| Medical water for injection(WFI)refers to water that meets the requirements under water for injection in the Chinese Pharmacopoeia.It plays a crucial role in pharmaceutical preparation and medical equipment cleaning,as it underpins the very foundation of the pharmaceutical industry.Nonetheless,the conventional vertical tube multi-effect distilled water machine,used both domestically and internationally,suffers from low energy efficiency.To address this issue,this article proposes a novel WFI preparation system.The ejector is a crucial constituent of this system,which has received widespread attention from academia despite its low cost and wide application.However,because the internal mixing process of the ejector involves many complex hydrodynamic problems,the current analysis regarding the mechanism of superheating at the ejector ports appears to be insufficient in its depth and comprehensiveness.Simultaneously,the intricate and dynamic operating conditions demand an exceptionally high degree of robustness of the ejector,but there are limited design approaches to enhance the robustness of the ejector.This research aims to improve the performance of the ejector and enhance its robustness by studying the superheating mechanism and structural optimization of the ejector,thereby improving system performance and reducing water production costs.Initially,the existing multi-effect distilled water machine has undergone significant improvements through the integration of horizontal tube falling film evaporators and an ejector,based on the multi-effect distillation with thermal vapor compression.The operational principles of each component were elaborated in detail,and the corresponding thermodynamic models were established and analyzed.An investigation into the factors that impact the gain output ratio of the system has been conducted,highlighting the necessity for further research on ejector.Subsequently,a one-dimensional model of ejector thermodynamics has been developed to design an ejector compatible for the WFI preparation system.Computational fluid dynamics(CFD)methods were utilized to analyze the effect of port superheat on the ejector.The results indicate that both primary and secondary superheat influence the entrainment ratio and nonequilibrium condensation intensity of the ejector,whereas the outlet superheat has a negligible impact on these parameters.This conclusion has guiding significance for the efficient operation of ejector.In light of the potential instability of power steam in the WFI preparation system,an optimization approach for the ejector has been proposed.The methodology aims to maximize the average entrainment ratio via the least squares fitting technique,which fits both the nozzle exit position(NXP)and the area ratio(AR)with entrainment ratio.The optimal structural parameters were determined to be 6.40 mm for NXP and 6.42 for AR.Following optimization of the ejector design,the average entrainment ratio of the ejector was improved by 3.62%compared to the reference ejector,thereby enhancing its robustness.Lastly,in order to assess the feasibility of the WFI preparation system,validate its model.as well as demonstrate the performance enhancement achieved by incorporating the ejector,a measurement and control platform was employed to assess the system.A subsequent analysis was executed to discern the influence of the ejector on the system’s comprehensive performance.This paper offers a reference for optimizing and enhancing the ejector used in WFI preparation systems.Through the analysis and optimization of the ejector,in comparison to traditional multi-effect distillation machines,the proposed system amplifies the gain output ratio by 60%,and the water production cost is reduced by approximately 38%.thereby showcasing its practical and economic significance. |
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