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Chouaieb S.,University of Monastir | Kriaa W.,University of Monastir | Mhiri H.,University of Monastir | Bournot P.,Institute Of Mecanique Of Marseille
Energy Conversion and Management | Year: 2016

The characteristics of microjet assisted CH4-H2/air flames in a turbulent mode are numerically investigated. Simulations are performed using the Computational Fluid Dynamics code Fluent. The Presumed PDF and the Discrete Ordinates models are considered respectively for combustion and radiation modeling. The k-ϵ Realizable model is adopted as a turbulence closure model. The Tesner model is used to calculate soot particle quantities. In the first part of this paper, the Presumed PDF model is compared to the Eddy Dissipation model and to slow chemistry combustion models from literature. Results show that the Presumed PDF model predicts correctly thermal and species fields, as well as soot formation. The effect of hydrogen enrichment on CH4/air confined flames under the addition of an air microjet is investigated in the second part of this work. The found results show that an inner flame was identified due to the air microjet for the CH4-H2/air flames. Moreover, the increase of hydrogen percentage in the fuel mixture leads to mixing enhancement and consequently to considerable soot emission reduction. © 2016 Elsevier Ltd. All rights reserved.

Kriaa W.,University of Monastir | Bejaoui S.,University of Monastir | Mhiri H.,University of Monastir | Le Palec G.,Institute Of Mecanique Of Marseille | Bournot P.,Institute Of Mecanique Of Marseille
Heat and Mass Transfer/Waerme- und Stoffuebertragung | Year: 2014

In this study, we developed a two-dimensional Computational Fluid Dynamics (CFD) model to simulate dynamic structure and heat and mass transfer of a vertical ceramic tiles dryer (EVA 702). The carrier's motion imposed the choice of a dynamic mesh based on two methods: "spring based smoothing" and "local remeshing". The dryer airflow is considered as turbulent (Re = 1.09 × 105 at the dryer inlet), therefore the Re-Normalization Group k - ε model with Enhanced Wall Treatment was used as a turbulence model. The resolution of the governing equation was performed with Fluent 6.3 whose capacities do not allow the direct resolution of drying problems. Thus, a user defined scalar equation was inserted in the CFD code to model moisture content diffusion into tiles. User-defined functions were implemented to define carriers' motion, thermo-physical properties. etc. We adopted also a "two-step" simulation method: in the first step, we follow the heat transfer coefficient evolution (Hc). In the second step, we determine the mass transfer coefficient (Hm) and the features fields of drying air and ceramic tiles. The found results in mixed convection mode (Fr = 5.39 at the dryer inlet) were used to describe dynamic and thermal fields of airflow and heat and mass transfer close to the ceramic tiles. The response of ceramic tiles to heat and mass transfer was studied based on Biot numbers. The evolutions of averages temperature and moisture content of ceramic tiles were analyzed. Lastly, comparison between experimental and numerical results showed a good agreement. © 2013 Springer-Verlag Berlin Heidelberg.

Baouab I.B.,University of Monastir | Said N.M.,University of Monastir | Mhiri H.,University of Monastir | Le Palec G.,Institute Of Mecanique Of Marseille | Bournot P.,Institute Of Mecanique Of Marseille
Defect and Diffusion Forum | Year: 2010

The present work consists in a numerical examination of the dispersion of pollutants discharged from a bent chimney and crossing twin similar cubic obstacles placed in the lee side of the source. The resulting flow is assumed to be steady, three-dimensional and turbulent. Its modelling is based upon the resolution of the Navier Stokes equations by means of the finite volume method together with the RSM (Reynolds Stress Model) turbulent model. This examination aims essentially at detailing the wind flow perturbations, the recirculation and turbulence generated by the presence of the twin cubic obstacles placed tandem at different spacing distances (gaps): W = 4 h, W = 2 h and W = 1 h where W is the distance separating both buildings. © (2010) Trans Tech Publications.

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