Abstract
To verify the effectiveness of the rotating cylinder method as a laboratory testing apparatus of foulant and/or deposited scale, an annular geometry heat-transfer tube with indirect electric heating was tested in more practical fouling and cleaning conditions.
Calcium sulfate foulant was used as a representative foulant of seawater, and experimentally expected to show typical asymptotic fouling curves, asymptotic value of which decreased with an increase of fluid velocity. A generalized fouling model was applied to estimate the fouling mechanism, and proved surface process to be a controlling mechanism of scale deposition.
The effectiveness of mechanical cleaning against the formed scale was quantitatively evaluated by using particle abrasion method. The removal test verified that the removing rate decreased asymptotically in inverse proportion to the overall particle load, and also that the dependence of the removing rate per unit particle concentration on the particle load was affected by the fluid velocity. The observed final residual fouling resistance decreased asymptotically with an increase of the particle concentration, and the suitable concentration of particle for mild cleaning was very low as compared with the operating condition of the fluidized bed heat exchanger.
