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Several series of batch and fixed bed column experiments have been carried out to study the methylene blue sorption and transport in sandy and clay soil under different experimental conditions. The non linear forms of the pseudo-second order kinetic model and the Freundlich and Langmuir isotherm models were used to quantify the maximum adsorption capacity of the used materials. The effects of several experimental factors (flow rate, initial concentration, saturation condition of soil and soil heterogeneity) on the breakthrough curves have been undertaken. Experimental data revealed that the breakthrough curves depend on flow rate, methylene blue inlet concentration, saturation condition of soil and soil heterogeneity. A two dimensional model based on Richards equation and advection–dispersion equation coupled with adsorption model was developed. A comparative analysis between this model and Thomas model showed the effectiveness of advection–dispersion model to describe the experimental breakthrough curves and particularly in an unsaturated heterogeneous medium. The advection dispersion model reproduces perfectly the transfer mechanisms in porous media and seems to be a useful tool to better understanding the physical processes and the effect of capillary barrier of methylene blue transport in unsaturated heterogeneous soil. The result shows also that the soil heterogeneity has a significant effect on methylene blue adsorption through unsaturated layered media. Furthermore, in the interface between two layers with different hydrodynamic proprieties, the adsorption capacity increases with a decrease in kinetic adsorption rate caused by the decrease in pore water velocity.

Energy conservation in buildings has been the focus of many studies since nearly one-third of global energy consumption is due to buildings. Phase change material (PCM) technology promises to be an attractive solution for energy saving in buildings since it is a passive and effective technology, as demonstrated in the literature. Therefore, this study focuses on the energy-saving performance of PCM-integrated buildings located in a Mediterranean climate to reveal their energy-saving potential. PCM is integrated both in external or internal south walls and roofs of buildings under four different climatic conditions. EnergyPlus, which is a well-known building simulation software, is adopted for building thermal analyses. The effects of melting temperature, location of PCM layer in the wall, thickness of PCM layer, type of envelope (wall or roof), and PCM double-layer system in the wall are investigated. The corresponding energy savings and CO2 emission reductions are obtained for the considered cases. The results showed that up to 41.6% reduction in energy demand can be obtained depending on the PCM application. Besides, PCM with a low melting temperature (21 °C) favored heating energy savings, while PCM with a high melting temperature (29 °C) favored cooling energy savings. Moreover, the double-layer PCM system provided higher energy savings than the single-layer PCM system, especially in warm and arid regions (Sousse and Tozeur). [ABSTRACT FROM AUTHOR]

Wind energy is a key driver for the transformation towards a sustainable energy system. From a certain point of view, the main parameter is to increase the turbines' height and the rotor's size to improve the economic aspect and performance. On the other hand, 'ducted wind turbines', which can significantly improve the performance of smaller wind turbines, are attracting much attention. The objective is to create system compatible with urban environments and at the same time improve the efficiency of ducted wind turbines. This article studies a configuration, namely a wind turbine equipped with a wind catcher system, by studying it both experimentally and numerically. First, the tests are carried out on the system without inserting the wind rotor. Then the results of the developed model are compared via experimental tests, showing that it is possible to accept wind from all directions and from different heights by using the wind collector system and the cones. The results also show that the maximum wind speed increases by 2.5 times in the middle of the cylindrical part where the turbine is planned to be placed. Finally, the effects of inserting a vertical axis wind turbine inside the cylindrical part of the system on its power coefficient are studied. The results show that the system significantly improves the maximum power coefficient of the turbine. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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.

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

An inverse problem was considered to estimate electrical conductivity distribution for the electrical resistance tomography. This technique allows to control the internal parameters by reconstructing the distribution of electrical conductivity of liquid/solid suspension. As an analytical tool, the quadrupole method was used to solve the forward problem in order to simulate the sensors voltage evolution. The inverse problem is solved using the Levenberg–Marquardt method. A major source of uncertainty in tomographic inversion is the data error. The effect of the measurement errors on the stability of the solution was investigated. In order to find the current injection strategy which gives more information about the electrical conductivity, sensitivity analysis was carried out. The effect of Levenberg–Marquardt coefficient and initial value of the conductivity on the stability of the scheme was analyzed. The developed algorithm can be employed to rebuild the electrical conductivity which permits to go back to the physical parameters of the suspension. [ABSTRACT FROM AUTHOR]

The main objective of this work is to investigate and validate the thermal quadrupole method, used in this paper as a semi-analytical method to solve the equations of a falling film in a heated microchannel studied experimentally. In the experimental section, we created a temperature gradient within the liquid, while monitoring the temperature using an infrared camera. Then, a numerical model is established and solved by the thermal quadrupole method. Finally, we conclude with a comparison between the experiments and the numerical study. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The description of flow transport through a porous media needs the knowledge of the permeability (k(h)/k(θ)) and water content functions (θ(h)). Traditional techniques for determining θ(h) involve stepwise equilibrium desorption or sorption experiments. k(θ) is often determined by steady state methods. Unfortunately, using the traditional way to determine these functions is often boring and time consuming. Earlier work has demonstrated the feasibility of using the inverse parameter estimation approach in determining these functions. In this work we propose to optimize some parameters of the soil hydraulic functions k(h) and θ(h) of the Van Genuchten's model, while being based on the results of the multi-step outflow experiments combined with the inverse method. The inverse problem is solved by using the Levenberg-Marquardt minimizing method of the least-squares norm. The results show that the model describes the process of drainage reasonably. The comparison of the measured and optimized values shows an agreement between measured and those optimized. [ABSTRACT FROM AUTHOR]