Interaction between particulate fouling and precipitation fouling: Sticking probability and deposit bond strength

Sticking probability (P) and deposit bond strength (ξ) are the two most important factors that determine the fouling process, but no calculation correlations were found for P and ξ in current models. This study investigated the interaction between particulate fouling and precipitation fouling based on the values of P and ξ, taking into account the growth characteristics of the combination of particulate fouling and precipitation fouling on the micro-surface of the heat transfer tube. Three kinds of fouling were measured continuously over 720 h in each of three individual tests: particulate fouling, precipitation fouling, and the combined fouling. In order to recognize the growth mechanism of the combined fouling on the heat transfer surface and to solve the engineering problems, this study provides a reliable method to calculated P and ξ. The results indicated that the solution of CaCO₃ mixed with the particles of SiO₂ at the mass ratio of 1:1 (CaCO₃:SiO₂) improved sticking probability. And the enhanced tubes, the helical ridge tube with start-number of 45 and start-number of 10, compared with the plain tube, would not easily stick, but hardly denude by flow which reduced the sticking probability and increased the deposit bond strength. For the helical ridge tube with start-number of 45, when compared with the helical ridge tube with start-number of 10, the particles were more likely to stick to the surface of, but the precipitation fouling was harder to occur. It was observed that deposits were difficult to remove once they were deposited by the particulate fouling or precipitation fouling on the surface of the helical ridge tube with start-number of 45.