Theoretical research on two-phase flow instability in parallel channels

Two-phase flow instability of two-channel system has been theoretically studied in the present study. Based on the homogeneous flow model, the parallel channels model and system control equations are established by using the control volume integrating method. Gear method is used to solve the system control equations. The marginal stability boundary (MSB) at different system pressure conditions is obtained. The typical MSB shape is usually a classical inclination “L” at some operation condition (i.e. the system pressure is low and the inlet resistance coefficient is small). The three-dimensional instability spaces (or instability reefs) with different inlet resistance coefficients are obtained. The three coordinates consists of phase change number (Npch), subcooling number (Nsub) and nondimensional pressure (P+). The lower part of the instability space is larger than the upper one. Increasing the system pressure or inlet resistance coefficient can strengthen the system stability. However, increasing the heating power destabilize the system stability. The influence of inlet subcooling on the system stability is multi-valued.