Nonlinear Dynamic Modeling of a Once-Through Steam Generator

A detailed, nonlinear, many lump, moving boundary dynamic model for a helical coiled once-through steam generator with nonuniform tube cross section is developed. Six flow regimes are employed in the model; each regime may consist of more than one section. The responses for two lumping cases (i.e., two sets, each with a different number of sections in the model) are compared with the same perturbations. Bases for selection of the number of sections and the calculational time step are suggested.

The steady state calculation for generating the state variable distributions along the tube coordinate is developed. Information obtained from the steady state distributions is compared with transient response at the final observation time. The comparisons for all individual steam generator input perturbations are satisfactory. Confidence in the correctness of the steady state calculation is obtained from the comparison of the steady state results with a set of design data.

Nonlinearity of the steam generator responses is studied. Comparison of the transient responses with two other models is given. The Fort St. Vrain 330 MW(e) steam generator is used as the reference design for this study.