Entropy Generation and Optimization of Laminar Forced Convection Air Cooling in a Horizontal Channel Containing Heated Sources

A forced convection air-cooling of two identical heat sources mounted in a horizontal channel is numerically studied. Four effects of Reynolds number, separation distance, height and width of the components on the flow structure and heat transfer inside the channel have been examined. The entropy generation minimization method (EGM) is employed to optimize the heat transfer and fluid flow in the channel. The flow field is governed by the Navier–Stokes equation and the thermal field by the energy equation. The finite volume method and the SIMPLER algorithm are used to solve the continuity, momentum, energy and entropy generation equations. Results show that the mean Nusselt number increases with increase of the following parameters: Reynolds number, separation distance, height and width of the components. However, these parameters increase the total entropy generation, and thus provokes the degradation of the fan energy. The optimal values of separation distance, height and width heat source are: [(Sopt= 1 with W=0.25, C=0.25, Re=50, η=1.134), (Copt=0.3 with W=0.25, S=0.25, Re=100, η=0.895) and (Wopt= 0.1 S=0.25, C=0.25, Re=200, η=1.004)], respectively, where η is the optimization factor (=Num/S_T^*) and is defined as the ratio of Nusselt number to the total entropy generation. Finally, the optimal and the best configuration for maximum heat transfer and minimum entropy generation is observed at Re=50, S=1, C=0.25 and W=0.25

Synthesis, characterization and photocatalytic behavior of Ag doped TiO2 thin film

Superlattices and Microstructures 85 (2015) 255–265In this study, structure, microstructure, optical properties and photocatalytic degradation of Rhodamine B (RhB) have been investigated in an aqueous heterogeneous media containing pure and Ag doped TiO2 nanostructures thin films which were prepared by a simple sol–gel route. Thermal analysis demonstrated that Ag content decreased the temperature of anatase-to-rutile phase transformation. X-ray diffraction analysis confirmed that the prepared nanostructures crystallize within anatase-type structure and that the dopant Ag ions were not fully incorporated within TiO2 host lattice, meanwhile both the refractive index and optical band gap were affected by Ag concentration. The photodegradation of Rhodamine B under UV-C radiation by using pure and Ag-doped TiO2 nanostructures showed that Ag played an important role in a significant improvement of the photodegradation efficiency and that the optimum content of Ag ions was found to be 0.5% molar rati

Optimization of a rear system based on titanium nitride for a flexible CuInSe2 solar cell

International audienceFlexible thin film solar cells represent the future. This study concentrates on making CuInSe2 based solar cells non rigid by depositing the rear molybdenum contact onto inox 316.In order to overcome the Inox316 disadvantages such as the metallic impurities diffusion and the surface roughness, a bi-layer TiN/Ti have been introduced between the Mo rear contact and Inox 316. Two techniques have been employed: spray pyrolysis for CuInSe2 and by cathodic magnetron sputtering for Mo/TiN/Ti. CuInSe2 layers deposited onto glass substrates present high crystallinity with (112) preferred orientation at 550 °C. However, these properties disappear for CuInSe2 on Inox316 with missing peak (112) and fall in the ratio Se/Cu from 1.9 to 1.1.According to EDS analysis, these results may be due to the Fe and Cu diffusion from Inox316 to CuInSe2 film, this is why the presence of TiN/Ti bi-layer improves the surface condition of Inox 316 and reduces Iron presence from 9.7 % to 1.9 % and Cr from 3.8 % to 0.5 %; this confirms its efficiency to improve the solar cell performance using Inox316 substrate

Antioxidant Activity and Phenolic Content of Extracts of Wild Algerian Lingzhi or Reishi Medicinal Mushroom, Ganoderma lucidum (Agaricomycetes)

Mushrooms can be employed as functional food or medicines for prevention and treatment of several chronic diseases, since they are rich sources of bioactive metabolites. Nonetheless, the therapeutic value of Algerian mushrooms remains largely unexplored. There\u2019s no work concerning the different medicinal properties of the endemic Ganoderma lucidum in Algeria. The present study aims to compare the antioxidant potential of an endemic specimen collected at the forest of lake Tonga in the national park of EL Kala in North-East of Algeria with findings from other countries. To this end, the contents of phenolics and flavonoids were determined, using three solvents of increasing polarity (chloroform, ethyl acetate and butanol). The mushroom specimen was identified as G. lucidum based on strong molecular evidence using ITS, LSU and SSU sequences.Our study has shown that ethyl acetate extract contained higher total phenolic (171.1\ub11.06\u3bcg GAE/mg and 102.5\ub10.69 \u3bcg PE/mg extract) and flavonoid contents (25.48\ub10.13\u3bcg QE/mg and 40.45\ub10.83\u3bcg RE/mg extract) than in other mushroom extract (chloroform and butanolic). The ethyl acetate extract showed a good antioxidant activity in DPPH (28.51\ub10.24 \u3bcg/mL), ABTS\u2022+ (10.06\ub10.13 \u3bcg/mL), Galvinoxyl radical (15.46\ub10.48 \u3bcg/mL), Reducing power (22.74\ub10.30 \u3bcg/mL), CUPRAC (21.36\ub10.04 \u3bcg/mL) and Phenanthroline assay (12.87\ub10.26 \u3bcg/mL).These results suggest that G. lucidum could be used as a source of strong natural antioxidants for the food and pharmaceutical industries

γ-Ray irradiation effect on GdBO3/silica:Ce3+ composite prepared by sol gel method

Samples of GdBO3 doped with Ce3+ embedded in amorphous silica matrix were obtained by sol gel process and heat-treat at 1000°C for 2h in argon atmosphere. After elaboration, the samples were irradiated with γ-rays using cobalt (60Co) source in the dose range from 1 to 5kGy. The irradiation effect of γ-rays on structural and optical properties of the synthesized samples were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transforms infrared spectroscopy (FTIR) and photoluminescence spectroscopy. XRD and TEM-EDS results reveal that γ-ray irradiation reduces the crystallite size from 55nm to 30nm. It is found from FTIR study that the absorption bands intensity assigned to structural groups containing BO4 and BO3 units as well as the banding of Si-O-Si bond increases with γ-ray dose up to 4kGy. While photoluminescence measurements show that the emission bands attributed to the 5d→4F transition of Ce+3 ion intensity decreases, it is still significant even after irradiation to a dose of 5kGy. From this results it is concluded that the γ-ray irradiation up to a dose of 5kGy improve the structural and morphological quality of the synthesized GdBO3/silica: Ce3+ without altering significantly its luminescence properties