CALCIUM-SULFATE SCALE FORMATION DURING SUBCOOLED FLOW BOILING

Fouling of heat transfer surfaces during subcooled flow boiling is a f requent engineering problem in process industries. Nevertheless, only few experimental and theoretical investigations on this subject can be found in the literature. In this investigation the effect of operatin g parameters on the deposition of calcium sulphate on heat transfer su rface during subcooled flow boiling was studied. A large number of exp eriments were performed to determine the mechanisms controlling deposi tion. Fluid velocity, surface and bulk temperatures, concentration and ionic strength of calcium sulphate solutions were varied systematical ly. Finally, a mechanistic model is suggested for prediction of foulin g resistances, which is in good agreement with the experimental data. In this model mass transfer effects are considered for those parts of the surface where heat is transferred by forced convective heat transf er and concentration effects for those parts where bubble formation oc curs. (C) 1997 Elsevier Science Ltd.