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 degrees C, ice at - 5 degrees C, cold storage maintained at - 25 degrees C, and a plate or blast freezer at - 40 degrees 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.