling the fouling geometry as an eccentric annulus, a finite d ifference procedure in bipolar coordinates has been developed to predi ct the effect of fouling on the thermal performance. Theoretical predi ctions for a range of geometry, thermal conductivity and variable conv ection boundary conditions are presented. It is shown how, for a range of foulant thickness, eccentricity and thermal conductivity, the rate of heat transfer to a given size tube can be reduced or increased. Th e case of non-homogeneity of the fouling is explored with a view to ex tending the analysis towards varying thermal conductivity.