THE INVESTIGATION IN THE DENSITY-WAVE INSTABILITY OF A UNIFORMLY HEATED CHANNEL AT A SUPERCRITICAL PRESSURE USING A THREE-REGION NONLINEAR MODEL

Since the instability problems, especially density-wave instability, may deteriorate the heat transfer and safe operation of a supercritical heated system, it is essential to clarify the nonlinear characteristics of a supercritical fluid system, particularly that after the occurrence of instability. At present, the nonlinear dynamic model for supercritical heated system is quite spare in the literatures due to the complexity and dramatic change in flow properties of a supercritical fluid system. Therefore, this study develops a nonlinear dynamic model of a supercritical uniformly heated channel by dividing the channel into three regions with polynomial profile approximations between flow density and flow enthalpy. The present nonlinear dynamic model validated against the available experimental data could reasonably apply to explore the density-wave stability boundaries of a uniformly heated channel with supercritical water. Nonlinear characteristics of the system are investigated in this study. Increasing inlet flow resistance would stabilize the system, whereas increasing outlet flow resistance or heating power would destabilize the system.