Theoretical investigation of two-phase flow instability between parallel channels of natural circulation in rolling motion

Highlights: • A program of two-phase flow instability of natural circulation is proposed. • The calculation results matched well with the experiment data. • The influence of natural circulation thermal parameters are analyzed. • The influence of rolling condition are analyzed. - Abstract: In present work, the two-phase flow instability between rectangular parallel channels of natural circulation under static and rolling conditions was coupled studied theoretically. Models including two-phase flow instability, natural circulation system components, and the additional force were established in combination based on the homogenous model. A computational program was written in FORTRAN language which was solved by Gear multi-value method by using control volume integrating method. The program was validated with experiments, and the results matched well with the experiment data. The marginal stability boundary (MSB) maps under different parameters were obtained by using nondimensional numbers N_sub and N_pch. The influence of different kinds of pressure drop, inlet subcooling temperature of heating channels, system pressure, valve resistance, venturi flowmeters resistance, structure height, rolling condition, and the interaction effect of natural circulation and two-phase flow instability between rectangular parallel channels were analyzed. The results show that with the increase in system pressure and venturi flowmeters resistance, the system stability of natural circulation is enhanced. The influence of inlet subcooling temperature is nonlinear. The increase in valve resistance leads to the instability of system. The increase in structure height does not change system stability significantly. The rise in rolling angle and period both reduce the system stability.