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numerical Study of Mixed Convection in an Isosceles Trapezoidal Cavity with Several Outlets: Application for Primary Air Draft in ASUTO Charcoal Stove

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Modern Mechanical Engineering 2022年第2期12卷 45-61页

作者： Gagnon Koffi Apedanou kokou n’wuitcha Yendoubé Lare Kossi napo Laboratoire sur l’Energie Solaire Chair Unesco Faculté des Sciences Université de Lomé Lomé Togo Laboratoire sur l’Energie Solaire Groupe Phénomènes de Transfert et Energétique (LES-GPTE) Faculté des Sciences Université de Lomé Lomé Togo

Mixed convection of heat and mass transfer in an isosceles trapezoidal cavity has been studied numerically. Constant heat flux is imposed through four outlets and the grid is insulated. The inclined walls are maintained in natural convection while the lower horizontal wall is adiabatic. These conditions reflect the air draft zone of the ASUTO charcoal stove. The governing two-di- mensional flow equations have been solved by using the finite difference method and Thomas’s algorithm. The investigations are conducted for different values of Richardson (Ri), Reynolds number (Re) and inclination angles of sidewalls. The results are presented in terms of streamlines, isotherms, moisture contours. It was found that for Reynolds number (Re) equal to 100, the flow pattern is strongly dependent on the inclination angle and Richardson number. Thus, for high Richardson number (Ri) values (10, 100), the dominance of natural convection over the flow structure decreases with the decreasing of the inclination angle of sidewalls of the cavity. For Ri = 1, an optimum air draft corresponds to an inclination angle in the vicinity of 22° while for Ri = 10 or 100 (in dominance of natural convection), the optimum inclination angle for air draft is in the vicinity of 15°.

关键词： Mixed Convection Heat and Mass Transfer Trapezoidal Cavity ASUTO Charcoal Stove Richardson number Several Outlets

Soil nature Effect Investigation on the Ground-to-Air Heat Exchanger for the Passive Cooling of Rooms

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Open Journal of Fluid Dynamics 2022年第4期12卷 321-341页

作者： kokou n’wuitcha Yendouban Kolani Yawovi nougblega Magolmèèna Banna Belkacem Zeghmati Department of Physics Solar Energy Laboratory University of Lome Lome Togo Department of Physics Laboratory of Mathematics and Physics University of Perpignan Perpignan France

The building sector consumes much energy either for cooling or heating and is associated to greenhouse gas emissions. To meet energy and environmental challenges, the use of ground-to-air heat exchangers for preheating and cooling buildings has recently received considerable attention. They provide substantial energy savings and contribute to the improvement of thermal comfort in buildings. For these systems, the ground temperature plays the main role. The present work aims to investigate numerically the influence of the nature of soil on the thermal behavior of the ground-to-air heat exchanger used for building passive cooling. We have taken into account in this work the influence of the soil nature by considering three types of dry soil: clay soil, sandy-clay soil and sandy soil. The mixed convection equations governing the heat transfers in the earth-to-air heat exchanger have been presented and discretized using the finite difference method with an Alternate Direction Implicit (ADI) scheme. The resulting algebraic equations are then solved using the algorithm of Thomas combined with an iterative Gauss-Seidel procedure. The results show that the flow is dominated by forced convection. The examination of the sensitivity of the model to the type of soil shows that the distributions of contours of streamlines, isotherms, isovalues of moisture are less affected by the variations of the nature of soil through the variation of the diffusivity of the soil. However, it is observed that the temperature values obtained for the clay soil are higher while the sandy soil shows lower temperature values. The values of the ground-to-air heat exchanger efficiency are only slightly influenced by the nature of the soil. nevertheless, we note a slightly better efficiency for the sandy soil than for the sandy-clayey silt and clayey soils. This result shows that a sandy soil would be more suitable for geothermal system installations.

关键词： Soil Temperature Laminar Regime Ground-To-Air Heat Exchanger Heat Transfer Geothermal System

Modeling of Heat Transfers in Bioreactive Household Waste Storage Facilities: Spatial and Temporal Distributions

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Journal of Sustainable Bioenergy Systems 2022年第3期12卷 37-56页

作者： Komlan D. D. Aoukou kokou n’wuitcha Kalifa Palm Magolmèèna Banna Belkacem Zeghmati Department of Physics Solar Energy Laboratory University of Lome Lome Togo Research Institute in Applied Sciences and Technologies Ouagadougou Burkina Faso Department of Physics Laboratory of Mathematics and Physics University of Perpignan Perpignan France

In order to enhance the production of biogas and to study the thermal behavior of waste, a numerical study of fluid flows and heat transfers within household waste was developed to predict the distributions of thermal fields. The mathematical model is based on the conservation of mass and energy equations. The resulting system of equations is discretized using the finite volume method and solved using the Thomas algorithm. The results of the model studied are compared with the numerical and site measurements results from other authors. The results have been found to be in good agreement. The results show that the mathematical model is able to reproduce the thermal behavior in anaerobic phase in landfills. The isotherms revealed that temperatures are lower in the upper part of the waste cell, very high in the core and decrease slightly in the bottom of the cell due to the biodegradation of waste.

关键词： Household Waste Biogas Temperature Heat and Mass Transfer Mathematical Model

Influence of Leachate Recirculation on Landfill Degradation and Biogas Production

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Energy and Power Engineering 2023年第1期15卷 37-51页

作者： kokou n’wuitcha Komlan Déla Donald Aoukou Yawovi nougbléga Magolmèèna Banna Xavier Chesneau Department of Physics Solar Energy Laboratory University of Lome Lome Togo Department of Physics Laboratory of Mathematics and Physics University of Perpignan Perpignan France

Population growth combined with the rising standard of living of people around the world is the reason for the ever-increasing production of waste which management is costing states a lot of money for its disposal. Among available waste treatment techniques, landfill is one of the most promoted waste management techniques with the emergence of the bioreactor concept. However, the control of biodegradation parameters in order to accelerate waste stabilization is an important issue. For environmental and economic reasons, the technique of leachate recirculation by injection into the waste is increasingly used to improve the degradation of landfilled waste. The injection of leachate is possible using vertical boreholes, horizontal pipes, infiltration ponds or a combination of these. Indeed, moisture is the main factor in waste degradation and biogas production. The migration of leachate to the bottom of the landfill creates low moisture in the upper areas of the landfill reducing the growth of microbial populations. This results in low or no biogas production. The main objective of the present work is to develop a numerical model of leachate recirculation by injection into the waste to rewet the waste and restart biological activity. The analysis of the results shows that the diffusion of the wet front increases with time and depth. The lateral widening of the wet front is slow in relation to the progression of the wet front towards the bottom of the waste cell. This indicates the predominance of gravity effects over diffusion phenomena. The results reveal that the distributed re-injection is the best mode of leachate recirculation because the moisture distribution on the whole waste mass is totally satisfactory and the biogas generation is more important. Leachate recirculation campaigns should be done periodically to rewet the waste, boost microbial activity and hope for a quicker stabilization of the landfill.

关键词： Moisture Leachate Recirculation Biogas Distributed Reinjection Landfill

Modeling Submicron Particles Collection in Laminar Forced Convection Gas Flow by a Rectangular Venturi Scrubber

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Open Journal of Air Pollution 2016年第1期5卷 10-26页

作者： Serge Wendsida Igo kokou n’wuitcha Belkacem Zeghmati Xavier Chesneau Département Energie Institut de Recherche en Sciences Appliquées et Technologies (IRSAT/CNRST) Ouagadougou Burkina Faso GPTE-LES Département de Physique Université de Lomé Lomé Togo Laboratoire de Mathématiques et Physique des Systèmes (LAMPS) Perpignan France

Venturi scrubbers are usually used for large particles cleaning in turbulent gaseous flow. In this work, submicron particles scrubbing in laminar forced convection dusty air flow in a rectangular venturi scrubber have been numerically simulated. Hydrodynamics effects and scrubbing process are investigated in detail. Results are presented as flow velocity, axial pressure, streamlines pattern, particles and droplets mass fraction profile, and collect efficiency. They show that venturi scrubbers can be efficient for submicron particles scrubbing. In fact, a better collect efficiency is obtained at high particles-droplets residence time, high ratio droplets concentration/particles concentration, low venturi diameter ratioand low Reynolds numbers. There is a critical Reynolds number value for which the collect efficiency becomes very low and tends to be constant.

关键词： Venturi Scrubber Submicron Particles Diffusion Laminar Flow Collect Efficiency

Management of Traumatic Brain Injuries at the Kara Regional Hospital

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Surgical Science 2024年第2期15卷 19-27页

作者： Tamegnon Dossouvi Tchaa Hodabalo Towoezim Abdel Kader Moumouni kokou Kanassoua Iroukora Kassegne Ekoue David Dosseh Department of General Surgery Dapaong Regional Hospital University of Kara Kara Togo Department of Traumatology and Orthopaedics Kara University Hospital University of Kara Kara Togo Department of neurosurgery Kara University Hospital University of Kara Kara Togo Department of General Surgery Kara University Hospital University of Kara Kara Togo Department of General Surgery Kara Regional Hospital University of Kara Kara Togo Department of General Surgery Sylvanus Olympio University Hospital of Lomé University of Lomé Lomé Togo

Introduction: Traumatic Brain Injury (TBI) is a major public health problem causing significant morbidity and mortality in young adults. This study aimed to describe the epidemiological, diagnostic, therapeutic, and evolutionary aspects of TBI. Materials and Methods: This was a prospective, descriptive study conducted from 1 April 2022 to 31 March 2023 on patients admitted to and treated for cranioencephalic trauma in the General Surgery department of Kara Regional Hospital. Results: Eighty-three (83) patients with cranioencephalic trauma were managed out of 773 patients admitted to the department during the study period. The mean age was 34 ± 14.98 years and the sex ratio was 3.6 in favour of men. Motorbike taxi drivers were the social group most affected (n = 33, 40%). The causes of trauma were dominated by public road accidents (n = 80;96%). TBI was mild (n = 40;48%), moderate (n = 35;42%) and severe (n = 8;10%). Cerebral CT scans were performed in 19 patients (23%). Cerebral contusion (n = 4) was the most frequent cerebral lesion. Six patients (7%) with severe head injuries were transferred to Kara University Hospital. Six deaths (7%) occurred in patients with severe head injuries. The main sequelae were intermittent headaches in all patients reviewed, and memory problems (6%). Conclusion: Traumatic brain injuries are common at Kara Regional Hospital. Severe cranial trauma is less frequent but leads to death because of financial difficulties and limited technical facilities.

关键词： Traumatic Brain Injury Road Accident Motorcyclist Cerebral Contusion Togo

Chebyshev polynomial-based Ritz method for thermal buckling and free vibration behaviors of metal foam beams

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Applied Mathematics and Mechanics(English Edition) 2024年第5期45卷 891-910页

作者： n.D.nGUYEn T.n.nGUYEn Faculty of Civil Engineering Ho Chi Minh City University of Technology and EducationHo Chi Minh City 71309Viet Nam Faculty of Engineering and Technology Kien Giang UniversityChau Thanh 92000Viet Nam

This study presents the Chebyshev polynomials-based Ritz method to examine the thermal buckling and free vibration characteristics of metal foam *** analyses include three models for porosity distribution and two scenarios for thermal *** material properties are assessed under two conditions,i.e.,temperature dependence and temperature *** theoretical framework for the beams is based on the higher-order shear deformation theory,which incorporates shear deformations with higher-order *** governing equations are established from the Lagrange equations,and the beam displacement fields are approximated by the Chebyshev *** simulations are performed to evaluate the effects of thermal load,slenderness,boundary condition(BC),and porosity distribution on the buckling and vibration behaviors of metal foam *** findings highlight the significant influence of temperature-dependent(TD)material properties on metal foam beams'buckling and vibration responses.

关键词： Ritz method Chebyshev function buckling vibration metal foam beam higher-order beam theory(HOBT)

Compression properties of cost-efficient porous expanded clay reinforced AA7075 syntactic foams fabricated by industrial-oriented die casting technology

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China Foundry 2024年第1期21卷 60-70页

作者： İsmail Cem Akgün Çağın Bolat Ali Gökşenli Faculty of Mechanical Engineering Istanbul Technical University34437İstanbulTurkey Faculty of Engineering Samsun University55420SamsunTurkey

In today’s manufacturing industries,hard competition between rival firms makes it compulsory for researchers to design lighter and cheaper machine components due to the megatrends of cost-effectiveness and *** this point,aluminum syntactic foams(ASFs)are new-generation engineering composites and come into the upfront as a *** to their features like low density,sufficient elongation,and perfect energy absorption ability,these advanced foams have been considerably seductive for many industrial sectors *** this study,an industrial-oriented automatic die casting technology was used for the first time to manufacture the combination of AA7075/porous expanded clay(PEC).Micro evaluations(optical and FESEM)reveal that there is a homogenous particle distribution in the foam samples,and inspections are compatible with the other ASF ***,T6 aging heat treatment was operated on one half of the produced foams to explore the probable impact of aging on the compressive *** results show that PEC particles can be an alternative to expensive hollow spheres used in the previous ***,a favorable relationship is ascertained between the aging treatment and mechanical properties such as compression strength and plateau strength.

关键词： die casting porous materials metal matrix sytanctic foams expanded clay compressive deformation

Towards defining soil quality of Mediterranean calcareous agricultural soils:Reference values and potential core indicator set

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International Soil and Water Conservation Research 2024年第1期12卷 145-155页

作者： Germán A.Durán Daniel Sacristán Edelweis Farrús Jaume Vadell Institut de Recerca i FormacióAgrària i Pesquera de les Illes Balears C/Eusebi Estada14507009PalmaSpain Plant Biology Department University of Valencia46100BurjassotValenciaSpain Soil and Environmental Quality Department Centro de Investigaciones sobre Desertificación-CIDE(CSIC-Universitat de València-Generalitat Valenciana)Carretera Moncada-Náquera km 4.546113MoncadaValenciaSpain Universitat de les Illes Balears Cra.De Valldemossakm 7507122PalmaSpain

To avoid soil degradation,adapt to climate change and comply with the Sustainable Development goals 2030(Un General Assembly),establishing the quality/fertility of the agricultural soils of the Mediterranean region and evaluate how these evolve with time is *** enables adequate management practices to be *** Mediterranean calcareous region has received little attention in this sense,in spite its soil ***,24 different representative calcareous agricultural soils of the Mediterranean region,including the main management strategies of agricultural soils(rainfed and irrigated),were sampled from the island of Mallorca;and their physical,chemical and biological properties *** values obtained for most of the soil characteristics allowed to establish an initial approach to the reference values for the type of calcareous agricultural soils considered,and to clearly distinguish the effect of rainfed or irrigation management practices on soils properties and *** enzyme activities were not stimulated by the irrigation conditions assayed or they were only in dry conditions,suggesting optimum enzyme activities could be obtained when alternating dry and humid soil *** organic carbon,calcium carbonate and active lime revealed of significant importance in the collection of ***,the results obtained clearly indicate the heterogeneity of the region and its implications on the different soil ***,this study could serve as a starting point to adequately establish the quality(fertility)for Mediterranean calcareous agricultural soils and their reference values by conducting further research in this region and including more type of soils.

关键词： Soil fertility Mediterranean agricultural soils Calcareous soils Soil enzymes Soil management