CFD study of a variable area ratio ejector using R600a and R152a refrigerants

In the present paper, the numerical results for two 1 kW cooling capacity ejectors with variable primary nozzle geometry are presented using R152a and R600a as working fluids. Working fluids were selected based on the criteria of low environmental impact and good performance in the range of operating conditions adequate for using solar thermal energy as primary heat source. Variable area ratio was achieved by applying a movable spindle at the primary nozzle inlet. Numerical results clearly show that adjusting spindle position resulted in a significant improvement of the entrainment ratio compared to a fixed geometry ejector when the operating conditions were different from design values. This increase in ejector performance was as high as 177% for low condenser pressures. Diagrams are also presented for both refrigerants that can be used to find spindle positions that maximise ejector performance under variable operating conditions.

► A numerical analysis of two ejectors with variable geometry is presented using CFD.
► Ejector performance with two working fluids (R152a and R600a) is analysed.
► Variable area ejector results in better performance than fixed geometry design.
► Optimal spindle positions are presented depending on operating conditions.
► R600a is a good choice for working fluid in the range of tested conditions.