Presence Of Reaction Research Articles

Optical and radiative characterisation of alumina–silica based ceramic materials for high-temperature solar thermal applications

Optical and radiative properties of alumina–silica based ceramic materials are determined in the spectral range of 0.2–2.5 µm. The effects of material thermal treatment on the material structure, composition as well as optical and radiative properties are investigated using the commercial CARBO HSP materials and in-house fabricated samples with sintering temperatures of 1400∘C and 1500∘C. The material structure and composition are characterised using scanning electron microscopy, X-ray micro computed tomography, powder X-ray diffraction and scanning transmission electron microscopy. Directional–hemispherical reflectance and transmittance of the samples are obtained using dispersive spectroscopy. A two-step inverse methodology consisting of an analytical solution based on the modified two-flux approximation and iterative Monte Carlo ray-tracing is developed and applied to infer the transport scattering albedo and the transport extinction coefficient, respectively. The structural and compositional investigation revealed that the presence of chemical reactions between Al2O3 and SiO2 to form mullite during the thermal treatment in the preparation process. The investigated samples are strongly absorptive in the spectral range of 0.2–0.4 µm, in which the transport scattering albedo is close to 0. Scattering is the dominant attenuation mechanism in the spectral range of 1.5–2.5 µm, in which the transport scattering albedo is above 0.8. The absorptive index of the in-house prepared samples sintered at 1400∘C is one to two orders of magnitude smaller than that of the commercial material in the spectral range of 0.2–2.5 µm. However, the absorptive index of the samples sintered at 1500∘C has similar values and is 25% smaller than that of the commercial material in the spectral ranges of 0.4–0.7 µm and 1.5–2.5 µm, respectively. The sample absorption increases with thermal treatment temperature because of higher extents of sintering.

Kinetic multi-layer model of film formation, growth, and chemistry (KM-FILM): Boundary layer processes, multi-layer adsorption, bulk diffusion, and heterogeneous reactions.

Large surface area-to-volume ratios indoors cause heterogeneous interactions to be especially important. Semi-volatile organic compounds can deposit on impermeable indoor surfaces forming thin organic films. We developed a new model to simulate the initial film formation by treating gas-phase diffusion and turbulence through a surface boundary layer and multi-layer reversible adsorption on rough surfaces, as well as subsequent film growth by resolving bulk diffusion and chemical reactions in a film. The model was applied with consistent parameters to reproduce twenty-one sets of film formation measurements due to multi-layer adsorption of multiple phthalates onto different indoor-relevant surfaces, showing that the films should initially be patchy with the formation of pyramid-like structures on the surface. Sensitivity tests showed that highly turbulent conditions can lead to the film growing by more than a factor of two compared to low turbulence conditions. If surface films adopt an ultra-viscous state with bulk diffusion coefficients of less than 10-18 cm2 s-1 , a significant decrease in film growth is expected. The presence of chemical reactions in the film has the potential to increase the rate of film growth by nearly a factor of two.

Effects of Thermal Radiation on Temperature and Concentration on MHD Free Convection Flow Past a Vertical Porous Plate in the Presence of Chemical Reaction and Heat Source Parameter

Objective: To study the effects of chemical reaction and heat source parameter on MHD Free Convection Flow Past a Vertical Porous Plate. Method: The problem is represented by coupled non-direct fractional differential conditions. The non-dimensional conditions of the issue have been tackled mathematically utilizing the Finite-Element strategy. Findings: The effects of governing parameters such as chemical reaction, heat source, permeability, radiation and many others are discussed quantitatively with the help of graphs in these flow fields like velocity, temperature, concentration with the help of skin friction, Nusselt number and Sherwood number. Novelty: The accurateness of the solution to the problem was verified by comparing it with the published previously. The compatibility between the results was found to be high. To strengthen the validity of the numerical results were presented in this work. Keywords: Temparature; Concentration; Chemical reaction; Mass diffusion; Eckert numeral; Radiation; MHD; Time dependent variable

Effect of non-Newtonian flow due to thermally-dependent properties over an inclined surface in the presence of chemical reaction, Brownian motion and thermophoresis

The aim of present study is to investigate the convective heat and mass transfer in steady MHD boundary layer flow of an electrically conducting micropolar fluid over an inclined surface. Partial differential equations resulting from the mathematical modeling of the phenomenon are reduce to nonlinear ODEs, and a finite difference based scheme has been adopted to iteratively find the numerical solution by employing the successive over-relaxation (SOR) method. A self-developed computer code has been used in the MATLAB environment. Influence of chemical reaction, Brownian motion, thermophoresis, and viscous dissipation on the relevant features of the flow are discussed and analyzed through graphs and tables. Temperature dependent thermal conductivity and viscosity enhances the flow velocity. Wall suction slows down the flow in the boundary layer and brings the optimum value of the velocity very nearer to the inclined plane. The magnetic field affects the shear stress and viscous dissipation that is parallel due to suction. A decrease in the fluid temperature is noticed throughout the boundary layer for Prandtl number, Schmidt number, and suction parameter whereas an opposite trend is seen for temperature-dependent thermal conductivity, injection parameter, magnetic field, Brownian motion, and thermophoresis.

Analysis of unsteady magnetohydrodynamic radiative thin liquid film flow, heat and mass transfer over a stretching sheet with variable viscosity and thermal conductivity

The present article is related to the study of magnetohydrodynamic (MHD) heat and mass transfer in a thin liquid film over a permeable unsteady stretching surface in the presence of chemical reaction, applied magnetic field, viscous dissipation, and thermal radiation with variable viscosity and thermal conductivity. Computed results for unsteadiness parameter, temperature ratio parameter, radiation parameter in the presence/absence of the viscous dissipation and Ohmic heating are analyzed and discussed. The computed results reveal that the viscous and Ohmic dissipations reduce the temperature gradient profiles in the thin liquid film. Further, the thermal radiation decreases the cooling rate of the thin liquid film but the reverse effect is seen by increasing the Prandtl number.

Chemical reaction impact on MHD natural convection flow through porous medium past an exponentially stretching sheet in presence of heat source/sink and viscous dissipation

This study investigates the viscous dissipation impact on free convection MHD flow through a porous medium over an exponentially stretching surface in presence of chemical reaction. The basic governing PDEs are converted into non-linear ODE's by using similarity transformations and then using the Keller-box method, numerical solutions are obtained. The flow features of boundary layers along with the bounding surface are identified and analysed using diagrams. It is noted that the increase in the Eckert number, Radiation and Magnetic parameter (M) increases the temperature profiles, while the increase in the chemical reaction parameter, porosity and Schmidt number decreases the concentration profile. To validate the results, a comparative study between the present study and previously published results for a particular case is conducted and good agreement is found between them.

Thermal Diffusion and Diffusion Thermo Effects on Casson Nanofluid Flow in the Presence of Chemical Reaction with Inclined Magnetic Field

Present paper studies the thermal-diffusion and diffusion-thermo effects on Casson nanofluid flow in the presence of chemical reaction with inclined magnetic field. A similarity analysis was used to transform the system of partial differential equations, together with boundary conditions into a system of dimensionless couple ordinary differential equations. A robust spectral collocation method has been adopted to obtain the solution of the transformed flow equations with corresponding boundary conditions. The impact of various controlling parameters on dimensionless velocity, temperature and nanoparticle concentration are presented graphically and discussed. The effect of the flow pertinent parameters on skin friction, Nusselt number and Sherwood number are presented in tabular form. Finally, an increase in Prandtl number and thermophoresis parameter reduce the temperature field of the flow, while increase in Eckert number enhanced the temperature profile.

Thermal radiation and Joule heating effects on a magnetohydrodynamic Casson nanofluid flow in the presence of chemical reaction through a non-linear inclined porous stretching sheet

The present study explores the thermal and Joule heating effect of Casson nanofluid flow with chemical reaction over an inclined porous stretching surface. The results of heat source/sink, viscous dissipation, and suction are regarded. The new physical governing equations of partial differential flow equations are converted into nonlinear ordinary differential equations and are numerically resolved employing the implicit finite difference technique. The influence on velocity, temperature, and concentration fields of many flow variables are addressed. The numerical and graphical findings are defined for the numerous related attentiveness flow parameters. The empirical data reported are compared with the published outcomes.

Analytic Treatment for Electrical MHD Non-Newtonian Fluid Flow over a Stretching Sheet through a Porous Medium

In this study, an attempt has been made to investigate the mass and heat transfer effects in a BLF through a porous medium of an electrically conducting viscoelastic fluid subject to a transverse magnetic field in the existence of an external electric field, heat source/sink, and chemical reaction. It has been considered the effects of the electric field, viscous and Joule dissipations, radiation, and internal heat generation/absorption. Closed-form solutions for the boundary layer equations of viscoelastic, second-grade, and Walters’ B ′ fluid models are considered. The method of the solution includes similarity transformation. The converted equations of thermal and mass transport are calculated using the optimal homotopy asymptotic method (OHAM). The solutions of the temperature field for both prescribed surface temperature (PST) and prescribed surface heat flux (PHF) are found. It is vital to remark that the interaction of the magnetic field is found to be counterproductive in enhancing velocity and concentration distribution, whereas the presence of chemical reaction, as well as a porous matrix with moderate values of the magnetic parameter, reduces the temperature and concentration fields at all points of the flow domain.

Hall and Ion Slip Influence on Mixed Convective Magnetohydrodynamic Oscillatory Flow through a Permeable Medium in Presence of Thermal Diffusion

The aim of this study is to analyze the effect of Hall and ion slip on viscous incompressible electrically conducting fluid bounded by a vertical porous plate in the presence of chemical reaction and thermal radiation subject to oscillatory suction. The resulting coupled non-linear partial differential equations are solved analytically by applying perturbation technique. The influences of various non-dimensional parameters on velocity, temperature and concentration profiles were discussed numerically.

Hall and Ion Slip Influence on Mixed Convective Magnetohydrodynamic Oscillatory Flow through a Permeable Medium in Presence of Thermal Diffusion

The aim of this study is to analyze the effect of Hall and ion slip on viscous incompressible electrically conducting fluid bounded by a vertical porous plate in the presence of chemical reaction and thermal radiation subject to oscillatory suction. The resulting coupled non-linear partial differential equations are solved analytically by applying perturbation technique. The influences of various non-dimensional parameters on velocity, temperature and concentration profiles were discussed numerically.

Compuational study on transport of thermal energy and mass species in power law rheological fluid with hybrid nanostructures in the presence of chemical reaction

Power law rheological model is used for mathematical modeling of simultaneous transport of heat and energy via hybrid nanoparticles distributed in heat generating fluid exposed to magnetic field. Governing conservation laws, correlation between thermos-physical properties fluid, solid particles, suitable no-slip momentum and temperature boundary conditions are provided system of boundary value problems which are solved numerically using finite element method (FEM). The FEM simulations are used in capturing the dynamics of physical parameters on the momentum transport and heat energy transfer under the influence of non-uniformly moving surface which is being heated in non-uniform manner. Power law fluid flow experiences retardation as intensity of magnetic field is increased. Hybrid nanofluid is more heat generative than mono nanofluid and power law index causes a decrease in flow. Consequently, convective transport of heat is compromised. Generative and destructive chemical reactions have opposite trend on transport of species in power law fluid.

State function‐based flash specifications for open systems in the absence or presence of chemical reactions

AbstractDiverse engineering fields require flash calculations like isothermal flash, isenthalpic flash, and isentropic flash. They can be cast as minimization of a thermodynamic state function and solved by Michelsen's Q‐function approach. Flash calculations for open systems, that is, systems where chemical potentials are specified instead of the mole numbers for some components, also belong to this scope. By analyzing the construction of Q‐functions through Legendre transforms, we extend this approach to the flash for open systems in the absence or presence of chemical reactions, resulting in general formulations for various specifications. For systems without reactions, the classical framework using mole numbers as independent variables is employed; for those with reactions, the modified‐RAND framework is employed. We present examples for open systems at constant temperature and pressure. Using the Q‐function minimization, we can solve multicomponent nonreactive or reactive systems at a specified chemical potential with quadratic convergence over a wide range of conditions.

Unsteady MHD oscillatory visco-elastic fluid flow through an inclined channel in presence of chemical reaction with Soret and Dufour effects

The purpose of present paper is to analyze the Soret and Dufour effects on an unsteady magneto hydrodynamic oscillatory flow of radiative, visco-elastic fluid through an inclined channel filled with saturated porous medium with non-uniform wall temperature in presence of first-order chemical reaction. The governing dimensionless momentum equation coupled with the energy and mass diffusion equations are solved analytically. The expressions for velocity, temperature, concentration, skin friction, Nusselt number and Sherwood number are obtained and are analyzed graphically for various values of the dimensionless flow parameters.

Heat and mass transfer flow of nanofluids in presence of chemical reaction with partial slip conditions

Journal of Applied Mathematics and Computational Mechanics, Prace Naukowe Instytutu Matematyki i Informatyki, Politechnika Częstochowska, Scientific Research of the Institute of Mathematics and Computer Science, Czestochowa University of Technology

Heat and Mass Transfer Effects on MHD Flow Past an Inclined Porous Plate in the Presence of Chemical Reaction

The impact of heat and mass transfer effects on an MHD flow past an inclined porous plate in the presence of a chemical reaction is investigated in this study. An effort has been made to explain the Soret effect and the influence of an angle of inclination on the flow field, in the presence of the heat source, chemical reaction and thermal radiation. The momentum, energy and concentration equations are derived as coupled second order partial differential equations. The model is non-dimensionalized and shown to be controlled by a number of dimensionless parameters. The resulting dimensionless partial differential equations can be solved by using a closed analytical method. Numerical results for pertaining parameters, such as the Soret number (Sr), Grashof number (Gr) for heat and mass transfer, the Schmidt number (Sc), Prandtl number (Pr), chemical reaction parameter (Kr), permeability parameter (K), magnetic parameter (M), skin friction (τ), Nusselt number (Nu) and Sherwood number (Sh) on the velocity, temperature and concentration profiles are presented graphically and discussed qualitatively.

Role of dipole interactions in Darcy–Forchheimer first-order velocity slip nanofluid flow of Williamson model with Robin conditions

Ferrofluids (FF) have numerous applications in biomedical, industrial and mechanical engineering. It characteristics make it helpful for a wide range of uses like in computer hard drives, loudspeakers, rotating shaft motors, magnetic resonance imaging (MRI) and so many others. In this communication, characteristics of magnetized first order Darcy–Forchheimer ferrofluid slip flow of non-Newtonian (Williamson fluid) towards a flat surface of stretched sheet in the presence of chemical reaction, Brownian motion, activation energy, thermophoresis diffusion, mixed convection and Robin condition is addressed. Appropriate similarity transportations are used to alter the complicated and nonlinear PDE’s into ODE’s and computational results are obtained through bvp4c technique (built-in-shooting). Furthermore, the engineering quantities (skin friction coefficient, Nusselt number, Sherwood number) are numerically elaborated with the help important flow parameters. In summary, a proper location of magnetic dipole can adjust the heat and mass transfer rate and flow field to fit the practical application.

CO2 capture by modified hollow fiber membrane contactor: Numerical study on membrane structure and membrane wettability

This work aims at capturing CO2 from natural gas using a verified finite element mathematical model by improving the membrane wettability, membrane structure, the type of absorbents used in the system, and the physical parameters like membrane porosity and the number of fibers used in hollow fiber membrane contactor (HFMC). The model is developed to simulate the CO2 removal using membranes by considering mass transfer equations in the presence of chemical reactions. Simulations were performed using a membrane system including 10 fibers with 175 mm length, 830 μm outer fiber radius and 450 μm inner fiber radius. The effect of adding montmorillonite nanoparticles (MMT) in weight percentages of 1%, 3%, and 5% to the PVDF membrane was perused to demonstrate the influence of membrane structure modification on system performance. The results show that the modification of membrane structure with montmorillonite nanoparticles could increase the efficiency of the system in the removal of CO2 particles by 8%. Four absorbents including MEA (monoethanol amine), PZ (piperazine), TEA (triethanolamine), and EDA (ethylenediamine) are used to identify the most effective absorbent where PZ absorbent shows the highest and EDA absorbent has the lowest carbon capture efficiency. Wettability is found to have a considerably negative impact on membrane carbon capture capacity. For instance, the modeling results show that even a 10% wetting of the membrane reduces the efficiency of the CO2 removal process by more than 47%. In addition, the results illustrate that the increase in membrane tortuosity and gas velocity have negative impacts on the separation process, while increase in the absorbent concentration, packing density and porosity enhance the separation of CO2.

Effect of Chemical Reaction on Bioconvective Flow in Oxytactic Microorganisms Suspended Porous Cavity

In this paper, the bioconvective flow in a porous square cavity containing oxytactic microorganism in the presence of chemical reaction is investigated. The bioconvection flow and heat transfer in porous media are formulated based on the Darcy model of Boussinesq approximation. The governing partial differential equations are solved using the Galerkin finite element method. The computational numerical results are exhibited by the streamlines, isotherms, isoconcentrations of oxygen, isoconcentrations of microorganisms, average Nusselt number, average Sherwood numbers of oxygen concentration and microorganisms. The effects of key parameters such as bioconvection Rayleigh number (Rb), chemical reaction parameter (Kr) and thermal Rayleigh number (Ra) are presented and analyzed. It can be deduced that the chemical reaction reduces the strength of isoconcentrations of both oxygen and microorganisms. It has been revealed that the chemical reaction has a greater effect on the swimming of the microorganisms, average Nusselt number, and average density number.

THERMO—DIFFUSION AND HALL EFFECT ON RADIATING AND REACTING MHD CONVECTIVE HEAT ABSORBING FLUID PAST AN EXPONENTIALLY ACCELERATED VERTICAL POROUS PLATE WITH RAMPED TEMPERATURE

Numerical investigation is undertaken to study the effects of thermo-diffusion and Hall current on unsteady magneto-hydrodynamic convective flow of a viscous, incompressible, electrically conducting, radiating and heat absorbing fluid past an exponentially accelerated infinite vertical porous plate with ramped temperature in the presence of chemical reaction. A uniform magnetic field is applied transversely in the direction of the flow. The governing system of partial differential equations along with initial and boundary conditions is transformed to dimensionless form and then solved by employing finite element method. The impact of various flow parameters on the primary and secondary fluid velocities, fluid temperature and fluid concentration as well as shear stress, rate of heat and mass transfer at the plate are displayed through the graphs and tables. It can be observed that the temperature profiles are slower in case of ramped temperature plate than that of isothermal plate.