Study on secondary side flow of steam generator with coupled heat transfer from primary to secondary side

• Secondary side of steam generator is simulated with porous media model.
• Heat transfer from primary to secondary side is taken into account.
• Localized flow characteristics of secondary side are obtained.
• Parameters to analyze FIV damage, fouling and separator load are obtained.

Thermohydraulics characteristics in the secondary side of AP1000 steam generator (SG) are simulated based on the porous media models. The drift flux two-phase flow model coupled with a simplified flow boiling model is utilized. The heat transfer from primary side fluid to secondary side fluid is calculated three-dimensionally during iterations. The resistances caused by downcomer, tube bundle, support plates and primary separators are considered. Three-dimensional distributions of velocity, temperature, pressure, enthalpy, density, void fraction and flow vapor quality are obtained from the calculation by using the CFD code ANSYS FLUENT. Flow-induced vibration (FIV) damage is analyzed based on the cross flow velocity over the U-bend region of the outmost U-tube. The most severe FIV damages occur at the angles of −0.544 rad on the cold side and 0.353 rad on the hot side with maximum cross flow energies of 1145.2 J/m3 and 658.9 J/m3, respectively. Fouling is expected to deposit at the bottom of tube bundle since the velocity there is close to zero. The flow vapor qualities of mixture flowing into separators vary from each other significantly, with the maximum and minimum flow vapor quality in separators of 0.659 and 0.073, which is a severe challenge to the capacity design of separators.