Parameters Thermal Diffusivity Research Articles

Consequences of Thermal Diffusion and Chemical Reaction on Mixed Convection MHD Casson Fluid through Porous Media with Inclined Plates

In this present article, we analyzed the effects of Thermal diffusion and chemical reaction on nonlinear mixed convection MHD flow of viscous, incompressible and electrically conducting fluid past an inclined porous channel under the influence of thermal radiation and chemical reaction. The transformed conservation equations are solved analytically subject to physically appropriate boundary conditions by using two term perturbation technique. The numerical values of fluid velocity, fluid temperature and species concentration are displayed graphically whereas those of skin friction coefficient, rate of heat transfer and rate of mass transfer at the plate are presented in tabular form for various values of pertinent flow parameters. It is observed that the velocity is decreased with increasing magnetic field parameter. The resultant velocity and concentration has enhances with increasing thermal diffusion parameters. The study is relevant to chemical materials processing applications.

Effects of Diffusion Thermo and Thermal Diffusion on an Unsteady MHD Dissipative Squeezing Flow of Casson Fluid Over Horizontal Channel in the Presence of Radiation and Chemical Reaction

This study analyses the impacts of Diffusion thermo and thermal diffusion on the magneto hydrodynamic (MHD) squeezing Casson fluid flow through a porous medium under the slip condition with viscous dissipation the presence of chemical reaction and thermal radiation. The flow is produced when two plates are compressed together in close proximity to one another. Using similarity variables may successfully convert partial differential equations (PDEs) to ordinary differential equations (ODEs). The shooting technique was used to perform the numerical analysis, which entailed solving the competent governing equations with dominating parameters for a thin liquid layer. This was done to determine the results of the study. It is essential to evaluate the numerical results in light of previously conducted research to validate the current answers. According to the results, an increase in the distance between the two plates leads to a rise in the velocity and the wall shear stress. The velocity diminishes due to an increase in the Hartmann and Casson parameters, whereas the reverse behaviour has been observed in the case of temperature and concentration. The opposite behaviour has been observed in temperature with increasing Diffusion thermo and thermal diffusion parameters.

A Comparative Study of Newtonian and Non-Newtonian Nanofluids with Variable Thermal Conductivity Over a 3-D Stretching Surface

This study presents a comprehensive numerical and statistical analysis of the flow, heat/mass transfer management of Newtonian and non-Newtonian nanofluid over a bidirectional Darcy-Forchheimer stretching sheet. The external effects of MHD, Joule heating, thermal radiation, heat generation/absorption, Brownian motion, thermal diffusion and chemical reaction are taken into account. It is presumed that the thermal conductivity of fluid varies linearly with temperature. The non-linear coupled P.D.Es are converted into nonlinear coupled O.D.Es using similarity transformation. These equations are solved using MATLAB by implementing four-stage Lobatto IIIa formula and the outcomes of numerous flow parameters are presented graphically. In addition to numerical investigations, a comprehensive statistical analysis is performed using R-software to evaluate the sensitivity of key input parameters towards variable thermal conductivity. The values of local wall friction, local wall heat flux, and wall mass flux for various parameters are tabulated. The study reveals that the heat transmission is significant for dilatant fluids (156.8%) when compared to the pseudoplastic fluids (113.8%). Enriching the values of the Brownian motion parameter suppresses the molecular diffusion while a contrary nature is observed for the thermal diffusion parameter. Further, the mass transfer coefficient shows a very strong negative correlation with variable thermal conductivity parameter for Shear thinning fluids, whereas for Newtonian and Shear thickening fluids it shows a very strong positive correlation.

Physics-informed ConvNet: Learning physical field from a shallow neural network

We introduce a novel methodology for solving nonlinear partial differential equation (PDE) on regular or irregular domains using physics-informed ConvNet, which we call the PICN. The network structure consists of three parts: 1) a convolutional neural network for physical field generation, 2) a pre-trained convolutional layer corresponding to the finite-difference filters to estimate differential fields of the generated physical field, and 3) an interpolation network for loss analysis in irregular geometry domains. From a CNN perspective, the physical field is generated by a deconvolution layer and a convolution layer. Unlike the standard Physics-informed Neural Network (PINN) approach, the convolutions corresponding to the finite-difference filters estimate the spatial gradients forming the physical operator and then construct the PDE residual in a PINN-like loss function. The total loss function involving boundary conditions and the physical constraints in irregular geometry domains can be calculated from an efficient linear interpolation network. The theoretical analysis of PICN convergence is performed on a simplified case for solving a one-dimensional physical field, and several examples of nonlinear PDE of solutions with multifrequency characteristics are executed. The theory and examples confirm the effective learning capability of PICN for the physical field solution with high-frequency components, compared to the standard PINN. A series of numerical cases are performed to validate the current PICN, including the solving (and estimation) of nonlinear physical operator equations and recovering physical information from noisy observations. First, the ability of PICN to solve nonlinear PDE has been verified by executing three nonlinear problems including ODE with sine nonlinearity, PDE involving nonlinear sine-square operators, and Schrödinger equation. The proposed PICN has been assessed by solving some nonlinear PDE on irregular domains such as star-shaped domain, bird-like domain, and starfish domain. Moreover, PICN is applied to identify the thermal diffusivity parameters in an anisotropic heat transfer problem from noisy data, and a denoising display of the temperature field from strong noisy data with standard deviations ranging from 0.1 to 0.4. The numerical results demonstrate the high accuracy approximation and fast convergence performance of PICN. The potential advantage in approximating complex physical field with multi-frequency components indicates that PICN may become an alternative efficient neural network solver in physics-informed machine learning. This paper is adapted from the work originally posted on arXiv.com by the same authors (arXiv:2201.10967, Jan 26, 2022). The data and code accompanying this paper are publicly available at https://github.com/zengzhi2015/PICN.

Analysis of MHD Richardson Flow Past An Exponentially Stretched Infinite Plate with Suction and Cross-Diffusion Effects

The present paper investigate the effects of magnetic field (MHD), Richardson and suction on an exponentially expanded infinite plate by studying the convective heat and mass transfer of a non-Newtonian incompressible viscous and electrically conducting fluid. Cross-diffusion impacts are also taken into consideration. The governing partial differential equations (PDEs) are transformed into ordinary differential equations through the application of well-posed similarity transformation variables (STVs). Thus, the transformed dimensionless equations are solved analytically by integrating factor approach and the resulting solutions are simulated with an efficient stability numerical algorithm known as Mathematica. The results are displayed in tabular and graphical forms while the effects of various parameters on the velocity, temperature, concentration, skin–friction coefficient, Nusselt and Sherwood numbers are discussed in details. It was found that velocity falls when magnetic field and suction parameters increase. Also, the temperature and nanoparticle concentration decreases as suction number rises but are enhanced as diffusion-thermo and thermal-diffusivity parameters rise. An increase in Richardson and Prandtl numbers leads to a decrease in skin-friction and upsurge in the rate of heat transportation. The results of this study can be used to advance the design, operation, and performance of various systems encountered in industrial and scientific applications.

A Nanofluid Boundary Layer Flow Over a Stretching Body in the Presence of Porous Medium

A numerical approach is presented to investigate fluid concentration, velocity and temperature like flow characteristics for the nano fluid boundary layer flow over a stretching sheet in the presence porous medium. The equations of ordinary differentiation are obtained from the governing equations of partial differentiation using similarity transformations. The reduced equations of ordinary differentiation have solved numerically using both Spectral Collocation Method and Shooting Technique which involves R-K Fehlberg and N-R method. The computation results are drawn for dimensionless parameters like Lewis number, Brownian motion parameter, thermophoresis parameter, thermal diffusivity, Prandtl number and porous parameter on the fluid flow, concentration and temperature characteristics. The computation results dictates that the enhancement of the porous parameter diminishes the flow whereas temperature and concentration enhance in this region. Due to nanofluid there is a rise in thermal conductivity of fluid flow. The polymer drawing and extrusion, casting, hot rolling, metal cooling and lot of engineering processes made use of the computational results and information understood very well.

Application of Heat and Mass Transfer to Convective Flow of Casson Fluids in a Microchannel with Caputo–Fabrizio Derivative Approach

It has been demonstrated that fractional derivatives exhibit a range of solutions that are helpful in the engineering, medical, and manufacturing sciences. Particularly in analytical research, investigations on using fractional derivatives in fluid flow are still in their infancy. Therefore, it is still being determined whether fractional derivatives may be represented geometrically in the mechanics of the flow of fluids. However, theoretical research will be helpful in supporting upcoming experimental research. Therefore, the aim of this study is to showcase an application of Caputo–Fabrizio toward the Casson fluid flowing in an unsteady boundary layer. Mass diffusion and heat radiation are taken into account while analyzing the PDEs that governed the problem. Dimensionless governing equations are formed from the fractional PDEs by utilizing the necessary dimensionless variables. Once the equations have been transformed into linear ODEs, the solution may then be found by applying the Laplace transform technique. Inverting Laplace transforms by Stehfest’s and Tzou’s Algorithm is then used to retrieve the original variables and the solutions as concentration, temperature, and velocity fields. Graphical illustrations sketched using the Mathcad program are used to show how physical parameters affect temperature, velocity, and concentration profiles. Findings show that the velocity, temperature, and concentration profiles have been improved by thermal radiation, mass diffusion, and fractional parameters. The fractional derivative is a more general derivative due to its nonlocal and flexible nature the flow model that is formulated by applying the fractional derivative is suitable to address the memory effect. The present fractionalized results of velocity, concentration, and temperature are more general and applicable to the wide range of orders of fractional derivatives.

Effect of Magnetic field on Unsteady Mixed convection Micropolar Nanofluid flow in the Presence of Non-Uniform Heat Source/Sink.

: The idea of the current investigation is to study the two-dimensional unsteady mixed convection MHD flow of a micro-polar nanofluid with non-uniform heat source/sink. Effects of radiation, reaction, thermo-diffusion, and viscous dissipation are considerednanoparticles are suspended in water base fluid. The governing non-linear system of PDEs is transformed into a system of ODEs using the similarity transformation and HAM is employed for obtaining solutions. Effects of different physical parameter on momentum, microrotation, energy, and concentration profiles are discussed through graphs. From graphical results, it is concluded that the unsteady parameter and magnetic parameter tend to improve the motion of the fluid. It is also seen that microrotation is raised in the shrinking sheet and reduced in the stretching sheet with the increase in the unsteady parameter. The mass transfer process improved with thermal diffusion parameter while delayed with chemical reaction.

Interactions between two adjacent convection rolls in turbulent Rayleigh-Bénard convection

Neighboring convection rolls are experimentally found to be stable in either counter-rotating or co-rotating states, with stochastic switching between the two states. These states are quantitatively described by analytic solutions of a low-dimensional stochastic model in which turbulent thermal diffusion between the rolls provides the forcing that stabilizes both states, using the same turbulent thermal diffusivity parameter that characterizes heat transport. This is presented within a generalized model framework that can account for the geometry of the convection cells and other forces.

Variable thermophysical properties of magnetohydrodynamic cross fluid model with effect of energy dissipation and chemical reaction

In this study, magnetohydrodynamic cross fluid model is used to formulate the 2D boundary layer equations of fluid moving on the parabolic surface. The surface is assumed to be in vertical shape due to the convection. The underlying effects of viscous dissipation and chemical reaction are modeled to observe the transportation of heat and mass rate. To understand fluid behavior, the thermophysical properties are considered as variable because they have huge influence in food processing, viscometers, lubricants and various industrial works. The assumed geometry of fluid flows is similar in shape of bullet, submarine, aircraft and car’s bonnet, namely paraboloid surface. The modeled equations of cross fluid with mentioned effects are obtained in form of PDEs and then converted these equations in form of ODEs by assuming set of scaling transformations. For the sake of numerical and graphical outcomes, the resulting equations are solved numerically on Matlab software via BVP4c method. Results achieved across velocity indicate that the decay happens by numerous values of Weissenberg number, power law index, viscosity parameter and Hartmann number. The temperature and concentration fields attained increasing influence by thermal conductivity coefficient, Eckert number and thermal diffusivity parameter.

Entropy Analysis on Magneto-Convective and Chemically Reactive Nanofluids Flow Over a Stretching Cylinder in the Presence of Variable Thermal Conductivity and Variable Diffusivity

The current paper is on the boundary layer flow of a magnetohydrodynamic nanofluids (Cu, Al2O3 nanoparticles with base fluid water) flow over a linearly stretching cylinder. We have analyzed the entropy generation with heat and mass transfer in mixed convection, thermal radiation, viscous dissipation, variable thermal conductivity, variable mass diffusivity, and binary chemical reaction with activation energy. Convective boundary conditions are also considered here. No such attempt is yet made by the researchers on hybridization and entropy optimization model by considering variable thermal conductivity and variable mass diffusivity with binary chemical reaction with convective boundary conditions induced by a stretching cylinder. The efficient implicit Runge-Kutta-Fehlberg method with shooting technique is used for numerical solutions to the transformed-converted non-linear system of equations. The study is motivated by analyzing the effects on the nanofluid velocity, skin friction coefficient, temperature distribution, Nusselt number, nanoparticles concentration, and Sherwood number inside the boundary layer. The impact of solid volume fraction, chemical reaction, and activation energy with entropy generation is the key findings of the current investigation. Variable thermal conductivity and variable diffusivity parameters hike temperature and concentration profile, respectively. Entropy and Bejan number are increasing functions for curvature parameters.

Processing to pass unsteady MHD flow of a second-grade fluid through a porous medium in the presence of radiation absorption exhibits Diffusion thermo, hall and ion slip effects

ABSTRACT ‘This research aims to look at the consequences of diffusion thermo, Hall, ion slip, and radiation absorption on the unsteady MHD turbulent rotational flow of second-grade fluid through porous materials while also regarding the outcomes of the chemical retort and heat absorption. When the ratio between the number of collisions between fluid electrons in a cyclotron and the number of collisions between electrons and atoms is large, Hall effects (the Hall parameter) become important. The regular perturbation approach investigates the outlines of velocity segments, temperature dispersion, and concentration. The statistics for shear stress, the Nusselt numeral, and the Sherwood factor are written down on the panel. Graphs show how changes in different physical parameters cause changes in a fluid’s speed, temperature, and concentration patterns. In the end, it can be said that the primary and secondary velocities speed up significantly as the Hall and ion-slip parameters get bigger. This effect was also seen in the shearing stress’s axial and transverse components. The increasing importance of the thermal diffusion parameter increases both the initial and secondary velocities’.

Thermal Diffusivity of Concrete Samples Assessment Using a Solar Simulator.

The thermal properties of pavement layers made of concrete with varying bulk densities are a particularly interesting topic in the context of development road technologies. If a hybrid layer system is used as a starting point, with thin asphalt layers (from 1 cm to 4 cm) laid on top of a foam concrete layer, thermal properties begin to play a crucial role. The main research problem was to create a test method enabling the assessment of the influence of solar heating on the thermal parameters of the building material, especially cement concrete. For this reason, this paper is concerned specifically with the assessment of a new methodology for testing and calculating the value of the thermal diffusivity coefficient of samples made of concrete varying bulk densities. In this case, using the proprietary concept the authors built a solar simulator using a multi-source lighting system. The analysis of the results of laboratory tests and numerical analyses allowed the authors to observe that there is a strong correlation between the bulk density of samples heated and the thermal diffusivity parameter, which appears in the unidirectional heat transfer equation. The strength of this relationship has been expressed with the coefficient of determination and amounts to 99%. The calculated values of the coefficient of thermal diffusivity for samples made of foam concrete range from 0.16×10-6m2s to 0.52×10-6m2s and are lower (from 2.5 to 8 times) than the value determined for samples made of typical cement concrete.

Fluid properties of an unsteady MHD free stream flow over a stretching sheet in presence of radiation

AbstractVariable fluid properties with thermal radiation in an unsteady magnetohydrodynamics free stream incompressible flow over a stretching sheet has been considered. The thermal diffusivity and viscosity of the fluid varies linearly with temperature. The governing partial differential equations are moulded to ordinary differential equations using time‐dependent similarity variables and the stream function. RKF technique with shooting method has been implement to find the solution numerically. In the current analysis the impact of unsteadiness, magnetic field, radiative parameter, variable fluid viscosity and thermal diffusivity parameter on heat and flow behavior with the free stream parameter have been studied. Transition point observed in the velocity profiles with an change in unsteadiness parameter and the effect of magnetic field is reduced in the presence of free stram velocity. The velocity and the temperature gradient are computed on the surface and their outcomes with different parameters have been analyzed in the results shown graphically and in tabular form.

On a question of non-constant thermal diffusivity of soils

The general heat conductivity equation includes time- and depth-dependent soil properties (soil heat capacity and thermal conductivity). The simplified form of the heat conductivity equation contains only the soil thermal diffusivity parameter. Numerical solutions of the general and simplified equations were compared to quantify the possibility of equation reduction. Two test runs for soils with different compositions were done. The thermal regime for both peat soil and dark chestnut soil does not change significantly after using a simplified heat equation according to model estimations. The maximal soil temperature discrepancy was about 0.5 °C for peat soil and 2.2-3.3 °C for dark chestnut soil, which results in 4-6% error in methane efflux estimations.

Numerical Analysis of Nanofluid on Stagnation Flow Past a Stretching Sheet in the Presence of Magnetohydrodynamics (MHD), Convective Heating and Double Diffusive Effects

The article provides a specific section of the model, which incorporates Soret-Dufour and convective heating effects, to emphasise the intricacies of the mathematical model for Nanofluid on stagnation flow towards a stretched sheet in the presence of a magnetic field. The revised governing equations in the form of linear ordinary differential equations were solved utilising shooting methods and a Runge-Kutta-Felhberg-integration technique. The plot used to explain the change in velocity, temperature, and concentration was based on a storey in which different characteristics appeared first on the graphs. Tables may also be used to analyse skin friction and the Nusselt and Sherwood values, both of which are essential in engineering. Following that, we will look at how the new method compares to previously known approaches in a few different situations. The main findings of this investigation are: the velocity profiles are increasing with increasing values of velocity ratio parameter and the reverse effect is observed in presence of Magnetic field parameter. The temperature profiles are rising with increasing the numerical values of Thermophoresis, Brownian motion, Diffusion thermo, Biot number parameters and the temperature profiles are decreasing with increasing values of Prandtl number. Also, the concentration profiles are rising with the increasing values of Thermophoresis, Thermal diffusion parameters and reverse effect is observed in case of Brownian motion parameter.

Strong Resonant Light Absorption Band on Sub-Oxidized Metal Titanium Nanostructures

Nanopatterned or roughed metallic structures have received considerable attention due to the effective light absorption capability via optical effects of light confinement or photonic excitation of surface plasmon polaritons.1, 2, 3, 4, 5 However, individual metallic structures have limited light capture. To augment the solar light utilization, coupling of different absorption modes was developed within three-dimensional architectures.6, 7 Among these, the absorbers using dielectric-nanostructures interactions showed effective light harvesting, which exhibited enhanced photocatalysis and water splitting activities. Here, we present a solid visible light absorber made of proper sub-oxidation of metal Ti through a facial approach.First, surface nanostructures were prepared using a chemical etching process on cleaned metal Ti foils. Then, a thermal sub-oxidation was employed to diffuse oxygen into the sub-surface region of the metal Ti, forming titanium-oxides nanocomposites. The titanium-oxides are composed of titanium suboxides on the sub-surface of metal Ti nanostructures. The surface sharpness of nanostructures was checked by atomic force microscopy (AFM) and scanning electron microscopy (SEM) (Figure 1), showing favorable surface nanostructures. The nanostructures of quasi-prisms with sharp nano-curvatures allow light concentration in a more vigorous intensity. The affluent sharp edges of nanostructures could behave as “hot spots”. In Figure 2, the UV-vis absorption spectra of the as-prepared specimen disclose a strong resonant light absorption in the visible region with an almost four times enhancement. The resonant absorption band position and intensity are adjustable by controlling thermal diffusion parameters and surface structures.Our observation is quite distinctive from the absorption spectra of single phases, anatase or rutile phase TiO2, and the cases of mixed-phase TiO2-x nanoparticles. To our best knowledge, this is the first demonstration of uniquely strong resonant visible absorption band by sub-oxidized metal Ti nanostructures. The absorber is of particular interest in a wide range of extensive photo-responsive applications, such as optoelectronic devices, photovoltaics, and photocatalysis. The approach represents a new pathway to enable photonic absorption within nanostructures, not only for metal Ti but also for other related metallic structures. Acknowledgments: The authors acknowledge the research grants from EEA (European Economic Area)-Norway-Romania project# GRAFTID, RO-NO-2019-0616, EEA-Poland-NOR/POLNORCCS/PhotoRed/0007/2019-00, and the Research Council of Norway projects #314012 and #245963/F50.References Montoya JH, Seitz LC, Chakthranont P, Vojvodic A, Jaramillo TF, Norskov JK. Materials for solar fuels and chemicals. Nat Mater 16, 70-81 (2016).Chen X, Liu L, Huang F. Black titanium dioxide (TiO2) nanomaterials. Chem Soc Rev 44, 1861-1885 (2015).Robatjazi H, Zhao H, Swearer DF, Hogan NJ, Zhou L, Alabastri A, McClain MJ, Nordlander P, Halas NJ. Plasmon-induced selective carbon dioxide conversion on earth-abundant aluminum-cuprous oxide antenna-reactor nanoparticles. Nat Commun 8, 27 (2017).Atwater HA, Polman A. Plasmonics for improved photovoltaic devices. Nat Mater 9, 205-213 (2010).Maier SA, Brongersma ML, Kik PG, Meltzer S, Requicha AAG, Atwater HA. Plasmonics-a route to nanoscale optical devices. Adv Mater 13, 1501-1505 (2001).Shi X, Ueno K, Oshikiri T, Sun Q, Sasaki K, Misawa H. Enhanced water splitting under modal strong coupling conditions. Nat Nanotechnol 13, 953-958 (2018).Choi D, Shin CK, Yoon D, Chung DS, Jin YW, Lee LP. Plasmonic optical interference. Nano Lett 14, 3374-3381 (2014). Figure 1

Darcy–Forchheimer Relation Influence on MHD Dissipative Third-Grade Fluid Flow and Heat Transfer in Porous Medium with Joule Heating Effects: A Numerical Approach

The current investigations are carried out to study the influence of the Darcy–Forchheimer relation on third-grade fluid flow and heat transfer over an angled exponentially stretching sheet embedded in a porous medium. In the current study, the applied magnetic field, Joule heating, thermaldiffusion, viscous dissipation, and diffusion-thermo effects are incorporated. The proposed model in terms of partial differential equations is transformed into ordinary differential equations using suitable similarity transformation. The reduced model is then solved numerically with the help of MATLAB built-in function bvp4c.The numerical solutions for velocity profile, temperature profile, and mass concentration under the effects of pertinent parameters involved in the model are determined and portrayed in graphical form. The graphical effects of the skin friction coefficient, the Nusselt number, and the Sherwood number are also shown. From the displayed results, we conclude that when the Joule heating parameter is enlarged, the velocity and the temperature of the fluid are increased. We observed that while enhancing the viscous dissipation parameter (Eckert number) the fluid’s velocity and temperature increase but decreases the mass concentration. By increasing the values of the thermal-diffusion parameter, the velocity distribution, the temperature field, and the mass concentration increase. When the diffusion–thermo parameter rises, the velocity field and the temperature distribution increase, and the reverse scenario is seen in the mass concentration. The results of the current study are compared with already published results, and a good agreement is noted to validate the current study.

Convective Heat and Mass Transfer in Third-Grade Fluid with Darcy–Forchheimer Relation in the Presence of Thermal-Diffusion and Diffusion-Thermo Effects over an Exponentially Inclined Stretching Sheet Surrounded by a Porous Medium: A CFD Study

The current study aims to investigate the thermal-diffusion and diffusion-thermo effects on heat and mass transfer in third-grade fluid with Darcy–Forchheimer relation impact over an exponentially inclined stretching sheet embedded in a porous medium. The proposed mechanism in terms non-linear and coupled partial differential equations is reduced to set of ordinary differential equations by employing an appropriate similarity variable formulation. The reduced form of equations is solved by using the MATLAB built-in numerical solver bvp4c. The numerical results for unknown physical properties such as velocity profile, temperature field, and mass concentration along with their gradients such as the skin friction, the rate of heat transfer, and the rate of mass transfer at angle of inclination α=π/6 are obtained under the impact of material parameters that appear in the flow model. The solutions are displayed in forms of graphs as well as tables and are discussed with physical reasoning. From the demonstration of the graphical results, it is inferred that thermal-diffusion parameter Sr velocity, temperature, and concentration profiles are augmented. For the increasing magnitude of the diffusion-thermo parameter Df the fluid velocity and fluid temperature rise but the opposite trend in mass concentration is noted. The current results are compared with the available results in the existing literature, and there is good agreement between them that shows the validation of the present study.

Equivalent thermal diffusivity of natural and recycled aggregate concrete at temperature up to 350 ⁰C

The paper presents the evolution of equivalent thermal diffusivity with temperature of concretes with natural coarse aggregates and recycled concrete aggregates. Thermal diffusivity was evaluated based on the temperature measurements made on cylindrical samples using so-called "inverse technique". Thermal diffusivity parameter was estimated for concretes manufactured with different replacement ratios of natural by recycled coarse aggregate (0, 50 and 100 %) produced by crushing the worn-out concrete pavement that was dismounted after exploitation period. The diffusivity of concrete was tested up to 350 ◦C. The progressive decrease of thermal diffusivity was observed, and the lowest D values were obtained for higher recycled concrete aggregates content. The results were presented against the background of other authors results and referred to the D values proposed in EUROCODE 2.