Thermal inertia characteristics and prediction methods for transcritical CO2 power cycle regenerator

In CO2 power cycles, the accurate prediction of regenerator thermal inertia is essential for improving the dynamic response performance. Therefore, the spatiotemporal evolution of dynamic heat transfer characteristics of CO2 within the regenerator under varying operating conditions was investigated in this study. On this basis, key parameters for characterizing dynamic heat transfer behavior are proposed, including temperature dynamic fitting function (F(t)) and thermal equilibrium time (dt). Subsequently, computational correlation equations for these key parameters are established. Finally, a new predictive method for regenerator thermal inertia is established, and its reliability is verified. The results indicate that, in the near-critical region, variations in CO2 density facilitate the establishment of thermal equilibrium, whereas local peaks in specific heat capacity lead to an increase in dt. By contrast, the effects of density and viscosity on dt were found to be insignificant. 316 L stainless steel has a longer dt than aluminium. Moreover, dt increased with increasing channel length and solid thickness. Solid heat storage capacity is the most significant factor affecting dt. Under randomly selected disturbance conditions, the maximum time averaged prediction error of the proposed method is 1.85%. The novelty of this work lies in revealing the mechanism by which thermophysical parameters variations of CO2 in the near-critical region affect thermal inertia, and in proposing characteristic parameters and a corresponding prediction method for thermal inertia. The findings establish a theoretical basis for cycle control design to improve load-following capability, operational flexibility, and safety under wide-ranging operating conditions.