CFD analysis of steam superheater operation in steady and transient state

• Published in: Energy (Oxford) 2020-05, Vol.199, p.117423, Article 117423
• Main Authors: Granda, Mariusz, Trojan, Marcin, Taler, Dawid
• Format: Article
• Language: English
• Subjects: CFD modelling; Computational fluid dynamics; Computer applications; Finite element method; Flue gas; Fluid dynamics; Fluid flow; Gas temperature; Heat; Heat flow; Heat transfer; Heat transmission; Hydrodynamics; Non-stationary; Parameters; Steam; Steam superheater; Temperature distribution; Transient; Tubes; Turbulence models; Wall temperature; y plus
• ISSN: 0360-5442; 1873-6785
• DOI: 10.1016/j.energy.2020.117423

A CFD (Computational Fluid Dynamics) model of steam superheater in stationary and non-stationary state was presented in the paper. The developed model allows for obtaining detailed distributions of selected steam and flue gas parameters and wall temperature of the steam superheater tubes. The transient state presented in the paper refers to the operation of the steam superheater at the moment of attemperator activation. Two cases are considered when solving a transient state. First, when the Courant-Friedrichs-Levy (CFL) condition is satisfied (the time step must be small enough to keep up with all the changes within nodes of the grid). Second, when the CFL condition is not satisfied (each time step is solved separately and treated as a stationary state, it can be as large as needed). The paper also describes the influence of the SST and k-ε turbulence models as well as mesh parameters on the obtained results. In the case of the SST turbulence model and y+ = 1 relative error of the bulk temperature at the steam and flue gas outlet concerning the values obtained from measurements is 0.2% and 0.7% respectively. For the k-ε model, the relative error is 3.2% for the steam temperature and 7.3% for the flue gas temperature. In addition, the heat flow transferred from the flue gas to the steam and the heat flow absorbed by the steam from the flue gas was determined to verify the quality of the calculations. The differences between the obtained heat flow values were at the level of 0.4%.