Energetic, environmental and economic assessment of multi-evaporator CO₂–NH₃ cascade refrigeration system for seafood application

Refrigeration plays a vital role in ensuring quality and safety of seafood. In a tropical country like India, the seafood industry has a relatively larger cooling load throughout the supply chain due to higher temperature differences between ambient and chilled seafood. The cooling demands in a seafood processing plant are typically at four different temperature levels. Supply of chilled water at 2 °C, ice at − 5 °C, cold storage maintained at − 25 °C, and a plate or blast freezer at − 40 °C. Commonly, a multi-evaporator multi-stage refrigeration system with refrigerants like R22, R404A, or NH₃ are used in India. However, R22 and R404A have harmful effects on the environment due to their high global warming potential. This study proposed an all-natural multi-evaporator CO₂–NH₃ cascade refrigeration system (CRS). For comparison, the refrigeration demands in a surimi (seafood) processing and storage plant located in Mumbai were utilized. The study revealed that CO₂–NH₃ CRS has the highest COP and the lowest annual energy consumption followed by conventional NH₃ system. CO₂–NH₃ CRS exhibited 6.2%, 12.3% and 3.2% less energy consumption compared to R22, R404A, and NH₃ systems, respectively. Similarly, CO₂–NH₃ CRS also showed the lowest total equivalent warming impact which is 26.8%, 44.3% and 3.2% less compared to R22, R404A, and NH₃ systems, respectively. Furthermore, CO₂–NH₃ CRS also presented relatively better results in terms of annual cost rate and life cycle cost.