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INTERNATIONAL JOURNAL OF CHEMICAL REACTOR ENGINEERING Volume 1 2003 Article A12 Performance Enhancement of Photocatalytic Reactor Utilizing Flow Instability Kanheya Mehrotra∗ Ajay Kumar Ray† ∗National University of Singapore, arun3112@rediffmail.com †National University of Singapore, aray@eng.uwo.ca ISSN 1542-6580 Copyright c©2003 by the authors. All rights reserved. Performance Enhancement of Photocatalytic Reactor Utilizing Flow Instability Kanheya Mehrotra and Ajay Kumar Ray Abstract A detailed analysis has been performed for a heterogeneous photocatalytic

Flow of Polyethylene. 2. Molecular Weight Dependence and Low-Temperature Anomaly, Macromolecules 29 (1996) 4115-4119. [19] Wang SQ, Drda PA, Inn YW: Exploring Molecular Origins of Sharkskin, Partial Slip, and Slope Change in Flow Curves of Linear Low Density Polyethylene, J. Rheol. 40 (1996) 875-898. [20] Pérez-Gonzáles J, de Vargas L, Pavlínek V, Hausnerová B, Sáha P: Temperature Dependent Instabilities in the Capillary Flow of a Metallocene Linear Low Density Polyethylene Melt, J. Rheol. 44 (2000) 441-451. [21] Han CD, Lamonte RR: A Study of Polymer Melt Flow

analysis based on a fast Fourier transformation (FFT) were used as numeric tools applied to register and control the extru- sion process. The flow of molten polymer was studied under various processing conditions, giving an oppor- tunity to split high frequency pressure fluctuations by means of the autocorrelation function and fast Fourier transform, and to create, in the future, a catalogue of data which can be used to define particular distortions in tech- nological investigations. Keywords: autocorrelation; flow instabilities; frequency analysis; LLDPE

Laser Doppler Velocimetry. In addition to the experimental ap- proach, we used Computational Fluid Dynamics analysis to complete the flow study. Numerical and experimental investigations reveal a class of instabilities of the Taylor-Dean flow not previously observed in the Taylor-Couette flow due to the cylinder rotation neither in the Dean flow due to the external pumping fluid. KEYWORDS: flow, instabilities, shear wall, Taylor-Couette-Dean fluency INTRODUCTION Taylor-Couette flow refers to the viscous flow in the fully filled annulus of concentric rotating

REFERENCES [1] Molenaar J, Koopmans RJ: Modeling polymer melt-flow instabilities. J. Rheology 38 (1994) 99-109. [2] Georgiou GC, Crochet MJ: Time-dependent compressible extrudate-swell problem with slip at the wall. J. Rheology 38 (1994) 1745-1755. [3] Venet C, Vergnes B: Experimental Characterization of Sharkskin in Polyethylenes, J. Rheology 41 (1997) 873-892. [4] Graham MD: The sharkskin instability of polymer melt flows. Chaos 9 (1999) 154-163. [5] Denn MM: Extrusion instabilities and wall slip. Annu. Rev. Fluid Mech. 33 (2001) 265-297. [6] Barone JR

frequency, and the porosity of the porous medium on the growth rate of the unstable mode is examined analitically. Routh's test of stability is applied to confirm the above results. PACS: 47.20.-k; 47.55.Mh; 47.65.+a; 52.30.-q; 52.35.-g. Key words: Hydrodynamic Stability; Flows through Porous Media; Magnetohydrodynamics; Plasma flow; Instabilities in Plasma. 1. Introduction The instability of a plane interface separating two uniform superposed streaming fluids under varying assumptions of hydrodynamics and hydromagnetics, has been discussed by Chandrasekhar [1

Fluctuations of the non-Newtonian fluid flow in a Kenics static mixer: An experimental study

The measurements for a Kenics static mixer were carried out using Laser Doppler Anemometer (LDA). The test fluid was non-Newtonian solution of CMC, Blanose type 9H4. The velocity data inside the 5th Kenics insert were collected for the axial components at five levels of Reynolds number, Re = 20 ÷ 120. Velocity fluctuations were also analyzed in the frequency domain, after processing them with the help of the Fast Fourier Transform (FFT) procedure. The spectra of fluctuations provided information about level of the fluctuations in the observed range of Reynolds number. The obtained data were then also used to plot the velocity profiles for the fifth insert of the Kenics mixer. It was concluded that in the investigated range of Reynolds numbers (Re = 20 ÷ 120) a strong dependence of the velocity profiles and the flow fluctuations on Reynolds number was observed.

Abstract

In this paper the application of model predictive control (MPC) to a two-mode model of the dynamics of the combustion process is considered. It is shown that the MPC by itself does not stabilize the combustor and the control gains obtained by applying the MPC algorithms need to be optimized further to ensure that the phase difference between the two modes is also stable. The results of applying the algorithm are compared with the open loop model amplitude responses and to the closed loop responses obtained by the application of a direct adaptive control algorithm. It is shown that the MPC coupled with the cost parameter optimisation proposed in the paper, always guarantees the closed loop stability, a feature that may not always be possible with an adaptive implementations.

Alaa-Eldin M. Adris Abstract A novel fluidized bed membrane reactor with internal catalyst circulation is being developed for the production of high-purity H2 from an autothermal re- former. In order to provide guidance to pilot reactor testing, a cold model was built to study the influence of reactor configuration on hydrodynamics and cata- lyst circulation. It was found that catalyst circulation was reproducible, but that parallel non-communicating flow channels could lead to flow instability. Solids circulation was found to be adequate for design of the

, thereafter velocity decreases. Another important observation is that for large n , flow instability is marked which has been discussed above analyzing the limiting cases of the governing equation. Further, another contribution is well marked due to the presence of porous medium ( Fig. 3 ). Contribution of porous medium has two parts: Figure 2 (a) Horizontal velocity profiles (b) Horizontal velocity profiles Figure 3 Horizontal velocity profiles (i) k p , linear Darcy model (ii) F , nonlinear Forchheimer’s contribution. This shows that k p clearly reduces velocity for