Analysis of Density Wave Oscillations in Helically Coiled Tube Once-Through Steam Generator

Abstract EN

Helically coiled tube Once-Through Steam Generator (H-OTSG) is one of the key equipment types for small modular reactors.

The flow instability of the secondary side of the H-OTSG is particularly serious, because the working condition is in the range of low and medium pressure.

This paper presents research on density wave oscillations (DWO) in a typical countercurrent H-OTSG.

Based on the steady-state calculation, the mathematical model of single-channel system was established, and the transfer function was derived.

Using Nyquist stability criterion of the single variable, the stability cases were studied with an in-house computer program.

According to the analyses, the impact law of the geometrical parameters to the system stability was obtained.

RELAP5/MOD3.2 code was also used to simulate DWO in H-OTSG.

The theoretical analyses of the in-house program were compared to the simulation results of RELAP5.

A correction factor was introduced to reduce the error of RELAP5 when modeling helical geometry.

The comparison results agreed well which showed that the correction is effective.