Radiative and conductive transfer for a gas/soot mixture between diffuse parallel plates

Abstract

This study examines the interaction of conductive and radiative transfer for a radiatively participating medium contained between two infinite, isothermal, opaque, and diffuse plates. The nongray medium consists of absorbing gases of carbon dioxide and water vapor and soot particles. The soot volume fraction is introduced to describe the degree of participation of the soot in the radiant exchange process. Solutions for the medium-temperature distributions and wall heat fluxes were acquired by the finite analytic with radiation method. Results are reported to ascertain the influence of the soot volume fraction, plate separation distance, and surface emittances on the heat transfer between the plates. The soot radiation dominates the absorbing gas radiation and significantly reduces the heat transfer. a <x> Nomenclature S* 8 absorptivity and emissivity weighting factors soot weighting factor mixture absorptivity and emissivity weighting factors soot emissivity polynomial coefficients parameter defined by Eq. (4) soot-volume fraction coefficient soot-volume fraction volume-to-volume total exchange areas volume-to-volume and volume-to-surface directed flux areas number of soot temperature polynomials thermal conductivity, W/m-K plate spacing, m number of volume zones number of gray components for gas and soot conduction-to-radiation parameter, kK T u /4aT* sum of partial pressures for absorbing gases, atm heat flux, W/m 2 volumetric radiant energy absorbed, W/m 2 dimensionless heat flux, q/4r u oT* dimensionless volumetric absorbed radiant energy, Q S SG, SS dimensionless overall heat flux dimensionless distance between zones, _ surface-to-volume and surface-to-surface total exchange areas SG*,SS* = surf ace-to-volume and surface-to-surface directed flux areas T = temperature, K y = spatial variable, m € = surface emittance 0 = dimensionless temperature, T/T U K = mixture absorption coefficient, m" 1 K g -absorbing gas absorption coefficient, (atm-m)" 1 K S = soot absorption coefficient, m" 1 K T = mixture total absorption coefficient, m" 1

Statistical modeling of thermal radiation transfer in buoyant turbulent diffusion flames

“…The following values were reported in [1]: C 0 = 3.7-7.5 for coal, C 0 = 6.3 for oil, C 0 = 4.9 for propane, and C 0 = 4.0 for acetylene soot. It can be shown that data [30] approximately correspond to C 0 = 7.0, while data [27] are close to those obtained with C 0 = 5.0. Thus, the data available on soot absorption exhibit wide scatter.…”

“…(8), with data from [26], is in good agreement with that calculated from the exponential wide band model for a wide range of path lengths. Second, in addition to gas components, the model [26] has been extended by including soot contribution [27], which is extremely important for sooty luminous flames modeled here.…”

Numerical simulations of the radiative transfer in a 2D axisymmetric turbulent non-premixed methane–air flame using up-to-date WSGG and gray-gas models

“…In the WSGG model, the entire spectrum is represented by a few bands having uniform absorption coefficients, each band corresponding to a gray gas. The weighting coefficients account for the contribution of each gray gas, such as in [2,3]. In a recent study, Demarco et al [4] assessed several radiative models, such as the narrow band, wide band, GG and global models such as the WSGG and spectral-line-based WSGG (SLW).…”

Um estudo numérico da influência da radiação sobre a turbulência em uma chama turbulenta 2D axissimétrica

“…The weighting coefficients account for the contribution of each gray gas, and can be interpreted as the fractions of the blackbody energy in the spectrum region where the gray gases are located. In practice, those coefficients are obtained from fitting total emittances computed from experimental-gas-data, such as those presented in Smith et al (1982) and Smith et al (1987). In a recent study, Demarco et al (2011) assessed several radiative models, such as the narrow band, wide band, GG and global models, such as the WSGG and spectral-line-based WSGG (SLW).…”