A comparison of refrigerants in a two-stage ejector-expansion transcritical refrigeration cycle based on exergoeconomic and environmental analysis

A comprehensive energy, exergy, exergoeconomic and environmental comparison between carbon dioxide, ethane and nitrous oxide as the refrigerants of a two-stage ejector-expansion transcritical refrigeration cycle is carried out. All of the obtained results are attained by optimizing COP subject to gas cooler and intercooler pressures in different values of gas cooler and evaporator temperatures. It is observed that the compressors operating pressure and temperature levels in the cycle for ethane are lower than other refrigerants, which leads to higher system safety and lifetime. Furthermore, the highest COP and exergy efficiency in a wide range of gas cooler temperature belongs to the ethane. The nitrous oxide refrigerant has the lowest product unit cost, which is about 4.2% lower than that of the ethane refrigerant with the highest product unit cost. Therefore, ethane is the most preferable refrigerant from energy and exergy aspects and nitrous oxide is suitable based on exergoeconomic viewpoint.