Simulation of a carbon dioxide (R-744) refrigeration system for fishing vessel

Abstract

The paper describes architecture of a prototype industrial CO2 trans-critical system for production of refrigerated sea water (RSW) for either fishing vessels or land-based process plants. The refrigeration system was designed to cover cooling demands of RSW (up to 450 kW), air-conditioning (up to 170 kW) and freezing equipment (up to 82 kW at -25 °C). Four system design cases were evaluated: one stage compression, twostage expansion with auxiliary compressor, three stage expansion with parallel compressors and two stage expansion supported by ejector. The optimum high side pressure level and the effectiveness of internal heat exchanger were investigated to optimize the four system designs with respect to capacity, seawater temperature and COP. The system performance was evaluated for fish chilling on-board , including both chilling and temperature maintenance periods. Analysis shows a 28% difference in energy demand after 42 hours of operation, when applying the ejector supported solution. Considering that electricity onboard fishing vessels is provided by fossil fuel based generators, the decrease in energy demand results in lower total greenhouse gas emissions.