Two-dimensional numerical study of temperature field in an anode supported planar SOFC: Effect of the chemical reaction

In the present work the effect of the chemical reaction on the temperature field in an anode supported planar SOFC is numerically studied by the aid of a two-dimensional mathematical model. For the model development the mass transport phenomena, the energy conservation, the species flow governed by Darcy’s law and the electrochemistry are coupled. The finite difference method is used to solve numerically the system of the equations.The temperature field within each component of the SOFC (interconnection, cathode, anode and electrolyte) is calculated via the mathematical model which is implemented in FORTRAN language. The model results demonstrate the effect of different expressions of the chemical heat source, expressed in terms of enthalpy and entropy, on the temperature field and the location of the higher temperatures that occur within the SOFC during its operation.     

Optimisation of microwave‐assisted extraction of prune (Prunus domestica) antioxidants by response surface methodology

Optimal conditions for microwave‐assisted extraction (MAE) of total phenols (TP), epicatechin gallate and antioxidant activity from prune (Prunus domestica), rejected in transformation process of plum to prune, were determined by response surface methodology. The central composite design was used to study the effects of three independent variables: microwave power, irradiation time and solvent polarity on the TP, epicatechin gallate and antioxidant activity. Epicatechin gallate was identified as a major phenolic compound in prune extract by RP‐HPLC. Microwave power and irradiation time significantly affected all responses (P < 0.01). The highest TP (598.89 mg GAE/100 g prune) was obtained using water as an extraction solvent at 500 W, during 115 s. However, the optimal conditions for epicatechin gallate extraction were ethanol 80%, 435 W and 120 s. MAE is more efficient than conventional extraction method to obtain TP from prune. The experimental values were reasonably close to the predicted values confirming the validity of the predicted models.     

Corrosion study of single crystal Ni–Mn–Ga alloy and Tb<Subscript>0.27</Subscript>Dy<Subscript>0.73</Subscript>Fe<Subscript>1.95</Subscript> alloy for the design of new medical microdevices

Once placed in a magnetic field, smart magnetic materials (SMM) change their shape, which could be use for the development of smaller minimally invasive surgery devices activated by magnetic field. However, the potential degradation and release of cytotoxic ions by SMM corrosion has to be determined. This paper evaluates the corrosion resistance of two SMM: a single crystal Ni–Mn–Ga alloy and Tb_0.27Dy_0.73Fe_1.95 alloy. Ni–Mn–Ga alloy displayed a corrosion potential (E _corr) of −0.58 V/SCE and a corrosion current density (i _corr) of 0.43 μA/cm². During the corrosion assay, Ni–Mn–Ga sample surface was partially protected; local pits were formed on 20% of the surface and nickel ions were mainly found in the electrolyte. Tb_0.27Dy_0.73Fe_1.95 alloy exhibited poor corrosion properties such as E _corr of −0.87 V/SCE and i _corr of 5.90 μA/cm². During the corrosion test, this alloy was continuously degraded, its surface was impaired by pits and cracks extensively and a high amount of iron ions was measured in the electrolyte. These alloys exhibited low corrosion parameters and a selective degradation in the electrolyte. They could only be used for medical applications if they are coated with high strain biocompatible materials or embedded in composites to prevent direct contact with physiological fluids.     

Evaluation of the energy parameter J on rubber-like materials: Comparison between experimental and numerical results

The general purpose of our study is the determination of the energy parameter J when dealing with fracture of rubber-like materials. The energy parameter J is expressed in a multiplicative form in which a calibration factor is introduced in order to take into account the finite dimensions of the specimen. The parameter J, issued from fracture tests performed on S.E.N.T specimen of an E.P.D.M rubber is compared with the the J integral which is computed using a finite element procedure for the non-linear elastic materials with large deformation. The numerical results are in good agreement with the experimental data when considering the deeply cracked specimen (a/w ≥ 0.5). Below this limit, a divergence is pointed out which is attributed to a lack of accuracy of the identification procedure used to determine the experimental calibration factor. When this one is determined using the numerical J integral results, a better concordance is obtained.     

Performance of CF/PA12 composite femoral stems

This study presents the microstructural and mechanical behavior of the CF/PA12 composite material developed as well as its biomechanical performance when used for the fabrication of femoral stems. The static tests were performed to evaluate the compressive and flexural modulus as well as the ultimate compressive and bending strength. It was found that CF/PA12 composite had bone-matching properties in the same order of magnitude as cortical bone in the femur. Density and void content measurements were also done to assess the consolidation quality. Dynamic fatigue testing was conducted on both CF/PA12 cylinders and femoral stems to evaluate the long term durability and mechanical reliability of the composite. Compression–compression cyclic loading was used at a frequency of 6 Hz with loads varying between 17 kN and 22 kN for the composite cylinders while a frequency of 10 Hz and load of 2300 N was employed for the femoral stems. Results indicate that the fatigue performance of CF/PA12 composite surpasses by far the required fatigue performance for total hip prosthesis (THP) stems. The overall performance of the CF/PA12 femoral stems confirms that this composite is an excellent candidate material for orthopedic applications such as THP stems.     

Photoelectrochemical conversion of CO2 using nanostructured PbS–Si Photocathode

Journal of Applied Electrochemistry - A n-type nanostructured PbS thin films were prepared by chemical bath deposition onto flat Silicon (Si) and Silicon nanowires (SiNWs) which were derived from...     

Influence of Internal and External Parameters in Temperature of Hybrid PV/T Water Collector

The combination of photovoltaic system with a thermal to form the hybrid PVT （photovoltaic thermal）, which together will generate electricity and heat. This energy depends on the input that is to say the energy of solar radiation, temperature and speed wind and output which is the operating temperature of the system. This production also depends on the mode of heat removal. The authors present in this article; a study by a numerical simulation of the thermal behavior of a prototype hybrid sensor through the development of an energy balance that involves heat exchange between the different components of the hybrid sensor, and it will allow us to study the influence of internal and external parameters on the temperature variation in the different layers of the prototype PV/T studied.     

On the effect of the transversal aspect ratio on the double-glazed solar air heater performance

The transversal aspect ratio of solar air heaters (SAHs) is a critical geometric parameter that influences the heat transfer from the absorber plate to the working fluid and, accordingly, the overall heat loss level. The present work addresses the effect of the aspect ratio on the performance of a solar air heating system and the behavior of heat transfer coefficients (HTCs) within it and along the flow channel. A mathematical model of energy-balance equations was formulated to examine and analyze the double-glazed solar air heater thermal behavior. The Eismann correlation, which is more accurate than Holland's correlation, was employed to determine the HTC between the two glass covers. The useful energy, Nusselt number (Nu), efficiency, overall loss, and HTCs as a function of the aspect ratio were evaluated across the collector length. On the basis of the findings, the higher the ratio, the better the efficiency of the SAH. Indeed, increasing the collector's cross-sectional aspect ratio (r) up to 19 increases useful energy efficiency by more than 87%, Nu by 84%, thermohydraulic efficiency from 0.4 to 0.76, and overall heat loss by 1.15 W/(m² K). Furthermore, reducing r from 19 to 2 will improve the collector power from 1.855 to 3.473 kW.     

Experimental and analytical investigation of the cylindrical part of a metallic vessel reinforced by filament winding while submitted to internal pressure

In this work, we present an experimental and analytical investigation of a hydrogen storage vessel. This vessel is made of a carbon/epoxy envelope coated on a metal liner. In the theoretical part, an analytical model is proposed in which the laminate composite is assumed to be an anisotropic purely elastic material, whereas the liner is considered as an elasto-plastic material. The suggested analytical model provides an exact solution for stresses and strains on the cylindrical section of the vessel solution submitted to mechanical static loading. The aim of the experimental part is to validate the results of the theoretical model by manufacturing and testing some prototype vessels. Some analytical results are compared with the finite element solutions, a good correlation is observed.     

Study of hydrogen production by three strains of Chlorella isolated from the soil in the Algerian Sahara

In this study, the photosynthetic hydrogen production rates by some strains of green microalgae were investigated. Three strains of Chlorella isolated from arid soil and foggaras's water in the Algerian Sahara were used. Chlorella sorokiniana strain Ce, Chlorella salina strain Mt and Chlorella sp strain Pt6 produced hydrogen gas under sulphur-deprived conditions, but its rate was dependent on strain type and oxygen partial pressure in medium. In C. sorokiniana strain Ce, the maximum value of hydrogen accumulated was 147 ml at 222 h at 2% of O₂ pressure. Compared to C. sorokiniana strain Ce, C. salina strain Mt and Chlorella sp strain Pt6 produced less amount of hydrogen, but they were able to sustain with an O₂ partial pressure of up to 11–15.4%. Our data were compared with hydrogen production by Chlamydomonas reinhardtii. In this communication, the relationship between physiological behaviour, biochemical characteristic (starch and protein) and rates gas production (O₂ and H₂) was also specified.