Environmental Engineering Research Center (EERC), Faculty of Chemical Engineering, Sahand University of Technology, P.O. Box 513551996, Sahand New Town, Tabriz, Iran.
Department of Chemical and Petroleum Engineering, University of Tabriz, P.O. Box 5166616471, Tabriz, Iran.
Environ Sci Pollut Res Int. 2017 Oct;24(28):22427-22441. doi: 10.1007/s11356-017-9827-2. Epub 2017 Aug 12.
In this work, the experimental evidence is presented for two basic issues including oxygen mass transfer and shear analysis on the microorganism containing medium on the most prominent sections of the bioreactor. Computational fluid dynamics (CFD) methodology reproduces shear rate values for specific impeller designs using the commercial code (Fluent 6.2). CFD calculates volumetric mass transfer coefficient based on the Higbie's penetration theory. Four types of impeller are used. The spherical probe is used to measure flow hydrodynamic parameters to obtain shear rate by electro-diffusion (ED) method. The obtained results are validated experimentally and it is shown that a fully axial pattern impeller represents more enhanced results than partially axial and radial. In this regard, experimental results for volumetric oxygen mass transfer coefficient (k a) confirm CFD predictions by acceptable deviations of 2.65, 8.90, and 9.20 for 0.15, 0.2, and 0.3 VVM, respectively. These results collaboratively indicate that LIGHTNIN-C 200 type operates more efficiently by reflecting the flow to the bottom corner stagnation areas with the minimum tolerable shear and the most velocity distribution uniformity. Furthermore, the values of k a improve by aeration rate. Conversely, increasing the rotational speed of impeller creates difficulties for cell growth due to the generated harsh shear condition. CFD provide a better understanding of how operational and geometrical variables may be manipulated to achieve a moderate shear rate and acceptable level of mass transfer.
在这项工作中，提出了两个基本问题的实验证据，包括微生物含介质在生物反应器最突出部分的传质和剪切分析。计算流体动力学（CFD）方法使用商业代码（Fluent 6.2）再现了特定叶轮设计的剪切率值。CFD 根据 Higbie 的渗透理论计算体积传质系数。使用了四种类型的叶轮。球形探头用于测量流体力参数，通过电扩散（ED）方法获得剪切率。获得的结果通过实验进行了验证，结果表明完全轴向叶轮比部分轴向和径向叶轮具有更显著的增强效果。在这方面，体积氧传质系数（k a）的实验结果通过可接受的偏差 2.65、8.90 和 9.20 分别为 0.15、0.2 和 0.3 VVM 证实了 CFD 预测。这些结果共同表明，LIGHTNIN-C 200 型通过将流反射到底部角落停滞区域，以最小的可容忍剪切和最均匀的速度分布来操作更有效。此外，k a 值随充气率的增加而提高。相反，叶轮转速的增加会由于产生的苛刻剪切条件而对细胞生长造成困难。CFD 提供了对操作和几何变量如何进行操纵以实现适度的剪切率和可接受的传质水平的更好理解。
