Effect of heaving motion on thermal efficiency of the supercritical CO2 Brayton cycle

The supercritical CO2 Brayton cycle has high thermal efficiency and compact structure. Therefore, it is widely applied to waste heat recovery (WHR) system of ship. The heaving motion has a prodigious effect on the thermal performance and flow of the fluid, which in turn would affect the efficiency of Brayton cycle. This paper focuses on the impact of the heaving condition on the heat exchanger and the Brayton cycle for the first time under the conditions of the marine WHR system. The effect of heaving motion on thermal efficiency is analyzed by calculating the temperature and mass flux at outlet for different heaving conditions. The numerical results indicate that the heaving motion causes great fluctuations in outlet temperature, outlet mass flux and cycle thermal efficiency which are fluctuated up to 81.6 K, 751.1 kg/(m2 center dot s) and 25.9 %, respectively. The effect of heaving motion on the Brayton cycle comes from the additional acceleration, the magnitude of the additional acceleration increases with the decrease of the period and the increase of the amplitude. This study provides complementary and constructive suggestions on the influence of marine conditions on the SCO2 Brayton cycle.