Effect of ejector critical area ratio on the performance of ammonia-water GAXE absorption refrigeration system

This article presents development of a new ۲D ejector model which is validated by experimental data used in literature. The ejector is combined with a GAX (generator-absorber heat exchange) absorption refrigeration cycle using an ammonia-water pair as the working fluid. Applying the conservations of mass, energy as well as the exergy balance, the combined cycle is analyzed from the viewpoints of first and second laws of thermodynamic. Three optimum critical area ratios are selected and the effect of generator and evaporator temperatures is investigated at the constant ejector area ratios. Results indicate that an increase in the evaporator temperature leads to an increase ofoptimum critical area ratio and entrainment ratio. Also, it is observed that increasing the evaporator temperature from ۰oC to ۱۰oC could raise the entrainment ratio by upto ۵۰%. It is found that at constant optimum critical area ratios increasing the generator temperature results in an increase of COP as well as second law efficiency. Meanwhile, exergy analysis reveals that the ejector is one of the highest irreversible sources in the cycle (۲۵% of total exergy destruction).