A movable boundary model for helical coiled once-through steam generator using preconditioned JFNK method

Helical coiled once-through steam generator (H-OTSG) is the largest and the most complicated heat exchanger in the high-temperature gas-cooled reactor (HTGR), whose performance plays an important role in the nuclear power plant design and dynamic behavior analysis. A mathematical model of H-OTSG is developed based on the movable boundary method and solved by the advanced fully implicit Jacobian-free Newton-Krylov algorithm. The physical-based preconditioners are proposed and analyzed in this work, which achieves high-performance in solving the nonlinear steam generator system. In order to evaluate the performance of the movable boundary model, the fixed fine mesh model is also considered. The comparison is made between these two models from the perspective of the computational efficiency and accuracy. The simulation results are validated by the HTR-10 steam generator design data, showing that both models agree well with the design data, but have their own features. The fixed fine mesh model has its advantages in the accuracy, while the movable boundary model can realize the high computational efficiency.