Mass transfer from ensembles of fluid spheres to a power-law liquid at moderate Reynolds and Peclet numbers

The steady convective mass transfer from ensembles of mono-size Newtonian fluid spheres to power-law liquids has been studied at moderate Reynolds and Peclet numbers. The species continuity equation segregated from momentum equations has been solved numerically using a finite difference method. A simple cell model has been used to account for the modification of the flow field due to the neighbouring droplets. Extensive numerical results have been obtained which elucidate effects of the Reynolds number (Re_o), Schmidt number (Sc), power-law index (n_o), internal to external fluid characteristic viscosity ratio (k) and the volume fraction of the dispersed phase (Φ) on the rate of mass transfer. The ranges of parameters considered herein are: 1?Re_o?200, 1?Sc?10000, 0.6?n_o?1.6, 0.1?k?50 and 0.2?Φ?0.6. For shear-thinning fluids (n_o<1), the rate of mass transfer is somewhat enhanced whereas for shear-thickening fluids (n_o>1), it decreased as compared to that in Newtonian fluids (n_o=1). A simple predictive correlation has been proposed which can be used to estimate the rate of mass transfer in liquid-liquid systems in a new application involving power-law continuous phase.     

Building Agility for Developing Agile Design Information Systems

Agile manufacturing relies heavily on the quality of information that organizations have and on their ability to organize and reuse it. Constant inflow of information and knowledge is the fuel of agile manufacturing. In the process of forming virtual enterprises, these new organizations have to be equipped with information systems that integrate their present legacy technology and improve upon it. To support the quick formation of virtual organizations, one must have the ability to develop such systems quickly. Over the past few years we have evolved, through collaborative projects with industry, an approach composed of methods and an information infrastructure called n-dim that improves the ability of becoming agile manufacturers of information systems, by responding quickly to information needs of new and evolving organizations. Following an analysis of the requirements of information systems for agile design, we discuss this approach; describe some of the infrastructure features; and present several examples of simple applications that illustrate them. We summarize by discussing the advantages and limitations of our approach.     

Effect of halogens on mercury conversion in SCR catalysts

The effect of halogen acids HCl, HBr and HI on mercury conversion was studied in a laboratory-scale SCR reactor using simulated flue gases, and is presented here. Two types of commercially available SCR catalysts, Honeycomb and Plate type catalysts, were used in these studies. HBr and HI both had shown much stronger effects on mercury conversion than HCl. Both HBr and HI oxidized more than 85% of the gas phase mercury at a low concentration of 2 ppm. The age of the catalyst and the type of catalyst also have an effect on mercury conversion. A larger extent of mercury oxidation was observed in the presence of a Honeycomb catalyst than with the Plate catalyst.     

Effect of power-law fluid behavior on momentum and heat transfer characteristics of an inclined square cylinder in steady flow regime

The governing equations describing the momentum and heat transfer phenomena of power-law non-Newtonian fluids over a heated square cylinder at 45° of incidence in the two-dimensional (2-D) steady flow regime are solved numerically. Extensive results on the detailed structure of the flow and temperature fields as well as on the gross engineering parameters are presented over the following ranges of conditions: 0.2 ? n ? 1; 0.1 ? Re ? 40 and 0.7 ? Pr ? 100. At low Reynolds numbers, the flow remains attached to the surface of the cylinder. This seems to occur for all values of power-law index, at least up to about Re = 1. On the other hand, twin standing vortices were seen to form at Re = 10 for all values of power-law index considered herein. The influence of the Reynolds number and power-law index is delineated on the detailed structure of the flow field (streamlines), wake characteristics and surface pressure distribution as well as on the value of drag coefficients. Similarly, the effect of Prandtl number is studied on forced convective heat transfer for the two commonly encountered boundary conditions, namely, constant temperature or constant heat flux prescribed on the surface of the cylinder. Using the computed numerical results, simple heat transfer correlations are obtained in terms of the Nusselt number as a function of the pertinent governing parameters thereby enabling the prediction of the rate of heat transfer between the fluid and the immersed cylinder. In addition, variation of the local Nusselt number on the surface of the inclined of square cylinder and representative isotherm plots are also presented to elucidate the effect of Reynolds number, Prandtl number and power-law index on the heat transfer phenomenon.     

Improved Spectrum Sensing Schemes Using Prewhitening and Weights Under Spatially Correlated Noise

Wireless Personal Communications - Nowadays, wireless sensor network (WSN) has emerged as the most developed research area. Different research have been demonstrated for reducing the sensor...     

静态条件下碳酸盐岩三维孔隙网络的溶蚀改造及其对孔隙结构的影响

为了确定溶蚀对碳酸盐岩孔隙结构的影响,保持pH值和HCl溶液浓度等参数不变,使用泥质灰岩和颗粒灰岩作为研究样品在不同温度下进行了溶蚀实验、X射线微型CT成像、岩石薄片分析实验。研究确定了碳酸盐岩溶蚀释放的Ca~(2+)浓度与时间的关系;溶蚀前后的孔径分布表明温度和孔径变化之间没有相关性,颗粒灰岩中的孔径变化更显著,说明孔径变化主要受岩石本身的物性(初始孔隙度和渗透率)和不稳定矿物的丰度(与晶体形状、大小和矿物类型有关)控制。2种碳酸盐岩在不同温度下的孔喉半径变化量非常小,为0.003～0.040 mm,增加倍数为1.3～3.5,平均为1.7;孔喉长度变化量为0.05～0.35 mm。孔喉半径、长度和连通性的微小变化对渗透率也有很大影响,渗透率变化量高达1 000×10~(-3)μm~2。     

Steady Flow of Power Law Fluids across a Circular Cylinder

The momentum equations describing the steady cross‐flow of power law fluids past an unconfined circular cylinder have been solved numerically using a semi‐implicit finite volume method. The numerical results highlighting the roles of Reynolds number and power law index on the global and detailed flow characteristics have been presented over wide ranges of conditions as 5 ≤ Re ≤ 40 and 0.6 ≤ n ≤ 2. The shear‐thinning behaviour (n < 1) of the fluid decreases the size of recirculation zone and also delays the separation; on the other hand, the shear‐thickening fluids (n > 1) show the opposite behaviour. Furthermore, while the wake size shows non‐monotonous variation with the power law index, but it does not seem to influence the values of drag coefficient. The stagnation pressure coefficient and drag coefficient also show a complex dependence on the power law index and Reynolds number. In addition, the pressure coefficient, vorticity and viscosity distributions on the surface of the cylinder have also been presented to gain further physical insights into the detailed flow kinematics.     

WINGLET-TYPE VORTEX GENERATORS FOR PLATE-FIN HEAT EXCHANGERS USING TRIANGULAR FINS

Vortex generators in the form of delta winglet pairs have already been proposed by many researchers for enhancement of the heat transfer rate in plate-fin heat exchangers. In this work, the enhancement potential of triangular fins (which are widely used inserts between the plates of the plate-fin heat exchanger) having delta winglets mounted on their slant surfaces has been computed. The performance of this combination is evaluated for varying angles of attack of the winglet and different thermal boundary conditions. The performance of the combination of triangular fins and winglets with stamping on the slant surfaces also has been evaluated.     

Novolak resins: structure elucidation by multidimensional NMR techniques and correlation with lithographic performance

Photo‐active chemicals blended with novolak resins, solvents and certain other additives serve as photoresists and are the real workhorses of the burgeoning microlithography industry, which plays a key role in making electronic circuits for ICs and VLSIs at micron and sub‐micron levels. It has been realized over the years that the microstructure of these matrix polymers (novolak resins) is very crucial for better lithographic performance. Although various analytical techniques exist for characterizing novolak resins, precise and unambiguous structural details are obtained only through NMR experiments. In this paper, we review the applications of a range of NMR experimental techniques to the structure elucidation of novolak polymers and co‐polymers. Such information is seen to lead to the design of high‐performance photoresists. The optimum percentage of the different phenolic units in novolak resins, which is very crucial for lithographic performance, can also be determined using these spectroscopic techniques. Using DEPT and INEPT ¹³C NMR spectra of novolak resins, two formulae have been developed for quantitative estimation of the lithographic performance of photoresists. On the basis of a comparison of the NMR spectra of a photoresist before and after photolysis, the mechanism of action of a photoresist can be probed, and this should lead to a deeper insight into the design of high‐performing photoresists. Copyright © 2003 Society of Chemical Industry