Thermo-economic investigation and multi-objective optimization of a novel enhanced heat pump system with zeotropic mixture using NSGA-II

This paper seeks to develop a mathematical model to analyze a novel ejector enhanced heat pump system from the thermodynamics viewpoint, and optimize the system by an elitist multi-objective non-dominated sorting genetic algorithm (NSGA-II). Zeotropic mixture (R600/R143a) is used as the system working fluid, and a booster is added to the conventional ejector enhanced system to improve the coefficient of the performance (COP). A code has been developed in MATLAB software to analyze the performance of the system by changing the value of different variables. The system is compared with a conventional system and the results showed that the COP of the proposed system can be higher than the conventional system up to 25%. Exergy analysis indicates that the highest exergy destruction (7.784 kW) is associated with the ejector. Moreover, thermo-economic analysis shows that the unit cost of the product of the system is 133.596 $/GJ. Further, the results show that the highest performance of the system is achievable using R143a/R600 mixture fluid with an R600 mass fraction of 0.45. Furthermore, the results demonstrate that exergetic efficiency, and heating load increase with the condenser temperature, while COP and unit cost of product decrease. Considering multi-objective NSGA-II, the optimum values of COP, exergy efficiency, and unit cost of the product are 2.78, 25.9%, and 113.57 $/GJ, respectively.