Abstract
Flow accelerated corrosion remains an active damage in heat recovery steam generators. A recent case took place in tubes downstream an inlet header of a high-pressure economizer harp after six years of operation. The harp includes an inlet header, an outlet header, tubes, and connecting pipes conveying water between harps. The patterned damage raised concerns about the header design. Thus, this research examined the effects of design variables including chromium content, header size, and the number of connecting pipes on the FAC. A CFD model with k-ε RNG turbulence model and the Chilton-Colburn analogy was employed to predict FAC rates. Design of experiments was applied to generate a data set for ANOVA analysis. From the results, increasing chromium content most effectively reduces the FAC rate, followed by adding more connecting pipes and their interaction. Adding more pipes redistributes peak velocities to more tubes and reduces peaks magnitude. A 50% reduction in peak velocity is observed when the number of pipes increased from 3 to 7. Although increasing header size has smaller impact, it theoretically reduces flow acceleration and pressure drops at downstream tubes’ entrances, leading to more uniform flow and reduced FAC rates. The regression model, with R-squared of 0.995, accurately predicts FAC rates. Optimal design variables, 3.16% Cr steel, 85.64 mm header diameter, and 7 connecting pipes yield an FAC rate of 0.0359 mm/year, with a 2.68% deviation from the CFD prediction. The proposed methodology and findings provide valuable insights for optimizing HRSG header design to mitigate FAC.
Publication details
- Authors: Khunphakdee, P., Phuakpunk, K., Piemjaiswang, R., Chalermsinsuwan, B.
- Published in: (2025) Results in Engineering, 26, pp. 105321.
- Year: 2025
- DOI: 10.1016/j.rineng.2025.105321