Study of applying adjoint sensitivity based parametric global optimization method to designing $S-CO_2$ power cycle for SFR application

Abstract

The $S-CO_2$ power cycle is a cycle in which the working fluid is $CO_2$ and the compression is performed near the critical point. Due to abrupt changes in thermodynamic properties near the critical point, the $S-CO_2$ cycle is characterized by simplicity of construction, relatively small component size, and high efficiency. Therefore, it has been actively studied in various energy related areas such as thermal power, solar heat, and waste heat recovery industries. Recently, applying the $S-CO_2$ cycle as the power system to the next generation nuclear power plant is also suggested in the nuclear energy research. Previous studies revealed the optimum layout and the design point of the $S-CO_2$ cycle for SFR application and evaluated the off-design behavior as well. However, the design optimization was performed only through the brute force method. Furthermore, the off-design behavior evaluation showed that a better operating point could be found, but the optimum was not obtained. In this thesis, an optimal design methodology is proposed for cycle design for SFR applications, and build an optimal operation strategy for the off-design conditions. The research is conducted through the adjoint method, which is the method to analyze sensitivity quickly and precisely by solving the dual problem. Design optimization and optimal operation strategy are established through the adjoint. As a result, it has been confirmed that both the optimum design point and the optimum operating point can be obtained quickly.