Variable Thermal Conductivity Research Articles

Enhancement of heat transfer due to nonlinear radiative Burgers nanofluid with triple diffusion and heat source effects

This investigation predicts the assessment of mass and heat transfer due to Burgers nanofluid. The investigation is further supported by triple diffusion flow. Variable thermal conductivity is accounted to endorse the thermal flow. In the heat equation, the extension is suggested by utilizing the external heat source and nonlinear radiated phenomenon. Computations for modeled problems are achieved by the shooting method. The fundamental role of parameters governing flow is noticed which is physically attributed. It is observed that the heat transfer rate is enhanced due to the modified Dufour number. The solutal concentration declined for the regular Lewis number. Furthermore, the nanoparticles concentration reduces due to the nano-Lewis number. The depicted results convey novel applications in chemical processes, cooling control systems, refrigeration, solar energy, extrusion processes, etc.

Variable thermal conductivity and mass diffusivity effects in a free convective flow of doubly stratified non-darcian porous medium over a vertical plate

The research in this article is carried out to study incompressible and unsteady free convective flow on a semi-infinite isothermal vertical plate in a doubly stratified non-Darcian porous media with variable mass diffusivity and variable thermal conductivity. The governing non-linear partial differential equations of flow were calculated by applying an implicit finite difference scheme of Crank-Nicolson type. Various parametric impacts on concentration profiles, temperature, velocity, as well Sherwood number, Nusselt number and skin friction, were examined and presented in graphs. It is examined that there exists a significant temperature decrease for high Darcy number in stratified fluids. Also, it is detected that the presence of stratification produces a considerable drop in skin friction while increases the mass and heat transfer rate. Comparison of current outcomes well agreed with the available solutions.

Analysis of thermal conductivity variation in magneto-hybrid nanofluids flow through porous medium with variable viscosity and slip boundary

Hybrid nanoparticles, which are nanoparticles composed of multiple materials or phases, find applications in various fields due to their unique properties resulting from the combination of different materials. In such fluids, viscosity changes significantly in response to alterations in temperature or pressure. For example, these fluids become less viscous as they are heated and more viscous as they are cooled. Similarly, in certain situations, the application of a temperature variation can cause a change in viscosity. This property is commonly observed in materials like polymers and some oils. The article aims to investigate the heat transfer and flow behavior of fluid from an elastic sheet of hybrid nanoparticles, considering the temperature-dependent variable viscosity and thermal conductivity. The obtained equations for the mathematical model are partial differential equations converted to ODEs by applying a suitable similarity transformation. The findings show that the magnetic field opposes fluid motion. Our main findings are that adding nanoparticles to the base fluid significantly increased its heat conductivity. This improvement has great potential for uses requiring effective heat transmission, especially in engineering systems where heat dissipation plays a crucial role. The study also reveals the complex relationships that influence thermal conductivity, including slip boundary effects, viscosity fluctuations, magnetohydrodynamic effects, and porous media dynamics. Understanding these interactions is critical for optimizing heat transport processes in porous media applications. Comprehending these interplays is essential for refining heat transport mechanisms in applications involving porous media. The graphical representations are used to explain the physical behavior of various model parameters. Previous outcomes are also contrasted with the current ones. The findings show that the magnetic field opposes fluid motion.We range the subsequent list of values for parameters in every graph unless indicated accordingly.ϵ=0.1,Pr=2,M=0.5,R=0.2,K=5,fw=0.1,s=0.1 ,λ=1,φ1=0.02,φ2=0.04.

Exploring the effects of TiO2${\rm TiO}_2$–Ag/water hybrid nanofluid on MHD flow over a permeable exponentially stretching–shrinking sheet with radiative heat transfer and slip conditions

AbstractThe objective of this article is to study the importance of velocity and thermal slip in the exponentially stretching or shrinking sheet with the megnetohydrodynamic (MHD) hybrid nanofluid flow along with magnetic field, radiative, heat generation effects. This study has practical importance in enhancing heat transfer efficiency, improving energy conversion and optimizing thermal management systems. The findings can also contribute to the development of sustainable energy systems and aid in assessing the stability and safety of nanofluid applications. The governing partial differential equations are transformed into nonlinear ordinary differential equations using similarity transformation. The ODEs are solved using bvp4c solver in MATLAB. The dual solutions are achieved for specific range of the stretching or shrinking parameter and mass suction parameter. The first solution is physically significant after considering stability analysis. The hybrid nanofluid has numerous real‐life and industrial applications, such as microelectronics, manufacturing, naval structures, nuclear system cooling, biomedical, and drug reduction. The skin‐friction increases but Nusselt number decreases over the stretching sheet whereas the opposite effect shows over shrinking sheet for the both solution with the increasing velocity slip parameter. On the other hand, The Nusselt number decreases over the shrinking or stretching sheet for both solutions with the increasing in the thermal slip parameter. The skin friction increases over shrinking sheet but decreases over stretching sheet for the first solution with increasing silver volume fraction parameter and porosity parameter (). Enhancing magnetic field parameter leads to the skin friction increases over the shrinking sheet but decreases over stretching sheet but Nusselt number shows opposite trend. The Nusselt number decreases over shrinking sheet but increases over stretching sheet for the first solution with increasing porosity parameter (). The Nusselt number decreases over shrinking or stretching sheet as the increases heat generation () and variable thermal conductivity parameter () but Nusselt number shows opposite trend as the increases radiative parameter ().

Influence of stress history on thermal conductivity of saturated fine-grained soils

This research investigated variations in thermal conductivity <i>k</i> for normally consolidated (NC) and overconsolidated (OC) saturated fine-grained soils at different levels of vertical effective stress. A series of undrained heating tests were performed using a specially designed consolidometer with central radial heating arrangement and temperature measurements within a soil specimen. For different soils investigated in this research, <i>k</i> correlated well with soil consolidation characteristics (compression index <i>λ</i> and swelling index <i>κ</i>) and vertical effective stress <i>σ</i><sub>v</sub>ʹ at both NC and OC states. However, the rates of increment of steady- and transient-state values of <i>k</i> (<i>k</i><sub>st</sub> and <i>k</i><sub>tr</sub>, respectively) with <i>σ</i><sub>v</sub>ʹ differed from one soil to another. For OC clays, both <i>k</i><sub>tr</sub> and <i>k</i><sub>st</sub> increased with preconsolidation stress <i>σ</i><sub>c</sub>ʹ. A set of equations were proposed to estimate both <i>k</i><sub>st</sub> and <i>k</i><sub>tr</sub> for saturated fine-grained soils as functions of <i>σ</i><sub>v</sub>ʹ, <i>λ</i>, <i>κ</i>, and stress history. At a particular value of <i>σ</i><sub>v</sub>ʹ, the dependence of <i>k</i> on overconsolidation ratio (OCR) and <i>σ</i><sub>c</sub>ʹ marked the importance of considering stress history in the determination of <i>k</i>. The influence of soil mineral composition on <i>k</i> was also explored. Quantification of soil mineralogical composition and available data on mineral thermal conductivity enabled prediction of <i>k</i><sub>tr</sub> with reasonable accuracy.

Irreversibility Analysis for Magnetized and Nonlinear Convection Flow of Carreau Fluid Past a Nonlinear Surface with Higher-Order Adherence Factor

Studying entropy generation allows scientists and engineers to optimize processes, design more efficient systems, and develop sustainable technologies. These studies aim towards minimizing energy losses, reducing environmental impacts, and advancing the frontiers of thermodynamics and energy science. As such, the current investigation expunges the dynamics of heat, flow, entropy and irreversibility analysis for a magnetized and dissipative Carreau fluid flow over a nonlinearly stretching sheet. The model is subject to thermal and electrical conductivity variations, higher-order adherence factors and nonlinear convective motion over an inclined nonlinear surface. Herein, the heat source in the flow system is considered space and temperature-dependent. The mathematical model presented in PDE systems is transformed to ODEs via similarity transformation. Numerically, the solutions to the distribution profiles are approximated via Chebyshev Collocation Method (CCM) with the pseudospectra (differentiation matrix) technique. In the limited case, the results here benchmark existing literature. Our findings identified that thermal irreversibility dominated the entire flow system, further entropy generation and irreversibility enhancement requires more thermal energy. We as well elucidate that alteration of both heat source modulation affects the heat transfer coefficient while Joule heating effect generates inner energy which induces the Carreau fluid energy. Carreau fluid, Entropy generation Momentum slip, Nonlinear Convection, Pseudo spectral method

Study of mass and heat transfer for peristaltic transport of cross nanofluid through a curved channel

AbstractNanoparticles have significant applications in drug delivery systems, heat exchanges, treatment of several diseases and chemical reactions. The Cross non‐Newtonian nanofluid model for heat and mass transfer inspection with diethylene glycol‐based fluid is highlighted in this study. The magnesium aluminate nanoparticles are used to evaluate nanofluid characteristics. The current investigation explores the numerical results for magnetohydrodynamics (MHD) peristaltic movement of Cross‐nanofluid via a curved channel under the influences of thermal radiation, heat sink/source and Joule heating. The effects of viscous dissipation, thermophoretic, variable thermal conductivity and Brownian diffusion coefficients in the presence of mass and thermal convection are also taken into consideration. Flow problem is modeled using fundamental conservation laws, and the resulting nonlinear partial differential equations (PDEs) are reduced to a system of nonlinear ordinary differential equations (ODEs) by employing long wavelength and a small Reynolds number approximations. Simplified systems of ODEs are addressed by adopting numerical technique via the NDSolve built‐in command in Mathematica. Furthermore, graphical presentations explain the behavior of relevant flow parameters. Results indicate that better values of the magnetic number and the thermophoresis parameter increase the rate of mass transfer. Results indicate that the nanofluid's temperature increases by improving values of the Brinkman number and falls with the thermal radiation parameter. It is also stated that the nanofluid's velocity reduces near the lower wall for greater values of Hartman number. Moreover, heat transfer rate improves for larger values of the heat generation parameter and curvature parameter.

Magnetohydrodynamic study of Micropolar fluid flow in the porous walled channel with variable viscosity and thermal conductivity: HAM Solution

This article examines the production of entropy and the heat transfer rate in the passage of micropolar fluid through a channel. The micropolar fluid takes place through the porous walled channel under the presence of an external magnetic field acting in the perpendicular direction of the flow. In this work, the thermal conductivity and viscosity of the fluid is considered variable and are the function of the temperature. Here, we consider two-dimensional creeping flow with two different forms of temperature boundary conditions, namely, Newtonian heating (NH) boundary constraints and specified surface temperature (SST) boundary conditions. The flow of the micropolar fluid in the proposed problem is governed by the coupled non-linear PDEs. These PDEs are first transformed into the ODEs by the use of some suitable similarity transformations and then obtained ODEs are further solved by using the semi-analytic Homotopy Analysis Method (HAM). This article shows the effect of various flow parameters on the fluid’s velocity, heat transfer rate, temperature of the fluid, and entropy production for both types of thermal boundary conditions. Through this article, it is concluded that the entropy production is minimal for Newtonian heating (NH) boundary conditions as compared to specified surface temperature (SST) boundary conditions. This result suggests that the NH boundary condition is more suitable for electrical appliances as compared to the SST boundary condition. This type of model is applicable in nuclear reactors, engineering appliances, heat reservoirs, etc.

Heat transfer analysis of magnetohydrodynamics peristaltic fluid with inhomogeneous solid particles and variable thermal conductivity through curved passageway

PurposeThe particle distribution in a fluid is mostly not homogeneous. The inhomogeneous dispersion of solid particles affects the velocity profile as well as the heat transfer of fluid. This study aims to highlight the effects of varying density of particles in a fluid. The fluid flows through a wavy curved passage under an applied magnetic field. Heat transfer is discussed with variable thermal conductivity.Design/methodology/approachThe mathematical model of the problem consists of coupled differential equations, simplified using stream functions. The results of the time flow rate for fluid and solid granules have been derived numerically.FindingsThe fluid and dust particle velocity profiles are being presented graphically to analyze the effects of density of solid particles, magnetohydrodynamics, curvature and slip parameters. Heat transfer analysis is also performed for magnetic parameter, density of dust particles, variable thermal conductivity, slip parameter and curvature. As the number of particles in the fluid increases, heat conduction becomes slow through the fluid. Increase in temperature distribution is noticed as variable thermal conductivity parameter grows. The discussion of variable thermal conductivity is of great concern as many biological treatments and optimization of thermal energy storage system’s performance require precise measurement of a heat transfer fluid’s thermal conductivity.Originality/valueThis study of heat transfer with inhomogeneous distribution of the particles in a fluid has not yet been reported.

Impact of swift heavy ion-induced point defects on nanoscale thermal transport in ZnO

Near-surface nanoscale thermal conductivity (k) variation of ion-irradiated single-crystalline ZnO was studied by time-domain thermoreflectance. ZnO was irradiated by 710 MeV Bi swift heavy ions (SHI) in the 1010–1013 ion/cm2 fluence range to investigate the progression of radiation damage both from single ion impacts and ion path overlapping regimes. Structural characterization using X-ray diffraction, Raman spectroscopy, and transmission electron microscopy indicated the absence of amorphization. The degradation in kwas attributed primarily due to phonon scattering on point defects. The results of measured k were used to validate several models including the semi-analytical Klemens-Callaway model, and a novel hybrid modeling approach based on the Monte-Carlo code TREKIS coupled with molecular dynamics simulations which captures the effects of single ion and ion path overlapping regimes, respectively. The findings promote a novel approach to developing radiation-controlled thermally functional materials.

Innovative stochastic finite difference approach for modelling unsteady non-Newtonian mixed convective fluid flow with variable thermal conductivity and mass diffusivity

A novel stochastic numerical scheme is introduced to solve stochastic differential equations. The development of the scheme is based on two different parts. One part finds the solution for the deterministic equation, and the second part is the numerical approximation for the integral part of the Wiener process term in the stochastic partial differential equation. The scheme’s stability and consistency in the mean square sense are also ensured. Additionally, a respective mathematical model of the boundary layer flow of Casson fluid on a flat and oscillatory plate is formulated. Wiener process terms perturb the model to be studied. This scheme will be solved in contexts including deterministic and stochastic. The influence of different parameters on velocity, temperature, and concentration profiles is demonstrated in various graphical representations. The main objective of this study is to present a reliable numerical approach that surpasses the limitations of traditional numerical methods to analyze non-Newtonian mixed convective fluid flows with varying transport parameters. Our objective is to demonstrate the capabilities of the new stochastic finite difference scheme in enhancing our comprehension of stochastic fluid flow phenomena. This will be achieved by comprehensively examining its mathematical foundations and computer execution. Our objective is to develop a revolutionary method that will serve as a valuable resource for scientists and engineers studying the modeling and understanding of stochastic unstable non-Newtonian mixed convective fluid flow. This method will address the challenges posed by the fluid’s changing thermal conductivity and mass diffusivity.

Cooling optimization of asphalt pavement by topology optimization and cooling mechanism analysis

The higher temperature in the hot summer area will seriously damage the safety and comprehensive performance of the asphalt pavement, thus it must be cooled down quickly and orderly. At present, the cooling pavements are designed mainly based on engineering experience, and the quantitative relationship between design objective and variable is not constructed during the design process. In addition, it is difficult to determine whether the material distribution of cooling pavement is optimal. These limit the further improvement of the pavement cooling effect. In this study, the relationship between the design objective (minimum average temperature of upper layer) and design variable (thermal conductivity of pavement) of cooling pavement was built by numerical simulation, and the cooling pavement with the best cooling effect was obtained by topological optimization technology. The influence of the initial value and distribution of the thermal conductivity on the average temperature were explored during the design process. The thermal effect analysis and thermal resistance were used to determine cooling mechanism of optimized cooling pavement. The topology optimization results demonstrated that the minimum average temperature could be obtained when the initial value of the thermal conductivity gradually increased with the increase in pavement depth. The optimized cooling pavement showed good cooling effect at night. The thermal effect analysis results showed that the design of optimized cooling pavement reduced the net heat absorption and the heat transfer efficiency of the pavement, and increased the thermal resistance inside the pavement, thus achieving the pavement cooling. Compared with the ordinary asphalt pavement, the pavement surface temperature and interior temperature could be reduced by up to 9.18 °C and 13.29 °C, respectively. The maximum heat absorption, dissipation and net heat flux absorption of the optimized cooling pavement were decreased by 65.59 %, 63.87 % and 59.40 %, respectively. The reduction of the net heat flux absorption and heat release in the optimized cooling pavement are conducive to mitigating the high temperature rutting and the heat island effect at night, respectively. Finally, the indoor irradiation test was carried out to evaluate the cooling effect of optimized model. The temperatures of optimized group at 7 cm and surface were 5.29 °C and 2.5 °C lower than those of control group, respectively. The effectiveness of the topology optimization design for cooling pavement were verified.

Effect of Radiation on Casson Hybrid Nano-fluid Flow over an Inclined Surface Using Blasius Rayleigh-Stokes Variable: Application in Solar Aircraft

Solar energy is the most important heat source from the sun, with photovoltaic cells, solar power plates, photovoltaic lights, and solar pumping water being widely used. This study looks at solar energy analysis and a method for increasing the efficacy of solar aircraft by combining solar and nano-technological energy. To enrich the research on solar aircraft wings, the study is built on the investigation of heat transfer by employing a hybrid nano-fluid past inside the parabolic trough solar collector (PTSC). The thermal source is referred to as the solar radiative flow. The heat transfer efficiency of the wings was validated for different qualities such as porous medium, viscous dissipation, play heating, and thermal energy flow. The modelled energy and momentum equations were controlled by utilizing the Galerkin-weighted residual method (GWRM). This study used two types of nano-solid particles, copper (Cu) and zirconium dioxide (ZrO2), in ethylene glycol (EG) as the standard fluid. Various control parameters for velocity, temperature outlines, frictional factor, and Nusselt number were explained and shown in figures and tables. Also, analyses reveal that the thermal profile reduces with an increase in variable thermal conductivity parameters. This study will be of considerable economic value to marine engineers, mechanical engineers, physicists, chemical engineers, and others since its application will help them improve their operations. The findings revealed that the magnetic term is positively impacted by the Cu-ZrO2/EG hybrid nanofluid's thermal distribution.

Variable thermal conductivity in context of Green‐Naghdi theory of thermo‐microstretch solids

AbstractThe present work aims to study the influence of variable thermal conductivity in generalized thermoelastic solid with microstretch within the framework of the Green‐Naghdi theory. The analytical methodology is adopted for obtaining exact expressions of displacement components, stresses, couple stresses, micro stress distribution and temperature distribution. The effect of variable thermal conductivity is illustrated graphically in two and three dimensions for the above physical quantities by taking different values of thermal conductivity.

Nonlinear-Mixed Convection Flow with Variable Thermal Conductivity Impacted by Asymmetric/Symmetric Heating/Cooling Conditions

Nonlinear-Mixed Convection Flow with Variable Thermal Conductivity Impacted by Asymmetric/Symmetric Heating/Cooling Conditions

Reflection of plane waves in a nonlocal double poroelastic semiconducting medium with variable thermal conductivity and mass diffusivity

AbstractThe present investigation is concerned with the reflection phenomena of plane waves in a homogeneous, isotropic, nonlocal, photothermoelastic semiconducting medium under the effects of double porosity, variable thermal conductivity and mass diffusivity. The formulation is applied to generalized thermoelasticity based on the Lord–Shulman theory. The problem is solved analytically and it is shown that there exist six coupled longitudinal waves in addition to an independent transverse wave in the considered medium. The amplitude ratios and energy ratios of these reflected waves have been calculated analytically and computed numerically for a specific material with the help of MATLAB programming. The numerical results of reflection coefficients are presented graphically to show the effects of double porosity, photothermal transport process, nonlocality, variable thermal conductivity and mass diffusivity. It is verified that during reflection phenomena, the sum of energy ratios is equal to unity at each angle of incidence and there is no energy dissipation at the boundary surface. Some special cases of interest have also been inferred from the current investigation.

Nanofluid dissipative stagnation point flow of Casson type over a stretched sheet influenced by a variable surface heat flux and magnetic field

The studied problem focuses on the flow of Casson nanofluid induced by a stretched surface in the presence of a magnetic field and exposed to variable surface heat flux, with an emphasis on enhancing thermal efficiency. This research aims to highlight the flow of Casson nanofluid at the stagnation point on a stretching sheet, taking into account the influence of heat generation and variable thermal conductivity. The fluid being examined exhibits a steady-state two-dimensional flow. The formulation of the model involves deriving partial differential equations, which are later converted into ordinary differential equations using similarity transformations. This particular research stands out by introducing an innovative mathematical model for Casson nanofluid, taking into account variable surface heat flux and covering several implications that have not been explored in current literature. We utilize the shooting method to compute numerical solutions for the formulated equations. Graphical representations are used to illustrate the numerical results for velocity, concentration, and temperature distribution. Furthermore, tabulated findings encompass the Sherwood number, skin friction coefficient, and local Nusselt number. A comparison with a previous study from the literature was conducted, demonstrating a robust agreement between our results and theirs. Several compelling findings indicate that the local Nusselt number rises as the velocity ratio parameter, suction parameter, thermal conductivity parameter, and heat flux exponent increase. Conversely, the Casson parameter, magnetic number, heat generation parameter, and thermophoresis parameter are observed to lower the local Nusselt number.

Impact of Variable Thermal Conductivity and Viscosity on Powell-Eyring Fluid in the Presence Of Thermal Radiation through a Porous Medium

This work uses a mathematical model to investigate the impact of physical factors on the non-isothermal flow of Powell-Eyring fluid with variations in thermal conductivity and viscosity through a porous medium. The governing equations defining the flow, mass, and energy transfer issue are converted into nonlinear ordinary differential equations via selected transformation variables, and the resultant problem is numerically solved using the Galerkin weighted residual technique. This approach is implemented with Maple 18 program. The examination of the findings revealed that the radiation parameter, variations of thermal conductivity, and viscosity characteristics had a substantial impact on the flow system. This presentation includes a visual picture and explanation of how different physical characteristics affect the flow system.

Irreversibility scrutiny of SWCNT and MWCNT nanofluid convective flow using Darcy-Forchheimer rule in an upright microchannel with variable thermal conductivity and Brownian motion and thermophoresis

Carbon nanotubes are used to attain greater thermal transfer rates in a various of enormous applications in the field of microsystem, emission, conductive polymers, fibers, and fabrics. Hence the aim of this article is to explore the entropy generation analysis of single wall carbon nanotubes and multiwall carbon nanotubes flow in an upright micro channel with variable thermal conductivity. The exponential heat source and non-linear thermal radiation were considered. The micro channel retains the no slip and convective boundary conditions. The Buongiorno model was used in this study, which emphasizes the light on Brownian motion and thermophoresis phenomena that occur during the fluid flow. Darcy- Forchheimer model is also taken into account. The governing equation numerically solved by employing Runge-Kutta Fehlberg's fourth-fifth order. The repercussion of this study upholds that the inflates of variable thermal conductivity magnify the thermal field. Entropy production inflates at right wall of the channel with augmented Brownian parameter and exhibits exactly opposite behavior at left wall of the channel. One of the important tasks of the investigation was to compare SWCNT and MWCNT. The findings confirmed that multiwall carbon nanotubes exhibit more magnificent heat and mass transfer than single wall carbon nanotubes.

Utilization of variable thermal conductivity and diffusion coefficient on non-Newtonian Prandtl model with modified heat and mass fluxes

PurposeThis study aims to analyze the Prandtl fluid flow in the presence of better mass diffusion and heat conduction models. By taking into account a linearly bidirectional stretchable sheet, flow is produced. Heat generation effect, thermal radiation, variable thermal conductivity, variable diffusion coefficient and Cattaneo–Christov double diffusion models are used to evaluate thermal and concentration diffusions.Design/methodology/approachThe governing partial differential equations (PDEs) have been made simpler using a boundary layer method. Strong nonlinear ordinary differential equations (ODEs) relate to appropriate non-dimensional similarity variables. The optimal homotopy analysis technique is used to develop solution.FindingsGraphs analyze the impact of many relevant factors on temperature and concentration. The physical parameters, such as mass and heat transfer rates at the wall and surface drag coefficients, are also displayed and explained.Originality/valueThe reported work discusses the contribution of generalized flux models to note their impact on heat and mass transport.