Abstract
A model of the two-stage carbon dioxide (R744) refrigeration system was designed to be able to simulate the
freezing process of pelagic fish. The modelling language Modelica was applied and 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 R744 unit was compared to a state of the art two-stage
R717 system. The results show that the R744 system architecture, when properly designed and equipped
with the energy-boosting components like ejectors, offers better overall energy performance and shorter
freezing time, compared to the conventional ammonia system. What is more, the R744 system enables
substantial reduction in the evaporation temperature in the low-pressure loop for further decreasing the
freezing time
freezing process of pelagic fish. The modelling language Modelica was applied and 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 R744 unit was compared to a state of the art two-stage
R717 system. The results show that the R744 system architecture, when properly designed and equipped
with the energy-boosting components like ejectors, offers better overall energy performance and shorter
freezing time, compared to the conventional ammonia system. What is more, the R744 system enables
substantial reduction in the evaporation temperature in the low-pressure loop for further decreasing the
freezing time
