Reducing energy consumption of a steam ejector through experimental optimization of the nozzle geometry

Abstract

Steam ejectors use pressurized vapor as the motive flow for running in steam cycles. The major parameter that affects the thermal energy consumption is the pressure of motive flow used in this device. In the current study, a malfunctioning experimental ejector is studied numerically to reveal the source of low evacuation rate from a suction chamber. This ejector was designed to operate under a motive pressure of 6 bar. However, the required vacuum in the suction vessel was not attained unless the pressure of motive steam was increased to 8 bar. The fastest and the most inexpensive way of improving the device performance was considered as replacing just the primary nozzle, with no further changes in ejector's body because, the ejector was connected to other unit facilities and hence the ejector replacement was very costly. The optimization procedure was performed through using numerical CFD (Computational Fluid Dynamics) simulations. The shape of internal supersonic nozzle was changed in many CFD analyses and the most optimized nozzle was selected for manufacturing. After installing the designed nozzle, an improved entrainment capability under the nominal pressure of 6 bar was observed and the desired vacuum level was attained.