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Baojun Shen,Xiaobin Zhan,Yu He,Zhibin Sun,Jiecai Long,Yili Yang,Xiwen Li 한국화학공학회 2021 Korean Journal of Chemical Engineering Vol.38 No.7
Planetary centrifugal bioreactors are promising candidates for cell culture platforms since there is no pollution caused by stirring blades. In this work, the fluid structure in a planetary centrifugal bioreactor was investigated using the computational fluid dynamics (CFD) method. The effects of operating conditions on the oxygen transfer rate (OTR), mixing efficiency and shear environment of the bioreactor were studied with the revolution speed (N) ranging from 60 to 160 rpm and the rotation-to-revolution speed ratio (i) from 2 to 1. The results show that the volumetric mass transfer coefficient (kLa), turbulence intensity, volumetric power consumption, and shear stress increase along with the increase of the revolution and rotation speeds. Furthermore, the rotation in the opposite direction to the revolution is beneficial to the performance of the bioreactor. The planetary centrifugal bioreactor has a higher kLa of 50- 200/h and a lower average shear stress of 0.01-0.05 Pa in comparison with conventional stirred tank bioreactors, which makes it suitable for biological culture of oxygen-consuming cells and shear-sensitive cells.
Analysis of the extrusion pressure of a cylindrical extruder for extruding highly viscous fluids
Zhibin Sun,Baojun Shen,Yu He,Jiecai Long,Xiaobin Zhan,Yujin Li,Xiwen Li 한국화학공학회 2022 Korean Journal of Chemical Engineering Vol.39 No.10
Extrusion pressure is crucial for the security and performance of a cylindrical extruder during the extrusion process. In this study, a validated CFD model was adopted to evaluate the relationship between the extrusion velocity, fluid viscosity, and the extrusion pressure of a cylindrical extruder while extruding highly viscous fluids. The simulated and experimental results of the extrusion pressure and velocity profiles show good agreement. This study reveals that extrusion pressure evolution can be divided into two stages during the extrusion process. At stage I, the distance between the ram and the bottom of the vessel (liquid height) is greater than the critical height and the extrusion pressure remains almost constant. At stage II, the distance is less than the critical height and the extrusion pressure increases exponentially. The results indicate that an increase in extrusion velocity and fluid viscosity leads to a linear increase in the extrusion pressure at stage I. Furthermore, by introducing a pressure number, Np, and a pressurerelated Reynolds number, Rep, a novel correlation of the extrusion pressure with the extrusion velocity, viscosity of highly viscous fluids and liquid height has been developed.
Yu He,Xiwen Li,Jiecai Long,Baojun Shen,Zhibin Sun,Yili Yang,Xiaobin Zhan 한국화학공학회 2021 Korean Journal of Chemical Engineering Vol.38 No.3
The twin cam mixer (TCM), as a general-purpose mixer, shares many attributes in common with 3D industrial mixers, like the internal mixer. We investigated the mixing process in a 2D TCM with two identical isosceles triangular cams rotating at 0.5 rpm. A 2D numerical model coupled with the species transport model was employed to study the influence of cam height-base ratio and eccentricity qualitatively and quantitatively, and both were found to have a significant effect on the mixing behavior of the mixer. Furthermore, a dimensionless parameter, named the modified pressurization coefficient, is put forward to quantify the geometry of the mixer. The logarithmic relationship between the modified pressurization coefficient and the mixing quality was discovered and expected to provide new ideas for establishing the relationship between the geometric parameters of a mixer and its mixing performance.