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.

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.

Radiation and Convection Heat Transfer in a Porous Bed

1968 ◽  
Vol 90 (1) ◽  
pp. 51-54 ◽  
Author(s):  
W. A. Beckman
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Collection Efficiency ◽  
Convection Heat Transfer ◽  
Heat Fluxes ◽  
Fluid Temperature ◽  
Radiation Heat ◽  
Radiation Heat Flux ◽  
Flowing Fluid ◽  
Porous Bed

The one-dimensional steady-state temperature distribution within an isotropic porous bed subjected to a collimated and/or diffuse radiation heat flux and a transparent flowing fluid has been determined by numerical methods. The porous bed was assumed to be nonscattering and to have a constant absorption coefficient. Part of the radiation absorbed by the porous bed is reradiated and the remainder is transferred to the fluid by convection. Due to the assumed finite volumetric heat transfer coefficient, the bed and fluid have different temperatures. A bed with an optical depth of six and with a normal incident collimated radiation heat flux was investigated in detail. The radiation incident on the bed at the fluid exit was assumed to originate from a black surface at the fluid exit temperature. The investigation covered the range of incident diffuse and collimated radiation heat fluxes expected in a nonconcentrating solar energy collector. The results are presented in terms of a bed collection efficiency from which the fluid temperature rise can be calculated.

Discrete Ordinates Method for Transient Radiation Transfer in Cylindrical Enclosures

2003 ◽  
Author(s):  
Kyunghan Kim ◽  
Zhixiong Guo
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Radiative Heat ◽  
Radiation Transfer ◽  
Radiation Heat Transfer ◽  
Discrete Ordinates ◽  
Radiation Heat ◽  
Discrete Ordinates Method ◽  
Transient Radiation ◽  
Tissue Welding

The Discrete Ordinates Method (DOM) for solving transient radiation transfer equation in cylindrical coordinates is developed for radiation heat transfer in participating turbid media in pico-scale time domain. The application problems addressed here are laser tissue welding and soldering. The novelty of this study lies with the use of ultrashort laser pulses as the irradiation source. The characteristics of transient radiation heat transfer in ultrafast laser tissue welding and soldering are studied with the DOM developed. The temporal distribution of radiative energy inside the tissue cylinder as well as the radiative heat flux on the tissue surface is obtained. Comparisons are performed between laser welding without use of solder and laser soldering with use of solder. The use of solder is found to have highly concentrated radiation energy deposition in the solder-stained region and reduce the surface radiative heat flux accordingly. Comparisons of transient radiation heat transfer between the spatially square-variance and Gaussian-variance laser inputs and between the temporally Gaussian and skewed input profiles are also conducted.

scholarly journals Numerical simulation of reacting flow in the combustion chamber and study of the impact of turbulent diffusion coefficients

2020 ◽  
Vol 12 (9) ◽  
pp. 168781402095497
Author(s):  
Evgenij Strokach ◽  
Igor Borovik ◽  
Fang Chen
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Chemical Reactions ◽  
Turbulence Model ◽  
Turbulent Diffusion ◽  
Diffusion Coefficients ◽  
Radiation Heat Transfer ◽  
Mixing Efficiency ◽  
Radiation Heat ◽  
The Impact

A methodology for combustion modeling with complex mixing and thermodynamic conditions, especially in thrusters, is still under development. The resulting flow and propulsion parameters strongly depend on the models used, especially on the turbulence model as it determines the mixing efficiency. In this paper, the effect of the sigma-type turbulent diffusion coefficients arriving in the diffusion term of the turbulence model is studied. This study was performed using complex modeling, considering the conjugate effect of several physical phenomena such as turbulence, chemical reactions, and radiation heat transfer. To consider the varying turbulent Prandtl, an algebraic model was implemented. An adiabatic steady diffusion Flamelet approach was used to model chemical reactions. The P1 differential model with a WSGG spectral model was used for radiation heat transfer. The gaseous oxygen (GOX) and methane (GCH4) operating thruster developed at the Chair of turbomachinery and Flight propulsion of the Technical University of Munich (TUM) is taken as a test case. The studies use the 3D RANS approach using the 60° sector as the modeling domain. The normalized and absolute pressures, the integral and segment averaged heat flux are compared to numerical results. The wall heat fluxes and pressure distributions show good agreement with the experimental data, while the turbulent diffusion coefficients mostly influence the heat flux.

Radiation Heat Transfer to the Leeward Side of a Massive Object Suspended Over a Pool Fire

2001 ◽  
Author(s):  
M. Alex Kramer ◽  
Miles Greiner ◽  
J. A. Koski
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Large Scale ◽  
Radiation Heat Transfer ◽  
Pool Fire ◽  
Windward Side ◽  
Leeward Side ◽  
Radiation Heat ◽  
Emissive Power ◽  
Inner Surface

Abstract A series of large-scale experiments were recently performed to measure heat transfer to a massive cylindrical calorimeter engulfed in a 30-minute circular-pool fire [1]. The calorimeter inner surface temperature was measured at several locations and an inverse conduction technique was used to determine the net heat flux. The flame emissive heat flux was measured at several locations around the calorimeter. Light winds of around 2 m/s blew across the calorimeter axis at the beginning of the test but diminished and stopped as the test continued. The winds tilted the fire so that the windward side of the calorimeter was only intermittently engulfed. As a result, the measured flame emissive power near the windward side was substantially less than the leeward surface. The variation of calorimeter temperature and heat flux was closely correlated with the measured flame emissive power.

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