Multi-objective optimization of cooling water package based on 3E analysis: A case study

The aim of this paper is multi-objective optimization of cooling water package based on exergetic, economic and environmental analysis (3E) employing the non-dominated sorting genetic algorithm (NSGA-II). The studied compression refrigeration cycle of cooling water package provides chilled water for cooling the plant equipment located in South Pars refinery of Iran. Different objectives scenarios as well as decision variables including various engineering constraints are simulated in EES software which makes a set of the MINLP optimization problems. In this study, four optimization scenarios i.e. the single-objective optimizations of thermodynamic, economic and environmental as well as the multi-objective optimization are performed. After comparing all the scenarios, the results show that the multi-objective optimization provides the most simultaneous satisfaction of all the 3E results leading to the exergy destruction reduction from 264.8 kW to 127.6 kW (the performance coefficient is increased from 3.872 to 7.088). Furthermore, the cold water production cost is reduced from 117.5 dollar/hour to 87.19 dollar/hour and the NOx emission is reduced from 4958 kg/year to 2645 kg/year. Finally, by employing the multi-objective optimization, the total cost of the refinery can be improved by 25.8%.