Investigating the effect of secondary inlet pressure on the performance of an ejector

The ejector is the most important part of the ejection refrigeration cycle. Due to the complexity and different phenomena, such as suction, mixing, and shock that occur inside the ejector, it requires separate and accurate analysis. This study, for the first time, numerically was investigated the effects of secondary inlet pressure on the ejector flow. The effects of this parameter on pressure, Mach number and temperature inside the ejector were studied. The governing equations were solved by the finite volume method and compressible, two-dimensional, axisymmetric and fully turbulent flow. By comparing numerical results with experimental and analytical results, there is a reasonable agreement between them. In order to obtain the best performance of an ejector, at different secondary inlet pressure, the entrainment ratio and exergy efficiency were computed and compared to reach the best condition. The results show that there is inverse flow at low pressure less than 0.8 bar, but it becomes better by increasing the pressure up to 1.5 bar and more than that, no improvement was found. By reducing the secondary inlet pressure from the optimal pressure of 1.5 bar until the reversal flow occurs, the entrainment ratio decreases by about 105% and the exergy efficiency by about 64%.