Multi-objective optimization and energy efficiency improvement for rotor duct in integrated energy recovery-pressure boost device

To reduce the volumetric mixing rate of the integrated energy recovery-pressure boost device, a novel symmetrical duct structure with diversion surface was proposed. The surrogate model-based multi-objective optimization framework was established, and obtained the optimal ducts V1 and V2 combined with computational fluid dynamics simulation. Numerical results indicate that optimized duct structure could promote the formation of plug flow and effectively improve the collision efficiency between high-pressure brine and low-pressure seawater, and the volumetric mixing rate corresponding to the ducts V1 and V2 was reduced by 31.52% and 22.18%, and the duct volume efficiency was increased by 16.04% and 19.56%, respectively. Finally, the performance of optimized device was verified through seawater reverse osmosis desalination system under actual working conditions. Experimental results showed that the mixing rate of optimized ducts had a significant decrease of 30.86% and 20.53% in the applicable range, and the energy recovery efficiency improved at most 5.41% and 7.55%, respectively. The optimized ducts could significantly reduce the specific energy consumption of the desalination system by 26.01% and 18.22%, respectively, and the specific energy consumption reached the lowest level of 3.02 kWh/m3, demonstrating the superiority of the structure and the accuracy and effectiveness of the optimization strategy.