No abstract

No abstract

The temperature profile and the radiative and convective wall-heat fluxes for a hydro-dynamically established flow of a nongray gas in a cylinder are calculated numerically for laminar or turbulent flow. Turbulent eddy viscosity is represented by a two-region model having a near-wall-region and a far-from-wall region. Gas properties are represented by the exponential-winged band model. The controlling parameters are Nrm, the ratio of radiation conductance to molecular conductance, τR,i, the maximum spectral optical depth of the radius for the ith gas band, Wi, a measure of the importance of the ith band, and Rt, the turbulent Reynolds number. Qualitatively the results for a gas with a single major band agree with a previous solution for a cylinder with internal heat generation. Radiative Nusselt number NuR increases nearly linearly with Nrm. Radiative flux increases with τR rapidly at first and then only slowly. Increasing Rt increases markedly the convective Nusselt number NuC and appreciably NuR. The gas layer effective transmissivity was found to increase with increasing Rt and decrease with increasing τR. Quantitative comparisons with the constant-volume-heat-source case show discrepancies of up to 10 percent in NuR and up to 25 percent in NuC.

No abstract

The radiative heat flux in a molecular gas within a cylinder is formulated in terms of an axial band absorptance. The axial band absorptance function is used to reduce the two angular, one spatial, and one spectral integrals encountered to one angular and one spatial integral such as is encountered in radiative transfer problems with spherical symmetry. A closed form is obtained for the axial band absorptance for the exponential-winged band model. Illustrative results are presented for a cylindrical gas volume with trapezoidal, parabolic, or Gaussian temperature profile. Mean beam length, absorptivity, and emissivity of a cylinder of gas are obtained as a function of the optical depth at the band head.