Contribution to the modeling of a voltage driven pulsed eddy current sensor for the characterization of conductive plates

We highlight some physical phenomena occurring in pulsed eddy current testing, through the modeling of the response of a voltage driven pulsed eddy current sensor for the characterization of the thickness and conductivity of a metallic conductive plate. We use the finite element time domain method coupled to the electric circuit equation in the eddy current sensor which consists of an air cored coil. The characterization parameters are obtained from the current variation in the coil. The effects of the thickness and conductivity are clearly distinguished by considering three metallic plates of different conductivities. Time and frequency approaches are considered. We show that the reconstitution of the coil response signal from its Fourier series expansion leads to a loss of important features of the latter, limiting thus the characterization parameters, since this reconstitution does not take account of the sub-transient phenomena, i.e., the time of diffusion of the electromagnetic field in the conductive plate. The numerical results are supported by measurements.     

Numerical simulation of exchange membrane fuel cells in different operating conditions

A two-dimensional, steady state model for proton exchange membrane fuel cell (PEMFC) is presented. The model is used to describe the effect operation conditions (current density, pressure and water content) on the water transport, ohmic resistance and water distribution in the membrane and performance of PEMFC. This model considers the transport of species and water along the porous media: gas diffusion layers (GDL) anode and cathode, and the membrane of PEMFC fuel cell.     

Transport phenomena effect on the performance of proton exchange membrane fuel cell (PEMFC)

The aim of this work is to present a two-dimensional transient model, of heat and mass transfer in a proton exchange membrane fuel cell (PEMFC). The model includes various conservation equations such as mass (hydrogen, oxygen, water concentration), Momentum and energy equations this model is combined with the electrochemical model.     

Kinetics study of microwave-assisted solvent extraction of oil from olive cake using hexane: Comparison with the conventional extraction

Microwave-assisted solvent extraction (MASE) of oil from olive cake can be used as an alternative for conventional solvent extraction (CSE).The present research showed that, compared to the CSE, the MASE gave better yields within very short times. The results obtained with this new procedure indicated that the radiation power and exposition time enhanced extraction ability.The Patricelli model has been applied to describe the MASE kinetic. The coefficients of determination were found to be very high in all the cases (R² ≥ 0.992) indicating a good fit of the experimental data at tested conditions. The results obtained were compared with those given by the same model in the case of the conventional extraction.Industrial relevanceOlive cake pollutes the environment around the Mediterranean basin where it is generated in great amounts within a short period (from November to March). To avoid this pollution, it must be treated. Its valorization by recovery of its residual oil using conventional solvent extraction is time-consuming and needs large volumes of solvent. Compared to this conventional technique, the microwave-assisted solvent extraction can be a nice alternative because it gives better yields within short times and consumes less solvent.     

Temperature field,H2 and H2O mass transfer in SOFC single cell: Electrode and electrolyte thickness effects

The temperature increment in electrodes and electrolyte of a fuel cell is mainly attributed to the chemical reaction and the irreversibilities. The aim of this work is to study the increasing temperature of a SOFC single cell under the influence of the electrode and electrolyte thicknesses for its type of heat source. The hydrogen and water field are also discussed according to anode thickness.     

One dimensional transient numerical study of the mass heat and charge transfer in a proton exchange membrane for PEMFC

The objective of our study is to quantify the mass water transferred by various modes: diffusion, convection and migration. For the water transfer, the principal forces considered in the model are, the convection force, the osmotic force (i.e. diffusion) and the electric force (migration). The first of these forces results from a pressure gradient, the second of a concentration gradient and the third of a protons' migration from the anode to the cathode, which has an effect on the dipole of the water molecules (resistance force to the advancement). The numerical tool used to solve the equations' system is the finite element method. The results obtained numerically considering this method are concentration profiles and concentration variation with time and membrane thickness. These results illustrate the contribution of each mass transfer mode.     

Study of the effect of gamma irradiation on the structure and properties of metallocene linear low density polyethylene containing hindered amines

The changes in the carbonyl index, the melt flow rate, the crystalline content and the ultimate tensile properties of metallocene linear low density polyethylene (mLLDPE) films subjected to gamma irradiation from 10 to 800 kGy, were investigated with and without hindered amine stabilizer (HAS). For comparative purposes, unstabilized and HAS stabilized low density polyethylene (LDPE) were also studied. The results indicated that under gamma irradiation, the HAS stabilizer did not have any influence on the oxidative stability of mLLDPE films as compared with unstabilized ones due probably to complexation reactions between the nitroxyl radicals of the stabilizer and the metallocene catalysts leading to inert species. Moreover, higher increases in melt flow index and crystalline content with a fast drop in ultimate tensile properties were observed for higher doses indicating the occurrence of chain scission. It was also found that the metallocene LLDPE structure had no significant effect on the radiation induced oxidative degradation kinetics when compared to LDPE. Whereas, the addition of HAS to LDPE significantly lowered the formation rates of carbonyls and subsequently improved the durability of the material by doubling the half-value-dose.     

Characterization of cellulose nanowhiskers extracted from alfa fiber and the effect of their dispersion methods on nanocomposite properties

In this study, cellulose nanowhiskers (CNW) were prepared from alfa fiber (Stipa tenacissima) by an alkali treatment at room temperature in association with a bleaching treatment followed by a sulfuric acid hydrolysis. Fourier Transform Infrared (FT-IR) spectroscopy was used to highlight the evolution of chemical composition. Atomic Force Microscopy and Zeta-sizer indicated that the transverse size of the particles varied between 30 nm and 170 nm. Thermal stability was higher for CNW as compared to alfa fiber. FT-IR, X-ray diffraction, and Thermogravimetric analysis studies confirmed the removal of hemicelluloses and lignin during the chemical treatment process. The swelling of CNW in water with Cloisite 30B (CNW/C30B) or with the Polyethylene glycol (CNW/PEG) was carried out. The properties of Polyvinyl Chloride (PVC) nanocomposites reinforced with CNW which was dispersed with two different methods were also compared. The results showed that the morphology of both samples have drastic differences which may explain the fact that the storage modulus prepared with CNW/C30B was higher than those prepared with CNW/PEG. However, PVC/CNW/PEG nanocomposites exhibited more thermal stability. In the end, the obtained CNW may have potential applications in alternative power sources as a reinforcement phase.