Parametric Study on Multiphase Flow in Mechanical Ejector

Abstract Ejectors are extensively utilized in scenarios where deeper vacuum levels are required. They are highly reliable due to the lack of moving parts. The performance of an ejector is highly dependent on several factors such as the design of the flow channel being used and flow properties of the fluids in use. A high-speed flow (it is called a motive flow) is induced, which creates a low pressure in downstream. This low-pressure enhances fluid suction from a second inlet. This second inlet can have some stored fluid or some trapped fluid that needs to be extracted. This is an old technology. When both the fluids are in same temperature, this equipment is called mechanical ejector. The enhancement ratio is the ratio between sucked flow and motive flow and generally this is in the range of 40-50% for mechanical ejector. When stream with high temperature is used to suck low temperature stream then the enhancement ratio increases to more than 100% and the equipment is then called a Thermo-compressor. In this study, a high-speed multiphase jet stream water and steam is released as motive flow in the middle of two other velocity inlets that concentrations of water and steam at stagnant condition, which is ready to be sucked into the flow channel. As a result of jet speed, a significant pressure drop is created, resulting in the suction of stagnant stream of water and steam from the suction inlet towards the outlet. The core objective is to analyze the resulting suction flow rate and its dependency on the steam jet velocity, and temperature. Numerical simulation is implemented to investigate the flow behavior of the steam-water mixture. The study is done using the multi-phase solver in ANSYS/FLUENT. This study focuses on the complex behavior of multiphase flows, where liquid and gas phases coexist and interact within the thermal compressor. Multiphase flow dynamics significantly influence suction performance, pressure distribution, and phase mixing, making their understanding essential for optimization. The interaction between steam and liquid water impacts flow stability, entrainment efficiency, and energy transfer. By analyzing these effects, the study aims to improve the control of key parameters such as velocity, temperature, and phase composition. A deeper understanding of multiphase flow behavior will contribute to enhancing the overall efficiency of thermal compressors. Results shows that enhancement ratio remains almost same for all different kind of changes. The plan was to suck liquid stream motived by steam, which was hugely challenging. Hence, two phases of water were used. Motive stream was composed by high percentage of steam with low percentage of water, while sucked stream was composed by low percentage of steam with high percentage of water. Both of the streams were started with 50-50 and then percentages were kept changing to reach desired composition, e.g. rich mixture of stream for motive steam and lean mixture of steam for sucked stream. Many cases were run to reach the current findings. A number of cases were run to conduct this parametric study.