Keywords: desalination, thermal vapour compression, ejector performance, ejector geometry, computational fluid dynamics, CFD, primary nozzle throat diameter, entrained flow, entrainment ratio, suction pressure, mixing chamber
Enhancement of ejector performance for a desalination system
This paper describes the use of Computational Fluid Dynamics (CFD) to investigate the performance of the ejector used in desalination applications that use air as the working fluid. A three-dimensional model for the CFD was used to investigate the effect of operating conditions and ejector geometry on ejector performance. The results show that ejector performance increases by increasing the primary nozzle throat diameter and the entrained flow reaches a maximum at a certain diameter; beyond this value, the entrained flow will decrease. Also, the entrainment ratio increases with an increasing suction pressure. Moreover, the results determine the optimum position with respect to the ejector's mixing chamber, which yields a maximum entrainment ratio. Also, the results determine the optimum constant area mixing length to diameter (L/D) ratio, which yields a maximum ejector performance. As this ratio increases, the entrainment ratio increases. Besides, the increase in entrainment becomes very small and can be neglected for an L/D ratio greater than 7.5. Also, for the high value of the primary pressure, constructing the constant area mixing section through multichannel tubes enhances ejector performance. A comparison between the present results and experimental results from other researchers gave a good agreement between them.