Chemical-looping combustion (CLC) is a next-generation combustion technology that shows great promise in addressing the need for high-efficiency low-cost carbon capture from fossil fueled power plants. Although there have been a number of experimental studies on CLC in recent years, computational fluid dynamics (CFD) simulations have been limited in the literature. In this paper, simulation of a CLC reactor is conducted using the Eulerian approach in the commercial CFD solver ansys fluent based on a laboratory-scale experiment with a dual fluidized bed CLC reactor. The solid phase consists of a Fe-based oxygen carrier while the gaseous fuel used is syngas. The salient features of the fluidization behavior in the air reactor and fuel reactor beds representing a riser and a bubbling bed, respectively, as well as the down-comer, are accurately captured in the simulation. This work is among the few CFD simulations of a complete circulating dual fluidized bed system for CLC in 3D in the literature. It highlights the importance of 3D simulation of CLC systems and the need for more accurate empirical reaction rate data for future CLC simulations.
Supersonic steam ejectors are widely used in many industrial applications, for example for refrigeration and desalination. The experimental evaluation of the flow field inside the ejector is relatively difficult and costly due to the occurrence of shock after the velocity of the steam reaches over the sonic level in the ejector. In this paper, numerical simulations are conducted to investigate the detailed flow field inside a supersonic steam (water vapor being the working fluid) ejector. The commercial computational fluid dynamics (CFD) flow solver ANSYS-Fluent and the mesh generation software ANSYS-ICEM are used to predict the steam performance during the mixing inside the ejector by employing two turbulence models, the k-ω SST and the k-ε realizable models. The computed results are validated against the experimental data. The effects of operating conditions on the efficiency of the ejector such as the primary fluid pressure and condenser pressure are studied to obtain a better understanding of the mixing process and entrainment. Velocity contours, pressure plots and shock region analyses provide a good understanding for optimization of the ejector performance, in particular how to increase the entrainment ratio.
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