Molecular Gas Radiation in a Laminar or Turbulent Pipe Flow

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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.

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