Thermodynamic analysis of a novel combined double ejector-absorption refrigeration system using ammonia/salt working pairs without mechanical pumps

Abstract

This paper proposed an absorption refrigeration system which employed two ejectors as cycle power source instead of mechanical pumps. Ammonia/lithium nitrate and ammonia/sodium thiocyanate solutions are applied as working pairs as well as an air-cooled type absorber are put up in this system. The liquid-vapor ejector is located at the inlet of the absorber, the steam-driven jet pump is set at the up-stream of the back flow of solution heat exchanger. Thermodynamic performance of this absorption refrigeration system has been comprehensively studied by numerical method; thus, comparison has been made with the conventional absorption refrigeration system. The result indicates that, compared with conventional air-cooled absorption refrigeration cycles, this novel combined double-ejector refrigeration cycle (DEARC) sacrifices part of refrigerant which leads to a decline of system COP value. But still, COP of DEARC can reach 0.6354, which is sufficient for practical use under exhaust heat conditions. Pressure ratio of liquid-vapor and the absorber outlet solution temperature are both two factors which make it possible to improve the system performance furthermore. Vapor consumption ratio is another key factor which has great influence to system performance. The wider range of generating temperature and the air-cooled type absorber of DEARC make it easy for the whole system to achieve miniaturization and simplification.