Variable Thermophysical Characteristics Research Articles

Chemically reactive flow beyond constant thermophysical characteristics

Hydromagnetic chemically reactive flow over stretching wall is discussed. Formulation is based upon consideration of Reiner-Rivlin constitutive relation. Variable thermophysical characteristics are under consideration. Radiation, heat generation and dissipation impacts exist in thermal relation. Concentration expression subject to reaction with first order is considered. Modeling with entropy optimization is made. Appropriate transformations lead to relevant differential systems. Numerical study by ND-solve is carried out. Quantities under interest are graphically analyzed. An opposite behavior detected for magnetic parameter on entropy rate and velocity. Velocity field versus magnetic field parameter decreases whereas reverse impact witnessed for variable viscosity parameter. An enhancement in thermal distribution and entropy detected for radiation. Thermal distribution enhancement is observed for generation of heat and thermal conductivity variables. Chemical reaction for concentration has decaying impact. Results of Schmidt number for concentration are similar to that of chemical reaction. Brinkman number leads to entropy rate improvement. Entropy rate upsurges against variable viscosity and mass diffusivity parameters.

Natural convection with variable fluid properties of couple stress fluid with Cattaneo-Christov model and enthalpy process

The geometry under consideration for this flow problem, namely paraboloid surface is similar to aircraft and car bonnet, bullet shape, front shape of submarine, rockets and these types of are useful in manufacturing of formula F1 cars and airplanes. The flow of fluid over paraboloid surface has several applications in space science, industries, mechanical works and architecture. The aim of this study is to explore the Cattaneo-Christov heat and mass flux model in steady 2D couple stress fluid flow with variable thermo-physical characteristics near the parabolic surface. The effects of enthalpy and activation energy are also taken into consideration. The stretching in the layers of fluid is assumed at the surface of body. The problem is amended by using the law of conservation of momentum, energy and mass transfer. The non-linear governing partial differential equations are converted into ordinary differential equations by using self-similar form with similarity transformation. The resulting ODE's are numerically solved by bvp4c method. The conclusion indicates that the fluid moves quickly due to higher inputs of couples stress parameter and buoyancy parameter while the viscosity coefficient creates restriction in the fluid motion. The transference analysis of temperature and concentration enhances for higher impacts of thermal conduction and mass diffusivity coefficient. The thermal concentration relaxation parameters are the source of decline in the concentration and temperature of fluid. The heat transmission rate is maximum and mass transfer is minimum due to raising values of Dramkholer number. The impression of all parameters on different fields is listed in discussion section.

A Blasius boundary layer study for liquids and gasses with variable thermo-physical characteristics and radiative heat flux

A numerical study is presented to discuss the temperature dependent viscosity and the thermo-physical properties near a heated flat surface. Temperature dependent viscosity for liquids show decrease in mean velocity profile and enhancement in mean temperature profile, whereas for gasses, it shows reverse effect. Moreover, the thermo-physical properties are treated as variable as they affect the flow phenomena. The basic flow can be modeled in terms of the scaling transformation for the large Reynolds number. Using similarity solutions, the leading order equations are converted into a set of ordinary differential equations which have been solved by fifth order Runga-Kutta integration method and Newton Raphson method. All of the obtained results are investigated for the base flow, concentration and temperature profiles and physical interpretation has been provided in the form figures and tables. The impact of viscosity for gases show an increase behavior in velocity profile but for liquids opposite impact is noticed. The variable conductivity and mass diffusivity parameters rise the temperature and concentration profiles. The temperature profile increases for increasing values of radiation parameter. Comparison has been made with past literature and the results show good agreement.

Comparative analysis of Yamada-Ota and Xue models for hybrid nanofluid flow amid two concentric spinning disks with variable thermophysical characteristics

The surprising features of carbon nanotubes such as featherweight, mechanical permanence, outstanding electrical and thermal conductivities, and physicochemical aptness make them impeccable material for electrochemical contraptions. Having such astounding physiognomies in mind our purpose in this study is to make a comparison of the performance of Yamada-Ota and Xue models for a nanofluid flow amidst two rotating disks in a spongy medium. The majority of nanofluid flow models in the available literature considered constant thermal conductivity and viscosity. Nevertheless, here the whole scenario is deliberated with variable characteristics. The novelty of the envisaged mathematical model is enriched considering the chemical species of both types amalgamated with the entropy generation minimization analysis keeping in view the liquid and gaseous states. The numerical solution of the governing system is obtained by using the bvp4c function of the MATLAB software. The graphical outcomes of arising parameters solid nanoparticles volume fraction (0.005≤φ2≤0.06), variable viscosity (−5≤θr≤2.5), thermal conductivity (1.0≤ε≤2.0), surface catalyzed parameter (0.0≤Kvs≤0.3), homogeneous reaction parameter (0.3≤Kc≤0.7), heterogeneous reaction parameter (0.3≤Ks≤0.7), Brinkman number (0.2≤Br≤0.6), and temperature difference parameter (0.5≤α1≤1.2), versus associated profiles are analyzed logically. It is examined that for positive values of variable viscosity parameter (gases) the axial velocity declines, nevertheless, an increase in velocity distribution is seen for negative values of variable viscosity parameter (liquids).

Variable thermo-physical characteristics of Carreau fluid flow by means of stretchable paraboloid surface with activation energy and heat generation

The present study is based on the flow of two dimensional Carreau fluid with heat generation and activation energy over the surface of paraboloid. The thermophysical properties such as viscosity, thermal conductivity and thermal diffusivity are chosen to be temperature dependent. The stretching in the fluid layers is presumed at the surface of object. This problem is modified by using law of conversation of momentum, mass, heat and concentration. The governing PDEs are transformed into dimensionless form by using appropriate similarity transformations. The numerical and graphical results are obtained via solving the ordinary differential equations by “RK4” technique with shooting method through MATLAB software. The impacts of key parameters on velocity, temperature and concentration fields are solved numerically and graphically. The power law index and variable viscosity parameter shows increment in velocity field. The temperature of fluid rises due to high values of heat source parameter while temperature shows reduction with Prandtl number. The cause of increment in concentration of fluid is due to activation energy and thermal diffusivity parameter.

Theoretical and numerical investigation of entropy for the variable thermophysical characteristics of couple stress material: Applications to optimization

Transportation of heat and mass along with irreversibility analysis for the flow of Couple stress fluid past over a nonlinear stretched surface is reported in this exploration. The novel features and purpose of this report is to notice the involvement of variable thermophysical characteristics i.e. (variable magnetic field, thermal conductivity, diffusion coefficient) for the couple stress model. Flow is produced over a non-linear stretched surface under constant pressure. Variable wall temperature, wall concentration and variable magnetic field are observed. Thermal transport is influenced by thermal radiation. Conducting mass in the light of Fick's second law is derived by adding a chemical reaction. Flow presenting partial differential equations describing the conservation laws are modelled under boundary layer approximation in Cartesian coordinate system. Similarity transformation is used to convert these coupled nonlinear fluid flow equations into ordinary differential equations. The converted nonlinear coupled system of differential equations is solved analytically using optimal homotopy procedure. Mathematical software Mathematica 11.0 is used to handle the computational complexity. Solution for velocity, temperature, concentration and entropy generation is displayed and it is discussed for the flow against numerous influential parameters. Numerical values for the dimensionless stresses, rate of heat and mass transfer is computed and tabulated. Moreover, limiting case of present exploration is compared to that of existing literature and an excellent agreement in results is noted. Also, it has been drafted that magnetic parameter retards the flow, whereas, the increment in ratio parameter and fluid parameter upsurges the velocity field.

Convective Heat Transfer Analysis of Hydromagnetic Micropolar Fluid Flow Past an Inclined Nonlinear Stretching Sheet with Variable Thermo-Physical Properties

The current work examines mixed convection boundary layer flow and heat transfer attributes in hydromagnetic micropolar fluid past a heated inclined sheet which stretches nonlinearly along the direction of flow. The impact of variable thermo-physical characteristics of the fluid together with the influence of magnetic field, thermal radiation and viscous dissipation are also checked on the flow field. The modelled governing equations are translated from partial to ordinary differential equations via relevant similarity transformations and the resulting equations are subsequently solved numerically by means of shooting techniques in company with Runge-Kutta integration algorithms. The reactions of the skin friction coefficient, Nusselt number, dimensionless velocity as well as temperature to variations in the emerging controlling parameters are illustrated through different graphs. In the limiting situations, the results obtained exhibit a strong relationship with the existing related works in literature. The facts emanated from this study also reveal that the thickness of the thermal boundary layer grows widely with a rise in the Eckert number and Biot number parameters whereas increasing the material (micropolar) and thermal conductivity parameters have opposite effects on the rate of heat transfer.

Instigated magnetic field effect on carbon nanotubes suspensions encompassing variable thermophysical characteristics

This communication aims to explore the instigated magnetic field and partial slip influence on nanofluid transport towards the curved stretching surface by taking into the account temperature and nanoparticles volume fraction dependent viscosity. The single and multi-wall carbon nanotubes (CNTs) are incorporated in the traditional industrial fluids namely, water and propylene glycol. The Curvilinear coordinate system is opted to model the physical flow problem and simplification is performed by utilizing appropriate transformation. The velocity, pressure, induced magnetic field and temperature distributions accompanied by surface drag force and heat flux are computed numerically by employing implicit finite difference scheme. Graphs and bar charts are drawn to examine the effects of prominent substantial parameters. Some pivotal findings are that the Nusselt number was increasing function of ϕ,λ* and Rd and decreasing function of k and N. The present study is a prototype and a benchmark in exploring induced magnetic field effects on CNTs transport over a curved surface and will lead to further investigation in future and may be beneficial in polymer industry and nanotechnology.

Analysis of thermal field within an urban canyon with variable thermophysical characteristics of the building's walls

In a typical urban configuration, a microclimatic analysis has been carried out. Using a CFD method, a N-S oriented urban street canyon, with a given H/W ratio, has been examined. The standard k-ε turbulence model has been used to simulate a three-dimensional flow field and to calculate the thermo-fluid dynamics parameters that characterize the street canyon. In this study has been analyzed the thermal flow field when the walls of the building change the properties of solar radiation absorption, in particular for α=0.2 and α=0.8. Solar radiation considered is that of 21/07 in Milan in two different hours: at 11:00 a.m. and at 02:00 p.m. The study shows the importance of the thermophysical properties of a wall, in the development of the thermal field and flow field. This is a very important topic, in terms of improvement of wellbeing and the quality of the air within the cities, through the choice of materials and colors of the facades of buildings.

Mathematical simulation of the process of cooling and freezing of bodies with variable thermophysical characteristics

A model and method are suggested for calculating the cooling and freezing of a rectangular block of fish as applied to rotory freezing units. A Fourier dimensionless heat-conduction equation is formulated with allowance for the variable character of the thermophysical properties of the object to be frozen. The presented results of the calculation carried out by the finite-difference method are in agreement with the experimental data.

Condensed Phase Reaction Waves with Variable Thermo-Physical Characteristics

We study the thermal propagation of a reaction wave through a condensed medium in the case when the thermal conductivity of the mixture may change in a jumpwise fashion at some critical temperature. This can occur, e.g., when the actual heat transfer processes are accounted for as a heat conduction process with an effective thermal conductivity. Then a change in the actual mechanism of heat transfer at some point in the reaction wave may result in a significantly different effective thermal conductivity. Our model also allows for the thermal conductivity of the product to be different from that for the initial reactants. We have determined the structure of uniformly propagating reaction waves and analyzed their stability. We have shown, in particular, that if the thermal conductivity is increased in a region just ahead of the reaction zone then the wave is either stabilized on destabilized depending on whether the width of this region is below or above a critical value.

The influence of variable thermophysical characteristics on the temperature field in a ceramic plate

We discuss an analytic method of determining the temperature fields in a rectangular plate of ceramic base type or a plate without inclusions. To increase the accuracy of the results obtained we take account of the temperature dependence of the coefficient of thermal conductivity and the specific heat capacity

Thermal stability of continuous media with variable thermophysical characteristics

Thermal stability of continuous media with variable thermophysical characteristics

Calculation of temperature fields

A method is discussed for solving heat-transfer problems in various regions for variable thermophysical characteristics. The method is based on the reduction of boundary-value problems of mathematical physics to infinite systems of linear algebraic equations which can be solved by the reduction method.

Analysis of inertial properties of thermal receivers with variable thermophysical characteristics

The dynamical characteristics of thermal receivers with temperature-dependent thermophysical coefficients are investigated.

Polymerization stresses in linear viscoelastic media

It is proposed to use a model of the hereditary type to take into account the stresses developing in the process of polymerization. The effect of the degree of polymerization (cure) on the viscoelastic properties of the material is taken into account by introducing a function analogous to the temperature shift function in time-temperature superposition. In this case the system of equations consists of the above-mentioned system of equations of viscoelasticity, the kinetic equation of the curing process, and the equation of heat conduction with allowance for the presence of sources and variable thermophysical characteristics.

Temperature field of an infinite plate with variable thermophysical characteristics

Nomograms are proposed to compute the temperature fields of simplest kind with a linear change in the thermophysical coefficients for boundary conditions of the third kind, which refine engineering computations of body heating.