Energy, exergy, economic and environmental analyses of a cascade absorption-compression refrigeration system using two-stage compression with complete intercooling

Cascade refrigeration system with multiple cooling temperature ranges can be found in many areas such as seafood processing and cold storage. Using multiple compressors respectively corresponding to different temperature ranges is the most common way to control the evaporation temperature and cooling capacity. However, such an approach is inefficient and uneconomical. In order to relieve this problem, a novel cascade absorption-compression refrigeration system using two-stage compression with complete intercooling (ACRSI) is proposed in this paper. A mathematic model based on energy, exergy, economic and environmental analyses is developed to evaluate the system performance at five operation parameters including the condensation temperature as well as the evaporation temperatures and the cooling capacities in two cooling temperature ranges. The parameter analysis is conducted to obtain the optimal middle temperature in the cascade condenser. The simulation results show that the optimal middle temperature is 11 °C, which cannot be influenced by two evaporating temperatures and cooling capacities. Meanwhile, the corresponding optimal COPI considering the consumption of waste heat is 0.5 and the optimal COPII ignoring the consumption of the waste heat is 3.25. The ECOP is 141.7% of the basic cascade absorption-compression refrigeration system (ACRS) and the average annual cost is $246,306.62, which is 82% of ACRS. Besides, the average annual environmental cost of ACRSI is only $580, which is significantly environmentally friendly.