scholarly journals Numerical Study of Heat and Mass Transfer during the Thermal Drying of Tropical Woods

2014 ◽  
Vol 08 (1) ◽  
Keyword(s):  
Water Content ◽  
Thermophysical Properties ◽  
Numerical Study ◽  
Wood Quality ◽  
Central Africa ◽  
Industrial Process ◽  
Self Control ◽  
Heat Equations ◽  
Wood Drying ◽  
Tropical Woods

A sector of utilization and transformation of wood give much money at the countries of the central Africa region. If we want to increase these advantages, it is important to do locally the first and second transformations of wood. Self-control of the wood drying is necessary to ameliorate a wood quality and to preserve an art work doing in wood. In this article, we are modeling a drying of one piece of bete wood (Mansonia altissima) with dimensions are 1m of length and thickness is no more than 25cm. We have used a literature to obtain a mass and heat equations and the thermophysical properties of the present wood. We have considered some thermophysical properties that we are unkempt in the precedent work [1]. We have experimentally obtained a relationship between a density of this wood with a water content. The others thermophysical properties come from the literature [1,2]. We have simulated a wood drying in the constant conditions and in the conditions of the bete drying table established by CIRAD Organization. A sensibility study is doing to validate a modeling. Then, the present modeling explains temperature, mass fraction of the vapor in air and water content evolutions during the industrial process of drying. This modeling can to be used for to overhaul a drying table of bete wood and the others of tropical woods. This work uses a gaseous pressure can be used to explain the drying with the high temperatures conditions.

Women in Gabon

2021 ◽  
Author(s):  
Claire H. Griffiths
Keyword(s):  
Central Africa ◽  
Early Period ◽  
Sub Saharan Africa ◽  
African Women ◽  
Female Population ◽  
History Of ◽  
Sub Saharan ◽  
Tropical Woods ◽  
New Research ◽  
Export Revenue

Gabon, a small oil-rich country straddling the equator on the west coast of Africa, is the wealthiest of France’s former colonies. An early period of colonization in the 19th century resulted in disease, famine, and economic failure. The creation of French Equatorial Africa in 1910 marked the beginning of the sustained lucrative exploitation of Gabon’s natural resources. Gabon began off-shore oil production while still a colony of France. Uranium was also discovered in the last decade of the French Equatorial African empire. Coupled with rich reserves in tropical woods, Gabon has achieved, since independence in 1960, a higher level of export revenue per capita of population than any other country in sub-Saharan Africa in the postcolonial era. However, significant inequality has characterized access to wealth through paid employment throughout the recorded history of monetized labor. While fortunes have been amassed by a minute proportion of the female population of Gabon associated with the ruling regime, and a professional female middle-class has emerged, inequalities of opportunity and reward continue to mark women’s experience of life in this little-known country of West Central Africa. The key challenge facing scholars researching the history of women in Gabon remains the relative lack of historical resources. While significant strides have been made over the past decade, research on women’s history in Francophone Africa published in English or French remains embryonic. French research on African women began to make a mark in the last decade of colonization, notably with the work of Denise Paulme, but then remained a neglected area for decades. The publication in 1994 of Les Africaines by French historian Catherine Coquery-Vidrovitch was hailed at the time as a pioneering work in French historiography. But even this new research contained no analysis of and only a passing reference to women in Gabon.

NUMERICAL STUDY OF ESTIMATING THE BLOW-UP TIME OF POSITIVE SOLUTIONS OF SEMILINEAR HEAT EQUATIONS

2018 ◽  
Vol 100 (4) ◽  
pp. 291-308
Author(s):  
K. Achille Adou ◽  
K. Augustin Touré ◽  
A. Coulibaly
Keyword(s):  
Positive Solutions ◽  
Blow Up ◽  
Numerical Study ◽  
Heat Equations

scholarly journals Numerical study of water and heat transfer in unsaturated clay-loam soil

2014 ◽  
Vol 5 ◽  
pp. A19
Author(s):  
Nacer Lamrous ◽  
Said Makhlouf ◽  
Nora Belkaid
Keyword(s):  
Water Content ◽  
Numerical Study ◽  
Climatic Conditions ◽  
Transfer Model ◽  
Climate Type ◽  
Transfer Equations ◽  
Loam Soil ◽  
Mass Transfers ◽  
Volume Method ◽  
The Mathematical Model

This present study is the numerical estimation of the temperature distribution and the water content distribution underground soil under the Mediterranean climate type. We use as input data of ambient temperature, air humidity and solar radiation, average values during 10 years estimated from data supplied by the local meteorological station (Tizi-Ouzou, Northern Algeria, 36°47′59″, North latitude and 4°1′59″, East longitude). A theoretical model, based on heat and water transfer equations, was established for an unsaturated soil submitted to the climatic conditions of this site. The mathematical model established in mono dimensional type, for a semi infinite transfer model, is based on Whitaker theory of heat and mass transfers in unsaturated porous medium (Withaker 1977, 1980) with the hypothesis that air pressure into soil porosity is equal to atmospheric pressure. The equations were discretized according to the finite volume method, which is more adapted for this type of problem, and were solved by the Newton-Raphson iterative method in the environment of Matlab software. The simulations have been done for two typical days (January 15 and May 15). Curves of temperature and water content evolutions in term of depth and time were obtained.

Efficient Operation of a Gas Turbine on Methanol Using Chemical Recuperation

2012 ◽  
Author(s):  
Christophe Duwig ◽  
Björn Nyberg ◽  
Marcus Thern
Keyword(s):  
Water Content ◽  
Gas Turbine ◽  
Waste Heat ◽  
Laminar Flame ◽  
Numerical Study ◽  
Co2 Removal ◽  
Efficiency Gain ◽  
Reference Case ◽  
Efficient Operation ◽  
Combustion Properties

Environmental and political concerns, together with new legislations, are pushing for a fuel shift in the power industry and more generally for many thermal applications. Adding to the coming decrease of oil and natural availability (or price increase), it opens avenues for new fuels. Among those, alcohols are strong candidates. In fact, short alcohols are easily produced and stored and require only moderate modifications of existing combustion systems. For example, operating an existing gas turbine (GT) on methanol requires moderate modifications (mainly in the combustion system). However, methanol can be used more efficiently. Unlike methane or other hydrocarbons that decompose at high temperature (1000K), methanol undergoes an endothermic decomposition at low temperatures (400K to 600K) to give CO and H2. It therefore opens avenue for coupling the GT with a chemical recuperation system. In other words, the methanol will be cracked using the waste heat of the flue gases with a gain in fuel heating value hence the original fuel is thermally upgraded. The present study will investigate the upgraded fuel combustion properties. The laminar flame speed of the upgraded fuel/air mixtures will be presented and compared to methane and methanol under conditions relevant to GT combustion. Several upgraded fuel compositions will be considered depending on the water content in the feed methanol. Further, we consider a recuperated micro GT (Turbec T100) based cycle fueled with methanol. The numerical study focuses on different thermodynamic cycles. Firstly, a reference case is considered assuming a direct fueled GT. Further, cycles including the cracker are studied keeping the power constant. The fuel efficiency gain due to the cracker will be investigated as function of the water content in the feed methanol. Finally, a case including CO2-removal will be presented and it will be shown that the cracker enables an efficient carbon capture and sequestration scheme.

scholarly journals Novel Dual Walling Cob Building: Dynamic Thermal Performance

Energies ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7663
Author(s):  
Kaoutar Zeghari ◽  
Ayoub Gounni ◽  
Hasna Louahlia ◽  
Michael Marion ◽  
Mohamed Boutouil ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Properties ◽  
Water Content ◽  
Wheat Straw ◽  
Numerical Study ◽  
Energy Performance ◽  
Climatic Conditions ◽  
Structural Walls ◽  
Hemp Shiv

This paper emphasizes the experimental and numerical study of new cob mixes used for insulation and load bearing wall elements. The experimental study provides complete datasets of thermal properties of the new walling materials, using cob with density ranging from 1107 kg/m3 to 1583 kg/m3 for structural walls and less than 700 kg m−3 for insulation walls. Various mixes of French soils and fibres (reed, wheat straw, hemp shiv, hemp straw, and flax straw) with different water contents are studied. The lowest average thermal conductivity is obtained for the structural cob mix prepared of 5% wheat straw and 31% of water content. The insulation mix, prepared with 25% reed and 31% water content, has the lowest thermal conductivity. Investigation of diffusivity, density, and heat capacity shows that, when thermal conductivity is lower than 0.4 W m−1 K−1, the decrease in cob density leads to better insulation values and higher heat capacity. Little variation is noticed regarding the density and heat capacity for cob mixes with thermal conductivity higher than 0.4 W m−1 K−1. Furthermore, the non-uniformity of local thermal conductivity and heat losses through the samples is due mainly to the non-uniform distribution of fibres inside the mixes inducing an increase in heat loss up to 50% for structural walls and 25% for insulation walls. Cob thermal properties are used in a comparative simulation case study of a typical house under French and UK climatic conditions. The energy performance of the conventional building is compared to a dual walled cob building, showing remarkable reduction in energy consumption as the cob walls, whilst maintaining comfortable indoor conditions without additional heating.

scholarly journals A mechanistic model for electrical conduction in soil–root continuum: a virtual rhizotron study

2018 ◽  
Author(s):  
Sathyanarayan Rao ◽  
Félicien Meunier ◽  
Solomon Ehosioke ◽  
Nolwenn Lesparre ◽  
Andreas Kemna ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Electrical Properties ◽  
Root Growth ◽  
Water Content ◽  
Soil Water ◽  
Water Uptake ◽  
Numerical Study ◽  
Root Segments ◽  
Bulk Electrical Conductivity ◽  
The Impact

Abstract. Electrical Resistivity Tomography (ERT) has become an important tool to study soil water fluxes in cropped field. ERT results translates to water content via empirical pedophysical relations that take soil physical properties into account, usually ignoring the impact of roots. Studies shows high root dense soils behaves quite differently than less root dense soils in terms of bulk electrical conductivity. Yet, we do not completely understand the impact of root segments on the ERT measurements. In this numerical study, we coupled an electrical model with a plant-soil water flow model to investigate the impact of plant root growth and water uptake on the ERT virtual experiment. The electrical properties of roots were explicitly accounted in the finite element mesh and we obtained the electrical conductivities of root segments by conducting specific experiments on real maize plants. The contrast between electrical conductivity of roots and soil depends on factors such as root density, irrigation, root age, and root water uptake pattern. Root growth and water uptake processes thus affect this contrast together with the soil electrical properties. Model results indicate a non-negligible anisotropy in bulk electrical conductivity induced by root processes. We see a greater anisotropy in a sandy medium when compared to a loamy medium. We find that the water uptake process dominates the bulk electrical properties. The Gauss-Newton type ERT inversion of virtual rhizotron data demonstrate that, when root-soil electrical conductivity contrasts are high, it can lead to error in water content estimates since the electrical conductivity is partly due to root. Thus, incorporating the impact of root in the pedophysical relations is very important to interpret ERT results directly as water content.

scholarly journals Effect of Wheat Straw Biochar on Thermophysical Properties of Loessial Soil

2021 ◽  
Vol 20 (3) ◽  
Author(s):  
B. W. Zhao ◽  
Y. Zhao ◽  
H. Liu ◽  
Y. Q. Li ◽  
K. X. Duan ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Diffusivity ◽  
Water Content ◽  
Thermophysical Properties ◽  
Heat Balance ◽  
Pyrolysis Temperature ◽  
Internal Heat ◽  
Loessial Soil ◽  
Biochar Amendment

Soil thermophysical properties are the key factors affecting the internal heat balance of soil. In this paper, biochars (BC300, BC500 and BC700) were produced with wheat straw at the temperatures of 300, 500 and 700°, respectively. The effects of biochar amendment at the rates of 0%, 1%, 3%, and 5% on the thermophysical properties (thermal conductivity, heat capacity, and thermal diffusivity) of a loessial soil were investigated with and without water content respectively. Although the bulk density of soil significantly decreased with biochar amendment, due to enhancing soil porosity and organic matter content, the thermophysical properties of soil did not change largely with biochar amendment rate and pyrolysis temperature. Water content exhibited significant effects on the thermophysical properties of soils added with biochars, where the thermal conductivity and heat capacity of soil were linearly proportional to water content, the thermal diffusivity initially increased and then decreased with the increase of water content. In the meanwhile, there was no significant correlation between the biochar amendment rate or pyrolysis temperature and thermophysical properties. The results show that water content should be mainly concerned as a factor when the internal heat balance of loess soil is evaluated, even though the soil is amended with biochar.

Numerical Simulation of the Laser Infusion Process of a Ni-Cr-B-Si Cover Strengthened with Zirconium Oxide Particles

2021 ◽  
Vol 1037 ◽  
pp. 552-557
Author(s):  
Valery V. Alisin ◽  
Mikhail N. Roshchin ◽  
Janusz Gladyszewski
Keyword(s):  
Numerical Simulation ◽  
Process Modeling ◽  
Thermophysical Properties ◽  
Zirconium Oxide ◽  
Numerical Study ◽  
Powder Materials ◽  
Heat Current ◽  
Oxide Particles ◽  
Properties Of Materials ◽  
Positive Effect

The issues of the process modeling of wear-resistant covers infusion of the NiCrBSi system, strengthened by the addition of solid powder materials are studied in the article. The results of a numerical study of the effect of heat current and thermophysical properties of materials on the process of heating and infusion of the cover are presented. The statements about the advantages of powders based on ZrO2 are demonstrated. Particular attention is paid to the issue of cracking in the cover after infusion. The assumption is substantiated about the positive effect of the addition of ZrO2 powders on the increase in the crack resistance of the cover.

106 The influence of water content on thermophysical properties of shape memory gel

2016 ◽  
Vol 2016.51 (0) ◽  
pp. 11-12
Author(s):  
Taro SHISHIDO ◽  
Masato AKAMATSU ◽  
Hidemitsu FURUKAWA ◽  
Mitsuhiro YAMANO
Keyword(s):  
Shape Memory ◽  
Water Content ◽  
Thermophysical Properties ◽  
Influence Of Water
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