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Jet loop reactors are used as apparatus to facilitate chemical or biological reactions. This type of apparatus is characterized by an internal circulation flow, essentially driven by the injection of liquid. The nozzle can also be used to inject and disperse gas. The internal fluid dynamics and thus the reactor behavior is significantly determined by the introduced momentum and by the internal gas distribution. To describe the mutual influence of a gas-consuming reaction and the internal fluid dynamics, a simplified model based on a momentum balance and a material balance was used. From the exemplary calculations, a critical range for non-selective reactions and for fluid dynamic stability is given. 相似文献
144.
Alvin W. Nienow 《化学,工程师,技术》2021,93(1-2):17-30
From the start of industrial biotechnology, there has been a perception that biological entities are damaged by stirring, so-called ‘shear damage'. Often, it was the soft option to explain a loss of performance when it was due to other factors, such as bubble ingestion with proteins or on scale-up, where tip speed increased when it was due to decreased homogeneity, especially in pH. For many years, poor control and the range of analytical tools available made a more in-depth explanation difficult; and the concepts of ‘high' and ‘low shear' impellers, now largely disproven, increased it. Here, the size of the biological entity is compared to the Kolmogorov microscale of turbulence leading to a reasonably clear picture emerging. The article starts with the author's introduction to the issue approximately 42 year ago with enzymes, conveniently also the smallest entity; and finishes with the largest, filamentous fungi. 相似文献
145.
The design of a liquid/liquid contact apparatus necessitates the knowledge of fluid dynamics and mass transfer in the dispersion. Prediction of process parameters is challenging due to swarm and interfacial effects. Single drop investigations are suitable to enable a sophisticated dimensioning based on few simple experiments combined with published theories and correlations. In the first part of this article, the fundamentals of fluid dynamics and mass transfer in absence of interfacial effects were explained. Here, an overview of relevant interfacial phenomena and the influence of different substances typically occurring in technical applications as impurities or accompanying components is given. 相似文献
146.
Hyeon-Seok Seo Jin-Beak Kim Youn-Jea Kim 《Journal of Mechanical Science and Technology》2009,23(7):1840-1845
Many studies on air-conditioning systems are more focused on the individual thermal comfort rather than the thermal efficiency,
due to an increase in health concerns. There are several factors influencing the thermal comfort, such as temperature, humidity,
convection and air movement, etc. Numerical analyses were performed to investigate the effect of blade angle on the flow characteristics
in the vicinity of diffuser blades of a room air conditioner (RAC), with three different blade discharge angles of 45.1°,
58.6° and 116°. We used the commercial code FLUENT to calculate the two-dimensional steady thermal flow fields with different
impeller rotational velocities. The angular velocities were located within the range from 900 rpm to 1200 rpm. Turbulence
closure was achieved using a standard k-ɛ model. A moving reference frame (MRF) approach was adopted to simulate the flow
field generated by the impeller in an RAC. The results were graphically depicted with various geometrical configurations and
operating conditions.
This paper was presented at the 7th JSME-KSME Thermal and Fluids Engineering Conference, Sapporo, Japan, October 2008.
Youn-Jea Kim received his B.S. degree in Mechanical Engineering from Sungkyunkwan University, Korea, in 1982. He then received his M.S.
and Ph.D. degrees from the State University of New York at Buffalo in 1987 and 1990, respectively. Dr. Kim is currently a
Professor at the School of Mechanical Engineering at Sungkyunkwan University in Korea. Dr. Kim’s research interests include
gas dynamics, MEMS, and fluid-machineries, etc. 相似文献
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Rogério Fernandes Brito Solidônio Rodrigues de Carvalho Sandro Metrevelle Marcondes de Lima e Silva João Roberto Ferreira 《International Communications in Heat and Mass Transfer》2009
This work studies the heat influence in cutting tools considering the variation of the coating thickness and the heat flux. K10 and diamond tools substrate with TiN and Al2O3 coatings were used. The numerical methodology utilizes the ANSYS® CFX software. Boundary conditions and constant thermo physical properties of the solids involved in the numerical analysis are known. To validate the proposed methodology an experiment is used. The TiN and Al2O3 coatings did not show satisfying results during a continuous cutting process. It showed a slight reduction in the heat flux for the 10 (µm) TiN and Al2O3 coatings. 相似文献
150.
欧阳征标 《深圳大学学报(理工版)》1990,(Z1)
本文给出了用正交场作为自由电子激光器摆动场的设想,并用流体动力学理论研究了使用正交场摆动器的自由电子激光器.文中通过理论分析论证了在所研究的系统中存在自由电子激光不稳定性,从而肯定了正交场可以用作摆动场的设想. 相似文献