A two-dimensional theoretical and numerical model of biomass pyrolysis has been developed to determine the kinetic of wood particles pyrolysis in a fixed bed reactor. The adopted chemical model is coupled with a global transport bi-dimensional, and two temperatures model. The three modes of heat transfer (conduction, convection and/or radiation) between the solid and gas phases, and the wall are considered. The system of all unsteady and reactive equations is resolved by a finite volume method with a hybrid spatial interpolation and an implicit interpolation for time. The resulting algebraic equations are then resolved by using the bi-conjugate gradient stabilized and normalized method. The obtained model is validated in several experimental cases for data of one biomass particle. This model is applied to predict the pyrolysis phenomenon in a fixed bed of particles. Using the proposed numerical model the time space evolutions, of temperature and char fraction, are presented and discussed. In this configuration, the obtained numerical results agree with the experimental data found in the literature.
Abstract. In this study, heat transfer enhancement in porous medium was inspected. For this aims the lattice Boltzmann method was adopted to simulate mixed convection in porous domain. The Brinkman Forchheimer model was implemented to simulate porous channel including obstacles maintained at constant temperature. The velocity and the temperature are plotted at various parameters. The simulation was carried out for different porosity, Darcy and Reynolds. The Results show that by decreasing porosity, the heat transfer enhances. Also the result points that the obstacle position has effect on heat transfer.
The purpose of this paper is to study heat transfer and fluid flow in porous media with and without obstacle. The double-population thermal lattice Boltzmann is applied. The validation of the accuracy of our numerical code is done. We resort to a comparison between the present and the numerical results reported in previous studies on benchmark problems (the generalized Poiseuille flow). Then, the problem of a fluid sheared in a porous media is studied using two approaches of LBM: generalized lattice Boltzmann equation (GLBE) and simplified lattice Boltzmann equation (SLBE). The comparison of these models is achieved at a specific node and cross-section. It includes many dynamic parameters and covers all over the medium. It is so important to conclude that the GLBE is more suitable to study heat transfer in porous media. In the second part, the heat transfer is calculated through a porous media with hot obstacle. The effect of the obstacle dimension and position is presented. The dependence of fluid flow and heat transfer to several parameters is studied. We conclude by showing that the model presented here is particularly well-suited to study heat and mass transfer in porous media with many applications. transfer is calculated through a porous media with hot obstacle. The effect of the obstacle dimension and position is presented. The dependence of fluid flow and heat transfer to several parameters is studied. We conclude by showing that the model presented here is particularly well-suited to study heat and mass transfer in porous media with many applications. Key words: Lattice Boltzmann equation (GLBE and SLBE), porous media, thermal incompressible flow, convection, hot obstacleDetailed instructions for preparing your paper submitted to International Journal of Heat and Technology are given as follows. Please be responsible for the quality and appearance of your work.It's strongly recommended that you directly type over the template or just cut and paste from another document and use markup styles. Please keep in mind all the way through the preparation, do not modify page setup in this template, such as fonts, font sizes, line spacing, margin, uppercase and lowercase, the order of sections, etc. The abstract section is mandatory, with a word limit of 200 words. The scope, aims, results and conclusions may be summarized here. Avoid inserting any reference in this section. In the Keywords section, please capitalize the initial letter of each keyword. Enter the words or phrases in alphabetical order, separated by commas. There is a maximum of 5 keywords. [Abstract style: Times New Roman 9, justified]
In this paper, we present the transient modeling results of 2-D forward smoldering in a cylindrical configuration filled with a foam porous material. The objective of the study is to explain the effect of the heat losses from lateral boundaries in the front smolder propagation. The developed numerical code is capable of predicting the fire initiation and the smoldering (slow-burning) characteristics of foam insulation materials. The finite volume discretization and the bi-conjugate gradient stabilized method are used to solve the system governing equations. The chemical kinetics model is based on a first order pyrolysis reaction, followed by oxidation of the porous fuel and the carbonaceous char residual. This second oxidation reaction might promote the transition from smoldering to flaming and thus fire initiation. The gas and solid temperature, and the oxygen and the char mass fraction two-dimensional temporal evolutions are computed. Different heat and mass transfer coefficients are used to simulate the heat losses to the surrounding. Non-reacted foam regions are observed near the side wall, confirming experimental observations. The base case is chosen to represent the experimental conditions reported in the literature. The numerical predictions show very good agreement with the published experimental and 1-D numerical results.
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