Scaling Rules for Total Absorptivity and Emissivity of Gases

1984 ◽  
Vol 106 (4) ◽  
pp. 684-689 ◽  
Author(s):  
D. K. Edwards ◽  
R. Matavosian
Keyword(s):  
Radiation Heat Transfer ◽  
Scaling Exponent ◽  
Gas Temperature ◽  
Absorption Data ◽  
Gas Radiation ◽  
Functional Relationships ◽  
Radiation Properties ◽  
Band Absorption ◽  
The One ◽  
Total Emissivity

Hottel’s Rule and Penner’s Rule for estimating the total absorptivity of a homogeneous gas from a total emissivity chart or expression are generalized. The generalized rule is developed from an examination of the functional relationships between total and spectral molecular gas radiation properties. It gives a rational prescription for finding the absorptivity or emissivity at arbitrary pressure from the one-atmosphere total emissivity. Calculations of total properties from band absorption data correlations are used to find the needed map of pressure scaling exponent versus path-length-pressure product and gas temperature. Also addressed is the question of allowing for reflecting walls in the calculation of radiation heat transfer between a homogeneous gas and its enclosing walls. Both exact and high-accuracy-approximate calculations are shown to be possible using only total properties.

Total Band Absorption Models for Absorbing-Emitting Liquids: CCl4

1974 ◽  
Vol 96 (1) ◽  
pp. 27-31 ◽  
Author(s):  
J. L. Novotny ◽  
D. E. Negrelli ◽  
T. Van den Driessche
Keyword(s):  
Narrow Band ◽  
Absorption Process ◽  
Absorption Data ◽  
Gas Radiation ◽  
Spectral Integration ◽  
Absorption Models ◽  
Spectroscopic Information ◽  
Band Absorption ◽  
Two Parameter ◽  
Absorption Measurements

Predictions of the total band absorption are useful for describing the absorption process in calculations dealing with radiation interaction in absorbing-emitting liquids. Two two-parameter models, similar to the Elsasser and the statistical narrow band models used in gas radiation work, are developed for predicting the total band absorption in regions of the liquid CCl4 spectrum. The parameters, which are considered to be adjustable, can be determined from experimental total band absorption data or, if available, basic spectroscopic information. Results from the models are compared to experimental total band absorption measurements for CCl4 as well as a prediction based on spectral integration.

A Spray-Droplet Model for Diesel Combustion

1969 ◽  
Vol 184 (10) ◽  
pp. 28-35 ◽  
Author(s):  
J. Shipinski ◽  
P. S. Myers ◽  
O. A. Uyehara
Keyword(s):  
Experimental Data ◽  
Diesel Engine ◽  
Heat Release ◽  
Engine Speed ◽  
Chamber Pressure ◽  
Gas Temperature ◽  
Single Droplet ◽  
Burning Rates ◽  
Burning Model ◽  
The One

A spray-burning model (based on single-droplet theory) for heat release in a diesel engine is presented. Comparison of computations using this model and experimental data from an operating diesel engine indicate that heat release rates are not adequately represented by single-droplet burning rates. A new concept is proposed, i.e. a burning coefficient for a fuel spray. Comparisons between computations and experimental data indicate that the numerical value of this coefficient is nearly independent of engine speed and combustion-chamber pressure. However, the instantaneous value of the spray burning coefficient is approximately proportional to the instantaneous mass-averaged cylinder gas temperature to the one-third power.

scholarly journals Widely distributed exogenic materials of varying compositions and morphologies on asteroid (101955) Bennu

2021 ◽  
Author(s):  
Eri Tatsumi ◽  
Marcel Popescu ◽  
Humberto Campins ◽  
Julia de León ◽  
Juan Luis Rizos García ◽  
...  
Keyword(s):  
Near Infrared ◽  
Principal Component ◽  
Parent Body ◽  
Ordinary Chondrites ◽  
Near Infrared Reflectance ◽  
Spatially Resolved ◽  
Average Spectrum ◽  
Band Absorption ◽  
Rich Material ◽  
The One

Abstract Using the multiband imager MapCam onboard the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer) spacecraft, we identified 77 instances of proposed exogenic materials distributed globally on the surface of the B-type asteroid (101955) Bennu. We identified materials as exogenic on the basis of an absorption near 1 µm that is indicative of anhydrous silicates. The exogenic materials are spatially resolved by the telescopic camera PolyCam. All such materials are brighter than their surroundings, and they are expressed in a variety of morphologies: homogeneous, breccia-like, inclusion-like, and others. Inclusion-like features are the most common. Visible spectrophotometry was obtained for 46 of the 77 locations from MapCam images. Principal component analysis indicates at least two trends: (i) mixing of Bennu's average spectrum with a strong 1-µm band absorption, possibly from pyroxene-rich material, and (ii) mixing with a weak 1-µm band absorption. The endmember with a strong 1-µm feature is consistent with Howardite-Eucrite-Diogenite (HED) meteorites, whereas the one showing a weak 1-µm feature may be consistent with HEDs, ordinary chondrites, or carbonaceous chondrites. The variation in the few available near-infrared reflectance spectra strongly suggests varying compositions among the exogenic materials. Thus, Bennu might record the remnants of multiple impacts with different compositions to its parent body, which could have happened in the very early history of the Solar System. Moreover, at least one of the exogenic objects is compositionally different from the exogenic materials found on the similar asteroid (162173) Ryugu, and they suggest different impact tracks.

Relation of Fiber and Fabric Properties in Durable-Press Cottons

1969 ◽  
Vol 39 (5) ◽  
pp. 460-470 ◽  
Author(s):  
Hans-Dietrich Weigmann ◽  
Marjie G. Scott ◽  
Ludwig Rebenfeld
Keyword(s):  
Mechanical Properties ◽  
Chemical Treatments ◽  
Functional Relationships ◽  
Durable Press ◽  
Spun Yarn ◽  
Ethylene Urea ◽  
The One ◽  
Geometric Arrangements ◽  
Energy Absorbing ◽  
Fabric Structures

A cotton twill fabric was subjected to a durable-press treatment with dihydroxy dimethylol ethylene urea (Permafresh-183) of increasing severity. The mechanical properties of the fabrics and of single fibers withdrawn from the treated fabrics were evaluated and the relationships between fiber and fabric properties were analyzed. Statistically significant correlations between such important fabric properties as abrasion resistance, tear strength, tensile strength, and energy-absorbing capacity, on the one hand, and fiber mechanical properties, on the other, show conclusively that chemical treatments which alter fiber structure and properties are responsible for the modified fabric behavior. At the same time, the importance of fiber geometric arrangements in spun yarn and fabric structures, in terms of fabric properties, are pointed out. Thus, while this work has shown the functional relationships between fiber mechanical properties and fabric characteristics, careful attention must be given to fiber-fiber interactions, particularly in relation to chemical modification treatments.

The Influence of Real Gas Radiation On the Stability and Development of Benard Convection in a Two-Dimensional Layer

2021 ◽  
Author(s):  
Brent W. Webb ◽  
Vladimir Solovjov
Keyword(s):  
Rayleigh Number ◽  
Critical Rayleigh Number ◽  
Radiative Heating ◽  
Two Dimensional ◽  
Gas Temperature ◽  
Layer Depth ◽  
Real Gas ◽  
Gas Radiation ◽  
Induced Flow ◽  
Buoyancy Induced Flow

Abstract The influence of real gas radiation on the thermal and hydrodynamic stability is investigated in a two-dimensional layer of radiatively participating H2O and/or CO2 heated from below. The non-gray radiation effects of the two species are treated rigorously using a global spectral approach, the Spectral Line Weighted-sum-of-gray-gases model. The phenomena are explored by solving the full coupled laminar equations of motion, energy, and radiative transfer from the low-Rayleigh number, pure conduction-radiation regime through the onset of buoyancy-induced flow to the developed Bénard convection regime. The evolution of the thermal, velocity, and radiative heating fields is studied, and the critical Rayleigh number is characterized as a function of species mole fraction, average layer gas temperature, layer depth, wall emissivity, and the total gas pressure. It is found that participating radiation in the medium has the effect of stabilizing the layer, delaying transition to buoyancy-induced flow. The development of buoyancy-induced flow and temperature, along with the radiative heating are presented. It is found that the critical Rayleigh number in the radiatively participating gas layer can be more than an order of magnitude higher than the classical convection-only scenario. The onset of instability is found to depend on the species mole fractions, average gas temperature in the layer, wall emissivity, layer depth, and total pressure. Generally, all other variables being the same, H2O has a greater stabilizing influence on the layer than CO2.

REACTION-FRONT DYNAMICS IN A+B→C WITH INITIALLY-SEPARATED REACTANTS

Fractals ◽  
1993 ◽  
Vol 01 (03) ◽  
pp. 405-415 ◽  
Author(s):  
S. HAVLIN ◽  
M. ARAUJO ◽  
H. LARRALDE ◽  
A. SHEHTER ◽  
H.E. STANLEY
Keyword(s):  
Reaction Front ◽  
Reaction Rate ◽  
Reaction System ◽  
Diffusion Reaction ◽  
Dimensional System ◽  
Scaling Exponent ◽  
One Dimensional ◽  
Recent Developments ◽  
The One ◽  
Front Dynamics

We review recent developments in the study of the diffusion reaction system of the type A+B→C in which the reactants are initially separated. We consider the case where the A and B particles are initially placed uniformly in Euclidean space at x>0 and x<0 respectively. We find that whereas for d≥2 a single scaling exponent characterizes the width of the reaction zone, a multiscaling approach is needed to describe the one-dimensional system. We also present analytical and numerical results for the reaction rate on fractals and percolation systems.

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