Djamel Haddad

Industrial fire simulation and uncertainty associated with the Emission Dispersion Model

The use of numerical modeling in the field of industrial fire accidentology has become common nowadays and this tendency is expected to increase with the development of performance simulation tools. Despite the constant development of fire modeling tools, the current state of the art is not yet able to accurately predict fire phenomena. This gap between the reality and simulations is probably due to the presence of some level of uncertainty, which may occur from the meteorological inputs, diffusion assumptions, plume dynamics, or emission production. To cope with the presence of uncertainties in the input data, we propose an uncertainty analysis enabling to avoid as much as possible bad decisions that may have a large impact in domains such as safety. In this study, we are interested in the uncertainty propagation related to NO2 atmospheric dispersion resulting from a crude oil tank fire. Uncertainties were defined a priori for each of the following input parameters: wind speed, NO2 emission rate, and viscosity and diffusivity coefficients. For that purpose, a Monte Carlo approach has been used. In order to evaluate the importance of the considered parameters on the NO2 dispersion, new sensitivity indicator has been developed. The obtained results showed that the viscosity coefficient and the wind speed are the most significant input parameters with respect to NO2 concentration near to the source of fire, while the wind speed and the initial concentration are the important parameters for distant areas.

Inlet Methane Temperature Effect at a Planar SOFC Thermal Field Under Direct Internal Reforming Condition

In this work, an Anode Supported Planar Solid Oxide Fuel Cell (ASP_SOFC) is applied. The thermal fields are shown for a standard SOFC: yttria stabilized zirconia for the electrolyte, nickel/zirconia cermet for the anode, and doped lanthanum manganite (LSM) for the cathode. It is operating under direct internal reforming condition of methane gas.

Thermal field in SOFC fed by CH4: Molar fractions effect

Abstract In the present work, the anode supported solid oxide fuel cell (AS_SOFC) is fed by air and fuel at cathode and at anode channels respectively. The fuel is a mixture of five components: methane (CH4), hydrogen (H2), carbon dioxide (CO2), carbon monoxide (CO) and steam (H2O), where a reforming phenomenon; an external or an internal one appears. At the SOFC anode side, an indirect or direct reforming phenomenon happens.

Heat and Mass Transfer in the Growth of Titanium Doped Sapphire Material with the μ-PD Technique

In this work we have studied the heat and the mass transfer of titanium doped sapphire in the growth domain. The growth of this material (Ti+3: Al2O3) is performed using a relatively recent growing technique that is the micro-pulling down (µ-PD) [1]. This method presents several advantages over other growing methods [2] and allows a stable growth of shaped material with very good quality [3]. In this study we established a numerical, two-dimensional finite volume model in cylindrical coordinates with an axisymmetric configuration. The flow, the thermal transfer and the mass transfer are modeled by the differential equations of conservation of the mass, of quantity of the movement, energy and the species. This problem, which takes into account the convection-diffusion coupling, is discretized using the Finite Volumes Method (FVM). We focus on the physical properties of the molten zone and on the radial and axial distribution of titanium in the sapphire crystal fiber. Our model is in good agreement with experimental results.

Modeling of Heat Transfer in the PEMFC: Velocity Inlet and Current Density Effect

The purpose of this work is to present a two-dimensional transient model of the gas flow in the fuel cell (PEMFC). The model includes various conservation equations such movement and energy equations. The governing equations were resolved by the finite volume method. The objective of this work is to know the maximum temperature and its location in PEMFC and to determine the performance conditions of the fuel cell under the current density and velocity inlet effect. The polarization curve obtained numerically is compared with much numerical work. The numerical results show the regime flow effect and the nature of porous middle on the gas distribution in the membrane electrode assembly (MEA).

Double Diffusion Effects on Entropy Generation in Convective Heat and Mass Transfer

The aim of the present study is to examine the Dufour influence and Soret effects on entropy generation in convective heat and mass transfer for the case of a binary gas mixture with a single diffusive species in a square cavity. We numerically investigate the thermosolutal convection in a square cavity, where a binary mixture of incompressible fluid is confined under the conditions of both thermal and solutal gradients. Furthermore, we analyze the effect of Dufour and Soret on entropy generation. We find that, according to Grashof number values, the entropy generation could be mainly due to heat transfer or to fluid friction irreversibility and that the Soret and Dufour effects have great impact on the production of entropy.

Numerical Simulation of Cavity with an Upper Free Surface

In this paper, 3D numerical study of Benard-Marangoni instabilities in a horizontal liquid layer for a Rayleigh number Ra = 0 and aspect ratio A = 20. The layer is heated from below and cooled from above (vertical temperature gradient). The upper surface is assumed to be free and non-deformable. The surface tension at the free surface is linearly dependent on the temperature. Silicon oil with Prandtl number (Pr = 880) has been used as a working liquid. A parametric study has been carried out by considering the following parameters: the thermal Marangoni number (Ma), the Biot number (Bi). The governing equations were discretized by the finite volume method. The resolution of the coupling (pressure-velocity) was done with the projection method. A code has been elaborated with FORTRAN 6.6. Velocity vectors and temperature fields on the upper free surface are obtained.

Thermal fields of a planar SOFC fed by methane: Steam reforming and water gas shift reaction effect

This paper presents an analysis of the heat source effect on the thermal fields of an anode supported planar Solid Oxide Fuel Cell (SOFC). Heat sources are: i) heat source due to the endothermic steam reforming reaction and ii) heat source due to the exothermic water gas shift reaction. This study is studied by a 2-D numerical simulation, in the plane perpendicular to the gases flow, and requires a coupling of transport phenomena of energy and mass species. The law of flow is governed by Darcys law. The gases are air and fuel. The inlet fuel is composed by a mixture of methane CH4, hydrogen H2, carbon monoxide CO, carbon dioxide CO2 and steam H2O. Results are obtained by developing a program in FORTRAN language using the finite difference method. The results show the inlet gases temperature effect on the SOFC thermal fields.