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This work presents a comparative study of four drying processes of a porous media: superheated steam drying at atmospheric pressure (APSSD), humid air (HA), low pressure superheated steam drying (LPSSD) and vacuum drying (VD). A single porous particle model has been developed to simulate the four drying processes. The model is based on the method of averaging volume. Spherical porous particles of coal are used as the model material in this paper. The evaporation rates are equal for these processes in point called the inversion temperature. This temperature was calculated during the constant rate period (CRP) and the falling rate period (FRP). A variation in the values of inversion temperature was observed (363-503 K). The effect of drying parameters such as: particle radius, gas mass flux, permeability, porosity and operating pressure were investigated. Several researchers have reported the noticeable variation of the inversion temperature values according to the drying period used to calculate this key parameter. Our results are compared with those obtained from a front model reported in the literature. A good agreement is found.

Simultaneous heat and mass transfer inside a packed bed dryer between a fluid phase and corn kernels was studied. A developed two-phase model for evaluating the effect of bed shrinkage and non-constant physical properties on the drying efficiency was conducted. Experimental data were utilized to develop the governing equations of the bed shrinkage and structural parameters with moisture content inside the packed bed dryer. The developed model was verified by assessing predictions against experimentally obtained moisture content and temperature along the drying bed, as the standard errors of the experimental values compared to the model were found to be close to the accepted engineering accuracy of 5%. It has been concluded that the incorporation of bed shrinkage and alteration in properties within the operating model is capable of providing a more comprehensive and precise analysis of heat and mass transfer phenomenon in porous media drying, such as corn kernels.

In this work, we investigated the morphological effect of dichloromethane (DCM) on alfalfa (Medicago sativa) plant. We studied in vitro the influence of its concentration on alfalfa germination. The plants were placed in pots for 15 weeks, and exposed to increasing concentrations of DCM (50 µg L−1 and 84 mg L−1). In addition, we examined the effect of two manures (cow and sheep), which were applied to a contaminated soil, on alfalfa plant growth. The effect of the presence of dichloromethane is obvious even in plant–soil manure system. In fact, in the event of contamination, the soil–cow manure mixture represents the best setting medium for the Alfalfa plant compared to other environments, regardless of the contamination level. Indeed, the presence of two types of manure does not allow the suppression of the inhibitory effect of dichloromethane on the mass of the dry matter of the aerial part which is 18.38% for the cow manure-amended soil and 13.96% for the sheep manure-amended soil.

This work studied the effect of external conditions on the drying kinetics of a thin layer of corn during convective drying. The density and the specific volume of the corn grain were reported and the desorption isotherms of the corn were determined at three temperatures and for a water activity from 0.1 to 0.9 using the static gravimetric method. Initially, a thin layer of corn about 7 mm thick with an initial moisture content of 45% (d.b) was investigated, and the external conditions were tested. Afterwards, a comparison between the experimental convective drying of a packed bed and a thin layer was performed under the same conditions. Finally, the values of equilibrium moisture contents, water activities and temperatures obtained were fitted using seven sorption models. It was found that the experimental desorption data exhibited type II behavior, according to Brunauer’s classification. The GAB model was found as the most suitable semi-empirical model which was well suited to represent the desorption equilibrium moisture content of corn kernels in the suggested ranges of temperature and water activity. It can be concluded from the entropy–enthalpy compensation theory that the desorption process of the corn kernels is controlled by the enthalpy mechanism.

In the present study, a parametric study of a parabolic dish receiver system is investigated in order to determine the best configuration to achieve an optimal system performance.A series of numerical simulations has been conducted for four receiver tubes and two positions of the receiver inlet/outlet configurations: position 1 and position 2.The thermal analysis proves that the receiver’s inlet/outlet configuration effect is influenced by the geometric properties of the receiver.Numerical results show that with a “low” height receiver (H = 0.075 m, H = 0.048 m), position 2 gives the highest thermal efficiency, while position 1 ensures the greatest thermal efficiency value for the “elevated” height cylindrical receiver (H = 1.2 m, H = 0.468 m).Indeed, for the configuration with H = 0.075 m, the thermal efficiency increases by 62.6% from position 1 to 2. Moreover, by changing the position from 1 to 2, the thermal efficiency decreases by 53% for a configuration with H = 1.2 m. Keywords: Parabolic dish, Receiver, Solar heat flux distribution, Temperature distribution

In this work, we present field measurement data and modeling of air pollutant during one season at an urban area in Sousse, east Tunisia. We analyzed the average pollutant emission and we used our data to evaluate a dispersion model. The impact of various meteorological factors on pollutants concentrations has been studied. The model predicts that the concentrations of CO and CO2 in an urban area can reach 50 mg·m−3 and 185 mg·m−3 respectively. The height of the chimney, the wind velocity, the fuel nature, the air excess and the combustion temperature have an influence on the concentrations of pollutants and their dispersion.

In the manufacturing field, a growing interest is being held to the environment, to sustainability and more precisely saving energy and time. Combining thermomechanical with pure mechanical processes is an eco-friendly and profitable technique. In this paper, it is proposed to combine grinding and ball-burnishing processes. Further from reducing time, energy and cost of the manufacturing operations, this original combination is imagined to take benefit from thermomechanical history occurring while grinding to optimise ball-burnishing process in order to enhance the workpiece surface integrity. In this paper, the impact of this newly developed process on the surface and subsurface behaviour is studied through experiments and 3D FEM simulations. It is shown that performing simultaneously grinding and ball-burnishing processes leads to a thick surface layer up to several millimetres with compressive residual stresses state. This is an interesting result to increase sustainability of metallic workpieces by enhancing wear resistance, fatigue strength and fatigue lifetime.

This work represent the incorporation of information procurement (DAQ) equipment and programming to acquire information (LabVIEW) as well as real-time transport to show parameter appraises with regard to subsurface stream and transport issues. The main objective is to understand the mechanism of water and solute transfer in a sandy medium and to study the effect of some parameters on the transport of an inert tracer. In order to achieve this objective, a series of experiments were carried out on a soil column equipped with a tensiometer to monitor the state of saturation of the medium and by two four-electrode probes for measuring the electrical conductivity in the porous medium.

International audience; The main objectives of this study is to model the transport of methylene blue (MB) in homogenous and layered soils which has been studied experimentally by fixed bed column. The effect of soil stratification has been studied through numerical investigation based on the coupled solute transport model in three-layered soil. The effect of some significant parameters such as flow rate, initial concentration of MB, thickness of each layer and the numbers of layers on the breakthrough curves have been undertaken. A finite element analysis model was employed to predict the transport of MB in soils. A two dimensional model based on Richards equation and advection-dispersion equation coupled with adsorption model has been developed and an analytical model has been used to predict the dispersivity. The results shows that the soil heterogeneity has a significant effect on methylene blue (MB) adsorption through unsaturated layered media and the effect of the parameters of the upper layer of the soil is more significant than those of the lower layer but this effect can be controlled with the choice of the thicknesses of each layer.

The removal of dye from industrial wastewater is one of the most important subjects in water pollution regulation. Successive adsorption/desorption cycles of a basic dye, methylene blue, on internal almond shell, olive stone and rye straw were investigated by using fixed bed column experiments to study the adsorption capacity to remove the MB and adsorbents regeneration efficiency. The adsorption breakthrough curves were predicted by the Thomas model, Yoon Nelson model, and Wolborska model and modified dose-response model by using nonlinear regressive analysis. The adsorption capacity values obtained by this model are compared with the experimental capacity, noting an error of 16%, 27.8% and 18.9% for IAS, OS and RS respectively, but these errors are minimized in the second cycle to 22.98% and 6.06% for OS and RS respectively. The results show that the modified dose response model is more suitable for the description of breakthrough curves for three adsorbents only in the first cycle. The IAS presents the highest adsorption capacity and the best regeneration efficiency. Conversely, the RS presents lower adsorption capacity, whereas is not the hardest to regenerate.

The moisture sorption characteristics of two cement-based materials: hardened cement paste and mortar were investigated at 30, 50 and $$70\,^{\circ } \hbox {C}$$ for water activity ranging from 0.05 to 0.95. The sorption isotherms were typical type II sigmoidal curves according to BET classification. In both adsorption and desorption, an increase in temperature resulted in lower equilibrium moisture contents at corresponding values of water activity. The sorption isotherms exhibited hysteresis during a period water activity from 0.05 to 0.95. Some models were applied for analysing the experimental data. Nonlinear regression analysis was used for the determination of the parameters in the equations. Estimated parameters and fitting ability for sorption models were evaluated. Sorption isotherm data were used to determine the thermodynamic functions such as isosteric heat of sorption, sorption entropy, spreading pressure, net integral enthalpy and entropy. The Clausius–Clapeyron equation was used to evaluate the isosteric heats of sorption.

The use of organic dyes in many industrial products may threaten the water systems. For instance, the Methylene Blue (MB) is a cationic dye which is found in many industrial effluents (textile, cosmetic industries, paper and plastic). It is an important contaminant in soil and water bodies and it may induce health problems (Xing et al. in Desalination 259(1): 187–191 2010.

Soil hydraulic properties are necessary to study the transfer water and solute throught the unsaturated zone, but often cannot be measured because of practical and material constraints. The focus of this work is the hydrodynamic characterization in_situ of the industrial zones oil in the region of Soussein Tunisia by analysing two different inverse methods and experimental results of soilwater content. This study estimated the hydraulic parameters of Mualem and Van Genuchten model using the monitored soil water changes.

The discharged wastewater of textile industry, which contains persistent organic dyes, is one of the main causes of water contamination.

International audience; This paper investigates the implementation of an analytical model to determine the porosity of a granular material during reactive and nonreactive sintering. A graphical interpretation of this model is proposed to calculate the porosity by comparing the experimental shrinkage curve with the ideal one. For the nonreactive sintering, some examples have been taken from the literature to illustrate the application of this method for two granular materials (alumina and zircon). In the case of reactive sintering, we have used our experiments to study the sintering behavior of magnesium hydroxide. The shrinkage curve was determined by dilatometer and the porosity was measured by helium pycnometer. The comparison revealed that the porosity calculated from the model is fully consistent with the porosity measurements in the both cases.

In recent years, many researchers are interested in soil contamination by persistent organic pollutant and focus their studies on the impact of persistent pollutants on human health.

The present study aimed at developing a theoretical model to simulate the drying process of a porous particle in low-pressure superheated steam drying (LPSSD). Spherical and porous particles of ceramic and coal are used as the model material in this work. Experimental data for ceramic and coal particles reported in the literature were used for the model validation. The effect of particle thermophysical properties and operating variables is tested. Results showed that a decrease in pressure and an increase in the fluid temperature during drying lead to an elevation of mass flux during the constant rate period (CRP) and the falling rate period (FRP) of the drying process. Moreover, this increase in mass flux is more significant for particles with the highest effective porosity. Thus, we conclude that decreasing pressure and increasing the drying fluid temperature reduce the mass flow.

An experimental study to evaluate the convective heat transfer coefficient in a cylindrical packed bed of spherical porous alumina particles is investigated. The task consists in proposing a semi-empirical model to avoid excessive instrumentation and time consumption. The measurement of the bed temperature associated to a simple energy balances led to calculate the gas to particle heat transfer coefficient using a logarithmic mean temperature difference method. These experiments were performed at atmospheric pressure. The operating fluid is humid air. The gas velocity and temperature ranged from 1.7-3 m/s and 120-158?C, respectively. The data obtained was compared with the correlations reported in the literature. It is shown that the proposed model is in reasonable agreement with the correlation of Ranz and Marshall. Despite, many researches on experimental investigations of heat transfer coefficient in packed beds at low and average temperature are proposed, few studies presented calculation of convective heat transfer coefficient at high temperature (above 120?C). A possible application of the proposed model is drying and combustion.

Une etude experimentale du sechage convectif a haute temperature en vapeur d’eau surchauffee et du sechage a l’air d’une particule poreuse et spherique du bois (hetre) est presentee. Un dispositif de macro-TG, dans lequel une particule est suspendue et continuellement pesee au cours du sechage, est utilise. En prenant deux valeurs de la vitesse du fluide sechant (vapeur d’eau surchauffee ou air), nous avons mesure la teneur en eau et la temperature du produit au cours des deux procedes de sechage. Aussi, on a montre que le bois seche en vapeur d’eau surchauffee est nettement de qualite superieure a celle obtenue a l’air. En effet, la particule du bois sechee en vapeur d’eau surchauffee garde sa couleur naturelle alors que celle sechee a l’air noircit. Le procede de sechage en vapeur d’eau surchauffee repond alors au mieux a l’exigence la plus demandee par les industriels qui est qualite du produit. Parmi les applications possibles de sechage de ces particules est la fabrication du bois agglomere.

International audience; A model is presented for drying of a single porous particle with superheated steam and humid air. Experimental data for spherical porous ceramic particle reported in the literature were used for the validation of the model. An inversion temperature at which the evaporation rates within superheated steam and humid air are equal was predicted. The effect of thermophysical properties of the particle (permeability 10 À14 À 10 À17 m 2 , diameter 3 Â10 À3 À 10Â10 À3 m) and operating variables (gas mass flux 0.26 À 0.78 kg m À2 s À1 , drying agent temperature 120-200 C) is tested. The inversion temperature is shown to be affected by the thermophysical properties of the porous particle and of the drying agent. INTRODUCTION Superheated steam drying is an attractive technology that offers potential advantages such as reduced energy cost, smaller equipment, reduced emissions, reduced fire and explosion hazards, and improvements in product quality. [1-4] It can replace the air drying except for the thermally sensitive products. Wenzel and White [5] and Chu et al. [6] were the first to show experimentally that more intensive evaporation occurs in superheated steam than in air. Yoshida and Hyodo [7] demonstrated that superheated steam can provide an excellent medium for drying food products. Compared to humid air, superheated steam is cleaner, provides higher evaporation rate and there is less oxidation in food, thus reducing the loss in nutritional value during the drying process. The authors showed experimentally that the curves of evaporation rate with air and superheated steam would intersect at a point called the inversion temperature.

International audience; Among the numerous models developed to predict the shrinkage of materials during drying, the model developed by Katekawa and Silva [1] gives a general relationship between shrinkage and porosity with a limited number of parameters such as initial density of the wet product, true density of the solid phase, and true density of the liquid phase. A graphical interpretation of this model is proposed to visualize the changes of porosity by comparing the experimental shrinkage curve with an ideal one. Four examples are given to illustrate the applicability of the model using different materials (carrot, banana, xerogel, and sludge), two types of the solvent (water, iso-propanol), and two drying technologies (convective drying, freeze drying). Porosity calculations were found to be very consistent and complementary with porosity measurements.

International audience; This article deals with comparative study of low-pressure superheated steam drying (LPSSD) and vacuum drying using coal particles as model material. The focus is made on the inversion temperature, which means that the drying rate in the two drying processes becomes equal. This temperature is of great importance because it allows the choice of drying agent for given operating conditions. The effect of external and internal parameters on the drying kinetics and the inversion temperature were investigated. Several studies have shown discrepancies of inversion temperature values basing on the constant rate period (CRP) and the falling rate period (FRP). This work points out gaps in these temperature values using the two calculation methods.

International audience; The main objective of this work is to study experimentally and numerically a falling film in a micro-channel. The experimental section involves in creating a temperature gradient within the liquid, while monitoring the temperature using an infrared camera. A numerical model is established and solved by a semianalytical method called the thermal quadrupole method. Finally, we conclude with a comparison between the experiments and the numerical study.

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International audience; Based on a very simple model of mass conservation, three experimental properties (solid density, liquid density and initial bulk density) and the simultaneous acquisition of the reduced moisture content and the volume shrinkage during drying, a simple method is proposed to calculate the bulk porosity of a material during drying. This model allows a graphical interpretation to visualize the porosity change by comparing the experimental shrinkage curve with an ideal shrinkage curve. In the present work, several examples were taken from the literature to illustrate the application of this method to foodstuffs (apple, banana, carrot, garlic, pear, potato and sweet potato) with two different processes (convective drying, freeze-drying) and different drying conditions. Porosity calculations including error estimations showed a good agreement with experimental values reported in the literature.

International audience; A novel non-intrusive technique (stereo-correlation) was used to determine the apparent volume of a banana in convective drying condition. The volume was calculated using the 3D Digital Image Correlation method (3D-DIC), which provides the 3D shape of the banana during drying. The combination of this technique and mass measurement allows the calculation of the porosity using the model of Katekawa and Silva([1]) and the graphical interpretation presented by Madiouli et al.([2]) The banana shows an ideal shrinkage at the beginning of drying but stops shrinking at low moisture content, thus increasing the porosity up to 30-35%. The comparison of the experimental shrinkage and the calculated porosity with the experiments deduced from the literature enables us to conclude the effectiveness of the 3D-DIC technique as well as the porosity calculation model.

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International audience; A numerical study for the modelling of porous particles packed bed drying in one and two dimensions (1D and 2D) is presented in this work. This model is based on the averaging volume approach using two scale changes. Taking into account the non validity of the thermal equilibrium between the gas phase and the porous particle, a two temperatures model is then developed. The numerical resolution of macroscopic equations describing heat and mass transfer during the drying of a packed bed is carried out by the method of finite volume. Experimental data for spherical porous alumina particles reported in the literature were used for the validation of the model. A good agreement was found. The influence of particles thermophysical properties and operating variables is tested. A set of time-space evolution describes the progression of these variables with time, in the height and radius of the packed bed. The model results allow a better understanding of the heat and mass transfer mechanisms involved in a packed bed drying process.

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Combining grinding with burnishing called “REGAL” is a newly developed outstanding technique consisting in grinding and burnishing operating simultaneously. The purpose behind this innovative approach is to enhance the surface integrity of the workpiece obtained by REGAL if compared to grinding and burnishing performing each one apart. REGAL process is made possible thanks to the design and manufacturing of a mechanical fixing system capable of maintaining the burnishing ball next to the grinding wheel. An automated control table is needed to make small and precise lateral feeds in order to ensure high surface recovery rates obtained by the ball burnishing tool. The most influential parameters of REGAL process were identified and their impacts on surface integrity were studied in terms of forces, roughness and residual stress results. The experimental results have shown that further from gaining time and energy by combining two processes in one, REGAL process enhances drastically the quality of the surface obtained if compared to workpiece surfaces obtained after grinding and burnishing acting separately. In addition, simultaneous grinding and burnishing introduces compressive residual stress results at the surface and beneath it reaching a deeper depth than the depth obtained by burnishing at the same manufacturing conditions thanks to the physicochemical changes obtained by the simultaneous thermomechanical/purely mechanical loads applied to the workpiece. 3D numerical simulations of grinding, burnishing and REGAL were also conducted to understand the physical phenomena occurring that is responsible of getting a more compressive residual stress layer obtained by REGAL if compared to burnishing acting separately and are in adequacy with the experimental results.; Le procédé « REGAL » est une approche originale combinant deux procédés de fabrication différents, l’un thermomécanique (la rectification) et l’autre purement mécanique (le galetage), mis en œuvre simultanément. Pour cela, des modélisations et des simulations numériques 3D des différents procédés de rectification, de galetage et de rectification/galetage combiné ont été réalisées dans le but de mieux comprendre la physique à l’origine de l’obtention d’une meilleure intégrité de surface que celle obtenue par chaque procédé agissant séparément. Une démarche expérimentale a été développée sur la rectifieuse utilisée afin de pouvoir rectifier et galeter simultanément et un système de fixation de l’outil de galetage sur la broche de la rectifieuse a été conçu et fabriqué. Par ailleurs, l’avance automatique transverse de la rectifieuse utilisée est de l’ordre du mm par cycle alors qu’elle devrait être de l’ordre du μm/cycle pour le procédé de galetage. Ainsi, pour assurer un recouvrement total en galetage, il a été nécessaire de développer un système entièrement automatisé qui se positionne sur la table de la rectifieuse et qui permet d’avoir les bonnes avances par cycle avec une précision du dixième de micromètre. Des caractérisations de plusieurs facteurs de l’intégrité de surface ont été réalisées et ont montré que le procédé REGAL peut améliorer la qualité de la surface et introduire des contraintes résiduelles en compression à une profondeur plus importante que celle obtenue par le procédé de galetage agissant seul. La détermination expérimentale des contraintes résiduelles a permis de valider et de discuter les résultats des simulations numériques obtenus.Le procédé « REGAL » est une approche originale combinant deux procédés de fabrication différents, l’un thermomécanique (la rectification) et l’autre purement mécanique (le galetage), mis en œuvre simultanément. Pour cela, des modélisations et des simulations numériques 3D des différents procédés de rectification, de galetage et de rectification/galetage combiné ont été réalisées dans le but de mieux comprendre la physique à l’origine de l’obtention d’une meilleure intégrité de surface que celle obtenue par chaque procédé agissant séparément. Une démarche expérimentale a été développée sur la rectifieuse utilisée afin de pouvoir rectifier et galeter simultanément et un système de fixation de l’outil de galetage sur la broche de la rectifieuse a été conçu et fabriqué. Par ailleurs, l’avance automatique transverse de la rectifieuse utilisée est de l’ordre du mm par cycle alors qu’elle devrait être de l’ordre du μm/cycle pour le procédé de galetage. Ainsi, pour assurer un recouvrement total en galetage, il a été nécessaire de développer un système entièrement automatisé qui se positionne sur la table de la rectifieuse et qui permet d’avoir les bonnes avances par cycle avec une précision du dixième de micromètre. Des caractérisations de plusieurs facteurs de l’intégrité de surface ont été réalisées et ont montré que le procédé REGAL peut améliorer la qualité de la surface et introduire des contraintes résiduelles en compression à une profondeur plus importante que celle obtenue par le procédé de galetage agissant seul. La détermination expérimentale des contraintes résiduelles a permis de valider et de discuter les résultats des simulations numériques obtenus.