scholarly journals Numerical simulation of variable thermal conductivity on 3D flow of nanofluid over a stretching sheet

2020 ◽  
Vol 9 (1) ◽  
pp. 233-243 ◽  
Author(s):  
Nainaru Tarakaramu ◽  
P.V. Satya Narayana ◽  
Bhumarapu Venkateswarlu
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Stretching Sheet ◽  
Three Dimensional ◽  
Variable Thermal Conductivity ◽  
Normal Velocity ◽  
Transfer Coefficients ◽  
Similarity Transformations ◽  
Frictional Coefficients ◽  
The Impact

AbstractThe present investigation deals with the steady three-dimensional flow and heat transfer of nanofluids due to stretching sheet in the presence of magnetic field and heat source. Three types of water based nanoparticles namely, copper (Cu), aluminium oxide (Al2O3), and titanium dioxide (TiO2) are considered in this study. The temperature dependent variable thermal conductivity and thermal radiation has been introduced in the energy equation. Using suitable similarity transformations the dimensional non-linear expressions are converted into dimensionless system and are then solved numerically by Runge-Kutta-Fehlberg scheme along with well-known shooting technique. The impact of various flow parameters on axial and transverse velocities, temperature, surface frictional coefficients and rate of heat transfer coefficients are visualized both in qualitative and quantitative manners in the vicinity of stretching sheet. The results reviled that the temperature and velocity of the fluid rise with increasing values of variable thermal conductivity parameter. Also, the temperature and normal velocity of the fluid in case of Cu-water nanoparticles is more than that of Al2O3- water nanofluid. On the other hand, the axial velocity of the fluid in case of Al2O3- water nanofluid is more than that of TiO2nanoparticles. In addition, the current outcomes are matched with the previously published consequences and initiate to be a good contract as a limiting sense.

The Optimum Dimensions of Circular Fins with Variable Thermal Parameters

1980 ◽  
Vol 102 (3) ◽  
pp. 420-425 ◽  
Author(s):  
P. Razelos ◽  
K. Imre
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Variable Thermal Conductivity ◽  
Linear Variation ◽  
Transfer Coefficients ◽  
Base Thickness ◽  
Optimum Length ◽  
Heat Transfer Coefficients ◽  
Trapezoidal Profile ◽  
The Heat Transfer Coefficient

Optimum dimensions of circular fins of trapezoidal profile with variable thermal conductivity and heat transfer coefficients are obtained. Linear variation of the thermal conductivity is considered of the form k = k0(1 + εT/T0), and the heat transfer coefficient is assumed to vary according to a power law with distance from the bore, expressed as h = K[(r − r0)/(r0 − re)]m. The results for m = 0, 0.8, 2.0, and −0.4 ≤ ε ≤ 0.4, have been expressed by suitable nondimensional parameters which are presented graphically. It is shown that considering the thermal conductivity as constant, the optimum base thickness and volume of the fin are inversely proportional to the thermal conductivity of the material of the fin, while the optimum length and effectiveness are independent of the properties of the material used.

scholarly journals The Influence of Different Facings of Polyisocyanurate Boards on Heat Transfer through the Wall Corners of Insulated Buildings

Energies ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 1991 ◽  
Author(s):  
Tomas Makaveckas ◽  
Raimondas Bliūdžius ◽  
Arūnas Burlingis
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Flux ◽  
Thermal Insulation ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Thermal Bridge ◽  
Thermal Bridges ◽  
The Impact ◽  
Heat Flow Meter

Polyisocyanurate (PIR) thermal insulation boards faced with carboard, plastic, aluminum, or multilayer facings are used for thermal insulation of buildings. Facing materials are selected according to the conditions of use of PIR products. At the corners of the building where these products are joined, facings can be in the direction of the heat flux movement and significantly increase heat transfer through the linear thermal bridge formed in the connection of PIR boards with facing of both walls. Analyzing the installation of PIR thermal insulation products on the walls of a building, the structural schemes of linear thermal bridges were created, numerical calculations of the heat transfer coefficients of the linear thermal bridges were performed, and the influence of various facings on the heat transfer through the thermal bridge was evaluated. Furthermore, an experimental measurement using a heat flow meter apparatus was performed in order to confirm the results obtained by numerical calculation. This study provides more understanding concerning the necessity to evaluate the impact of different thermal conductivity facings on the heat transfer through corners of buildings insulated with PIR boards.

Heat Flux and Variable Thermal Conductivity Effects on Casson Flow and Heat Transfer due to an Exponentially Stretching Sheet with Viscous Dissipation and Heat Generation

2016 ◽  
Vol 14 (1) ◽  
pp. 167-174 ◽  
Author(s):  
Ahmed M. Megahed
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Flux ◽  
Heat Generation ◽  
Stretching Sheet ◽  
Variable Thermal Conductivity ◽  
Constant Heat Flux ◽  
Constant Heat ◽  
Flow And Heat Transfer ◽  
Exponentially Stretching

AbstractIn this paper, we introduce a theoretical and numerical study for the effects of thermal buoyancy and constant heat flux on the Casson fluid flow and heat transfer over an exponentially stretching sheet taking into account the effects of variable thermal conductivity, heat generation/absorption and viscous dissipation. The governing partial differential equations are transformed into coupled, non-linear ordinary differential equations by using suitable transformations. Numerical solutions to these equations are obtained by using the fourth order Runge-Kutta method with the shooting technique. The effects of various physical parameters which governing the flow and heat treansfer such as the buoyancy parameter, the thermal conductivity parameter, heat generation or absorption parameter and the Prandtl number on velocity and temperature are discussed by using graphical approach. Moreover, numerical results indicate that the local skin-friction coefficient and the local Nusselt number are strongly affected by the constant heat flux.

scholarly journals Magnetohydrodynamic stagnation point on a Casson nanofluid flow over a radially stretching sheet

2020 ◽  
Vol 11 ◽  
pp. 1303-1315
Author(s):  
Ganji Narender ◽  
Kamatam Govardhan ◽  
Gobburu Sreedhar Sarma
Keyword(s):  
Heat Transfer ◽  
Differential Equations ◽  
Stagnation Point ◽  
Radiation Effects ◽  
Stretching Sheet ◽  
Nonlinear Partial Differential Equations ◽  
Casson Nanofluid ◽  
Similarity Transformations ◽  
Program Language ◽  
The Impact

This article proposes a numerical model to investigate the impact of the radiation effects in the presence of heat generation/absorption and magnetic field on the magnetohydrodynamics (MHD) stagnation point flow over a radially stretching sheet using a Casson nanofluid. The nonlinear partial differential equations (PDEs) describing the proposed flow problem are reduced to a set of ordinary differential equations (ODEs) via suitable similarity transformations. The shooting technique and the Adams–Moulton method of fourth order are used to obtain the numerical results via the computational program language FORTRAN. Nanoparticles have unique thermal and electrical properties which can improve heat transfer in nanofluids. The effects of pertinent flow parameters on the nondimensional velocity, temperature and concentration profiles are presented. Overall, the results show that the heat transfer rate increases for higher values of the radiation parameter in a Casson nanofluid.

Cross-Diffusion Effects on MHD Cattaneo-Christov Flow of Casson Fluid Past a Convective Linear/Non-Linear Stretching Sheet

2018 ◽  
Vol 388 ◽  
pp. 96-113 ◽  
Author(s):  
Bujula Ramadevi ◽  
Janke Venkata Ramana Reddy ◽  
Vangala Sugunamma
Keyword(s):  
Heat Transfer ◽  
Stretching Sheet ◽  
Casson Fluid ◽  
Transfer Coefficients ◽  
Convective Boundary ◽  
Flow Equations ◽  
Cross Diffusion ◽  
Similarity Transformations ◽  
Flow Past ◽  
Non Linear

Through this article, we presented a comparative study for the MHD non- Newtonian fluid flow past a stretching sheet using Cattaneo-Christov heat flux model. The flow equations and the related convective boundary conditions have been altered as dimensionless ODEs by suitable similarity transformations. Further, these are resolved by employing fourth order Runge-Kutta method along with shooting technique. The influence of all flow regulating parameters on velocity, thermal and mass diffusive boundary layers are perceived through graphs. Also the variation in skin friction, mass and heat transfer coefficients for the same parameters are perceived via numerical values. The velocity of the flow past a linear stretching sheet is higher than that of the flow past a non-linear stretching sheet. But heat transfer performance in the flow via non-linear surface is better than that of flow via linear surface.

scholarly journals Heat transfer for two types of viscoelastic fluid over an exponentially stretching sheet with variable thermal conductivity and radiation in porous medium

2014 ◽  
Vol 18 (4) ◽  
pp. 1079-1093 ◽  
Author(s):  
V. Singh ◽  
Shweta Agarwal
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Boundary Layer ◽  
Porous Medium ◽  
Prandtl Number ◽  
Wall Temperature ◽  
Stretching Sheet ◽  
Variable Thermal Conductivity ◽  
Flow And Heat Transfer ◽  
Exponentially Stretching

An Analysis has been carried out to study the boundary layer flow and heat transfer characteristics of second order fluid and second grade fluid with variable thermal conductivity and radiation over an exponentially stretching sheet in porous medium. The basic boundary layer equations governing the flow and heat transfer in prescribed surface temperature (PST) and prescribed heat flux (PHF) cases are in the form of partial differential equations. These equations are converted to non-linear ordinary differential equations using similarity transformations. Numerical solutions of the resulting boundary value problem are solved by using the fourth order Runge-Kutta method with shooting technique for various values of the physical parameters. The effect of variable thermal conductivity, porosity, Prandtl number, radiation parameter and viscoelastic parameters on velocity and temperature profiles (in PST and PHF cases) are analyzed and discussed through graphs. Numerical values of wall temperature gradient in PST case and wall temperature in PHF case are obtained and tabulated for various values of the governing parameters. In this study Prandtl number also treated as variable inside the boundary layer because it depends on thermal conductivity. The results are also verified by using finite difference method.

Modeling of heterogeneous heat transfer in fabrics

2017 ◽  
Vol 88 (10) ◽  
pp. 1164-1172 ◽  
Author(s):  
Hua Shen ◽  
Atsushi Yokoyama ◽  
Sachiko Sukigara
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Mass Density ◽  
Three Dimensional ◽  
Longitudinal Direction ◽  
Equilibrium Temperature ◽  
High Heat ◽  
Transfer Coefficients ◽  
Contact Heat ◽  
Heterogeneous Model

Thermal comfort, an important factor when designing fabric, is strongly related to heat transfer in the fabric. Fabric is not homogeneous because the constituent yarns are interlaced at a certain weave angle, and the contact area between yarns varies. Therefore, heat transfer along the yarn in the fabric is not yet well understood. In this study, we developed a heterogeneous fabric model in which heat transfer along the longitudinal and transverse directions of the yarn is treated independently, and proposed a method for estimating the contact heat transfer coefficients for yarns. The geometrical fabric structure was constructed based on the cross section of three fabrics observed with a three-dimensional microscope. The parameters used were the mass density, specific heat, and thermal conductivity of the fibers and air. The heat flow calculated using the model was compared with that measured experimentally. Fairly good agreement was observed, verifying the validity of this heterogeneous model. The simulation results indicated that when the anisotropy of the fiber thermal conductivity is high, heat is transferred significantly faster along the longitudinal direction than along the transverse direction of the yarn, and the equilibrium temperature distribution is strongly influenced by heat transfer in the longitudinal direction.

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