Effects Of Variable Thermal Conductivity Research Articles

Thomson and rotation effects during photothermal excitation process in magnetic semiconductor medium using variable thermal conductivity

This study investigates a strong magnetic field acting over an elastic rotator semiconductor medium. The Thomson effect due to the magnetic field during the photothermal transport process is studied, and the thermoelectricity theory is used to explain the behavior of waves in the homogenous and isotropic medium under the effect of variable thermal conductivity. The variable thermal conductivity is considered as a linear function of the temperature. The two-dimensional deformation equations are used to describe the overlaps among plasma, electrical, thermal, and magneto-elastic waves. The charge density of inertia-particles is considered as a function of time for studying the induced electric current. The normal mode analysis is used to obtain the exact solutions of the physical field distributions as part of this phenomenon. To obtain the complete solutions of the physical field quantities, the certain mechanical loads, electromagnetic effects, thermal effects, and plasma recombination process are applied herein. The results of the physical distributions are graphically depicted and discussed in consideration of the internal heat source, rotation, and Peltier coefficient.

Reflection phenomena of waves through rotating elastic medium with micro-temperature effect

Abstract In this article, we analyzed the effect of variable thermal conductivity on reflected elastic waves. The waves are propagating through a thermoelastic medium rotating with some angular frequency. The concept of micro-temperature is also been considered, in which microelements of the medium contain a high temperature. A heat conduction phenomenon is encountered by dual phase-lag heat conduction model. P (or SV)-type wave is incident on the medium with some specific angle of incidence. After reflection from the surface incident, P-wave is converted into quasi longitudinal and quasi transverse waves and propagates back into the medium. Helmholtz’s potential function along with the harmonic wave solution is used to obtain the solution of the model. Analytically, we calculated the amplitude ratios and attenuation factor for each reflected wave against the angle of incidence. The obtained results are also represented graphically for different values of rotational frequency and variable thermal conductivity for a particular material.

Photo-thermal interactions in a semi-conductor material with cylindrical cavities and variable thermal conductivity

ABSTRACT This study investigates the photo-thermo-elastic interaction in an infinite semi-conductor material with cylindrical cavities. The effect of variable thermal conductivity through the photo-thermo-elastic transport process is studied using the coupled models of thermo-elasticity and plasma waves. The internal surface of the cylindrical cavity is loaded by a thermal shock varying heat. The eigenvalue method, under Laplace transform scheme, is used to get the analytical solution of the studied field distribution as parts of this phenomenon. A detailed analysis of the impacts of the variable thermal conductivity on the physical fields is debated. The numerical outcomes of the studied fields are displayed graphically. According to them, the variable thermal conductivity offers finite speed of the mechanical wave and the thermal wave propagations.

On numerical and analytical solutions for mixed convection Falkner-Skan flow of nanofluids with variable thermal conductivity

The originality of this study is the introduction of the effects of variable thermal conductivity and under the effect of an external magnetic field on the mixed convection in the Falkner-Skan system in a medium filled with nanoparticles (i.e. copper, alumina and magnetite-). The impacts of physical parameters such as variable thermal conductivity in the presence of an external magnetic field and nanoparticles are visualized in a system of coupled ordinary differential equations, which characterized the dynamic and the thermal distributions (velocity/temperature distributions), which are obtained using a numerical process using the Runge-Kutta-Fehlberg method (RKF) based on shooting technique, and analytically by the differential transform method (DTM). The results obtained as well as the comparison shows that the influence of variable thermal conductivity if compared with traditional case (constant of thermal conductivity) and the advantages of the analytical method (DTM) used.

Combined Effects of Variable Thermal Conductivity and Electrical Conductivity on Peristaltic Flow of Pseudoplastic Nanofluid in an Inclined Non-Uniform Asymmetric Channel: Applications to Solar Collectors

Abstract As conduction, convection, and radiation are fundamental modes of heat emitter and transfer, this paper looks at the influences of temperature-dependent thermal conductivity and thermal radiation on peristaltic flow of pseudoplastic nanofluids in an inclined non-uniform asymmetric channel. Inclined magnetic field is taken into consideration. As the Wiedemann–Franz law in metals, electrical conductivity has identical behavior as that of thermal conductivity; as freely animated evenness, electrons transfer not only electric current but also heat energy. Consequently, electrical conductivity should be depending on the temperature of nanoparticles. The related equations of momentum, mass, and concentration are reformulated using lubrication approximations (i.e., tiny or zero Reynolds number and long wavelength). The resulting system of nonlinear equations is solved semi-numerically with the aid of the parametric ND solve package using mathematica version 11. Results of velocity, temperature, and concentration distributions are obtained in the analytical three-dimensional forms. The streamline graphs are offered in the terminus, which elucidate the trapping bolus phenomenon. As a special case, a comparison is made and signified with the recently published results by Hayat et al. (2016, Soret and Dufour Effects in MHD Peristalsis of Pseudoplastic Nanofluid With Chemical Reaction,” J. Mol. Liq., 220, pp. 693–706). It's found that, the increases in thermal conductivity and electrical conductivity cause an increase in the temperature of nanofluid and the heat transfer rate gets induced so a better absorption of solar energy is gained.

Effect of Variable Thermal Conductivity on the Generalized Thermoelasticity Problems in a Fiber-Reinforced Anisotropic Half-Space

Fiber-reinforced materials have widespread applications, which prompt the study of the effect of fiber reinforcement. Research studies have indicated that thermal conductivity cannot be considered as a constant, which is closely related to temperature change. Based on those studies, we investigate the fiber-reinforced generalized thermoelasticity problem under thermal stress, with the consideration of the effect of temperature-dependent variable thermal conductivity. The problem is assessed according to the L-S theory. A fiber-reinforced anisotropic half-space is selected as the research model, and a region of its surface is subjected to a transient thermal shock. The time-domain finite element method is applied to analyze the nonlinear problem and derives the governing equations. The nondimensional displacement, stress, and temperature of the material are obtained and illustrated graphically. The numerical results reveal that the variable conductivity significantly influences the distribution of the field quantities under the fiber-reinforced effect. And also, the boundary point of thermal shock is the most affected. The obtained results in this paper can be applied to design the fiber-reinforced anisotropic composites under thermal load to satisfy some particular engineering requirements.

A Numerical Superintendence with Stability Exploration of Casson Nanofluid Flow in the Effects of Variable Thermal Conductivity and Radiation

A Numerical Superintendence with Stability Exploration of Casson Nanofluid Flow in the Effects of Variable Thermal Conductivity and Radiation

The effect of variable thermal conductivity on an infinite fiber-reinforced thick plate under initial stress

The effect of variable thermal conductivity on an infinite fiber-reinforced thick plate under initial stress

Effects of variable thermal conductivity of a small semiconductor cavity through the fractional order heat-magneto-photothermal theory

In this investigation, a theoretical discussion of a fractional model of a heat order equation of a semiconductor medium in form of a spherical small cavity is studied. The model is taken as one dimensional under the effect of magnetic field and initial stress. The variable thermal conductivity is considered as a linear function of temperature (which depends on temperature). The medium has been studied in the context of photothermal transport processes (excited by light). The model presents the interaction between the waves of plasma (carrier density of free electric charge), namely the elastic and the thermal waves. The Laplace transform method is used to solve the main equations in cylindrical coordinates. The numerical technique (which depends on the Fourier series expansion) is used to get the complete solutions of the main variables under investigation. The thermal and mechanical loads such as the ramp heat type and free traction are applied to the inner surface of the cavity to obtain the main physical fields. The numerical computations of some main physical fields are discussed and plotted graphically.

Magnetohydrodynamic nonlinear thermal radiative heat transfer of nanofluids over a flat plate in a porous medium in existence of variable thermal conductivity and chemical reaction

The effects of variable thermal conductivity and first-order chemical reaction on magnetohydrodynamic (MHD) flow with nonlinear thermal radiation of nanofluid over a flat plate in a porous medium have been studied in this paper. The governing system of ordinary differential equations has been solved numerically. Numerical results are presented both in tabular and graphical forms for solid volume fraction φ (), magnetic field parameter M (), permeability parameter P (), variable thermal conductivity parameter ε (), thermal radiation parameter Nr (), wall temperature excess ratio parameter (), Schmidt number Sc () and chemical reaction parameter λ () illustrating the effects on the velocity, temperature and concentration as well as on the skin-friction coefficient, local Nusselt number and local Sherwood number for four types of metallic or non-metallic nanoparticles, namely copper (), alumina (), titanium dioxide (TiO ) and silver (Ag) in the base-fluid water (Pr=6.8). The obtained results show that the effects of increasing the values of the variable thermal conductivity and wall temperature excess ratio parameters there is a decrease in the local Nusselt number value.

Effect of viscous dissipation and Joule heating on MHD radiative tangent hyperbolic nanofluid with convective and slip conditions

The forthright intention of this communication is to scrutinize the effect of variable thermal conductivity and thermal radiation on the magnetohydrodynamic tangent hyperbolic fluid in the presence of nanoparticles past a stretching sheet. For heat and mass transport phenomena, the collective stimulus of slip and convective conditions with the internal heating, viscous dissipation and Joule heating have been taken into account. The boundary layer equations of two-dimensional tangent hyperbolic nanofluid have been established with the help of boundary layer approximations. With the assistance of appropriate similarity transformation, the governing set of PDEs are rendered into the coupled nonlinear ODEs. The solution of the resulting ODEs is obtained with the help of the shooting technique. Furthermore, an authentication of the computed results is obtained through benchmark with the previously reported cases. The influence of various pertinent parameters on the velocity, temperature and concentration profiles has been analyzed graphically and discussed. The physical behavior of the velocity, temperature concentration, skin friction coefficient, the Nusselt and the Sherwood numbers have been investigated diagrammatically for various pertinent parameters. It is observed that the velocity profile is declined for the growing values of the Weissenberg number and the power law index, whereas the thermal and concentration fields are observed to enhanced for the same parameters. Our analysis depicts that the temperature and the concentration profiles are enhanced for the slip parameter and the Eckert number.

Effect of variable thermal conductivity and rotation of semiconductor elastic medium through two-temperature photothermal excitation

In the present investigation, a novel model of a rotating elastic semiconductor medium in the context of photothermal excitation is presented. This phenomenon has been studied using a two-temperature theory under the influence of hydrostatic initial stress. The governing equations are taken under the effect of variable thermal conductivity, which depends on temperature. The variable thermal conductivity has been observed as a linear function of temperature. The normal mode analysis is used to obtain the distributions of thermodynamic temperature, displacement, stress force, carrier intensity and the conductive temperature analytically. The linearity form of the physical quantities is taken into consideration. The mechanical forces and thermally insulated conditions are applied. The numerical simulation results are discussed and obtained graphically.

Analytical solution of fractional order heat equation under the effects of variable thermal conductivity during photothermal excitation of spherical cavity of semiconductor medium

In this investigation, the fractional model of heat equation in a semiconductor elastic medium with a spherical cavity is given. The model will be studied in one dimension with the influence of variable thermal conductivity which depends on the temperature. The medium has been investigated during the photothermal transport processes. The system of equations will explain the interference between the plasma–elastic–thermal waves. Laplace transform is applied to solve the governing equations. The complete solutions of main variables are obtained by using a numerical method based on Fourier series expansions. The thermal ramp type is applied on the inner surface of the cavity to obtain the physical quantities under investigation. The numerical computations of main physical quantities are illustrated and represented graphically. The time fractional order and the variable thermal conductivity have a great effect in main physical quantities.

Second Law Analysis of Dissipative Nanofluid Flow over a Curved Surface in the Presence of Lorentz Force: Utilization of the Chebyshev⁻Gauss⁻Lobatto Spectral Method.

The primary objective of the present work is to study the effects of heat transfer and entropy production in a nanofluid flow over a curved surface. The influences of Lorentz force and magnetic heating caused by the applied uniform magnetic field and energy dissipation by virtue of frictional heating are considered in the problem formulation. The effects of variable thermal conductivity are also encountered in the present model. The dimensional governing equations are reduced to dimensionless form by introducing the similarity transformations. The dimensionless equations are solved numerically by using the Chebyshev–Gauss–Lobatto spectral method (CGLSM). The rate of increase/increase in the local Nusselt number and skin friction coefficient are estimated by using a linear regression model. The expression for dimensionless entropy production is computed by employing the solutions obtained from dimensionless momentum and energy equations. Various graphs are plotted in order to examine the effects of physical flow parameters on velocity, temperature, and entropy production. The increase in skin friction coefficient with magnetic parameter is high for nanofluid containing copper nanoparticles as compared to silver nanoparticles. The analysis reveals that velocity, temperature, and entropy generation decrease with the rising value of dimensionless radius of curvature. Comparative analysis also reveals that the entropy generation during the flow of nanofluid containing copper nanoparticles is greater than that of containing silver nanoparticles.

Variable thermal conductivity approach for bioheat transfer during thermal ablation

The aim of the article is to present a mathematical model that predicts tissue temperature during thermal therapy (thermal ablation). The mathematical formulation of variable thermal conductivity of thermal wave bioheat transfer model for a generalized coordinate system due to external heat source during thermal ablation has been given. The governing bioheat transfer equation is simplified by Kirchhoff’s transformation. The numerical solution of the problem has been achieved using a finite difference scheme to discretize in space coordinate; the reduced system of second order ordinary differential equation is solved by the finite element Legendre wavelet Galerkin method (FELWGM). The obtained result from FELWGM is compared with exact analytical solution and shows good agreement. Parametric study is performed to evaluate the effect of variable thermal conductivity on tissue temperature distribution for different physical parameters and illustrated graphically. Particular cases are also deduced from present investigation. The effect of variability of thermal conductivity parameter, variability of time, generalized coordinate system, lagging time and external heat source coefficient on tissue temperature is discussed in detail. Thus, the consideration of the variable thermal conductivity is extremely beneficial for the clinical therapeutic application in the treatment of cancerous cells.

Variable aspects of double stratified MHD flow of second grade nanoliquid with heat generation/absorption: A revised model

Analysis of double stratifications in magneto-nanomaterials by nonlinear stretching sheet is addressed. Flow is generated due to stretching sheet with variable thickness. Incompressible liquid with the application of magnetic filed is considered. Energy expression is characteristics with additional effects of variable thermal conductivity and generation/absorption. Proper transformations are considered to dimensionless the governing systems. The non-linear system is then computed through homotopic scheme. Graphs depicting the consequences of numerous physical variables are presented and elaborated in detail. The numerically computed values of dimensionless skin friction is presented with physical insights.

Irreversibility Analysis of Dissipative Fluid Flow Over A Curved Surface Stimulated by Variable Thermal Conductivity and Uniform Magnetic Field: Utilization of Generalized Differential Quadrature Method.

The effects of variable thermal conductivity on heat transfer and entropy generation in a flow over a curved surface are investigated in the present study. In addition, the effects of energy dissipation and Ohmic heating are also incorporated in the modelling of the energy equation. Appropriate transformations are used to develop the self-similar equations from the governing equations of momentum and energy. The resulting self-similar equations are then solved by the Generalized Differential Quadrature Method (GDQM). For the validation and precision of the developed numerical solution, the resulting equations are also solved numerically using the Runge-Kutta-Fehlberg method (RKFM). An excellent agreement is found between the numerical results of the two methods. To examine the impacts of emerging physical parameters on velocity, temperature distribution and entropy generation, the numerical results are plotted against the various values of physical flow parameters and discussed physically in detail.

Combined effects of variable thermal conductivity and induced magnetic field on convective Jeffrey fluid flow with nth order chemical reaction

AbstractThis study addresses the impact of variable thermal conductivity and induced magnetic field on an unsteady two‐dimensional channel flow of an incompressible laminar mixed convective and chemically reacted Jeffrey fluid embedded in a non‐Darcy porous medium with an appropriate convective type boundary conditions. The suction/injection velocity distribution has been assumed to be in an exponential form. The set of transport equations is reduced into coupled ordinary differential equations by using appropriate similar variables, which are solved by shooting technique with Runge‐Kutta fourth‐order algorithm. The investigation is carried out for various emerging nondimensional parameters on the axial, radial velocities, temperature distribution, concentration, and induced magnetic fields and also with skin friction coefficient are discussed through graphs. The value of the local Sherwood and Nusselt numbers are analyzed numerically. We noticed that the effect of the induced magnetic field is increased with Strommer's number while it decreases for high magnetic Reynolds number.

Effect of Variable Thermal Conductivity during the Photothermal Diffusion Process of Semiconductor Medium

In this problem, we study the effect of variable thermal conductivity, which depend on temperature in the context of Photothermal diffusion (PTD). The PTD process is applied with thermoelasticity theory in chemical action. The model introduced describes the interaction between elastic-thermal-plasma waves, which based on the material properties of semiconductor elastic medium. The Laplace transform is used to solve the governing equations in one dimension of a thin circular plate. Some new constant will be appearing during the theoretical discussion. The mechanical forces and thermal loads are applied on the free surface of semiconductor to obtain the physical fields. The complete solutions in time domain are observed by using a numerical approximation method. The physical fields with some comparsions are presented analytically and graphically.

MHD stratified nanofluid flow by slandering surface

Current attempts focus on doubling the stratified effects of the magnetohydrodynamic flow of second grade nanoliquid over an impermeable surface stretching in a non-linear manner. The mathematical formulation is made using the boundary layer concept and assumptions of low magnetic Reynolds number. The non-linear stretching surface with variable thickness generates the flow. Incompressible non-Newtonian liquid is electrically conducted subject to a varying magnetic field. Heat transfer characteristics with heat generation/absorption, Joule heating and variable thermal conductivity effects are addressed. Novel features regarding Brownian motion and thermophoresis are also included. Mathematical representation of the considered aspects results in non-linear ODEs. The non-linear system is then computed and the derived solutions are adequate for convergence. The physical interpretation of quantities of interest are shown by graphical illustrations. The skin friction coefficient is also computed and inspected. Our computed results report that the influence of velocity ratio and Hartmann number result in similar velocity field characteristics. Furthermore, these aspects of nanoparticles, variable thermal conductivity and Hartmann number enhance the temperature distribution.