'Royal College of Obstetricians & Gynaecologists (RCOG)'
Abstract
BACKGROUND: In the recent development of regenerative medicine, the low yields of progenitor cells have limited the large-scale clinical applications. To overcome the limitation, a novel fluidized bed bioreactor has emerged. However, a detailed understanding of the fluid dynamics is still lacking. RESULTS: A three-dimensional modelling approach that couples computational fluid dynamics (CFD) and discrete element method (DEM) was used to simulate the liquid and solid flows in a bioreactor being designed for stem cells expansion. The model was validated by comparing the simulation results with literature experimental data (Chem. Eng. Sci. 60: 1889-1900 (2005)), which showed a good agreement. Using the validated model, the effects of the superficial liquid velocity, particle size and particle density on the solids volume fraction, shear stress on the particles and liquid-solid mass transfer coefficient of dissolved oxygen and glucose were analyzed. CONCLUSIONS: Simulation results show that particle size and density have an important impact on the shear stress distribution, and that the liquid velocity affects the shear stress distribution rather modestly when its value is beyond the minimum fluidization velocity. The liquid-particle mass transfer coefficient of dissolved oxygen and glucose can be improved by raising the liquid velocity, and the adoption of a high-density material allows the reactor to operate with higher liquid velocities before reaching shear stress heterogeneities. Furthermore, the two objectives, (i) maintaining lower and homogeneously distributed shear stress and (ii) improving mass transfer, pose conflicting requirements on certain design parameters which need to be carefully considered in the reactor design.</p
