Influence of marine conditions on thermal efficiency of SCO2 Brayton cycle for waste heat recovery

The supercritical CO2 Brayton cycle has great advantages for waste heat recovery in ships. The rolling motion would affect heat transfer as well as the efficiency of Brayton cycle, but few literature have studied the influence on the cycling efficiency. In view of this, the purpose of this paper is to obtain the effect of rolling motion the Brayton cycle and clarify its mechanism. Therefore, the heat transfer characteristics as well as thermal efficiency under rolling motion are calculated by numerical simulation coupled with the inertia force. The results show that rolling conditions lead to the instability of thermal performance in the heat exchanger and likewise the instability of thermal efficiency. Specially, as the rolling cycle decreases or the angle increases, fluctuations of outlet temperature and mass flux of supercritical CO2 are enhanced, which deteriorates the instability of thermal efficiency. The main reason for the instability is the influence of additional forces on the fluid under the rolling motion. In the axial view, the rolling motion has the strong influence on the fluid in the middle section of the heat exchanger, and has the significant effect on the fluid near the wall in the radial direction.