SIMULATION DU TRANSFERT DE CHALEUR ET DE QUANTITÉ DE MOUVEMENT DANS UN REACTEUR DE VAPODÉPOSITION

Les processus de transfert de chaleur et de quantité de mouvement sont étudiés dans un réacteur de vapodéposition à axe vertical à paroi froide. La résolution des équations de l'hydrodynamique et de la thermique en formulation elliptique (ψ, ω, θ) conduit à une description fine des distributions de température et de vitesse à l'intérieur du réacteur sous balayage d'un gaz neutre. Les résultats des calculs montrent la présence de forts gradients localisés autour du substrat, ainsi qu'un phénomène de recirculation pour les faibles débits gazeux. L'influence des divers paramètres a été également examinée. Le cas d'un réacteur à axe vertical et à paroi chaude a été abordé.Heat transfer and quantity of movement processus were studied within a cold wall vertical C.V.D. reactor. The resolution of hydrodynamic and thermic equations with elleptic formulation (ψ, ω, θ) lead to an accurate description of temperatures and velocities within the reactor under inert gas flow. The results show high gradients around the substrate and a recycling flow for low rates. The influence of several parameters and the case of a hot wall reactor were also presented

Heat transfer studies in cold CVD reactors using holographic interferometry

The evaluation of holographic interferograms has been reviewed to perform quasi-real time and more accurate measurements of temperature fields within CVD reactors. In this way a powerful image processing device has been annexed to our optical arrangement to perform suitable and fast data acquisition. The evaluation of holographic interferograms is achieved using Fast Fourier Transform algorithm. Temperature fields have been measured within a large cold wall CVD reactor for different cylindrical substrate diameters and also for a conic substrate. We present some useful empirical correlations between Nusselt and Rayleigh numbers. Our aim in this paper is to give some useful experimental data which could be used to improve the validity of mathematical models developed for CVD process

EXPERIMENTAL STUDY AND NUMERICAL SIMULATION OF HYDRODYNAMICS AND HEAT TRANSFER IN A COLD-WALL CVD REACTOR

A mathematical model including the NAVIER-STOKES and energy partial differential equations has been developed to predict the flow and temperature fields in a cold-wall CVD reactor. Particular attention is placed on understanding and explaining the influence of pressure on the hydrodynamics and heat transfer in the reactor. In order to validate the model predictions in the thermal aspect we used holographic interferometry to investigate the temperature gradients and to examine the thermal boundary layer thickness for several reactor inlet conditions. The comparison between the model predictions and experimental data shows good agreement

Optimisation du traitement thermique d'un phosphate application au phosphate du bassin gantour au maroc

Un protocole de traitement thermique d'un minerai phosphaté visant l'optimisation des dépenses de l'énergie destinée à la calcination est ici présenté. Nous avons mené une étude comparative de la calcination effectuée de deux manières différentes sur du phosphate brut. Cette méthode a été appliquée pour enrichir le phosphate sédimentaire issu d'un nouveau site du Bassin des Gantour (Maroc). Dans un premier temps, nous avons optimisé la température de calcination et le temps de séjour. En effet, les résultats montrent que le traitement à 800 °C pendant 30 min donne un minerai de meilleure concentration en phosphate. Il permet de diminuer le carbone organique et le dioxyde de carbone respectivement de 1,4 % à 0,15 % et 6,6 % à 1,8 %. Ainsi que l'augmentation de la teneur en P2O5 de 30,39 % à 34,23 %. De plus, il a été constaté un impact du refroidissement sur la distribution granulométrique. Dans un deuxième temps, il apparaît que la procédure de calcination suivie d'un refroidissement par 33 % de phosphate de même source (mélange à chaud) peut avoir d'importantes retombées sur l'économie de l'énergie et un gain de productivité tout en préservant l'environnement

Modeling and experimental investigation of the close-spaced vapor transport process for the growth of CuIn(S 0,4 Se 0,6 ) 2 thin films

International audienceThis paper reports the prediction of optimal conditions to grow good quality crystalline thin films using the Close-Spaced Vapor Transport process. A new configuration of the horizontal reactor is used and presented. A thermodynamic model is proposed for the Cu-In-S-Se-I system to describe the deposition of CuIn(S0,4Se0,6)2(CISS) compound. The simulation was performed using the SOLGASMIX software which gives the composition of the chemical system at the thermodynamic equilibrium. The model is based on the minimization of the Gibbs energy of the defined chemical system. The present study has allowed us to determine the influence of the source temperature (TS) and iodine pressure (PI2) on the growth of CISS thin films. The different compounds of the solid phase were predicted for various TS and PI2 values. The conditions of stoichiometric and quasi-stoichiometric deposition are 475 ≤ TS ≤ 525 °C and PI2 ≤ 3 kPa. Some deduced conditions from the theoretical prediction were tested experimentally. The CISS samples grown have been analyzed by X-ray diffraction and scanning electron microscope. The thin films, deposited in optimal conditions, are stoichiometric

Analysis of electrical conduction mechanism in the high temperature range of the nanostructured photoabsorber Cu 2 SnS 3

International audienceThe dynamic electrical conduction in the bulk ternary semiconductor compound Cu2SnS3 is studied for the first time in the high temperature range from 300 °C to 440 °C in the frequency range 1 kHz–1 MHz. New activation energy for conduction mechanism is obtained and its frequency dependence is analyzed. The Cole–Cole representation is almost half circular indicating a single contribution to total electrical conduction through the material. The activation energy for the mean relaxation process, obtained separately from the analysis of imaginary part Z″ of complex impedance Z* and from the equivalent electric circuit, is estimated to be (942 +74). The correlated barrier hopping model is considered to analyze the experimental data. The results are compared with those obtained previously in low temperature range

Analysis of electrical conduction mechanism in the high temperature range of the nanostructured photoabsorber Cu 2 SnS 3

International audienceThe dynamic electrical conduction in the bulk ternary semiconductor compound Cu2SnS3 is studied for the first time in the high temperature range from 300 °C to 440 °C in the frequency range 1 kHz–1 MHz. New activation energy for conduction mechanism is obtained and its frequency dependence is analyzed. The Cole–Cole representation is almost half circular indicating a single contribution to total electrical conduction through the material. The activation energy for the mean relaxation process, obtained separately from the analysis of imaginary part Z″ of complex impedance Z* and from the equivalent electric circuit, is estimated to be (942 +74). The correlated barrier hopping model is considered to analyze the experimental data. The results are compared with those obtained previously in low temperature range

Transport phenomena in a cold wall vertical reactor for metalorganic vapor phase growth of β-SiC layers

The deposition rate and uniformity in CVD reactors are function of transport phenomena. A mathematical model including the coupled mass transfer with hydrodynamics and heat transfer has been developed to predict reactant concentrations, flow patterns and temperature fields in a cold wall CVD reactor. The model consists of the partial differential equations describing the balance of mass, momentum, heat and species concentration and variable gas properties. The equations are solved numerically in two-dimensional, axisymmetric form using a control-volume-based finite difference technique. The model is applied to growth of silicon carbide layers obtained by LPCVD from the pyrolysis of tetramethylsilane. We present computed temperature, velocity and TMS concentration profiles. We compare predicted deposition rates with experimental result

Modeling and experimental investigation of the close-spaced vapor transport process for the growth of CuIn(S 0,4 Se 0,6 ) 2 thin films

International audienceThis paper reports the prediction of optimal conditions to grow good quality crystalline thin films using the Close-Spaced Vapor Transport process. A new configuration of the horizontal reactor is used and presented. A thermodynamic model is proposed for the Cu-In-S-Se-I system to describe the deposition of CuIn(S0,4Se0,6)2(CISS) compound. The simulation was performed using the SOLGASMIX software which gives the composition of the chemical system at the thermodynamic equilibrium. The model is based on the minimization of the Gibbs energy of the defined chemical system. The present study has allowed us to determine the influence of the source temperature (TS) and iodine pressure (PI2) on the growth of CISS thin films. The different compounds of the solid phase were predicted for various TS and PI2 values. The conditions of stoichiometric and quasi-stoichiometric deposition are 475 ≤ TS ≤ 525 °C and PI2 ≤ 3 kPa. Some deduced conditions from the theoretical prediction were tested experimentally. The CISS samples grown have been analyzed by X-ray diffraction and scanning electron microscope. The thin films, deposited in optimal conditions, are stoichiometric