Numerical Study on Performance of Refrigeration Cycle with Double Stage Ejector

In this paper، the performance of arefrigeration cycle with double stage ejector is studied. Also the effect of some working fluids، the ejector geometry including the diameter change in the part of constant diameter at the first and second stages and operating parameters on the entrainment ratio of the first and second stages in the ejector and coefficient of performance cycle (COP) are studied. A 2D model of the ejector is considered andthe continuity، momentum، energy، and state equations are numerically solved. The thermodynamic analysis is carried out to study the performance of the double stage ejector. The results show that using R245faand water as the working fluids in the cycle leads to the lowest and highest coefficients of performance (0. 799 and 1. 808 at TG=120oC and TC=12oC) respectively in comparison with other refrigerants. Increasing diameter of the mixing chamber in the second stage causes decrement in the COP at a constant diameter in the mixing chamber of the first stage. Also، increasing the diameter in the mixing chamber of the first stage causesincrease in the COP at a constant diameter in the mixing chamber of the second stage.