Techno‐economic assessment of novel and conventional working fluid mixtures for two‐stage double‐ and triple‐effect absorption refrigeration systems

Abstract

This work presents a systematic techno-economic assessment of 84 conventional and novel working fluid mixtures in two-stage, double-and triple-effect (Kangaroo) absorption refrigeration cycles. Rectifiers are modeled as staged distillation columns to capture appropriately the separation tasks. All mixtures are first evaluated based on process operating performance indicators including the coefficient of performance, the exergy efficiency, the cycle high pressure, the refrigerant and absorbent total flowrates, the total number of stripping stages and the distillate-to-feed ratios, subject to constraints ensuring feasible operation. The distillate-to-feed ratio, the number of stages in each rectifier and the individual flows of the refrigerant and the absorbent in different cycle circuits are considered as design parameters. The evaluation considers wide operating ranges, to identify the conditions that result in optimum values for the employed indicators. A multi-criteria approach is used to generate few, highly performing candidates which are further evaluated using economic criteria. A mixture of acetaldehyde/dimethylformamide is selected as the best performing working fluid which exhibits at best 39% lower cost per ton of cooling and 7% higher coefficient of performance than NH 3 /H 2 O in the tripeeffect cycle, with similar high performance observed in the double-effect cycle too. The same mixture exhibits at best 38% lower coefficient of performance and 1% lower cost per ton of cooling than H 2 O/LiBr.