Thermodynamic Analysis of an Electricity-Cooling WHR Cogeneration System Aboard Ships using Siloxanes as Working Fluids

Cogeneration system has become a valuable alternative approach for cascade waste heat recovery (WHR). In this paper, a novel electricity-cooling cogeneration system (ECCS) based on organic Rankine cycle-absorption refrigeration cycle (ORC-ARC) combined system is proposed to recover the waste heat of marine engine. ORC was adopted in the higher temperature cycle, in which alternatives D4, MDM and MM were selected as the working fluids. An ARC was adopted in the lower temperature cycle to recover the heat of the working fluid at the regenerator outlet in ORC. It aims to satisfy refrigeration requirement aboard ship, in which a binary solution of ammonia-water is used as the working pairs. Electricity output, cooling capacity, total exergy output, primary energy ratio (PER) and exergy efficiency are chosen as the objective functions. The results show that the additional cooling capacity is up to 10.9 MW, and such an ECCS has improved the exergy efficiency by 51% compared to the basic ORC. D4 shows the best performance and it is considered as the most promising working fluid in the three investigated alternatives.