Thermo-economic Analysis and Multi-Objective Optimization of Advanced Three-Stage Cascaded Refrigeration Technologies

Abstract

The rising global demand for refrigeration, driven by industrial, medical, and technological needs, necessitates advancing highly performing and environment-friendly cooling technologies. This study explores advanced refrigeration techniques to address the limitations of conventional vapor-compression refrigeration (VCR) systems, particularly in ultra-low temperature (ULT) applications. While widely used, conventional VCR systems suffer from significant performance degradation at temperatures lower than -40°C, primarily due to excessive compression ratios and high discharge temperatures. To overcome these challenges, cascade refrigeration systems (CRS) have emerged as a promising alternative, enabling ultra-low temperatures (ULT) by combining multiple refrigeration cycles. This research presents the modelling and analysis of two novel advanced three-stage cascade refrigeration systems: an advanced triple cascade refrigeration system (ATCRS) and an ejector-enhanced advanced triple cascade refrigeration system (EATCRS). The ATCRS integrates a suction-line heat exchanger (SLHX) and flash tank (FLT) to enhance thermodynamic performance, achieving an 8.57% improvement in coefficient of performance (COP) and a 7.24% increase in second law efficiency over traditional cascade systems. The EATCRS incorporates an ejector system in the medium-temperature circuit (MTC), further improving system efficiency. Compared to the ATCRS, the EATCRS demonstrates a 32.82% increase in COP and a 27.34% boost in exergy efficiency, significantly outperforming conventional systems as well as the ATCRS. Moreover, the economic analysis indicates that despite an initial 9.78% increase in annual costs due to the ejector integration, the EATCRS achieves a 25.73% reduction in costs compared to other advanced systems. This study fills a critical gap in the current research by providing a comprehensive analysis of three-stage cascade refrigeration systems equipped with advanced VCR modifications along with multi-objective optimization of both systems using ANN-based genetic algorithm identifying optimal operating points ensuring the maximum possible performance by keeping the system cost within acceptable limit. The results highlight the potential of these systems to accommodate the increasing demand for ultra-low temperature refrigeration while addressing critical environmental and economic concerns. This work lays the foundation for future research aimed at optimizing refrigeration systems to ensure energy sustainability and environmental protection.