Numerical investigation of circulating fluidized bed riser hydrodynamics for concentrating solar thermal receiver applications

Bilyaz, Serhat
Various heat transfer fluids and thermal storage materials are considered for concentrating solar power systems to improve the storage capability of the system which compensates the fluctuating behavior of the solar resources. Solid particles can be a good alternative since they have high sensible heat capacity. In addition, they are cheap, environmentally benign and chemically and mechanically stable at high temperatures. In this thesis, hydrodynamics of circulating fluidized bed solar receiver was numerically investigated. 2D axisymmetric Eulerian-Eulerian (Two-Fluid Method) Computational Fluid Dynamics (CFD) model was constructed in open source software MFIX. Sand particles having diameter of 550μm was used in receiver. Model options and parameters were examined by modeling an experimental bubbling fluidized bed study. Grid independence, various drag models, effect of frictional and collisional behavior between wall and particles and effect of turbulence were examined in that model. Afterwards, experimental validation of final model was performed by modeling an experimental circulating fluidized bed riser study. Wall boundary condition parameters, which are specularity coefficient and particle-wall restitution coefficient were adjusted to fit the mass flux results with experimental data and final validated model was applied to final riser receiver design. Hydrodynamic parameters like solid mass flux distributions, void fractions, solid and gas velocities and pressure drop along riser were presented and discussed. Results were similar to the results in experimental validation study and reasonable in the light of information available in the literature.


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Citation Formats
S. Bilyaz, “Numerical investigation of circulating fluidized bed riser hydrodynamics for concentrating solar thermal receiver applications,” M.S. - Master of Science, Middle East Technical University, 2015.