Nonlinear dynamic analysis of parallel three uniformly heated channels with water at supercritical pressures

This study develops a nonlinear dynamic model of parallel supercritical uniformly heated channels based on three-region methodology coupled with polynomial profile approximations between flow density and flow enthalpy. The validation results against the experimental data indicate that the present model has the capability to investigate the stability issues of parallel uniformly heated channels with supercritical water. Nonlinear characteristics, stability maps and parametric effects of three uniformly heated channels with supercritical water are investigated. The results illustrate that channel-to-channel interactions among three channels will drive the system more unstable due to a more asymmetric power distribution. In addition, the hottest channel with the highest steady state flow rate would oscillate with the largest amplitude and out-of-phase with the other less heated channels under constant total inlet flow rate condition. This study also reveals that the nonlinear oscillations between inlet flow velocity and outlet flow velocity in each channel tend to present out-of-phase. It could demonstrate that increasing the pressure drop of heavy fluid region (region 1) would stabilize the system, while increasing the pressure drop of light fluid region (region 3) would destabilize the system. The parametric studies on system stability of three uniformly heated channels suggest that increasing inlet flow resistance or enlarging the channel diameter would stabilize the system, while increasing outlet flow resistance or lengthening the channel length would destabilize the system.