Optimization of carbon dioxide ejector expansion transcritical refrigeration system with ANOVA and NSGA-II

Abstract

With a projected increase of over 30 % by 2050, refrigeration systems are already responsible for 17 % of all electrical energy. To address these critical environmental concerns and enhance overall efficiency while reducing costs, a shift to eco-friendly and neutral impact alternatives is imperative. When carbon dioxide (CO2) is used as a working fluid since it is a natural gas, coupled with optimized system configurations, it holds the promise to mitigate these challenges effectively. In this study, a novel transcritical refrigeration cycle with an ejector operating with CO2, is proposed to further improve system efficiency. To validate the system's performance, a comprehensive thermodynamic model was established, and published results were used for validation. Remarkably, the new system demonstrated higher energy and exergy efficiency when compared to existing systems documented in the literature. To identify the most influential factors affecting cycle performance, an ANOVA analysis was conducted. The evaporator temperature was shown to be the most important variable, impacting the COP, exergy efficiency, and overall cost of the product by a combined 81, 46, and 75 %, respectively. In addition, the Non-dominated Sorting Genetic Algorithm-II (NSGA-II) method was used to maximize the effectiveness of the system. This method of multi-objective optimization took into account both the thermodynamic criterion of exergy efficiency and the economic criterion of total product cost. The integration of these criteria in the optimization process allows for an environmentally friendly and economically viable NEETR cycle.