Computational Fluid Dynamics (CFD)
S. Akbarnejad; M. Ziabasharhagh
Abstract
This paper presents a novel 1D modeling approach to optimize steam ejector entrainment ratios, introducing new definitions of ejector efficiency and enhancement methods. Using the proposed model, an ejector is tailored for specific boundary conditions with available computational fluid mechanic ...
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This paper presents a novel 1D modeling approach to optimize steam ejector entrainment ratios, introducing new definitions of ejector efficiency and enhancement methods. Using the proposed model, an ejector is tailored for specific boundary conditions with available computational fluid mechanic results for validation. Dimensional and geometrical parameters are computed from the theoretical 1D model, and various geometries are explored using computational fluid mechanic to determine entrainment ratios. Innovative definitions of ejector efficiency are introduced. The first definition compares the entrainment ratio of the ejector to a system comprising a steam compressor, turbine, and mixer, yielding an efficiency of 13.5% under specified conditions. The second, more practical definition calculates the maximum achievable entrainment ratio, disregarding frictional losses, resulting in an efficiency of 70%. An algorithm is proposed to optimize ejector dimensions to approach this maximum. Using this algorithm, the optimum throat diameter was determined through computational fluid mechanic analysis, demonstrating an increase in the entrainment ratio from 0.7 to 1.25. The theoretical maximum value calculated by the 1D model is 1.282, indicating that 97.7% of the theoretical maximum was achieved in computational fluid mechanic simulations. This highlights the significant improvement in the entrainment ratio using the 1D model and delineates its limit under given conditions. The third definition establishes the theoretical maximum entrainment ratio given specific boundary conditions and dimensions, assuming no losses in the nozzle, mixing process, or diffuser; yielding an efficiency of 81% for the same ejector studied.
