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Converting solar energy efficiently into hydrogen is a promising way for renewable fuels technology. However, high-temperature heat transfer enhancement of solar thermochemical process is still a pertinent challenge for solar energy conversion into fuels. In this paper, high-temperature heat transfer enhancement accounting for radiation, conduction, and convection heat transfer in porous-medium reactor filled with application in hydrogen generation has been investigated. NiFe-Aluminate porous media is synthesized and used as solar radiant absorber and redox material. Experiments combined with numerical models are performed for analyzing thermal characteristics and chemical changes in solar receiver. The reacting medium is most heated by radiation heat transfer and higher temperature distribution is observed in the region exposed to high radiation heat flux. Heat distribution, O2 and H2 yield in the reacting medium are facilitated by convective reactive gas moving through the medium's pores. The temperature gradient caused by thermal transition at fluid-solid interface could be more decreased as much as the reaction chamber can store the transferred high-temperature heat flux. However, thermal losses due to radiation flux lost at the quartz glass are obviously inevitable.

This research was conducted in the framework of the feasibility study related to FOCUSED-Benin project, the 5th work package of the YES-PV NIG BEN project financed by the German Government through its Ministry of Research and High Education (BMBF). The FOCUSED Benin project’s major objective is to protect the environment through the utilization of solar energy for drying agricultural products and table salt harvesting. Salt is important in human daily life. It is used for conservation of food, softening water, industrial processes, road de-icing, food seasoning, etc. Seawater evaporation, salt mining, and salt brine are the major sources of salt production worldwide. However, in West Africa, particularly in Benin Republic, table salt is produced using methods that negatively impact the ecology of the mangrove. This study aimed at investigating the current status of salt production in Benin Republic, its impact on the mangrove and its related health issues. Field visits, meeting with associations of women salt producers in the coastal region of the country, allowed to quantify the number of women associations dealing with salt production, their difficulties, and the impacts on the mangrove. Salt is a seasonal activity and is produced from January to May. One kilogram salt production, along with health issues reported by salt producers, requires approximately 1 kg of firewood obtained by cutting down mangrove. Salt price varies from 250CFA (€0.38) to 400FCFA (€0.61) per kg depending on the season. The women salt producers are not aware of the ecological consequences of mangrove destruction. Sources of firewood are becoming increasingly scarce and prices prohibitive. Sensitization is not efficient. An alternative method of harvesting salt by solar drying and new ideas for implementing this activity in a participatory approach was discussed with the different associations of salt producers.

This paper investigated radiative heat transfer and thermal characteristics of Fe-based oxides coated SiC and Alumina reticulated porous ceramic structures as integrated solar thermochemical reactor. High-flux solar radiation absorption and axial temperature distribution in the ceramic foams reactor were analyzed by adopting surface-to-surface radiation model coupled to the P1 approximation for radiation heat transfer. The radiative heat transfer and thermal characteristics of different foam-type RPC structures, including SiC, CeO2, FeAl2O4, NiFeAlO4, Fe3O4/SiC, and NiFe2O4/SiC were evaluated. The mass flow rate and foam structural parameters, including the permeability, pore mean cell size, and extinction coefficients have significantly affected the axial temperature distribution, pressure drop, heat transfer, and fluid flow. Integrated porous structure to the solar receiver could maximize the incorporation of redox powder in the reacting medium, lower the pressure drop, and enhance the thermal performance of the thermochemical reacting system. SiC structure was the candidate materials in the case where more heat flux and high axial temperature distribution is needed. However, Fe-based oxide coated Al2O3 structure could be considered regarding the heat transfer enhancement along with the catalyst activity of oxygen carriers for solar thermochemical reacting system performance.

Thermal reduction of the partial oxidation of CH4 NiFe2O4 followed by oxidation with H2O and CO2 was numerically investigated for H2 and CO production. P1 radiation model was used to account for radiative heat transfer. The synergistic effect of the reactivity of Fe/Ni exhibited a very promising strategy for producing 45% of syngas with 2.54 ratios of H2:CO at the first step and 55% of syngas with 2.34 ratios of H2:CO at the second step. The increase in incident radiation heat flux to 437.69 kW/m2 resulted in higher reduction kinetics of species conversion until the formation of oxygen carriers consisting of 65% of FeO, 35% of Ni Fe and 2.6% of carbon deposition. However, during the reduction process, the decrease in total pressure to 0.05 MPa enhanced the species reactivity and the production of H2 and CO while minimizing carbon deposition. Moreover, the oxidation temperature, operating pressure and the concentration of oxidizing species have strong impacts on the oxidation kinetics. Unlike high thermal reduction process, increasing the total pressure to 1 MPa has favorable effects on syngas production at oxidation step.

Redox thermochemical reactor model integrated concentrating solar power technology is finding increased interest due to the enormous advantages of storing renewable energy into high-temperature heat flux and clean transportable fuel. From the perspective of designing a scalable direct solar irradiated receiver, the reactor optimum design and solar thermochemical energy storage performance have been investigated. Numerical models combined with experiments were developed for the analysis of engineering design parameters affecting the reactor efficiency. The shape of the cavity receiver including the size of the glass-covered target radiant received surface and reactor volume, especially the axial length of the heat-storing medium can be considered as important design issues for improving thermochemical energy storage efficiency. The reactor efficiency of storing sunlight with safer operating conditions is reported to 85.27% ± 0.85% during thermal charging up to 1787.725 K ± 30.58 K and 76.9% ± 0.11% during thermal discharging step at 1315. 16 K ± 7.53 K. Increasing heat losses via receiver insulation layer significantly affects the reactor thermal performance. This study demonstrated that the solar-driven thermochemical process has the potential of achieving high-temperature storable heat and solar fuel production. Appropriate geometric parameters were provided for the scalability from the perspective of industrial implementation.

This paper investigated CO2 utilization into energy density chemical using NiFe2O4@Alumina support porous-medium filled reactor heated by high-flux solar simulator. A combination of numerical and experimental studies is developed to investigate the synthesis and characterization of the redox materials, thermal characteristics, redox reaction kinetics, and redox performance of NiFe2O4@Alumina support porous oxide material. Moreover, thermal and chemical energy conversion efficiency of NiFe2O4@Alumina support was analyzed. Considering the difficulty related to designing and manufacturing porous-medium filled solar thermal receiver, this study could provide tremendous innovation values and pattern impacts in the field of solar thermochemical (STC) energy conversion into fuels and chemicals.

Mastery of thermal control in the craft distillation processing operations of fermented wine from Elaeis guineensis is needed to improve and enhance the resulting Beninese alcoholic drink, sodabi. In this study, craft distillation of palm-wines from three municipalities of southern Benin was investigated and the influences of wine vapour temperature on some physical-chemical parameters of the liquor produced were analysed. Palm wines, handcraft distilled, presented relative density values between 0.90 to 0.96, volumetric alcoholic strength from 35.16 to 46.29% (v/v), acetic acid content of 1.17 to 3.29 g/l and pH-values of 3.7– 4.2. A series of palm-wine distillations, from liquor-producing farms, controlled by maintaining the heating temperature at 94 ± 1 °C, was also performed. The values of characteristic parameters were then respectively 0.84 to 0.93, 38.05 to 52.72% (v/v), 0.35 to 0.39 g/l and 4 to 4.25. From analysis of these results, we conclude that the high values of wine heating temperature, wel...

This paper presents the results of thermophysical characterization of the powder resulting from the solar drying of Moringa oleifera leaves. The desorption isotherms of the powder, are determined by the gravimetric static method. The models of B.E.T, Smith, Henderson, Iglesias and GAB are used for the smoothing of the experimental points. The Clausius-Clayperon and Gibbs-Helmholtz equation are used for the determination of thermodynamic properties. The isotherms obtained are with type II. The theoretical curves of GAB present a better similarity with the experimental curve at 55°C. The monolayer moisture content (Xm) is 6.32 and 7. 24 % at 30° C; 5.13 and 6.3% at 35 °C; 5.1 and 5.9 % at 45 °C; 4.22 and 4.66 % at 55 °C respectively for BET and GAB models. Isosteric and entropic heats are more important for low values of moisture content. The activation energy of desorption of the powder in the range of temperatures tested is -10.1009539 kJ/mol. Isokinetic temperature (Tβ) and the mean harmonic temperature (Thm) are respectively 301.2435K and 300.12342K and the free energy (ΔGβ) is 302.18 J/mol. The desorption process of the Powder is non-spontaneous and is done by controlled mechanisms enthalpic.Keywords: Moringa oleifera, Thermophysical characterization, Desorption isotherm, Thermodynamic properties, Modelization

International audience; This paper presents a study of the hot plate method with two simultaneous temperature measurements, on the heated and unheated faces of a sample to characterize. The thermal properties of polyvinyl chloride, plaster and laterite were considered to be a representative range of building materials. A 1D quadrupolar model was developed to represent the temperature evolution on the two faces over time. Three-dimensional numerical modeling of a quarter of the testing device with COMSOL software allowed defining the domain of the 1D hypothesis validity. The analysis of estimation possibilities of materials’ thermal characteristics, with the developed method, revealed that thermal effusivity can be accurately estimated by using the temperature of the heated face at the beginning of heating. We showed that the simultaneous use of two temperatures enables the estimation of the thermal conductivity with a greater accuracy and over a shorter time interval than using the temperature of the heated face alone. We also demonstrated that under certain conditions (samples with a high ratio of thickness to width) the method with two temperature measurements enabled the estimation of the thermal effusivity and conductivity, while the method with one temperature allowed only the thermal effusivity to be estimated, because of 3D effects. This conclusion was confirmed by experimental results obtained with a mortar sample.

In this study, effects of drying temperature on the physico-chemical and microbiological characteristics of Waragashi were investigated. Three types of produced Waragashi were investigated. The first one (V1) was obtained after coagulation of milk, the second called coloured Waragashi (V2), was obtained by boiling V1 for three minutes in aqueous solution of Sorghum vulgaris panicle (15 g/L) and the third one, refined Waragashi (V3) was obtained by boiling for three minutes, the Waragashi V1 into aqueous solution of S. vulgaris panicle (15 g/L), salt (10 g/L) and potash (3 g/L). The three fresh Waragashis contained 64.26, 57.34 and 54.04% moisture, respectively, for white Waragashi (V1), colored Waragashi (V2) and refined Waragashi (V3), while dried samples varied between 12.28 and 15.57%. The corresponding dried Waragashi were firmer than the fresh ones. Moreover, the colored cheeses (V2) were firmer (60.08 ± 5.40N and 206.4 ± 13.70 N) than the refined one (38.57 ± 3.10 N and 55.89 ± 5.89 N). After 48 h of drying, all samples showed a decrease of micro-organisms (mesophilic total bacteria, lactic bacteria, yeasts and moulds, Enterobacteria and Staphylococcus spp.) counts. However, drying at 45°C preserve more the physico-chemical characteristics of Waragashi. Key words: Waragashi, cheese, drying, physico-chemical characteristics, microbiological quality.

As a result of the global warming, the atmospheric temperature in sub-Saharan regions of Africa may drastically increase, thus worsening the poor living conditions already experienced by people in those regions. Roof’s thermal insulation capacity may play key role in reducing indoor thermal comfort cost. In the present study, effort is put to model heat transfer through roofs in south Saharan regions. Validation of the model was achieved using the slightly sloppy galvanized aluminum-iron sheet roof. Atmospheric data were hourly measured during April and June in Ouagadougou, Burkina Faso. Solar energy values increase from 24.50±0.50 W/m2 in the morning to a maximum of 900.1±0.8 W/m2 in the early afternoon. Ambient temperature follows the same trend as solar radiation with a maximum at 40.0±0.2°C. Wind speed varies from 0.5 to 4.0±0.1 m/s. The measured roof inner wall temperatures agreed excellently with the developed model with a Nash-Sutcliffe Coefficient of Efficiency of 0.988. Energy flux entering the room through the roof varies from 63.1±0.3 W/m2 earlier in the morning to a maximum of 115.3±0.5 W/m2 in the earlier afternoon. These results shall help to better design human habitat under changing climate conditions in the sub-Saharan regions.

International audience; This paper dealed with the valorization of Benin natural resources through the development of new composite materials made of banana fibers-cement mortar which could be used as thermal insulator in building. The developed composites were formulated and made by substituting a mix of sand and cement, in mass fractions, with the banana trunk fibers previously washed with hot water and dried. Cement was dosed at 250 kg m-3 of mortar and the ratio W/C was equal to 0.7 for the samples. The effected thermal tests by the hot plate method using two temperature measurements had shown a decreasing of the thermal effusivity and conductivity when the proportion of fibers increased. One had obtained the respective relative deviations of 25.54%, 56.09% and 65.68% between the thermal conductivity of the reference sample, which was equal to 1.14 W m-1 K-1, and that of the composites. These results made the composites interesting thermal insulators in building with reduction of the normally used quantity of cement and sand and valorization of agricultural waste. The water absorption was also calculated for each sample.

The cake, from peanut seeds oil-extraction, is classically used for cattle feed manufacture and fertilizers. It may also well be valorized as crispy patties for human food. Several variants of peanut patties, "kluiklui", rolled into sticks, are very prized in Benin. This passion for patties, coupled with fairly high price of groundnut seeds, incited patties producers to innovative and ingenious manipulations. From then, crude or roasted maize flour was incorporated to replenish many groundnut variants patties. This article is devoted to study influences of applied torrefaction to maize grains giving added flour during formulation of fried groundnut's defatted dough into different variants on some physical (residual humidity, apparent density, volume expansion rate), mechanical (fracture strength) and organoleptic (color, crustiness, taste) properties of the produced patties. The results showed that torrefaction causes significant decrease of residual water content, volume expansion rate and breaking strength, making corresponding patties less crusty and less well-liked by consumers as proven by realized tasting results. However, torrefaction of maize flour also induced increase of the patties apparent density. Nevertheless, the latter was less affected in comparison with the previous three cited characteristics. The groundnut patties variants, blended of maize flour at respective rates of 5% and 10% (weight-in-mix), were the most affected by torrefaction process relatively to recorded feeble breaking strength values and thus, the best prized by patties consumers. Keywords : maize seeds, bulk density, expansion rate, breaking strength, crustiness, taste.

One of the major concerns in designing of prestressed beams in ultra-high performance fiber- reinforced concrete (UHPFRC) is improvement of their ductility fracture due to the nature of the materials used in their manufacture. This can induce plastic behaviours which it is necessary to take into account by designing of such structures, especially when they are of large spans. In the present work, it is proposed an analytical model in large deformation of a rigid plastic prestressed UHPFRC beam embedded at one end and having at other end rolled support. She is approached by a local uniform load and external moments to supports. The proposed non-linear model can find exact analytical solutions for the determination of the local arrows and the associated charge by the technique of Lagrange multiplier which allows finding the stationary points of differentiable function of one or several variables under constraints. The results of this work can be useful in designing and calculation of long span prestressed structures with plastic rigid behavior.

Moringa oleifera leaves are increasingly used as a dietary supplement. The present study deals with the estimation of its thermophysical properties. It is based on the Clausius-Clayperon and Gibbs-Helmholtz equations. This study required knowledge of the sorption isotherms obtained by the static gravimetric method in the relative humidity range of 5.4 to 97% and the temperatures of 30, 35, 45 and 55 °C. The BET models (1938), Smith (1947), Henderson (1952), Iglesias (1981) and GAB (1985) are used for the smoothing of the experimental points. The isotherms obtained are of type II and characterized by a sigmoid shape. The theoretical curves of GAB and Smith show a better similarity with the experimental curves. The monolayer moisture content (Xm) is 8.54/7.62% at 30 °C; 7.0/5.52% at 35 °C; 6.74/ 5.41% at 45 °C and 5.45/4.65% at 55°C respectively for the GAB and BET models. The net isosteric heat ( qst ) and desorption differential entropy ( ΔS ) tend towards zero for very high moisture contents. The activation energy of desorption of the Moringa oleifera leaves in the temperature range tested is -13.1010 kJ/mol. Isokinetic temperature ( Tβ ) and the average harmonic temperature ( Thm ) are respectively 314.172 K and 314.459 K while the free energy ( ΔGβ ) is 308.18 J/mole. © 2017 International Formulae Group. All rights reserved. Keywords: Desorption isotherm, Modelization, Isosteric heat, Differential Entropy, Activation energy

La qualite du beurre de karite depend des processus qui ont conduit a son obtention. Dans la presente etude, sont exposes les resultats de l’influence des operations thermiques impliquees dans les procedes traditionnels d’extraction du beurre de karite (Vitellaria paradoxa) au Benin. L’effet de l’interaction des operations thermiques (de cuisson, de sechage, de torrefaction, de friture, de fumage et de chauffage) appliquees au cours de differents procedes d’extraction (Lokpa et Peulh au Benin, Tchabal au Cameroun) a ete evalue. Differents echantillons de beurre ont ete obtenus par la methode Soxhlet a partir des fruits, des noix cuites, des noix cuites sechees, des amandes sechees, des amandes sechees et torrefiees, des amandes sechees et frites, des amandes fumees. Les indices d’acide, de peroxyde et de refraction des differents echantillons de beurre ont ete determines; de meme que la teneur en eau et la composition en acide gras. Les resultats obtenus ont montre que les operations thermiques permettent la reduction de l’acidite des beurres. Quant au taux de peroxyde, il diminue avec des temperatures superieures a 145 °C. Par ailleurs, les multiples resultats obtenus montrent que la chaleur n’a pas d’effet sur la composition en acides gras du beurre. © 2013 International Formulae Group. All rights reserved. Mots cles : Karite, procedes traditionnels, operations thermiques, beurre, qualite.

Une etude experimentale du sechage par convection forcee, en couche mince (0,5 a 3 cm d'epaisseur) a ete realisee sur trois produits agricoles (le manioc, le gingembre et le gombo) a l'aide d'une soufflerie a conditions aerauliques et thermiques controlees. Cette etude a permis d'apprecier le comportement thermodynamique des produits pour differentes conditions de sechage (temperature de l'air de sechage 40 et 55 °C, vitesses d'ecoulement 0,5 a 3 m.s -1 , humidite absolue d'environ 15 g eau /kg air sec ) et d'identifier les meilleures valeurs des parametres caracteristiques du sechage par la methode de la Courbe Caracteristique Sechage (CCS). Il a ete etabli des correlations semi-empiriques qui permettent d'approcher au mieux les courbes experimentales obtenues lors des essais de sechage et de l'etude des isothermes de desorption obtenues par la methode gravimetrique a controle discontinu du poids de l'echantillon.