Keywords: desalination, thermal vapour compression, air ejector, ejector geometry, ejector performance, entrainment ratio, primary nozzle exit
Experimental investigation of the effect of ejector geometry on its performance
This paper describes the experimental investigation of the performance of the ejector used in desalination applications, using air as the working fluid. The aim of this study is to investigate experimentally the effect of the operating conditions and ejector geometry on the ejector performance. The effect of the relative position of the primary nozzle exit within the mixing chamber on the performance of the ejector is also investigated. The results show that using a convergent?divergent nozzle enhances the performance of the ejector. Also, the ejector performance is improved by decreasing the primary nozzle throat diameter and also by increasing the suction pressure. Moreover, the performance of the ejector is affected by the nozzle position, and the optimum position, which yields a maximum entrainment ratio for all nozzles, is at the inlet of the mixing chamber section of the ejector. As the constant area-mixing length to diameter ratio L/D increases, the entrainment ratio increases. And the increase in the entrainment becomes very small and can be negligible for L/D greater than 7.5. The entrainment ratio increases with increasing primary pressure, and the entrained flow reaches a maximum at a certain primary pressure. Beyond this value, the entrained flow will decrease.