Effect of oxygen deprivation on soil hydrophobicity during heating

2005 ◽  
Vol 14 (4) ◽  
pp. 449 ◽  
Author(s):  
R. Bryant ◽  
S. H. Doerr ◽  
M. Helbig
Keyword(s):  
Heat Source ◽  
Forest Soils ◽  
Water Droplet ◽  
Oxygen Deprivation ◽  
Eucalypt Forest ◽  
Soil Hydrophobicity ◽  
Effect Of Oxygen ◽  
Penetration Time ◽  
Droplet Penetration ◽  
Heating Duration

Previous studies of the effects of heating on soil hydrophobicity have been conducted under free availability of oxygen. Under fire, however, soils may be deprived of oxygen due to its consumption at the heat source and inadequate replenishment in the soil. In the present study, effects of heating on soil hydrophobicity are examined for three initially hydrophobic Australian eucalypt forest soils under standard and oxygen-deprived atmospheres for temperatures (T) of 250–600°C and durations (tE) 2–180 min. Hydrophobicity assessments using water droplet penetration time (WDPT) tests indicate substantial differences between the absence and presence of oxygen. Heating to 250–300°C enhanced hydrophobicity from initial respective WDPTs of 2029 s, 361 s and 15 s to > 18 000 s for all samples under both atmospheres. Depending on heating duration, hydrophobicity was eliminated (WDPTs ~0 s) in air between 210 and 340°C, but under oxygen-deprived conditions between 400 and 510°C. Relationships between the destruction temperature for hydrophobicity TD and tE provide temperature–duration thresholds below which hydrophobicity persists under oxygen concentrations <21%. As established temperature–duration thresholds for hydrophobicity destruction are based on the free availability of oxygen, caution is advised in their applicability to field situations where heating under burning may occur in oxygen-depleted conditions.

Analysis of water droplet penetration in earth plasters using X-ray microtomography

2021 ◽  
Vol 283 ◽  
pp. 122651
Author(s):  
T. Mauffré ◽  
E. Keita ◽  
E. Contraires ◽  
F. McGregor ◽  
A. Fabbri
Keyword(s):  
Water Droplet ◽  
X Ray ◽  
Droplet Penetration

Effect of Oxygen Deprivation and Reoxygenation on Endothelin-Induced Contractions of Porcine Coronary Artery1

2015 ◽  
pp. 221-231
Author(s):  
David J. Schmidt ◽  
Denise Koth ◽  
Denise Jubenville ◽  
Robert F. Highsmith
Keyword(s):  
Oxygen Deprivation ◽  
Effect Of Oxygen

scholarly journals Effect of char layer on transient thermal oxidative degradation of polyethylene

2007 ◽  
Vol 11 (2) ◽  
pp. 23-36 ◽  
Author(s):  
Javad Esfahani ◽  
Ali Abdolabadi
Keyword(s):  
Heat Transfer ◽  
Heat Source ◽  
Solid Phase ◽  
Early Stage ◽  
Radiation Heat Transfer ◽  
Oxidative Degradation ◽  
Degradation Process ◽  
Thermal Oxidative Degradation ◽  
Char Layer ◽  
Effect Of Oxygen

A transient one dimensional model has been presented to simulate degradation and gasification of polyethylene, in early stage of fire growth. In the present model effect of oxygen on degradation and rate of polymer gasification while the sample is subjected to an external radiative heat source is numerically investigated. This model includes different mechanism, which affect the degradation process, such as in depth thermal oxidative decomposition, in depth absorption of radiation, heat transfer, volatiles advection in solid phase and convective heat transfer on surface. Also effects of radiative parameters, due to formation of char layer such as surface reflectivity and absorptivity on thermal degradation of polyethylene are investigated. The results for 40 kW/m2 heat source are reported and yielded realistic results, comparing to the published experimental data. The results show that an increase in oxygen concentration leads to considerable increase in gasification rate and also leads to sharp increase of surface temperature. .

Numerical Study of a Small Droplet Movement in a Microchannel under Heat Source

2019 ◽  
Vol 894 ◽  
pp. 104-111
Author(s):  
Thanh Long Le ◽  
Jyh Chen Chen ◽  
Huy Bich Nguyen
Keyword(s):  
Contact Angle ◽  
Heat Source ◽  
Water Droplet ◽  
Stokes Equations ◽  
Numerical Study ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Initial Position ◽  
Immiscible Fluids ◽  
Two Phase

In this study, the numerical computation is used to investigate the transient movement of a water droplet in a microchannel. For tracking the evolution of the free interface between two immiscible fluids, we employed the finite element method with the two-phase level set technique to solve the Navier-Stokes equations coupled with the energy equation. Both the upper wall and the bottom wall of the microchannel are set to be an ambient temperature. 40mW heat source is placed at the distance of 1 mm from the initial position of a water droplet. When the heat source is turned on, a pair of asymmetric thermocapillary convection vortices is formed inside the droplet and the thermocapillary on the receding side is smaller than that on the advancing side. The temperature gradient inside the droplet increases quickly at the initial times and then decreases versus time. Therefore, the actuation velocity of the water droplet first increases significantly, and then decreases continuously. The dynamic contact angle is strongly affected by the oil flow motion and the net thermocapillary momentum inside the droplet. The advancing contact angle is always larger than the receding contact angle during actuation process.

Earthworms in some Tasmanian forest soils in relation to bioturbation and soil texture profile

Soil Research ◽  
1997 ◽  
Vol 35 (6) ◽  
pp. 1231 ◽  
Author(s):  
M. D. Laffan ◽  
T. J. Kingston
Keyword(s):  
Forest Soils ◽  
Forest Type ◽  
Texture Profile ◽  
Earthworm Species ◽  
Eucalypt Forest ◽  
North Eastern ◽  
Earthworm Population ◽  
Subsurface Layers ◽  
Texture Contrast ◽  
Density And Biomass

Soil properties and earthworm population density were examined for 5 forest soils derived from Silurian-Devonian sandstones (Mathinna Beds) in north-eastern Tasmania. The soils occur along gradients of altitude, rainfall, and forest type; they include 2 with texture-contrast and 3 with gradational soil profile types. The density and biomass of the most abundant earthworm species Megascolex montisarthuri, and of all earthworm species combined, were found to be greater in gradational than in texture-contrast soils. A greater proportion of the earthworms in gradational soils than in texture-contrast soils was found to occur at soil depths exceeding 10 cm. The contrast was most pronounced between the 2 texture-contrast soils and the single gradational soil that occur under dry eucalypt forest. This paper explores the hypothesis that bioturbation of surface and subsurface layers by earthworms is an important mixing process that in gradational soils outweighs the counter tendency for soil particles to sort and thus form texture-contrast profiles.

scholarly journals Study of Fluids Motion in a Microchannel under Heat Source

2020 ◽  
Vol 2 (SI2) ◽  
pp. First
Author(s):  
Long Thanh Le
Keyword(s):  
Contact Angle ◽  
Heat Source ◽  
Water Droplet ◽  
Stokes Equations ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Immiscible Fluids ◽  
Navier Stokes ◽  
Two Phase ◽  
Receding Contact Angle

In this study, the numerical computation is used to investigate the transient thermocapillary migration of a water droplet in a Microchannel. For tracking the evolution of the free interface between two immiscible fluids, we employed the finite element method with the two-phase level set technique to solve the Navier-Stokes equations coupled with the energy equation. Both the upper wall and the bottom wall of the microchannel are set to be an ambient temperature. The heat source is placed at the left side of a water droplet. When the heat source is turned on, a pair of asymmetric thermocapillary convection vortices is formed inside the droplet and the thermocapillary on the receding side is smaller than that on the advancing side. The temperature gradient inside the droplet increases quickly at the initial times and then decreases versus time. Therefore, the actuation velocity of the water droplet first increases significantly, and then decreases continuously. The dynamic contact angle is strongly affected by the oil flow motion and the net thermocapillary momentum inside the droplet. The advancing contact angle is always larger than the receding contact angle during actuation process.

Effect of Oxygen Gas on the Decomposition of Dye by Pulsed Discharge in Water Droplet Spray

2011 ◽  
Vol 131 (8) ◽  
pp. 648-658 ◽  
Author(s):  
Taisuke Nose ◽  
Yuzo Yokoyama ◽  
Akira Nakamura ◽  
Yasushi Minamitani
Keyword(s):  
Water Droplet ◽  
Pulsed Discharge ◽  
Oxygen Gas ◽  
Effect Of Oxygen ◽  
Droplet Spray

scholarly journals Soil hydrophobicity: comparative study of usual determination methods

2015 ◽  
Vol 45 (2) ◽  
pp. 260-266 ◽  
Author(s):  
Eduardo Saldanha Vogelmann ◽  
José Miguel Reichert ◽  
Juliana Prevedello ◽  
Gabriel Oladele Awe ◽  
Dalvan José Reinert
Keyword(s):  
Water Drop ◽  
Soil Layer ◽  
Organic Matter Content ◽  
Soil Samples ◽  
Water Infiltration ◽  
Water Repellent ◽  
Hydrophobicity Index ◽  
Coefficients Of Variation ◽  
Soil Hydrophobicity ◽  
Penetration Time

Hydrophobic or water repellent soils slowly absorb water because of the low wett ability of the soil particles which are coated with hydrophobic organic substances. These pose significant effects on plant growth, water infiltration and retention, surface runoff and erosion. The objective of this study was to compare the performance of tension micro-infiltrometer(TMI) and the water drop penetration time (WDPT) methods in the determination of the hydrophobicity index of eighteen soils from southern Brazil. Soil samples were collected from the 0-5cm soil layer to determine particle size distribution, organic matter content, hydrophobicity index of soil aggregates and droplet penetration time of disaggregated and sieved soil samples. For the TMI method the soil samples were subjected to minor changes due to the use of macroaggregates to preserve the distribution of solid constituents in the soil. Due to the homogeneity of the soil samples the WDPT method gave smaller coefficients of variation unlike the TMI method where the soil structure is preserved. However, both methods had low coefficients of variation, and are thus effective for determining the soil hydrophobicity, especially when the log hydrophobicity index or log WDPT is >1.

EFFECT OF OXYGEN DEPRIVATION ON CORNEAL SENSITIVITY

2009 ◽  
Vol 58 (3) ◽  
pp. 434-439 ◽  
Author(s):  
MICHEL MILLODOT ◽  
DANIEL J. O'LEARY
Keyword(s):  
Oxygen Deprivation ◽  
Corneal Sensitivity ◽  
Effect Of Oxygen
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