Abstract
An ammonia / carbon dioxide (R717/R744) cascade model was designed to be able to simulate the freezing
process of pelagic fish. The modelling language Modelica was applied and it was implemented in the
simulation environment Dymola Control. Various simulations were performed for a typical design of the
freezing tunnel. The total energy consumption of the R717/R744 cascade unit was compared to a state of the
art two-stage R717 system. The results show that the R717/R744 cascade system architecture, when properly
designed, offers comparable overall energy performance at a reduced freezing time, compared to the
conventional ammonia system.
What is more, the cascade offers the possibility to reduce the evaporation temperature in the R744 bottom
cycle to further reduce the freezing time.
process of pelagic fish. The modelling language Modelica was applied and it was implemented in the
simulation environment Dymola Control. Various simulations were performed for a typical design of the
freezing tunnel. The total energy consumption of the R717/R744 cascade unit was compared to a state of the
art two-stage R717 system. The results show that the R717/R744 cascade system architecture, when properly
designed, offers comparable overall energy performance at a reduced freezing time, compared to the
conventional ammonia system.
What is more, the cascade offers the possibility to reduce the evaporation temperature in the R744 bottom
cycle to further reduce the freezing time.