Analytical and Numerical Studies of a Steam Ejector on the Effect of Nozzle Exit Position and Suction Chamber Angle to Fluid Flow and System Performance

Abstract

Nozzle exit position [NXP] plays a vital role in the performance of the ejector, but its values are specified in a range for the required operating condition. In this study instead of the range of values, a specific value, named as entrainment diameter is developed and its effect on the performance of the ejector is studied for several combinations of suction chamber angle using numerical method. The effect of the condenser and boiler pressures on the performance of the ejector are also studied to ensure the off-design operating conditions. The entrainment diameter of an ejector is derived analytically by solving one dimensional compressible fluid flow equations using MATLAB. To study the effect of entrainment diameter on the performance of the ejector, CFD technique is employed. Analytical and numerical results are validated with experimental data available in the previous studies. For 7 kW refrigeration capacity, it is inferred that the suction chamber angle of 18° and the corresponding entrainment diameter 90.8 mm with the NXP of 23.62 mm yield the maximum entrainment ratio. The study predicts that the performance of the ejector is highly influenced by the pressure increment at the exit of the nozzle, while the suction chamber angle is between 12° to 21°.

CFD analysis of operating condition effects on optimum nozzle exit position of a supersonic ejector using the refrigerant R134a

“…This distance is sometimes presented in its nondimensional form with respect to the throat diameter. This factor has a highly significant effect on the ejector efficiency when the operating conditions are different from the on-design conditions [4][5][6][7]. The existence of at least an optimum NXP that maximizes the ejector performance was stated in different studies (Table 1).…”

Analytical and Numerical Study on the Performance of ‎Supersonic Ejector at Different Operating Conditions ‎and Working Fluids

“…Experimental setups are costly and limited to study the number of design and operating parameters. The CFD also helps in flow visualization and shock prediction in supersonic ejector studies (Gagan et al 2014;Su and Agarwal 2016;Ramesh and Sekhar 2017;Ruangtrakoon et al 2013).…”