Optimal structure design of supercritical CO2 power cycle for waste heat recovery: An improved intelligent synthesis method

• An improved intelligent synthesis method is proposed. • Improving the compression process of the elementary cycle needed for synthesis. • Under different cooling conditions, the supercritical CO 2 cycle systems are compared. • The optimal system obtained by the improved intelligent synthesis method is better. When designing the system structure of the supercritical CO 2 cycle (S-CO 2 ), the optimal cycle structure may be missed by a priori specification of the up-bottom methods, such as the enumeration method and the superstructure method. The intelligent synthesis method, as a kind of bottom-up method, can break through this limitation. With the diverse compression process of the S-CO 2 cycle for waste heat recovery (WHR), the elementary cycle in the original intelligent synthesis method has obvious limitations. Therefore, the novelty of this paper is to propose an improved intelligent synthesis method based on the original intelligent synthesis method. The proposed method improves the compression process of the elementary cycle with a dual compression process, which could be extended for the application of S-CO 2 cycle structure design for WHR. Besides introducing the optimization results under different cooling conditions, the supercritical CO 2 cycle system obtained by the enumeration method, the superstructure method, the original and the improved intelligent synthesis methods are compared and analyzed. The results show that when the heat source temperature is 400–600 °C, the net power output of the optimal system obtained by the improved intelligent synthesis method is increased by 12.29–14.70 % and 3.08–4.22 % compared with two typical S-CO 2 cycle systems, by 0.36–1.88 % compared with the superstructure method and by 1.06–1.78 % compared with the original intelligent synthesis method, respectively.