Absorption Coefficients Of Gases Research Articles

Radiation due to CO2 or H2O and particles in cylindrical media

This study considers nongray, absorbing, emitting, anisotropically scattering, one-dimensional, radiative transfer in cylindrical media. The radiation transfer is due to a gas composed of either CCh or H2O, soot and particles. The temperature of these constituents is equal and uniform throughout the medium. The nongray effects are due to the spectrally discontinuous absorption/emission behavior of the gas and the spectrally continuous absorption/emission behavior of the soot. The absorption coefficient of the nongray gas is modeled according to Edwards' exponential wide-band models. The absorption coefficient of the soot is inversely proportional to wavelength. The scattering phase function of the gray particles is represented as the sum of an isotropic component and a delta-function. An accurate solution to this problem is obtained by using the Pi-approximation coupled with the integral form of the equation of transfer. The bandwidths are determined by utilizing the wide-band models, and the spectral integration is performed over all wavelengths according to a two-point quadrature for each band. Comprehensive parameter surveys are performed in order to establish a detailed understanding of the complex interaction between radiatively participating particles and molecular gases.

Experimental determination of the parameters of vibrational–rotational transitions in isotopic forms of CO2molecules

Measurements were made of the absorption coefficients of carbon dioxide gas in the isotopically substituted forms 12C16O2, 13C16O2, and 12C18O2. The Einstein coefficients, collisional line widths, and matrix elements of the dipole moments corresponding to the 0001–(1000, 0200)I,II transitions were calculated. The results were in good agreement with the available published data.

Preionization electron density and ion decay measurements in an x-ray preionized rare-gas-fluoride laser

Measurements have been made of the preionization electron number density produced by x-ray irradiation of typical rare-gas fluoride laser gas mixtures. The results obtained show significant deviations from predictions made by using the mass absorption coefficients of the individual laser gases. Those deviations are shown to be caused by interactions between the constituent gases of the laser mixture and ionization produced from areas of the laser chamber exposed to the x rays. Measurements of the decay of the ion species produced have also been made, indicating a rate in close agreement with diffusion-limited ion-ion recombination. An unexplained dependence of this rate on initial ion number density has been observed.

Photothermal Beam Deflection Spectroscopy of Complex Systems: Infrared Fourier Transform Band Shapes of Infrared-Absorbing Gases in Presence of Infrared-Absorbing Solids

Absfracf-Fourier transform infrared (FTIR) photothermal beam deflection (PBD) spectra were recorded over the 3900-4500 cm-’ range of solids absorbing weakly, medium-strongly, strongly, and very strongly in various spectral regions, as well as of carbons that absorb IR radiation very strongly over the entire spectral region, in the presence of IR-absorbing gases such as SOz or NO2, which exhibit absorption bands of different intensities at various wavenumbers. The gas over the solid absorbs IR radiation, and the extent of that absorption affects the intensity of the PED signal of the solid (which is itself a function of the solid’s texture) and also of the gas immediately above the solid’s surface, so that the net results which are observed are very complex indeed. It would be prudent to avoid such systems, but as they are frequently encountered in studies of the chemistry of reactions mcurring on solid surfaces, they must be examined. In view of the many variables, which include not merely the gas partial pressure and the relative absorption coefficients of gas and solid in specific wavenumber regions, but also the photothermal response of the solid as function of texture as well as the refractive indices and thermal properties of the gas, a phenomenological description of the IR PBD spectra of such IRabsorbing gas-solid samples is made using numerous FTIR PBD spectra of gas-solid systems.

Gas absorption in a multi-stage gas-liquid spouted vessel.

Gas holdup, bubble size distribution and gas absorption capacity coefficient in a multi-stage gas-liquid spouted vessel are observed in this study and it is confirmed that coalescence of gas bubbles observed in the calm uniformflow section in a single-stage spouted vessel can be avoided by introduction of perforated plates. Experimental results show that effect of physical properties of liquid on the capacity coefficient in a spouted vessel is more similar to that observed in an aerated mixing vessel than to that of a bubbling column. It is also observed that the gas absorption coefficient is proportional to the square root of the Sauter mean bubble diameter.

Radiative heat transfer in a cylindrical mixture of non-gray particulates and molecular gases

The interaction between particulate clouds and molecular gases with respect to radiative heat transfer in a one-dimensional cylindrical medium with black walls is investigated. The particulates are assumed to have a non-gray absorption coefficient with a power-law dependence on wavenumber. The absorption coefficient of the molecular gases is described by the exponential wide-band model. Heat transfer rates are found through the evaluation of internal and external total hemispherical emissivities of the particulate cloud and through evaluation of total band absorptances for the molecular gases, modified to account for the interaction with the particles. Simple, closed-form expressions for the total hemispherical emissivities and total band absorptance are also presented, resulting in good accuracy.

Radiative heat transfer in a plane-layer mixture of non-gray particulates and molecular gases

The interaction between particulate clouds and molecular gases with respect to radiative heat transfer in a one-dimensional, plane-parallel geometry is investigated. The particulates are assumed to have a non-gray absorption coefficient with a power-law dependence on wavenumber. The absorption coefficient of the molecular gases is described by the popular exponential wide-band model. Heat transfer rates are determined through the evaluation of internal and external slab emissivities of the particulate cloud and through evaluation of slab band absorptances for the molecular gases, modified to account for the interaction with the particles. Simple, closed-form expressions for the slab emissivities and slab absorptances are also introduced, resulting in good accuracy.

Nickel‐catalyzed hydrogenation of soybean oil: I. Kinetic, equilibrium and mass transfer determinations

AbstractThe kinetic and equilibrium constants were determined for the hydrogenation of soybean oil on a commercial nickel catalyst in a 300‐ml Parr batch reactor. These constants were used to calculate the hydrogen gas absorption coefficients by coupling mass transfer with reaction rate based on a Langmuir Hinshelwood model. The activation energy for the rate‐determining step was 23 kcal/g mol whereas the adsorption energy for hydrogen was −12.5 kcal/g mol. The gas absorption coefficients varied between 0.3 to 0.7 min−1 as the temperature ranged between 140–180 C.

Mathematical modelling of three-dimensional heat transfer from the flame in combustion chambers

In this article, mathematical modelling with the Monte-Carlo solution and the finite difference method is used to solve the integral-differential equations of the three-dimensional heat transfer process from flame in combustion chambers or furnaces. By using this kind of mathematical modelling, the combustion chamber volume and its walls can be divided into thousands of elements for calculation; both the temperature distribution of the gases in the combustion chamber volume and the heat flux distribution on its walls can be solved easily. With the modified method, statistical modelling calculation of the radiant energy, speeding up the convergence of the solution, consideration of the absorption coefficient of the gray gases in the combustion chamber as a function of the coordinate in space, and consideration of the influence of the fouling factor of the walls on heat transfer, make the calculated results quite satisfactory.

Absorption coefficients of various pollutant gases at CO_2 laser wavelengths, application to the remote sensing of those pollutants: errata

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text A. Mayer, J. Comera, H. Charpentier, and C. Jaussaud, "Absorption coefficients of various pollutant gases at CO2 laser wavelengths, application to the remote sensing of those pollutants: errata," Appl. Opt. 19, 1572-1572 (1980) Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

The measurement and interpretation of radiation from fly ash particles in large pulverized coal flames

Narrow wave-band measurements have been used to determine the absorption coefficient of combustion chamber gases in large utility boilers with an accuracy of about ±25%. Effective absorption efficiencies and refractive indices for, the fly ash have been deduced where dust burden details could be measured. Modifications to instrument design would improve the accuracy. The absorption characteristics were shown to be influenced by the chemical composition of the ash. For a brown and a sub-bituminous coal of high alkali ash the measurements indicated a very high specific surface in the furnace, incompatible with sizing of collected fly ash samples, and a very high wavelength dependence of absorption. Small molten particles in the furnace gases could account for the high apparent surface area and the wavelength dependence. Results for two bituminous coals with high ash fusion temperatures indicate that an absorption coefficient K ¯ a of 0.4 to 0.5 would be adequate for eingineering purposes. However this value appears to be strongly influenced by chemical composition of ash; the cloud surface area may be more dependent on inherent ash and combustion characteristics than on the total ash or the coal grind.

Absorption coefficients of various pollutant gases at CO_2 laser wavelengths; application to the remote sensing of those pollutants: addenda

A two-wavelength CO2 laser designed for atmospheric pollution measurements has been used for determining the absorption coefficients of thirteen gas pollutants at CO2 laser lines between 9.2 μm and 10.8 μm. All measurements were done with the pollutant at a low pressure in the presence of 1 atm of air. Sensitivities of about 5 ppb for a 1-km path have been obtained for ethylene.

Absorption coefficients of various pollutant gases at CO_2 laser wavelengths; application to the remote sensing of those pollutants

A two-wavelength CO(2) laser designed for atmospheric pollution measurements has been used for determining the absorption coefficients of thirteen gas pollutants at CO(2) laser lines between 9.2 microm and 10.8 microm. All measurements were done with the pollutant at a low pressure in the presence of 1 atm of air. Sensitivities of about 5 ppb for a 1-km path have been obtained for ethylene.

Combined Radiation—Convection for a Real Gas

A study of interaction of radiative transfer with convective transfer is presented for slug flow of an absorbing-emitting gas in a circular tube with an isothermal black wall. The zone method of solution is utilized to evaluate axial gas temperature and wall heat flux distributions using recently developed direct exchange areas for arbitrary zone width to radius ratio. Gas radiative properties are evaluated from the weighted sum of gray gases model with weighting factors and gray gas absorption coefficients applicable for an equimolal mixture of carbon dioxide and water vapor. Results are presented for several values of the governing parameters which are the Boltzmann and Stanton numbers, inlet gas and tube wall temperatures, as well as tube length to diameter ratio. Effects of cooling and heating of the gas are examined.

Determination of diffusion and absorption coefficients of gases and vapours in sealing material and calculation of the gas desorption from vacuum seals: Th Kraus and E Zollinger, Vakuum-Tech, 23 (2), 1974, 40–46 ( in German)

Determination of diffusion and absorption coefficients of gases and vapours in sealing material and calculation of the gas desorption from vacuum seals: Th Kraus and E Zollinger, Vakuum-Tech, 23 (2), 1974, 40–46 ( in German)

Definitions and dimensions for gas absorption coefficients

Definitions and dimensions for gas absorption coefficients

A Numerical Model of Thermal Radiation in a Dusty Atmosphere

Abstract A method is presented for numerically calculating the infrared radiative fluxes in a dusty atmosphere: a multicomponent planar medium which absorbs, emits, and anisotropically scatters radiation. The method utilizes number of different solutions, depending on the particular monochromatic properties of the medium. The most general solution, including dust and gas absorption and dust scatter, is an iterative numerical integration of the system of simultaneous differential equations for the intensity. If scattering is relatively unimportant in a particular spectral region, the equations are uncoupled from one another and a non-iterative numerical integration is used. In spectral regions with very strong gaseous absorption, the optically thick limit is employed. Elsasser's band-averaged gas transmissivities are represented by a weighted sum of exponential functions of optical path. This model provides gas absorption coefficients which may be treated as constant over specified fractions of a band. The...

Radiative heat transfer in furnaces: Further development of the zone method of analysis

Further development and testing of the zone method of analysis is described. In the zone method, the temperature and heat-flux distributions in a furnace are obtained by dividing the system into zones, and solving simultaneously energy balances on each zone. The present state of development of the method is discussed, and avenues for further development are considered. A method of including the effect of luminous radiation is described. For this the emissivity ofa cloud of soot particles is represented as the weighted sum of grey gases. It is also shown that the emissivity of a gas-soot mixture can be represented as the weighted sum of grey gases. The validity of this emissivity equation is examined by comparing calculated and measured distributions of radiation intensity through a luminous flame. Good agreement between calculated and measured traverses is found. With luminous flames, large variations in gas-absorption coefficient occur in furnaces.Methods of allowing for variations of gas-absorption coefficient when evaluating radiative “exchange areas” are discussed, and an approximate method is presented. A method of allowing for different types of heat sink in a surface zone is described. Themethod allows for the replacement of the composite surface with an equivalent grey surface having an effective emissivity and temperature. Also, surface energy factors are derived which enable the radiant energy at a surface to be divided in terms of the amount of heat absorbed by each type of sink in the zone. Experimental testing of the zone method of analysis is described. The zone method incorporatingthe abovementioned improvements was used to predict temperature and heat-flux distributions in the IJmuiden furnace. The initial conditions of flow pattern, heat release, and absorption coefficient were obtained from the experimentally measured properties in the furnace. The predictions were compared with measured values of gas temperature and surface heat flux, and good agreement was found. It is concluded from the agreement shown, that the zone method of analysis is a realisticmathematical model which can be used with some confidence for the calculation of heat transfer in furnaces.

Basic characteristics of high-frequency Stark-effect modulation of CO<inf>2</inf>lasers

The molecular Stark effect and its application to the of infrared laser radiation have been investigated both theoretically and experimentally. Using a density matrix approach, a quantum mechanical description of the effect of a time-varying electric field on the absorption coefficient and refractive index of a molecular gas near an absorption line has been formulated. For applications a quantity known as the modulation is of prime importance. Theoretical expressions for the frequency dependence of the depth show that the response to the frequency of a time-varying Stark field is separated into a nondispersive and a dispersive region, depending on whether the modulating frequency is less than or greater than the homogeneous absorption linewidth. Experimental results showing nondispersive at frequencies to 30 MHz are presented. In addition it is shown that the response of depth to Stark field amplitude is separated into linear and nonlinear regions, the field at which nonlinearities begin being determined by the absorption spectrum of the molecule being used.

Photoionization and Absorption Coefficients of OCS

Absolute absorption and photoionization coefficients of OCS gas have been measured in the 600–960-Å region using a 1-m Seya–Namioka-type scanning vacuum ultraviolet monochromator. The Hopfield helium continuum was used as a background source with photoelectric detection of the dispersed light. A number of peaks were observed in both the absorption and photoionization spectra at wavelengths that agree well with those of a high-resolution photographic spectrum. A series of the “apparent emission type” which converged at 17.931 eV had the Fano shape for a preionization process in both the absorption and ionization spectra. The total continuum underlying the band structure had been estimated, as well as that fraction due to ionization and to dissociation. Fluorescence emission was observed for all wavelengths of excitation in the Hopfield continuum. Peaks in the spectrum of the total fluorescence yield coincided in wavelength with absorption bands of Rydberg-type series converging to a limit at 16.04 eV. Maximum of the continuum underlying the fluorescence was at about 810 Å.