Thermophoresis and Brownian Effect for Chemically Reacting Magneto-Hydrodynamic Nanofluid Flow across an Exponentially Stretching Sheet

This comparative research investigates the influence of a flexible magnetic flux and a chemical change on the freely fluid motion of a (MHD) magneto hydrodynamic boundary layer incompressible nanofluid across an exponentially expanding sheet. Water and ethanol are used for this analysis. The temperature transmission improvement of fluids is described using the Buongiorno model, which includes Brownian movement and thermophoretic distribution. The nonlinear partial differential equalities governing the boundary layer were changed to a set of standard nonlinear differential equalities utilizing certain appropriate similarity transformations. The bvp4c algorithm is then used to tackle the transformed equations numerically. Fluid motion is slowed by the magnetic field, but it is sped up by thermal and mass buoyancy forces and thermophoretic distribution increases non-dimensional fluid temperature resulting in higher temperature and thicker boundary layers. Temperature and concentration, on the other hand, have the same trend in terms of the concentration exponent, Brownian motion constraint, and chemical reaction constraint. Furthermore, The occurrence of a magnetic field, which is aided by thermal and mass buoyancies, assists in the enhancement of heat transmission and wall shear stress, whereas a smaller concentration boundary layer is produced by a first-order chemical reaction and a lower Schmidt number.

Kinetic Analysis of Pyrolysis and Thermo-Oxidative Decomposition of Tennis String Nylon Wastes

Thermal degradation of nylon-6 tennis string nylon wastes in inert nitrogen and air atmospheres was investigated by means of multiple heating-rate thermogravimetric analyses. The results obtained under the heating rates of 5–20 K/min are compared in terms of degradation feature and specific temperature for two atmospheres. Using nonisothermal data, kinetic analysis was thoroughly conducted using various isoconversional model-free methods, including Starink, Madhusudanan–Krishnan–Ninan, Tang, Coats–Redfern, and Flynn–Wall–Ozawa methods. With these kinetic analysis methods, the activation energy over the entire degradation process was successfully calculated. By means of the model-fitting master-plots method, the first-order chemical reaction model was determined to be the most appropriate mechanism function for describing pyrolysis and oxidative thermal degradation of nylon-6 waste. Using kinetic parameters, satisfactory matching against experimental data resulted using the Coats–Redfern method for both cases. Furthermore, thermodynamic parameters such as changes in entropy, enthalpy, and Gibbs free energy during thermal degradation processes were evaluated.

MHD Free Convection from a Semi-infinite Vertical Porous Plate with Diffusion-Thermo Effect

An analytical solution for two-dimensional unsteady MHD free convective mass transfer flows of viscous incompressible optically thin fluid past a semi-infinite vertical porous plate in the presence of thermal radiation and chemical reaction is presented in this paper. A uniform magnetic field is applied normally to the plate with a first-order chemical reaction. The non-dimensional governing equations are solved analytically by using the regular perturbation technique. The effects of various physical parameters like radiation parameter Q, Dufour effect Du, chemical reaction parameter K, thermal Grashof number Gr, Hartmann number M, porosity parameter k, etc., are studied and demonstrated graphically. One of the significant findings of this analysis includes that an intensification of the chemical reaction effect causes a downfall in the fluid concentration. In contrast, another important outcome of the present study is that the rate of heat transfer and shear stress at the wall increases under the diffusion thermo effect or Dufour effect. Still, it tends to fall for high radiation. Further, the rate of mass transfer rises under the chemical reaction effect.

Non-Coaxially Rotating Motion in Casson Martial along with Temperature and Concentration Gradients via First-Order Chemical Reaction

The effect of non-coaxial rotation on the transport of mass subjected to first-order chemical reaction is studied analytically. The effects of thermal radiation, buoyancy, constructive and destructive chemical reactions along with Casson fluid in rotating frame are discussed. Time evolution of primary and secondary velocities, energy and solute particles are analyzed. The behavior of flow under the variation of intensity of magnetic field is also investigated. Evolutionary behavior of primary velocity is opposite to the evolutionary behavior of secondary velocity. The impact of buoyant force on primary velocity is opposite to the role of buoyant force on the secondary velocity. The evolutionary behavior of temperature is also examined and a remarkable enhancement in temperature is noticed. Thermal radiation causes the fluid to be cooled down as heat energy is escaped by thermal radiation. Evolutionary behavior of concentration is also analyzed and an increasing of concentration versus time is noted. Destructive chemical reaction results a remarkable reduction in the concentration and vice versa for generative chemical reaction.

Heat and Mass Transfer Impact on Differential Type Nanofluid with Carbon Nanotubes: A Study of Fractional Order System

This paper is an analysis of flow of MHD CNTs of second grade nano-fluid under the influence of first order chemical reaction, suction, thermal generation and magnetic field. The fluid is flowing through a porous medium. For the study of heat and mass transfer, we applied the newly introduced differential operators to model such flow. The equations for heat, mass and momentum are established in the terms of Caputo (C), Caputo–Fabrizio (CF) and Atangana–Baleanu in Caputo sense (ABC) fractional derivatives. This shows the novelty of this work. The equations for heat, mass and momentum are established in the terms of Caputo (C), Caputo–Fabrizio (CF) and Atangana–Baleanu in Caputo sense (ABC) fractional derivatives. The solutions are evaluated by employing Laplace transform and inversion algorithm. The flow in momentum profile due to variability in the values of parameters are graphically illustrated among C, CF and ABC models. It is concluded that fluid velocity showed decreasing behavior for χ, P, ℏ2, Mo, Pr, ℵ and Sc while it showed increasing behavior for Gr, Gm, κ and Ao. Moreover, ABC fractional operator presents larger memory effect than C and CF fractional operators.

Kinetics of the Release of Nicotinamide Absorbed on Partially Neutralized Poly(acrylic-co-methacrylic acid) Xerogel under the Conditions of Simultaneous Microwave Heating and Cooling

The kinetics of release of nicotinamide (NIAM) that was absorbed on partially neutralized poly(acrylic-co-methacrylic) (PAM) xerogel/hydrogel, under the conditions of simultaneous microwave heating and cooling (SMHC) were examined. The kinetics curves of NIAM release into an aqueous solution at temperatures of 308–323 K were recorded. By applying the model-fitting method (MFM), it was found that the kinetics of NIAM release can be modeled by a kinetic model of a first-order chemical reaction. The values of the release rate constants (kM) at different temperatures were calculated, and their values were found to be within the range 8.4 10−3 s −1−15.7 10−3 s−1. It has been established that the Arrhenius equation was valid even in the conditions of SMHC. The values of the kinetic parameters (activation energy (Ea) and pre-exponential factor (A) of the NIAM release process adsorbed on PAM xerogel/hydrogel were calculated as follows: Ea = 25.6 kJ/mol and ln (A/s−1) = 5.21. It has been proven that the higher value of the rate constant at SMHC in relation to CH is not a consequence of the overheating of the reaction system or the appearance of “hot-points”. The values of change of the enthalpy of activation (ΔH*) and the change of entropy of activation (ΔS*) were calculated as follows: ΔH* = +23.82 kJ/mol and ΔS* = −201.4 J/mol K. The calculated higher values of the kinetic parameters and thermodynamic parameters of activation are explained by the formation of a specific activated complex under SMHC, whose structure and degree of order are different than in the one formed under CH.

AN UNSTEADY MHD FLOW OF CASSON FLUID PAST AN EXPONENTIALLY ACCELERATED VERTICAL PLATE

An unsteady, magnetohydrodynamic, incompressible, radiative Casson fluid flow past an infinite vertical permeable plate, which is accelerated exponentially, in presence of heat sink parameter and first-order chemical reaction taking account of Soret effect, is considered. Governing equations are solved for the profiles of velocity, temperature and concentration with the help of Laplace transform. The effects of various physical parameters on velocity, temperature and concentration profiles are discussed with the help of graphs.

MHD Boundary Layer Flow of Casson Fluid Past an Inclined Plate in the Presence of Soret/Dufour Effects, Heat Source and First-order Chemical Reaction

The main objective of this study is to investigate the effects of the Casson fluid parameter on an incompressible, magnetohydrodynamic boundary layer flow of a Casson fluid past a moving porous inclined plate in the presence of heat source and first-order chemical reaction. The governing partial differential equations are converted into ordinary differential equations using similarity transformation and then are solved numerically, adopting bv4pc method. The effects of relevant parameters on the velocity, temperature and concentration profiles are analyzed graphically. Also, tabular form is used to present skin friction, heat transfer and mass transfer. This investigation reveals that the Casson fluid parameter enhances the fluid velocity, skin friction and Sherwood number, while the Nusselt number decreases.

Numerical modelling of convection-diffusion problems with first-order chemical reaction using the dual reciprocity boundary element method

Purpose The purpose of this paper is to describe an extension of the boundary element method (BEM) and the dual reciprocity boundary element method (DRBEM) formulations developed for one- and two-dimensional steady-state problems, to analyse transient convection–diffusion problems associated with first-order chemical reaction. Design/methodology/approach The mathematical modelling has used a dual reciprocity approximation to transform the domain integrals arising in the transient equation into equivalent boundary integrals. The integral representation formula for the corresponding problem is obtained from the Green’s second identity, using the fundamental solution of the corresponding steady-state equation with constant coefficients. The finite difference method is used to simulate the time evolution procedure for solving the resulting system of equations. Three different radial basis functions have been successfully implemented to increase the accuracy of the solution and improving the rate of convergence. Findings The numerical results obtained demonstrate the excellent agreement with the analytical solutions to establish the validity of the proposed approach and to confirm its efficiency. Originality/value Finally, the proposed BEM and DRBEM numerical solutions have not displayed any artificial diffusion, oscillatory behaviour or damping of the wave front, as appears in other different numerical methods.