Varying Heating Effect on Mixed Convection of Nanofluids in a Vented Horizontal Cavity with Injection or Suction

The problem of mixed convection heat transfer inside a horizontal vented enclosure through the lower and upper parts, respectively, of its left and right vertical walls is studied numerically using Al₂O₃-water nanofluid as working fluid. The bottom wall is subjected to a linearly varying (increasing or decreasing) heating temperature profiles, while the other boundaries are considered thermally insulated. The fresh fluid is admitted from the bottom part of the left vertical wall by injection or by the suction imposed on the opening of the right vertical wall. Based on numerical predictions, the conjugate effect of the Reynolds number and the nanoparticle concentration on fluid flow and heat transfer characteristics is studied. The obtained results demonstrate clearly the positive role of the nanoparticles addition on the improvement of the heat transfer rate and the mean temperature within the cavity. In addition, the flow structure and the temperature distribution inside the cavity are seen to be very sensitive to the variations of the Reynolds number, the imposed external flow mode, and the heating type. Results presented show that, in general, the decreasing heating mode is more favorable to the heat transfer in comparison with the case of the increasing heating mode. The cooling efficiency is found to be more pronounced by the injection/suction mode by applying the increasing/decreasing heating type.     

Modified method for transformer magnetizing characteristic computation and point-on-wave control switching for inrush current mitigation

This paper proposes a new model for the low-frequency transient analysis of a transformer, with a modified equation for calculation of the flux-current characteristic representing the saturation inductance of the transformer. The model is based on the V-I (voltage-current) no-load curves and uses the no-load reactive power losses. To validate the model, it was used to simulate the no-load magnetizing current in steady-state condition, as well as the transient inrush current at network frequency. Evaluation was done both by comparing the simulation results obtained with the proposed model and those available in the relevant literature, and by practical measurements. The experimental results presented in this paper were obtained via a laboratory setup and a data acquisition system based on the dSPACE board 1104. Moreover, a control switching to mitigate the transient inrush current in a transformer was developed and applied experimentally in the laboratory and also in the simulations. This control strategy was performed by taking into account the residual flux at the opening instant of the related circuit breaker. A comparative study was carried out showing the validity of the proposed model and the mitigation technique.     

Indirect P&O type-2 fuzzy-based adaptive step MPPT for proton exchange membrane fuel cell

Neural Computing and Applications - The output power of the fuel cell depends on the operating conditions, such as the temperature and membrane water content. Therefore, a robust maximum power...     

Assessment of interfacial polymerization modalities on the performance of polyaniline doped polyethersulphone hollow fiber membranes

Polyethersulfone hollow fiber membranes doped with polyaniline were coated by interfacial polymerization (IP) using different monomer pairs. The coated fibers were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, and atomic force microscopy, water contact angle (CA), porosity, and mechanical properties. Moreover, the performance of coated fibers has been tested at low to medium pressure by measuring pure water flux and magnesium sulfate salt solution. Characteristics and performance have been assessed and compared for all samples. Porosity decreased for all coated samples as compared to the raw sample. Optimum results were obtained using m-phenylenediamine and trimesoyl chloride depicting the lowest water CA (68°), highest Young's modulus (183 MPa), lowest pure water flux (0.28 LMH/bar), and the highest salt rejection (63% at 9 bar).     

Membrane-hydration-state detection in proton exchange membrane fuel cells using improved ambient-condition-based dynamic model

Proton-exchange-membrane fuel cells (PEMFCs) are a popular source of alternative energy because of their operational reliability and compactness. This paper presents an improved model to represent the semi-empirical voltage of PEMFCs to overcome the limitations of existing models. The proposed model considers variations in ambient conditions, such as the ambient temperature and relative humidity, to obtain the accurate output voltage that corresponds to variations in dynamic and static loads. The proposed model was developed by conducting several experiments on the Horizon PEMFC system under normal, humid, and dry ambient conditions. Subsequently, the model parameters corresponding to each case were optimised using the quantum lightning search algorithm (QLSA). Parameters demonstrating significant variations with ambient conditions were finally represented as a function of the ambient temperature and relative humidity via statistical regression analysis. The voltage obtained using the modified model was verified by conducting experiments on both the Horizon and NEXA PEMFC systems by varying the ambient temperature and relative humidity with root mean square error (RMSE) less than 0.5. As observed, the results we obtained using the modified model closely approximated those obtained using PEMFCs under various operating conditions, and in both cases, the PEMFC voltage was observed to vary with the ambient and load conditions. The inherent advantages of the proposed PEMFC model include its ability to determine the membrane-water content and water pressure inside PEMFCs. The membrane-water content provides clear indications regarding the occurrence of drying and flooding faults. Under normal conditions, this membrane water content ranges from 11 to 7 for both the Horizon and NEXA PEMFC system. The simulation results suggested using the threshold membrane-water-content level as a possible indicator of fault occurrence under extreme ambient conditions. The limits of the said threshold were observed to be useful for fault diagnosis within PEMFC systems.     

Isothermal Crystallization of Palm Oil-Based Fats with and without the Addition of Essential Oils

The objective of study was to evaluate the crystallization behavior of palm oil-based fats processed with and without the addition of essential oils (5% w/w) obtained from the flowers (EsOF) and stems (EsOS) of Pituranthos scoparius. Palm oil (PO) and a mixture of PO, soybean oil, and sunflower oil (Mix) were tested. The addition of the essential oils did not change the melting points of the fats but affected their crystallization behavior. A delay in crystallization was observed, evidenced by lower crystallization rates, and lower solid fat contents. This delay was comparable in the samples crystallized with EsOF and EsOS for the PO samples but EsOF was more efficient at delaying crystallization in the Mix sample. EsOF generated a less organized crystalline network in both samples (lower enthalpy values) while EsOS generated a more organized crystalline network (high enthalpy values) when used in the Mix sample. The addition of EsO also affected the crystal microstructure in some cases. While a slight increase in crystal size was observed for some PO samples crystallized with EsOF, no change or a decrease in crystal size was observed for the samples crystallized with EsOS. A slight decrease in crystal size was observed for Mix samples crystallized with EsOF while no effect was observed for these samples crystallized with EsOS. Results from this study show that these essential oils can be used as natural additives to modify the crystallization of fats for food applications and therefore widen their functional properties.     

Comparative Study of Fatty Acid Composition,Total Phenolics,and Antioxidant Capacity in Rapeseed Mutant Lines

There is limited variability within rapeseed germplasm in Morocco. Induced mutation was recently used to generate novel genetic variability and develop mutant lines combining desirable traits. In this context, nine promising advanced rapeseed M₂ mutant lines and the wild-type variety “INRA-CZH2” were evaluated for their seed oil content, fatty acid composition, total phenolic content (TPC), and free-radical scavenging activity (FRSA) by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 3-ethylbenzothiazoline-6-sulfonic acid (ABTS) methods. The results showed significant variability among all mutants in seed oil content (38.14–42.04%) and fatty acids (SAFA = 5.49–10.99%, MUFA = 50.33–71.62%, PUFA = 22.89–8.68%). The mutant H2M-5 exhibited the highest fraction of MUFA and the lowest proportion of SAFA and PUFA, while the mutant H2M-4 showed the highest SAFA and PUFA amounts and the lowest MUFA level. TPC varied from 2.16 to 4.35 mg GAE/100 g. The highest amount was found in the mutant H2M-1, which is about twice that of other mutants and the wild-type variety. FRSA differed significantly among the samples, and the variations observed for DPPH and ABTS methods were 40.5–59.28% and 40.31–59.86%, respectively. FRSA was positively correlated to TPC in the sampled oils (r = 0.801 and 0.802, P < 0.01). This is the first report emphasizing the biochemical potential of rapeseed varieties and novel mutants in Morocco. H2M-1, H2M-4, and H2M-5 were proposed for the Rapeseed National Breeding Program, as they showed higher levels in some biochemical traits of interest.