Development of hybrid method for coupled conduction-radiation heat transfer in two-dimensional irregular enclosure considering thermo-radiative effects and varying thermal conductivity

2019 ◽  
Vol 30 (4) ◽  
pp. 1815-1837
Author(s):  
Mehdi Zare ◽  
Sadegh Sadeghi
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Flux ◽  
Heat Source ◽  
Radiation Heat Transfer ◽  
Isotropic Scattering ◽  
Two Dimensional ◽  
Radiation Heat ◽  
Content Type ◽  
Irregular Enclosure

Purpose This study aims to perform a comprehensive investigation to model the thermal characteristics of a coupled conduction-radiation heat transfer in a two-dimensional irregular enclosure including a triangular-shaped heat source. Design/methodology/approach For this purpose, a promising hybrid technique based on the concepts of blocked-off method, FVM and DOM is developed. The enclosure consists of several horizontal, vertical and oblique walls, and thermal conductivity within the enclosure varies directly with temperature and indirectly with position. To simplify the complex geometry, a promising mathematical model is introduced using blocked-off method. Emitting, absorbing and non-isotropic scattering gray are assumed as the main radiative characteristics of the steady medium. Findings DOM and FVM are, respectively, applied for solving radiative transfer equation (RTE) and the energy equation, which includes conduction, radiation and heat source terms. The temperature and heat flux distributions are calculated inside the enclosure. For validation, results are compared with previous data reported in the literature under the same conditions. Results and comparisons show that this approach is highly efficient and reliable for complex geometries with coupled conduction-radiation heat transfer. Finally, the effects of thermo-radiative parameters including surface emissivity, extinction coefficient, scattering albedo, asymmetry factor and conduction-radiation parameter on temperature and heat flux distributions are studied. Originality/value In this paper, a hybrid numerical method is used to analyze coupled conduction-radiation heat transfer in an irregular geometry. Varying thermal conductivity is included in this analysis. By applying the method, results obtained for temperature and heat flux distributions are presented and also validated by the data provided by several previous papers.

scholarly journals Radiation Heat Transfer in a Complex Geometry Containing Anisotropically-Scattering Mie Particles

Energies ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3986 ◽  
Author(s):  
Ali Ettaleb ◽  
Mohamed Abbassi ◽  
Habib Farhat ◽  
Kamel Guedri ◽  
Ahmed Omri ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Fly Ash ◽  
Complex Geometry ◽  
Radiation Heat Transfer ◽  
Solid Particles ◽  
Isotropic Scattering ◽  
Isotropic Case ◽  
Radiation Heat ◽  
Radiation Heat Flux

This study aims to numerically investigate the radiation heat transfer in a complex, 3-D biomass pyrolysis reactor which is consisted of two pyrolysis chambers and a heat recuperator. The medium assumes to be gray, absorbs, emits, and Mie-anisotropically scatters the radiation energy. The finite volume method (FVM) is applied to solve the radiation transfer equation (RTE) using the step scheme. To treat the complex geometry, the blocked-off-region procedure is employed. Mie equations (ME) are applied to evaluate the scattering phase function and analyze the angular distribution of the anisotropically scattered radiation by particles. In this study, three different states are considered to test the anisotropic scattering impacts on the temperature and radiation heat flux distribution. These states are as: (i) Isotropic scattering, (ii) forward and backward scattering and (iii) scattering with solid particles of different coals and fly ash. The outcomes demonstrate that the radiation heat flux enhances by an increment of the albedo and absorption coefficients for the coals and fly ash, unlike the isotropic case and the forward and backward scattering functions. Moreover, the particle size parameter does not have an important influence on the radiation heat flux, when the medium is thin optical. Its effect is more noticeable for higher extinction coefficients.

Collocation Spectral Method for the Transient Conduction–Radiation Heat Transfer With Variable Thermal Conductivity in Two-Dimensional Rectangular Enclosure

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
Guo-Jun Li ◽  
Jian Ma ◽  
Ben-Wen Li
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Spectral Method ◽  
Radiation Heat Transfer ◽  
Variable Thermal Conductivity ◽  
Two Dimensional ◽  
Radiation Heat ◽  
Rectangular Enclosure ◽  
Collocation Spectral Method ◽  
Transient Conduction

The collocation spectral method (CSM) is further developed to solve the transient conduction–radiation heat transfer in a two-dimensional (2D) rectangular enclosure with variable thermal conductivity. The energy equation and the radiative transfer equation (RTE) are all discretized by Chebyshev–Gauss–Lobatto collocation points in space after the discrete ordinates method (DOM) discretization of RTE in angular domain. The treatment of variable thermal conductivity is executed using the array multiplication. The present method can deal with different boundary conditions with high accuracy, the Dirichlet one and mixed one, for example. Based on our new method, the effects of several parameters on heat transfer processes are analyzed.

Maxwell Fluids Unsteady Mixed Flow and Radiation Heat Transfer Over a Stretching Permeable Plate With Boundary Slip and Nonuniform Heat Source/Sink

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Liancun Zheng ◽  
Ning Liu ◽  
Xinxin Zhang
Keyword(s):  
Heat Transfer ◽  
Differential Equations ◽  
Heat Source ◽  
Mixed Boundary ◽  
Radiation Heat Transfer ◽  
Radiation Heat ◽  
Boundary Slip ◽  
Analytical Approximations ◽  
Maxwell Fluids ◽  
Source Sink

This paper presents an analysis for the unsteady mixed boundary-layer flow and radiation heat transfer of generalized Maxwell fluids toward an unsteady stretching permeable surface in presence of boundary slip and nonuniform heat source/sink. The governing partial differential equations are converted into nonlinear ordinary differential equations and analytical approximations of solutions are derived by homotopy analysis method (HAM). The effects of the unsteadiness parameter, nonuniform heat source/sink parameter, suction/injection parameter, thermal radiation parameter and slip parameter on the fluid flow, and heat transfer characteristics are shown graphically and analyzed.

Model to study the non-linear radiation heat transfer in the stagnation-point flow of power-law fluid

2015 ◽  
Vol 25 (5) ◽  
pp. 1107-1119 ◽  
Author(s):  
M. Mustafa ◽  
Ammar Mushtaq ◽  
T. Hayat ◽  
A. Alsaedi
Keyword(s):  
Heat Transfer ◽  
Power Law ◽  
Transfer Problem ◽  
Radiation Heat Transfer ◽  
Shear Thickening ◽  
Temperature Ratio ◽  
Radiation Heat ◽  
Content Type ◽  
Non Linear ◽  
Linear Radiation

Purpose – The purpose of this paper is to investigate non-linear radiation heat transfer problem for stagnation-point flow of non-Newtonian fluid obeying the power-law model. Power-law fluids of both shear-thinning and shear-thickening nature have been considered. Design/methodology/approach – Boundary layer equations are non-dimensionalized and then solved for the numerical solutions by fourth-fifth order Runge-Kutta integration based shooting technique. Findings – The results reveal an existence of point of inflection for the temperature distribution for sufficiently large wall to ambient temperature ratio. Moreover temperature increases and heat transfer from the plate decreases with an increase in the radiation parameter. Heat transfer rate at the sheet is bigger in dilatant (shear-thickening) fluids when compared with the pseudoplastic (shear-thinning) fluids. Originality/value – Different from the linear radiation heat transfer problem (which can be simply reduced to rescaling of Prandtl number by a factor containing the radiation parameter), here the energy equation is strongly non-linear and it involves an additional temperature ratio parameter w =T w /T ∞. This parameter allows studying the thermal characteristics for small/large temperature differences in the flow.

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