Molecular Gas Radiation in a Laminar or Turbulent Pipe Flow

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.

Combined Radiation Convection in Thermally Developing Poiseuille Flow with Scattering

“…Similar findings, particularly regarding the existence of a fully developed temperature profile, have been reported in analyses by Liu and Thorsen [11] and by Pearce and Emery [12]. Recently Balakrishnan and Edwards [10] compared their results for radiation and total Nusselt numbers at large distances from entry to the results of Wassel and Edwards [9] for thermally and hydrodynamically established turbulent flow in a pipe. These authors found that maximum errors in these Nusselt numbers were 2.2 percent and 7 percent, respectively, corresponding to radiation-to-conduction ratio of 10.…”

“…Figure 1 shows the geometry and coordinate system used. The governing equations in nondimensional form can be given as [19] , , d6 d 2 9 1 dq R * u(n) -= d£ d? ; 2 …”

“…A number of analyses of channel flows with combined radiation convection modes of heat transfer have been performed [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17], A significant number among these analyses [2][3][4][5][6][7][8][9] have assumed fully developed temperature distribution which reduces the partial integro-differential equation to an ordinary integro-differential equation. This equation is identical in appearance to that for the combined radiation-conduction problem for the same geometry, except for the presence of a source term (as a function of local and bulk mean temperatures).…”

Mixed convection heat transfer in horizontal rectangular ducts with radiation effects

“…However, heat transfer by mixed convection and radiation has not been studied extensively. Forced convection in a channel with radiation has been under investigation by many researchers [16][17][18][19] for ducts with prescribed heat fluxes and temperature distributions on wall surface. These studies used various approximate methods for radiative transport in the medium.…”

Measurement of the spatially distributed temperature and soot loadings in a laminar diffusion flame using a Cone-Beam Tomography technique

“…The emission bands of CO 2 and water vapour are centred in the infra-red region [24], which will not be recorded by the camera. Therefore, their interference can be neglected.…”