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Home>Products>Journal and Reviews>I.RE.Ch.E.>Latest issue
International Review of Chemical Engineering (Rapid Communications) - May 2009 - Papers
International Review of Chemical Engineering (Rapid Communications) - Papers
by Pouya Hajiani, Faďçal Larachi Vol. 1. n. 3, pp. 221-237
Abstract - Ferrofluids have been vastly wooed in diverse areas of engineering and research. This contribution briefly exposes some concepts specific to ferrofluids and how they relate to recent applications emerging in chemical engineering, including mass transfer enhancement, momentum transfer in laminar and turbulent pipe flows and in porous media flows, and the motion of magnetic nanoparticles in gas-liquid mass transfer mechanisms with/without external magnetic fields. The noticeable effects of magnetic fields on ferrofluid flow behavior will be surveyed as well as a discussion about common assumptions to simplify and solve some ferrohydrodynamic models. With respect to the intriguing features caused by dispersed magnetic nanoparticles on ferrofluid behavior, considerable theoretical and experimental work is left for mining new opportunities in chemical engineering on the subject of ferrofluid interactions between magnetic fields, mass, heat, and momentum transfer phenomena. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Ferrofluid, Laminar and turbulent flow, Porous media, Mass transfer enhancement.
Vol. 1. n. 3, pp. 238-242
Abstract - A new
process for the synthesis of nano composites of Mg, Li, Ni and Mg, Be,
Ni and Be has been developed using Parr Reactor System. The process
comprises preparing of Mg, Li, Be and Mg, Be, Ni salts solution and
mixing with 33% ammonium hydroxide as reducing agent The reactor is
heated up to 110 0C in a closed reactor system at atmospheric pressure
for 0.5 hours. Then hydrogen is introduced in the system at 500 Psig for
one minute. The hydrogen not only reduces the oxides of metals but also
generates pure nano alloy particles consisting of Mg, Ni, Li and Mg, Ni,
Be Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Trimetallic inorganic alloy materials, Auto clave chemical synthesis, SEM, TPD, XRD, hydrogen storage materials.
Vol. 1. n. 3, pp. 243-249
Abstract - Three different designs for adsorption calorimeters are presented, which use sensors based on the Seebeck effect. The noises of signals with respect to the baseline are evaluated on each one of the builded equipment and the detection limit of the thermal effects is expressed in µWatt. It was determined that the different designs and working conditions affect the baseline noise and the detection limit. Values of the noise in the baseline are between ± 100 µV and ± 0,5 µV and between 887,2 and 24 µWatt. These values allow making measures in the solid-gas interphase with very good precision. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Adsorption calorimeter, Noise baseline, Heat flow, Seebeck effect.
Vol. 1. n. 3, pp. 250-262
Abstract - The objective of the present work is to study how the combustion of crude oil layers floating on water is influenced by the aging of oil (degree of oil evaporation) and the formation of emulsions. The experiments are dealing with burning rate, time to the start of boilover, burned mass ratio. The results are discussed in relation to the main factors influencing the phenomenon : initial oil-layer thickness and pool diameter. The behavior of weathered crude oil agrees closely with the general behavior of single oils with increasing boiling point (the surface temperature will increase with weathering as the residual crude oil becomes less volatile). In contrast, the case of emulsions is more complex and somewhat difficult to model (thermal breakage of emulsified layers, boilover difficult to discern). Finally, the work is complemented by a study of smoke production. The procedure permits measurements of exhaust gas composition by means of a flow through system. Results show that weathering increases both yield of soot and CO but that emulsification decreases these yields. The former effect is due to a residual liquid progressively less volatil, the later to vaporised water interacting chemically in the flame. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Pool fire, Crude oil, Weathering, Emulsification, Smoke.
Vol. 1. n. 3, pp. 263-271
Abstract - The present study performs an analytical calculation on the problem of film condensation on a flat plate by taking into account the shear forces at the liquid-vapor interface. Based on the gravitational and interfacial shear forces applied to the liquid film, two limiting cases are investigated in calculating the liquid film thickness and the Nusselt number. The first case represents film condensation with high gravitational forces compared to interfacial shear ones while the second case considers high interfacial shear forces compared to gravitational ones. With the aid of these two limiting cases, an expression can be derived as a function of two dimensionless groups for the case of the two forces having comparable values to each other. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Film condensation, Assisted interfacial shear stress, Flat plate.
Vol. 1. n. 3, pp. 272-276
Abstract - A heat transfer problem of for micropolar fluids with magnetic effect past through a stretching sheet has been studied. Governing equations for heat convection equation of a stretching sheet, and continuity equation, momentum equation and energy equation of a micropolar fluid have been analyzed by a combination of the similarity transformation and a finite-difference method.. The paper studies of these dimensionless parameters, the Prandtl number Pr, the magnetic parameter M, the material parameter K and the Eckert number Ec, respectively. The numerical results indicate that, an increase in the magnetic parameter gives a decrease in the values of the velocities and Nusselt number, or an increase in the values of the shear stress, couple stress at the surface and temperature. The material parameter has the opposite effect of magnetic field parameter on the values of the velocities, temperature, and shear stress and Nusselt number. The temperature decreases as the Prandtl number increases or increases as the Eckert number increases. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Heat transfer, Magnetic field, Micropolar fluid, Stretching sheet, Finite difference method.
Vol. 1. n. 3, pp. 277-286
Abstract - In
the designing and improving of manufacturing processes, engineers are
dealing with complex systems and they are, more or less, using
systematic approaches. The sustainability process design searches for
the optimal process design, improved in economic, environmental and
social terms. Decisions over process selection, design and operation
necessarily involve trade-offs between cost, economic potential,
operability, safety, environmental impacts etc. Professional engineers
are involved in making different kinds of decisions, depending on the
criteria used. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Chemical process synthesis, Decision making, Sustainability criteria.
Vol. 1. n. 3, pp. 287-294
Abstract - The homogeneous combustion of coal has been theoretically and experimentally studied under various fluidizing and operating conditions in a fluidized bed combustor (FBC). The theoretical model was based on a kinetic approach coupled with the bed hydrodynamics and a volatiles evolution region within the bed, while the experiments were carried out in a calorimetric FBC. The modelling revealed that, for high-volatile coals with a particle diameter of 1 mm, the combustion of the original volatiles in the bed region may be as high as 61-79, 70-90 and 76-98 % for excess air levels ranging from 10 to 40 % and bed temperatures of 800, 850 and 900C respectively. For 3 mm coal diameters, the computed values of volatiles combustion in the bed were found to be in the ranges of 63-81, 71-92 and 77-99 % at similar operating conditions as mentioned above. From these model results, it is suggested that both diffusion and chemical kinetics control the evolution of volatiles for coal particle sizes smaller than 5 mm, while the mixing of volatiles and oxygen in the bed region dominates the combustion process. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
Keywords: Fluidized Bed Combustion, Volatiles Combustion, Devolatilization Kinetics.
Vol. 1. n. 3, pp. 295-296
Back in the eighties, instructors of chemical reaction engineering (CRE) courses had rather limited choices as far as undergraduate textbooks were concerned. Among the limited options were the two classics by O. Levenspiel and J.M. Smith, in addition to the book by C.G. Hill; however, all of these three textbooks were increasingly becoming out-of-date at the dawn of the internet age in the nineties. The textbook by H.S. Fogler, first published in 1987, has replaced Levenspiel worldwide as the leading textbook for the CRE course, according to a 1996 study published in Chemical Engineering Education. I believe this is still the case, as its fourth edition was published in 2006. In recent years, a growing number of texts on CRE have appeared. The book by G.W. Roberts (published earlier this year by Wiley) is the latest addition. This book covers the fundamental aspects of CRE and few of the more “advanced” topics. The fundamentals are covered in eight chapters and the advanced topics are covered in the last two chapters. Each chapter begins with a concise list of learning objectives, and ends with a summary of important concepts. The total number of pages is 439. The first chapter lays down the scope of applications of chemical reactions in modern-day technology, and the importance of chemical kinetics in the analysis and design of reactors. The proper “definition” of the reaction rate in single- and multi-phase systems is also introduced here. In the second chapter, the author presents what he calls “generalizations” concerning the reaction rate. These mainly revolve around the form of the rate expression. The next two chapters deal, for the most part, with the three ideal reactors: BR, CSTR, and PFR. The discussion is restricted to the sizing of isothermal systems; the systems embrace single as well as series and parallel reactors. The fourth chapter includes a brief qualitative discussion of transport effects in solid-catalyzed reactions; which might seem out-of-place to some readers.In the fifth chapter, a more fundamental look is taken at chemical kinetics, where elementary reaction mechanisms are presented, as opposed to the empirical generalizations given earlier. The author argues that this is necessary in order to broaden the training of “modern” chemical engineers. This idea however may not be shared by some CRE instructors, since the fundamentals of kinetics are typically covered in physical chemistry courses.Correlation of kinetic data is analyzed in detail in the sixth chapter. Both the differential and integral methods of data analysis are presented. This chapter ends with a brief discussion and an illustration of statistical methods in the analysis of reaction rates. Chapter seven includes the important topic of yield and selectivity in complex reactions. Design options are given for series, parallel, and series-parallel reactions. As the performance equations of BRs and PFRs, hosting multiple reactions, become nonlinear, the author includes an appendix explaining the details of how ODEs can be handled numerically. More specifically, details of the fourth-order Runge-Kutta method are presented and illustrated via a spreadsheet solution. Chapter eight is where the plot thickens in the typical CRE course, as the more realistic non-isothermal operation of reactors is analyzed. Energy balances are derived for the three ideal reactors. The issue of steady-state multiplicity in CSTRs and in PFRs with a feed/product heat exchanger configuration is discussed also in this chapter.The following two chapters cover advanced topics, namely, heterogeneous catalysis, and non-ideal flow in chemical reactors. In chapter nine, the emphasis is decidedly on internal and external diffusion-reaction interactions in porous catalysts, as well as on internal and external thermal gradients. The final chapter is devoted to analysis of non-ideal flow in tank and tubular reactors. This is a long chapter (can it be otherwise, I wonder) covering tracer-response techniques, RTD, the axial-dispersion model, among other topics. In any textbook, there must be compromises, and Roberts’s text is no exception. I choose to mention only three. It would have been prudent to include a more rigorous development of the stoichiometric relationships in the earlier chapters, especially regarding multiple reactions. Moreover, it would have provided added value to incorporate a discussion of whether steady-state multiplicity is possible in non-isothermal PFRs. Likewise, it would also have been preferable to demonstrate, in chapter nine, how transport effects reflect on industrial catalytic reactor performance. One of the strong points of the book is the inclusion of real reactions in the examples and in the problems at the end of most of the chapters. Another significant advantage is the style of writing, which lends itself to comfortable reading, especially for non-native English speakers. Overall, Roberts’s text is a welcome addition to the education literature. It is a highly readable undergraduate textbook for reactor analysis and design. Copyright © 2009 Praise Worthy Prize S.r.l. - All rights reserved
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