Thermo-economic-environmental optimization of injection mass flow rate in the two-stage compression refrigeration cycle (Case study: Mobarakeh steel company in Isfahan, Iran)

Abstract

One of the main challenges in designing the two-stage compression refrigeration cycles is determining the optimal operating condition of the inter-stage section. In this paper, the optimal mass flow rate of the injected refrigerant in an existing compression refrigeration cycle was investigated based on energy, exergy, environmental and economic analysis on the parameters such as coefficient of performance, power consumption, exergy destruction and efficiency. The optimization process was performed on the operational data of a two-stage compression refrigeration cycle in Mobarakeh Steel Company of Isfahan recorded over 6 working months, as a case study. Results showed that the maximum coefficient of performance and exergy efficiency are achieved at injection mass flow rate of 5.9 kg/s. Furthermore, it was found that the variation of ambient temperature and consequently the temperature of chilled water entering the evaporator has no effect on the optimal mass flow rate of the injected refrigerant. Finally, 16,600 GWh/year energy saving, 9700 ton/year CO2 reduction and 1.9 million $/year cost saving can be achieved in Iran's industrial sector through employing two-stage compression refrigeration cycle with optimal injection system.