Velocity Of Chemical Reaction Research Articles

New Similarity Solutions of Magnetohydrodynamic Flow Over Horizontal Plate by Lie Group with Nonlinear Hydrodynamic and Linear Thermal and Mass Slips

The viscous laminar magnetohydrodynamic convective boundary layer flow with the combined effects of chemical reaction and nonlinear velocity slip and linear thermal and concentration slips have been considered across a flat plate in motion. Using a non-dimensional transformation attained by the single parameter continuous group method, the governing equations are transformed into a system of nonlinear ordinary similarity equations, then, the solutions of the coupled system of equations are constructed for velocity, temperature, and concentration functions by using the numerical methods. Among the parameters that have been looked at are the buoyancy parameter N, the nonlinear slip parameter {mathrm{n}}_{1}, the order of chemical reaction n, the Prandtl number Pr, and the Schmidt number Sc. An investigation was made on the profiles with respect to mixed convection parameter uplambda , order of chemical reaction n, arbitrary index parameter {mathrm{n}}_{1}, velocity slip parameter a, thermal slip parameter b, mass slip parameter c, suction parameter fw, magnetic parameter M. Verification of the results were possible due to comparison of two numerical methods to obtain the solution to the differential equations. The present study indicates that, for a range of values of the magnetic parameter, the wall shear stress decreases with increasing mixed convection. Moreover, for a variety of mixed convection parameter instances, the wall heat transfer decreases with increasing perpendicular magnetic effect.

High-Temperature Surface Oxide Growth Kinetics of Al–Si–Zr Bulk Alloys and Ribbons

A typical modification technique of the functional properties of Al–Si based alloys is the addition of some third element in trace level. In the present work, ternary Al–Si–Zr bulk and ribbon alloys have been prepared. The kinetics of high-temperature surface oxidation has been studied by thermogravimetric method. It was found that at the start of the experiment the chemical reaction velocity is rate-controlling while for longer times the (oxygen) diffusion is the rate-controlling process. Activation energy of the two stages of oxidation has been obtained. Additional studies such as thermochemical analysis, optical and electron microscopy, and microhardness tests have been done.

Heat and mass transfer on MHD convective unsteady flow of a Jeffrey fluid past an inclined vertical porous plate with thermal diffusion Soret and Aligned magnetic field

This article has the objective of examining to perform unstable magnetohydrodynamic flow over an inclined plate enclosed in a penetrable mechanism with Soret-aligned magnetic field and chemical reaction. Once momentum and energy and mass are equal, they can be combined using the diffusion equation to yield the dimensionless momentum/energy/mass model. Aligned Magnetic field, Jeffrey Parameter, Inclined angle, and Chemical Reaction Model outlines are used to study the effect of numerous physical parameters on boundary layer properties, including Soret temperature, chemical reaction velocity, Temperature and concentration on the resulting heat accumulation profile, are tested using parametric models. The findings derived from skin friction, Nusselt number, and Sherwood numbers are included in the tables provided for several parameters. It is observed from the results that the velocity profile increases with increase Thermal and Mass Grashof Numbers, Jeffery Parameter and Porous media but the opposite trends are seen with increase in the magnetic field parameter, inclined parameter and Aligned magnetic field parameter. One of the important findings of this analysis includes that intensification in the Newtonian heating effect causes a gradual downfall in the rate of heat transfer at the plate and the concentration of the fluid decreases under the impact of chemical reaction. Their physic- Chemical features have been dealt with in detail. This fluid flow model has several industrial applications in the field of chemical, polymer, medical sciences, etc.

Soret and Dufour effects on MHD boundary layer flow of non-Newtonian Carreau fluid with mixed convective heat and mass transfer over a moving vertical plate

In this analysis, the mixed convection boundary layer MHD flow of non-Newtonian Carreau fluid subjected to Soret and Dufour effects over a moving vertical plate is studied. The governing flow equations are converted into a set of non-linear ordinary differential equations using suitable transformations. For numerical computations, bvp4c in MATLAB package is used to solve the resulting equations. Impacts of various involved parameters, such as Weissenberg number, power-law index, magnetic parameter, thermal buoyancy parameter, solutal buoyancy parameter, thermal radiation, Dufour number, Soret number and reaction rate parameter, on velocity, temperature and concentration are shown through figures. Also, the local skin-friction coefficient, local Nusselt number and local Sherwood number are calculated and shown graphically and in tabular form for different parameters. Some important facts are revealed during the investigation. The temperature and concentration show decreasing trends with increasing values of power-law index, whereas velocity shows reverse trend and these trends are more prominent for larger values of Weissenberg number. For stronger magnetic field, velocity decreases, while the temperature and concentration increase. It was also found that for shear thinning fluid the drag coefficient exhibits an increasing character when Weissenberg number increases, but for shear thickening fluid the drag coefficient shows the contrary nature. For small values of Dufour number, heat transfer rate enhances with increasing Soret number, but for higher values of Dufour number it slightly dies down with Soret number and the mass transfer rate reacts oppositely. In addition, due to increasing chemical reaction rate, the concentration and velocity decrease.

Experimental and numerical study on combustion characteristics of super lean H2–O2 premixed laminar flame in argon atmosphere

This paper presents an experimental and numerical research on super lean premixed H2–O2 flames under argon atmosphere in a combustion bomb with constant volume, and applied CHEMKIN to perform simulation for the flames. The high-speed schlieren photography is employed to record the development process of expanding spherical flame, and laminar burning velocities of super lean premixed H2–O2–Ar flames with different back pressures under argon atmosphere are calculated, and the influence of equivalence ratio and initial pressure on flame instability is analyzed, and the mass burning fluxes are calculated by simulation and flame structure and rate of elementary reactions is analyzed. The results show that, with equivalence ratio decrease, laminar flame velocity and mass burning flux will decline; with initial pressure increase, laminar flame speed will decline and mass burning flux will increase. For flame stability, when initial pressure rises, the hydrodynamic instability on hydrogen flame surface is enhanced, more easily resulting in cellular instability. As pressure rises, Lewis number and density ratio under each pressure will approximate to constant values, therefore, flame thickness is the main factor influencing flame instability when initial pressure rises. When equivalence ratio decreases, unequal diffusion instability often occurs easily under leaner conditions during flame development. According to simulation results, the laminar flame velocity is the result of interaction between the chain branching reaction and the chain termination reaction and the changes of equivalence ratio will affect above two reactions. For flame structure, the results show that when equivalence ratio is small, chemical reaction velocity of hydrogen gas burning will decline and reaction zone will enlarge, besides, H and OH concentration will also decline. As equivalence ratio decreases, the maximum H mole fraction constantly declines, which is consistent with the changing trend of laminar flame velocity with equivalence ratio.

RADIATION EFFECT ON MAGNETOHYDRODYNAMIC CARREAU NANOFLUID FLOW PAST NON-LINEAR PERMEABLE HEATED STRETCHING SHEET WITH PARTIAL SLIP

The motion of a Carreau nanofluid past an infinite vertical non-linear permeable stretching sheet embedded in a non-Darcy porous medium is investigated. It is stressed by a uniform external magnetic field. The thermal radiation and heat generation are taken in consideration as well as Brownian motion with thermophoresis, chemical reaction and partial slip velocity at the boundary layer. The nonlinear partial differential equations describing the motion with heat and mass transfer are transformed to non-linear ordinary differential equations and solved by using Runge-Kutta method with approbriate boundary conditions. The effects of the physical parameters of the problem on the obtained solutions are discussed numerically and graphically. Through the section of discussion the skin friction and the rate of heat and mass transfer are computed. It is found that these physical parameters play an important rules to control the obtained velocity, temperature and concentration of the fluid.

Study on Influencing Factos of Wet Oxidation Technology

For refractory organic wastewater treatment, this water treatment industry is difficult, wet oxidation technology can effectively play a role. The effect of chemical reaction is closely related to the process conditions of operation (that is the influencing factors). The influencing factors of wet oxidation technology include nine aspects: reaction temperature, reaction pressure, reaction time, stirring strength, influent pH value, influent concentration, salt effect of influent, nature of influent, reaction heat of wastewater and amount of air needed. Among these factors, the reaction temperature is an important influence factor, and the relationship between the chemical reaction velocity constant and temperature follows the arenius formula.

Heat transfer on the cross flow of micropolar fluids over a thin needle moving in a parallel stream influenced by binary chemical reaction and Arrhenius activation energy

Emerging engineering and industrial needs made the prime concern of this article to investigate the thermal management on the cross flow of micropolar fluids over a thin needle moving in a parallel stream. The flow is subject to binary chemical reaction and Arrhenius activation energy. The mathematical model of the considered physical problem consists of coupled nonlinear partial differential equations: conservation of mass, momentum, energy, and concentration equation. The dimensionless transformed governing equations subject to the given boundary conditions have been solved directly by the Runge-Kutta Fehlberg fourth- fifth-order method followed by the shooting technique. Graphical results relative to the interaction effects of dynamic thermo-physical dimensionless parameters such as Richardson parameter, Dufour number, Soret number, Prandtl number, temperature ratio parameter, nondimensional activation energy, chemical reaction parameter and velocity ratio parameter controlling the flow, heat and mass transfer features are presented and analyzed. It can be seen, from the study, that the skin friction due to angular velocity reduces with increase in size of the needle and it upsurges due to the increase in material parameter. The obtained numerical results revealed that the augmented Richardson parameter is in favor of a greater heat transfer enhancement. The obtained results show a better agreement of this model with the previously published results.

Experimental investigation of sewage sludge solid waste conversion to syngas using high temperature steam gasification

Sewage sludge from wastewater treatment facilities needs to be treated before it can be disposed of. While it is typically processed through an anaerobic digestion process, sludge can also be a good feedstock for alternative fuel production. High-temperature steam gasification is a process that decomposes organic materials into synthesis gas (syngas) with a high hydrogen concentration. In this study, a lab-scale steam gasification system which converts sewage sludge into valuable syngas was developed and experimentally evaluated. This study specifically focuses on investigating the chemical kinetics of syngas generation and feedstock decomposition in a batch process. The syngas generation rates and concentrations of syngas constituents were measured, and changes in carbon balance during gasification were tracked with respect to time, which shows how reaction rates vary over time. It was found that variations in steam flow rates modified the gasification reactions both thermodynamically and hydrodynamically. The gasification processes were fitted into logistics curves to understand the effects of different steam flow rates. The results indicate that the chemical reaction velocity can be controlled to achieve optimum operating conditions, which potentially can reduce both processing time and steam consumption while maximizing the syngas yield. This study would contribute more to the complete understanding of the sewage sludge gasification processes and the kinetics of the gasification chemical reactions.

Chemical reaction and thermal radiation effects on boundary layer flow of nanofluid over a wedge with viscous and Ohmic dissipation

In this article the influence of thermal radiation on magnetohydrodynamic (MHD) flow of Cu-water nanofluid past a wedge in the occurrence of viscous-Ohmic dissipation and chemical reaction has been analyzed. The non-linearity numerical approach called RKF of the 4–5th order have been used with a shooting technique to find the results of velocity, temperature and concentration field for several points of employing parameters. The skin friction coefficient, Nusselt number and Sherwood number are examined in detail and the results are illustrated by figures and tables. The outcomes declared that the concentration boundary layer width diminishes with an increase in the values of the chemical reaction parameter and velocity profiles increase with increase in the magnetic field parameter.

ИССЛЕДОВАНИЕ ВЗАИМОСВЯЗИ ТОКА ИОНИЗАЦИИ И МАКСИМАЛЬНОГО ИНДИКАТОРНОГО ДАВЛЕНИЯ ПРИ СГОРАНИИ БЕНЗОВОЗДУШНОЙ СМЕСИ, ОБОГАЩЕННОЙ ВОДОРОДОМ

Ion current occurring in the result of chemical reactions of hydrocarbon fuel combustion is called the chemi-ionization current. The analysis of the research works displayed that the chemi-ionization current value can characterize the intensity and velocity of chemical reactions of burning in the combustion chamber of a piston engine, and therefore, the efficiency of heat generation during the combustion in the internal combustion engine. The paper shows that the study of the interrelationship of ion current and indicated combustion pressure determining, to the greatest extent, the workflow efficiency is the critical task, especially for gasoline engines with hydrogen transfer. The goal of the paper is to analyze the dependence of indicated combustion pressure and ion current under various initial conditions of fuel-air mixture combustion. Based on the experimental studies carried out on the single-cylinder motor unit UIT-85, the authors obtained data on the ion current occurring on the ionization sensor electrode remote from the ignition spark plug in the result of the flame front passing through it. Using the Kistler’s piezoelectric pressure sensor combined with the ignition spark plug, the authors created the indicator diagrams. The paper presents the data on the processing of the ion current peaks and the indicated pressure and the diagrams of their dependence on the mixture composition under various initial conditions. As the result of the study, the authors presented the diagram of the interrelationship of maxima of indicated pressure and ion current when varying the mixture composition at various crankshaft speeds, mass fraction of hydrogen added to the fuel-air mixture, compression and two angles of ignition advance.

Изучение кинетики окисления сульфидного цинкового концентрата в печи кипящего слоя

In order to optimize the operation of the fluidized bed furnace for annealing sulphide zinc concentrates, in particular, to save oxygen for blowing, it is necessary to model thermal processes. For this purpose, the oxidation kinetics of the charge and its basic components – zinc and iron sulfides – was studied under laboratory conditions. The experiments were carried out with the simultaneous thermal analysis tool NETZSCH STA 449 F3; they showed that oxidation reactions of zinc and iron sulfides with oxygen proceed in the intrakinetic region. At the sample weight of 10 mg, the thickness of the reactant layer is less than the penetration depth of oxygen into the layer. Therefore, the expression for the change of a single particle mass can be used. It allowed one to obtain the empirical dependence for determining the reaction velocity constant during zinc concentrate annealing for further calculation of the gas generation in the fluidized bed. The authors also obtained the distribution of the oxygen concentration along the height of the charge layer and calculated the average value of the effective oxygen concentration as a function of the reactant layer thickness. The gas generation analysis in the fluidized bed during zinc concentrate annealing with the use of the obtained constants of chemical reaction velocities allowed one to obtain the formula to determine the specific consumption of the annealed zinc concentrate depending on the oxygen concentration in blowing.

Model of non-ideal detonation of condensed high explosives

The Zeldovich-Neumann-Doering theory of ideal detonation allows one to describe adequately the detonation of charges with near-critical diameter. For smaller diameters, detonation velocity can differ significantly from an ideal value expected based on equilibrium chemical thermodynamics. This difference is quite evident when using non-ideal explosives; in certain cases, this value can be up to one third of ideal detonation velocity. Numerical simulation of these systems is a very labor-consuming process because one needs to compute the states inside the chemical reaction zone, as well as to obtain data on the equation of state of high-explosive detonation products mixture and on the velocity of chemical reaction; however, these characteristics are poorly studied today. For practical purposes, one can use the detonation shock dynamics model based on interrelation between local velocity of the front and its local curvature. This interrelation depends on both the equation of state of explosion products, and the reaction velocity; but the explicit definition of these characteristics is not needed. In this paper, experimental results are analyzed. They demonstrate interrelation between the local curvature of detonation front and the detonation velocity. Equation of detonation front shape is found. This equation allows us to predict detonation velocity and shape of detonation wave front in arbitrary geometry by integrating ordinary differential equation for the front shape with a boundary condition at the charge edge. The results confirm that the model of detonation shock dynamics can be used to describe detonation processes in non-ideal explosives.

MATHEMATICAL MODELING OF LEACHING PROCESS OF RED MUD IN ORDER TO OBTAIN THE KINETICS PARAMETERS

The use of the waste of the Bayer process, red mud, is due to its chemical and mineralogical composition that shows a material rich in oxides of iron, titanium and aluminum. Some studies conducted show that this waste can be applied as a source of alternative raw material for concentration and subsequent recovery of titanium compounds from an iron leaching process, which is present in higher amounts, about 30% by weight. To obtain a greater understanding about the leaching kinetics, the information of the kinetic data of this process is very important. In this context, the main objective of this work is the development of a mathematical model that is able to fit the experimental data (conversion / extraction iron, titanium and aluminum) of the leaching process by which is possible to obtain the main kinetic parameters such as the activation energy and the velocity of chemical reactions as well as the controlling step of the process. The development of the mathematical model was based on the model of core decreasing. The obtained model system of ordinary differential equations was able to fit the experimental data obtained from the leaching process, enabling the determination of the controlling step, the rate constants and the activation energies of the leaching process.

A new concept of auxiliary fuel injection through tuyeres in blast furnaces developed by numerical simulations

The Injection of powdered materials in blast furnaces is a great option for reducing costs, increasing productivity and satisfy the environmental norms. Thus, this paper presents a study on the use of a flame stabilization system with rotation, designed to promote greater coal injection in the combustion zone, reducing losses and increasing the efficiency of the equipment. A physical model was used to evaluate scattering of pulverized fuel and is compared with numerical results in the same scale. In the second step, a combustion model was added to the numerical simulation, using dimensions of a real blast furnace. Fields like temperature, velocity and behavior of chemical reactions were analyzed. The results showed that double lances promote better particle injection when compared with simple lance for reduced material injection. The new injection system proposed, with swirl numbers of 0.12 and 0.24, promoted a better injection of both reduced material and temperature in the raceway zone. The swirl 0.24 showed superior performance when compared to other injection systems.

Thermal Analysis for Velocity, Kinetics, and Enthalpy Reaction Measurements in Microfluidic Devices

The aim of this work is to present new devices for the measurement of velocity, kinetics, and enthalpy of chemical reactions occurring in a microfluidic chip, co-flow, or droplets flow. The thermal analysis goes from the macroscopic approach by microcalorimetry to microscopic analysis inside the microchannel by IR thermography. Concerning microcalorimetry, the enthalpy is deduced from the measurement of the global heat flux dissipated by the chemical reaction as a function of the molar flow rate. A validation is presented on a well-known acid-base reaction. This device can be combined with an IR camera for local characterization. The processing of the measured temperature fields allows the estimation of properties of great importance for chemical engineers, such as heating source distribution (i.e., the kinetics) of the chemical reaction along the channel. A validation experiment of a temperature field processing method is proposed with the Joule effect. From such a previous experiment, a Peclet field is estimated and used in a further step in order to study an acid-base co-flow configuration. Finally, a first tentative of thermal characterization inside droplets flow during an acid-base chemical reaction is also presented.

Well-data-based prediction of productivity decline due to sulphate scaling

Sulphate scaling can have a disastrous impact on oil production in waterflood projects with incompatible injected and formation waters. This is due to precipitation of barium/strontium sulphate from the mixture of both waters and the consequent permeability reduction resulting in loss of well productivity. The system where sulphate scaling damage occurs is determined by two governing parameters: the kinetics coefficient characterising the velocity of chemical reaction and the formation damage coefficient reflecting permeability decrease due to salt precipitation. Previous work has derived an analytical model-based method for determination of two coefficients from laboratory corefloods during quasi-steady state commingled flow of injected and formation waters. The current study extends the method for determination of kinetics and formation damage coefficients from production well data consisting of barium concentrations in the produced water and of well productivity decline. We analyse production data for five wells from giant offshore field A, submitted to seawater flooding (Campos Basin, Brazil), and obtain values of the two sulphate scaling damage parameters. The two coefficient values were used for prediction of productivity decline for these wells. The values of kinetics and formation damage coefficients as obtained from either laboratory or field data vary in the same range intervals. These results validate the proposed mathematical model for sulphate scaling damage and the analytical model-based method “from lab and wells to wells”.

Characterize Scaling Damage From Pressure Measurements

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 112500, "A New Method To Characterize Scaling Damage From Pressure Measurements," by T. Carageorgos, M. Marotti, and P. Bredrikovetsky, SPE, North Fluminense State University, prepared for the 2008 SPE International Symposium and Exhibition on Formation Damage Control, Lafayette, Louisiana, 13-15 February. The paper has not been peer reviewed. Productivity-decline prediction is based on mathematical modeling with well-known model coefficients. The sulfate-scaling system contains two governing parameters: the kinetics coefficient, λ, characterizing the velocity of chemical reaction, and the formation damage coefficient, β, showing how the permeability decreases because of salt precipitation. This paper extends previous works with commingled injection of two incompatible waters into the same core with two different ratios of formation water (FW) to seawater (SW). Introduction Barium- and strontium-sulfate scaling is a major problem in waterflood projects with incompatible formation and injected waters. Barium sulfate and resulting scale causes formation damage near the production-well zone. This phenomenon is attributed to precipitation of barium and strontium sulfates from the mixture of both waters and the consequent permeability reduction resulting in loss of well productivity. The chemical incompatibility between the injected SW, which is high in sulfate ions, and the FW, which originally contains high concentrations of barium, calcium, and/or strontium ions, may reduce well productivity, making the waterflood project uneconomical. A reliable model that is capable of predicting such scaling problems would help in planning a waterflood project. It also could aid in selecting an effective scale-prevention technique by predicting scaling tendency, type, and potential severity. A reliable predictive model must use well-known values of the model coefficients. The mathematical model for sulfate scaling contains two phenomenological parameters: λ from the active-mass law of chemical reaction showing how fast the reaction and precipitation occurs, and β reflecting the permeability decrease caused by sulfate-salt deposit. Both coefficients depend on rock-surface mineralogy, pore-space structure, temperature, and brine ionic strength. Therefore, they cannot be calculated theoretically for natural reservoirs and must be deter-mined from laboratory corefloods. Reagent- and deposition-concentration profiles during reactive flows are nonuniform, so the sulfate-damage parameters cannot be calculated directly from laboratory measurements. They must be determined from laboratory coreflood data by use of inverse-problem solutions. The λ can be calculated from break-through concentration in a quasisteady-state coreflood with commingled injection of FW and SW. Then β can be determined from the pressure-drop increase during flooding.

Characteristic of Nanoporous SiO<sub>2</sub> Thin Film Prepared by Sol-Gel Method with Catalyst HF

The characteristic of nanoporous SiO2 thin film prepared by sol-gel method with catalyst HF was studied by scanning electron microscopy, Fourier transform infrared, HP analyzer series and ellipsometry. Results showed the incorporation of HF effectively adjusted the pore size and distribution, and lowered the leakage current density and dielectric constant. This might be related to the weak acidity of HF, which properly controlled the velocity of chemical reaction in solution, and to the introduction of strong Si-F bonds, which had the lower electronegative and the larger volume.

Finite differences study of ignition in a methane–air mixture flow

A detailed simulation of the ignition process and premixed flames propagation, taking into account molecular transport, chemical reaction, thermodynamics and convection, is built by making use of the implicit finite difference scheme with the help of the Tridiagonal Matrix Algorithm. The velocity of chemical reaction is expressed by means of Arrhenius form of first order in both fuel and oxygen. The main objective of this work is to define numerically in two cases, u=0.1 m/s and u=0.4 m/s, the ignition temperature of the methane–air mixture with different air excess coefficients in the mixture. In addition, the effect of the thickness of the region ignition and of ignition location on the transient behavior of the flame was studied.