CO2-mixture-based ship waste heat recovery system (SWHRS) with multiple energy outputs and composition-adjustable mixture

To ameliorate the adaptability of the ship waste heat recovery system (SWHRS) to the variable energy demand, this paper proposes a CO2-mixture-based SWHRS providing refrigerating output as well as adjustable heating and electrical output. The adjustability deriving from mixture composition regulation profits from liquid separation condensers. A scientific vessel YUKUN is selected as the recovery target, the energy demand characteristics of which in different seasons (spring/autumn, summer, and winter) and conditions (sailing and berthing) are exploited to determine six operating modes. Well-designed configurations of SWHRS's subsystems with different energy exportation emphases improve the matching of SWHRS to changes in energy demand. Moreover, composition adjustment corresponding to various energy requirements further modifies the energy conversion tendency of waste heat to heating or electrical energy desired by the target ship. Comparative research demonstrates that SWHRS possesses certain superiority over the non-adjustable system due to the regulation of mixture composition corresponding to variation in energy requirement. Thus, the SWHRS can reduce the fuel consumption rate by 4.9% to 17.2% compared to the original waste heat recovery system in YUKUN at different modes. Based on actual operating data, the SWHRS can realize a decline of 10.3% in the annual fuel consumption rate. Hence, a fuel charge of 245 000 USD could be saved for YUKUN equipped with SWHRS for one year.