Numerical study of primary steam superheating effects on steam ejector flow and its pumping performance

The effects of primary steam superheating on steam condensation in nozzle and the performance of steam ejector were investigated using CFD (computational fluid dynamics) method. Using a wet steam model being proposed in our previous study, simulations based on the primary steam with five superheated levels were performed, and the results demonstrate the superheating operation of the primary steam weakens the spontaneous condensation intensity and postpones its occurrence within the nozzle vicinity. Due to the droplets nucleation refinement for the condensation of superheated steam, the mixing process between the primary and the secondary fluids is improved. Consequently, a higher entrainment ratio is achieved. However, the superheating operation may not exceed 20 K, as its contribution on entrainment ratio improvement is not as significant as 0 K-20 K superheating, and too much superheating will requires more energy as input, which is not a practical solution to further improve the steam ejector pumping performance.