In this paper, comparative energy, exergy and economic analysis of natural refrigerant couples working in a cascade refrigeration system incorporated with a flash tank in its higher temperature cycle and a flash intercooler with indirect sub-cooler in its lower temperature cycle have been done. An analysis is conducted using seventeen refrigerant couples from eight natural refrigerants, namely R717, R290, R600a, R744, R744a, R170, R1150 and R1270. Comparison based on COP, exergy efficiency, system cost rates, and exergy destruction rate, to identify the best alternative refrigerant couple, is performed. Thermodynamic optimization has also been carried out with evaporator temperature, condenser temperature, LTC condenser temperature, cascade temperature difference, de-superheating and subcooling parameter of LTC intercooler, as six design variables. To evaluate the economic accountability of refrigerant couples a simple payback analysis has been done at the thermodynamic optimal conditions of the system. Results of analysis and optimization show that R717-R290 is the best refrigerant couple for this system from thermodynamic as well as economic points of view. The maximum COP and exergy efficiency obtained is 1.917 and 39.14% respectively and the corresponding total annualized system cost is 836,395 $/yr for R717-R290 refrigerant couple.

在本文中，已经对在具有较高温度循环的闪蒸罐和带有间接过冷器的闪蒸中冷器的较低温度循环的级联制冷系统中工作的天然制冷剂对进行了比较能量，火用和经济分析。使用来自八个天然制冷剂的17个制冷剂对进行分析，这些天然制冷剂分别为R717，R290，R600a，R744，R744a，R170，R1150和R1270。根据COP，火用效率，系统成本率和火用破坏率进行比较，以确定最佳的替代制冷剂对。还使用蒸发器温度，冷凝器温度，LTC冷凝器温度，级联温度差，LTC中冷器的过热度和过冷参数作为六个设计变量进行了热力学优化。为了评估制冷剂对的经济责任，已在系统的热力学最佳条件下进行了简单的投资回收分析。分析和优化结果表明，从热力学和经济角度来看，R717-R290是该系统的最佳制冷剂对。对于R717-R290制冷剂对，获得的最高COP和最高能效分别为1.917％和39.14％，相应的年化系统总成本为836,395美元/年。