Performance evaluation of a multi-evaporator NH3-CO2 cascade refrigeration system with IHX for seafood processing industry

Abstract

Seafood processing typically has cooling demands at four different temperatures within the range -40 °C to 0 °C. An NH3-CO2 cascade refrigeration system equipped with an internal heat exchanger (IHX) is proposed for the same. The proposed system has two evaporators operating above the cascade condenser with NH3 as working fluid while two other evaporators are operating below the cascade condenser and have CO2 as working fluid. IHX in the sub-critical CO2 refrigeration system produces required sub-cooling at the exit of the condenser, increasing the refrigeration effect, and thus the overall performance improves. The cascade temperature is optimized and the performance of the system is found to be superior to the conventional NH3 system for various operating conditions. The effects of refrigeration loads, evaporation temperatures, and ambient temperature on the performance of the proposed cascade system are also analyzed.