2-PHASE FLOW INSTABILITIES IN HELICAL TUBES OF ONCE-THROUGH STEAM-GENERATORS

Helical tube is one type of once-through stream generators in integrat ive nuclear device. The thermal-hydrodynamic instabilities in helical tubes of a once-through steam generator (HTOTSG) with exit-steam super heated were studied by using multi-variable liner-frequency-domain the ory. Based on the drift-flux model, a small perturbation method, as we ll as Laplace transformation theory, was empolyed to linearize the sys tem of partial differential equations. A computer code called HTOTSGM- D was developed to investigate the influences of inlet flow rate, inle t subcooling, heat flux, and system pressure on oscillations. The calc ulated results showed that the above factors must be considered compre hensively in once-through steam generator design and operation, even t hough the installation of the entrance throttles was still an effectiv e way to stabilize the system.