Design and performance analysis of a multi-nozzle ejector with extended operating range for multi-effect distillation with thermal vapor compressor systems

In multi-effect distillation with a thermal vapor compressor (MED-TVC) system, the supersonic ejector recovers secondary steam through the primary flow, which is a promising energy-saving technology. However, the ejector often deviates from its designed operating conditions owing to fluctuations in the heat source vapor pressure. Notably, when the primary pressure falls below 70 % of the design value, ejector performance deteriorates sharply, significantly affecting the efficiency of the MED-TVC system. To solve this problem, a multi-nozzle ejector with a dual auxiliary nozzle (MNE-DAN) was developed in this study, modeled using three-dimensional computational fluid dynamics, and validated experimentally. When the primary flow pressure was reduced by 300 kPa, the MNE-DAN maintained the entrainment ratio (ER) above 0.35, whereas the conventional ejector failed. Three key parameters of the MNE-DAN were optimally designed, and the best parameters were the bottom position, circular nozzle, and two auxiliary nozzles. Moreover, to address the pressure fluctuation problem of the MED-TVC system, the optimal switching strategy based on three operating modes was proposed to achieve the ER of 0.35–0.89 in the entire operating range of 260–500 kPa, extending the effective operating range (380–500 kPa) of the conventional ejector. The proposed MNE-DAN design offers a simpler structure with significant performance improvements, making it more suitable for applications in commercial MED-TVC systems.