锯齿斜翅管表面碳酸钙析晶污垢初始阶段结垢特性

Characteristics of the Initial Stage of CaCO 3 Crystallization Fouling on Saw-tooth Oblique Fin Tube

进行光管和锯齿斜翅管在不同碳酸钙浓度和流速下的动态结垢实验,得到碳酸钙浓度、流速和锯齿斜翅管对碳酸钙析晶污垢结垢过程的影响。结果表明:浓度增大使溶液中均相成核速率和所形成晶核的生长速率增大,使溶液换热表面界面的污垢晶粒浓度和成垢离子浓度均增大,前者使更多的污垢附着换热面而后者使表面异相成核速率和生长速率增大。流速增大使光管表面形成的晶核、污垢晶体和污垢热阻均减少而诱导期延长;使锯齿斜翅管初始成核增多,但诱导期延长、而结垢量和污垢热阻减小。锯齿斜翅管在清洁状态和结垢状态下均具有比光管更大的总换热系数、更小的污垢热阻,尽管结垢量略多。

To investigate the effect of CaCO3 concentration and velocity on CaCO3 scaling fouling process on plain and saw-tooth oblique fin tubes, experiments have been done at different CaCO3 concentration and velocity on the two kinds of tubes. The results show that the homogeneous nucleation rate and the growing rate are both increased when CaCO3 concentration increases. This makes the scaling particle concentration and foulantions concentration increase. The former increase gets more scaling on tubes and the later enlarges the heterogene- ous nucleation rate and growing rate. Higher velocity decreases the nucleation of scaling, scaling crystal and fouling resistance, but it can prolong the induction period. Higher velocity increases nucleation rate on saw-tooth oblique fin tube first, but the induction period extends and the mass of scaling and fouling resistance decrease. Saw-tooth oblique fin tube has a bigger heat transfer coefficient than plain tube at both clean and fouling conditions and it has smaller fouling resistance and a little more scaling.