Thermodynamic analysis and optimization of an irreversible Ericsson cryogenic refrigerator cycle Mohammad Hossein Ahmadi a,⇑ , Mohammad Ali Ahmadi b a Department of Renewable Energies, Faculty of New Science and Technologies, University of Tehran, Tehran, Iran b Department of Petroleum Engineering, Ahwaz Faculty of Petroleum Engineering, Petroleum University of Technology (PUT), Ahwaz, Iran article info Article history: Received 19 August 2014 Accepted 21 September 2014 Keywords: Decision making Ericsson refrigerator Cooling load Power input Optimization abstract Optimum ecological and thermal performance assessments of an Ericsson cryogenic refrigerator system are investigated in different optimization settings. To evaluate this goal, ecological and thermal approaches are proposed for the Ericsson cryogenic refrigerator, and three objective functions (input power, coefficient of performance and ecological objective function) are gained for the suggested system. Throughout the current research, an evolutionary algorithm (EA) and thermodynamic analysis are employed to specify optimum values of the input power, coefficient of performance and ecological objective function of an Ericsson cryogenic refrigerator system. Four setups are assessed for optimization of the Ericsson cryogenic refrigerator. Throughout the three scenarios, a conventional single-objective optimization has been utilized distinctly with each objective function, nonetheless of other objectives. Throughout the last setting, input power, coefficient of performance and ecological function objectives are optimized concurrently employing a non-dominated sorting genetic algorithm (GA) named the non-dominated sorting genetic algorithm (NSGA-II). As in multi-objective optimization, an assortment of optimum results named the Pareto optimum frontiers are gained rather than a single ultimate optimum result gained via conventional single-objective optimization. Thus, a process of decision making has been utilized for choosing an ultimate optimum result. Well-known decision-makers have been performed to specify optimized outcomes from the Pareto optimum results in the space of objectives. The outcomes gained from aforementioned optimization setups are discussed and compared employing an index of deviation presented in this work. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Among the different models for refrigeration systems, the Ericsson cycle is one of the most important ones which have been utilized in various engineering designs. Several engineering compa- nies have used the Ericsson cycle to manufacture practical systems in order to produce very low temperatures. These efforts have led to the development of novel designs for these cycles. Walker and col- leagues [1], Leff and Teeters [2] have mentioned that in the study by Curzon and Ahlborn [3] and Wu [4], the straightforward calculation made by the authors is not applicable for a reversed Carnot cycle since there is no ‘Natural Maxima’ in these cycles. Blanchard [5] utilized the Lagrangian approach of undeter- mined multiplier for a given heating load to obtain the COP of an endoreversible Carnot heat pump operating at minimum power input. In recent years, Wu [6,7], Wu and colleagues [4], Chen and colleagues [8], Chen [9], Ahmadi and colleagues [10], Chen and Yan [11], Kaushik [12], Tyagi [13–15] demonstrated the optimal performance as a function of working circumstances by employing the concept of finite time thermodynamics following the work of Curzon and Ahlborn [3] on the different irreversible and endore- versible cycles for various operating circumstances. Angulo-Brown [16] introduced the ecological function as E p ¼ P o  T L _ S gen (T L is the sink temperature, P o is the power output, and _ S gen is the entropy generation rate) for a finite time Carnot heat engine. The author obtained that at the maximum power output, the thermal effi- ciency is nearly the average of the Carnot efficiency and the C–A efficiency. When the heat sink temperature T L is not equivalent to the environmental temperature T 0 , Yan [17] suggested that it is more appropriate to utilize the ambient temperature in the eco- logical function. The study of ecological optimization of different http://dx.doi.org/10.1016/j.enconman.2014.09.064 0196-8904/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: mohammadhosein.ahmadi@gmail.com (M.H. Ahmadi). Energy Conversion and Management 89 (2015) 147–155 Contents lists available at ScienceDirect Energy Conversion and Management journal homepage: www.elsevier.com/locate/enconman