On an experimental method of determining the total radiation extinction coefficient of furnace gases

1966 ◽  
Vol 10 (1) ◽  
pp. 91-92
Author(s):  
A. S. Nevskii
Keyword(s):  
Experimental Method ◽  
Extinction Coefficient ◽  
Total Radiation ◽  
Furnace Gases ◽  
Radiation Extinction ◽  
Radiation Extinction Coefficient

Numerical Evaluation of Radiation Extinction Coefficient Using Fractal Geometry for Vegetation Modeling

2009 ◽  
Vol 56 (4) ◽  
pp. 360-377 ◽  
Author(s):  
A. Lamorlette ◽  
A. Collin ◽  
P. Boulet ◽  
O. Séro-Guillaume
Keyword(s):  
Extinction Coefficient ◽  
Fractal Geometry ◽  
Numerical Evaluation ◽  
Vegetation Modeling ◽  
Radiation Extinction ◽  
Radiation Extinction Coefficient

Estimation of the radiation extinction coefficient of natural fuel beds

2004 ◽  
Vol 13 (1) ◽  
pp. 65 ◽  
Author(s):  
Gilberto C. Vaz ◽  
Jorge C. S. André ◽  
Domingos X. Viegas
Keyword(s):  
White Light ◽  
Extinction Coefficient ◽  
Laboratory Experiments ◽  
Pine Needles ◽  
Light Radiation ◽  
Parallel Beam ◽  
Standard Formula ◽  
Maximum Angle ◽  
Radiation Extinction ◽  
Radiation Extinction Coefficient

. The standard formula used to estimate the radiation extinction coefficient, kb (m–1), of solid porous natural fuel beds is examined and tested against laboratory experiments with isotropic beds of pine needles in the range of packing ratio, β, of 0.01–0.02. To measure kb in the tests, a setup using a parallel beam of white light radiation was constructed. The error of the standard formula is observed to be smaller than 10%. Similar tests were performed for a non-isotropic bed of pine needles with β ≈ 0.02, in which the maximum angle of inclination of the needles was limited to 30°, for two directions of incidence of radiation: horizontal and vertical. For each one of these two cases, original estimation formulae for kb are proposed alternative to the standard one. In these cases it is concluded that, while the standard formula may be in error by up to 20%, the new formulae have errors around 5% or smaller.

scholarly journals Enhanced extinction of visible radiation due to hydrated aerosols in mist and fog

2015 ◽  
Vol 15 (1) ◽  
pp. 291-337 ◽  
Author(s):  
T. Elias ◽  
J.-C. Dupont ◽  
E. Hammer ◽  
C. R. Hoyle ◽  
M. Haeffelin ◽  
...  
Keyword(s):  
Extinction Coefficient ◽  
Formation Process ◽  
Significant Proportion ◽  
Liquid Water Content ◽  
Ambient Conditions ◽  
Visible Radiation ◽  
Large Variability ◽  
Accumulation Mode ◽  
The Mean ◽  
Radiation Extinction

Abstract. The study assesses the contribution of aerosols to the extinction of visible radiation in the mist-fog-mist cycle. Measurements of the microphysical and optical properties of hydrated aerosols with diameters larger than 400 nm, composing the accumulation mode, which are the most efficient to interact with visible radiation, were carried out near Paris, during November 2011, in ambient conditions. Eleven mist-fog-mist cycles were observed, with cumulated fog duration of 95 h, and cumulated mist-fog-mist duration of 240 h. In mist, aerosols grew up by taking up water at relative humidities larger than 93%, causing a visibility decrease below 5 km. While visibility decreased down to few km, the mean size of the hydrated aerosols increased, and their number concentration (Nha) increased from approximately 160 to approximately 600 cm−3. When fog formed, droplets became the strongest contributors to visible radiation extinction, and liquid water content (LWC) increased beyond 7 mg m−3. Hydrated aerosols of the accumulation mode co-existed with droplets, as interstitial non-activated aerosols. Their size continued to increase, and a significant proportion of aerosols achieved diameters larger than 2.5 μm. The mean transition diameter between the accumulation mode and the small droplet mode was 4.0 ± 1.1 μm. Moreover Nha increased on average by 60% after fog formation. Consequently the mean aerosol contribution to extinction in fog was 20 ± 15% for diameter smaller than 2.5 μm and 6 ± 7% beyond. The standard deviation is large because of the large variability of Nha in fog, which could be smaller than in mist or three times larger. The particle extinction coefficient in fog can be computed as the sum of a droplet component and an aerosol component, which can be approximated by 3.5 Nha (Nha in cm−3 and particle extinction coefficient in Mm−1). We observed an influence of the main formation process on Nha, but not on the contribution to fog extinction by aerosols. Indeed in fogs formed by stratus lowering (STL), the mean Nha was 360 ± 140 cm−3, close to the value observed in mist, while in fogs formed by nocturnal radiative cooling under cloud-free sky (RAD), the mean Nha was 600 ± 350 cm−3. But because visibility (extinction) in fog was also lower (larger) in RAD than in STL fogs, the contribution by aerosols to extinction depended little on the fog formation process. Similarly, the proportion of hydrated aerosols over all aerosols (dry and hydrated) did not depend on the fog formation process. Measurements show that visibility in RAD fogs was smaller than in STL fogs because: (1) LWC was larger in RAD than in STL fogs, (2) droplets were smaller, (3) as already said, hydrated aerosols composing the accumulation mode were more numerous.

scholarly journals Enhanced extinction of visible radiation due to hydrated aerosols in mist and fog

2015 ◽  
Vol 15 (12) ◽  
pp. 6605-6623 ◽  
Author(s):  
T. Elias ◽  
J.-C. Dupont ◽  
E. Hammer ◽  
C. R. Hoyle ◽  
M. Haeffelin ◽  
...  
Keyword(s):  
Extinction Coefficient ◽  
Formation Process ◽  
Liquid Water Content ◽  
Cycle Duration ◽  
Ambient Conditions ◽  
Visible Radiation ◽  
Large Variability ◽  
Accumulation Mode ◽  
The Mean ◽  
Radiation Extinction

Abstract. The study assesses the contribution of aerosols to the extinction of visible radiation in the mist–fog–mist cycle. Relative humidity is large in the mist–fog–mist cycle, and aerosols most efficient in interacting with visible radiation are hydrated and compose the accumulation mode. Measurements of the microphysical and optical properties of these hydrated aerosols with diameters larger than 0.4 μm were carried out near Paris, during November 2011, under ambient conditions. Eleven mist–fog–mist cycles were observed, with a cumulated fog duration of 96 h, and a cumulated mist–fog–mist cycle duration of 240 h. In mist, aerosols grew by taking up water at relative humidities larger than 93%, causing a visibility decrease below 5 km. While visibility decreased down from 5 to a few kilometres, the mean size of the hydrated aerosols increased, and their number concentration (Nha) increased from approximately 160 to approximately 600 cm−3. When fog formed, droplets became the strongest contributors to visible radiation extinction, and liquid water content (LWC) increased beyond 7 mg m−3. Hydrated aerosols of the accumulation mode co-existed with droplets, as interstitial non-activated aerosols. Their size continued to increase, and some aerosols achieved diameters larger than 2.5 μm. The mean transition diameter between the aerosol accumulation mode and the small droplet mode was 4.0 ± 1.1 μm. Nha also increased on average by 60 % after fog formation. Consequently, the mean contribution to extinction in fog was 20 ± 15% from hydrated aerosols smaller than 2.5 μm and 6 ± 7% from larger aerosols. The standard deviation was large because of the large variability of Nha in fog, which could be smaller than in mist or 3 times larger. The particle extinction coefficient in fog can be computed as the sum of a droplet component and an aerosol component, which can be approximated by 3.5 Nha (Nha in cm−3 and particle extinction coefficient in Mm−1. We observed an influence of the main formation process on Nha, but not on the contribution to fog extinction by aerosols. Indeed, in fogs formed by stratus lowering (STL), the mean Nha was 360 ± 140 cm−3, close to the value observed in mist, while in fogs formed by nocturnal radiative cooling (RAD) under cloud-free sky, the mean Nha was 600 ± 350 cm−3. But because visibility (extinction) in fog was also lower (larger) in RAD than in STL fogs, the contribution by aerosols to extinction depended little on the fog formation process. Similarly, the proportion of hydrated aerosols over all aerosols (dry and hydrated) did not depend on the fog formation process. Measurements showed that visibility in RAD fogs was smaller than in STL fogs due to three factors: (1) LWC was larger in RAD than in STL fogs, (2) droplets were smaller, (3) hydrated aerosols composing the accumulation mode were more numerous.

A non-destructive optical experimental method to predict extinction coefficient of glass fibre-reinforced thermoplastic composites

2018 ◽  
Vol 106 ◽  
pp. 215-221
Author(s):  
Benoit Cosson ◽  
André Chateau Akué Asséko ◽  
Myriam Dauphin
Keyword(s):  
Experimental Method ◽  
Glass Fibre ◽  
Extinction Coefficient ◽  
Thermoplastic Composites ◽  
Glass Fibre Reinforced ◽  
Non Destructive

Experimental and Numerical Study of Premixed Combustion within Porous Media

2012 ◽  
Vol 557-559 ◽  
pp. 1572-1583
Author(s):  
De Bo Li ◽  
Qi Sheng Xu ◽  
Yue Liang Shen ◽  
Zhi Yong Wen ◽  
Ya Ming Liu
Keyword(s):  
Heat Transfer ◽  
Extinction Coefficient ◽  
Numerical Study ◽  
Radiation Heat Transfer ◽  
Convection Heat Transfer ◽  
Flame Velocity ◽  
Convection Heat ◽  
Ceramic Foams ◽  
Porous Burner ◽  
Radiation Extinction

A transient numerical model and experimental study of combustion and heat transfer for methane and oxygen within a two-section porous burner are presented in this paper. It is found that the maximum flame velocity is influenced by the combined effects of extinction coefficient and convection heat transfer coefficient, and that the minimum flame velocities of ceramics with various pore densities have slight differences at different equivalence ratios, while maximum flame velocities have large differences. In addition, the flame velocity depends not only on the interfacial convection heat transfer, but also on the radiation heat transfer of the ceramic foams, which is in accordance with our numerical simulation. Meanwhile, the numerical research in the present paper indicates that radiation extinction coefficient or pores per inch is not the only reason to characterize the heat regeneration effect of ceramic foams.

Experimental Method in Antiquity.

1964 ◽  
Vol 19 (6) ◽  
pp. 419-419
Author(s):  
Frank P. Jones
Keyword(s):  
Experimental Method
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