Kamel Guedri

Numerical Study of the Swirl Effect on a Coaxial Jet Combustor Flame Including Radiative Heat Transfer

A numerical study of the swirl effect on a coaxial jet combustor flame including radiative heat transfer is presented. In this work, the standard k-ϵ model is applied to investigate the turbulence effect, and the eddy dissipation model (EDM) is used to model combustion. The radiative heat transfer and the properties of gases and soot are considered using a coupled of the finite-volume method (FVM), and the narrow-band based weighted-sum-of-gray gases (WSGG-SNB) model. The results of this work are validated by experiment data. The results clearly show that radiation must be taken into account to obtain good accuracy for turbulent diffusion flame in combustor chamber. Flame is very influenced by the radiation of gases, soot, and combustor wall. However, swirl is an important controlling variable on the combustion characteristics and pollutant formation.

Application of the Finite-Volume Method to Study the Effects of Baffles on Radiative Heat Transfer in Complex Enclosures

A finite-volume radiation model for participating gray media in 2-D and 3-D complex rectangular enclosures with obstacles is developed. The step and the bounded high-order resolution curved-line advection method (CLAM) schemes are examined. Using the blocked-off-region procedure, the present model is capable of predicting radiative heat transfer in enclosures with obstructions and baffles. In order to validate the formulations derived here a square cavity with one or three baffles and finned internal cylinder, then a three-dimensional complex heat recuperator of a pilot plant of biomass pyrolysis with obstructions and baffles, are studied. It should be pointed out that the developed code using the CLAM scheme is accurate and convenient for computational thermal calculations. For the considered heat recuperator, the presence of baffles enhances radiative heat flux and contributes to the increase of the mean medium temperature.

Evaluation of the FTn Finite Volume Method for Transient Radiative Transfer in Anisotropically Scattering Medium

In this paper, we formulated, applied, and tested the FTn Finite Volume Method (FTn FVM) for transient radiative transfer in three-dimensional absorbing, emitting, and anisotropically scattering medium. Both the STEP and the Curved-Line Advection Method (CLAM) are introduced for spatial discretization of the transient radiative transfer equation. The results show that FTn FVM reduces largely the ray effects and it is more accurate than the standard FVM. Also, using both STEP and CLAM schemes, FTn FVM has smaller convergence time than the standard FVM for all cases. On the contrary, the STEP scheme is faster than the CLAM scheme but it has less accuracy. Then, the effects of optical thickness, scattering albedo, and anisotropy factor on incident radiation and radiative flux are presented and discussed.

Improved finite volume method for three-dimensional radiative heat transfer in complex enclosures containing homogenous and inhomogeneous participating media

ABSTRACT The paper presents a modified finite volume method for the solution of the radiative transport equation, which implements the FTn angular discretization along with the bounded high-resolution curved line advection method to alleviate ray effect and false scattering, respectively, and consequently improve the accuracy of the final results. Using the blocked-off-region procedure, the present formulation is capable of treating blockage effects caused by inner/outer obstructing bodies. The developed methodology based on the combination of the above methods is evaluated against five three-dimensional test cases considering either homogenous or inhomogeneous participating media. For all cases, the predictions reveal the mitigation of false scattering and ray effects consequently the improvement of accuracy, employing this model for solving radiation heat transfer in industrial applications. In industrial application, the radiative heat transfer problem is solved for a unity boiler furnace where an inhomogeneous medium is assumed. The effects of the scattering albedo, walls emissivity and walls temperature are investigated.

MODELING OF RADIATIVE HEAT TRANSFER IN 2D COMPLEX FURNACE OF BIOMASS PYROLYSIS FUMES: A STUDY OF SHADOW EFFECT

The radiative heat transfer problem is investigated numerically for 2D complex pilot plant of biomass pyrolysis composed by two pyrolysis chambers and a heat recuperator. In order to increase gases residence time and heat transfer, the heat recuperator is provided with many inclined, vertical, horizontal, diffuse and gray baffles of finite thickness and has a complex geometry. The Finite Volume Method (FVM) is applied to study radiative heat transfer. The blocked-off region procedure is used to treat the geometrical irregularities. Seven cases are considered in order to demonstrate the effect of adding baffles on the walls of the heat recuperator and on the walls of the pyrolysis rooms then choose the best case giving the maximum heat flux transferred to the biomass in the pyrolysis chambers. Shadow effect caused by the presence of the baffles is also studied.© 2009 ASME