Applications of infrared band model correlations to nongray radiation

Internal forced convection to mixtures of inert gases

Basic formulations, analyses, and numerical procedures are presented to study radiative interactions in gray as well as nongray gases under different physical and flow conditions. After preliminary fluid-dynamical considerations, essential governing equations for radiative transport are presented that are applicable under local and nonlocal thermodynamic equilibrium conditions. Auxiliary relations for relaxation times and spectral absorption models are also provided. For specific applications, several simple gaseous systems are analyzed. The first system considered consists of a gas bounded by two parallel plates having the same temperature. Within the gas there is a uniform heat source per unit volume. For this system, both vibrational nonequilibrium effects and radiation conduction interactions are studied. The second system consists of fully developed laminar flow and heat transfer in a parallel plate duct under the boundary condition of a uniform surface heat flux. For this system, effects of gray surface emittance are studied. With the single exception of a circular geometry, the third system is considered identical to the second system. Here, the influence of nongray walls is also studied.

Radiative energy transfer in molecular gases


 The effect of real gas volumetric radiation on the thermal development in laminar parallel plate channel flow of H2O and/or CO2 in the case of gas cooling has been investigated numerically. The non-gray radiation effects of the gas have been treated using a global spectral approach, the Spectral Line Weighted-sum-of-gray-gases model. The results reveal that gas radiation results in significantly higher total heat transfer to the cooled channel wall, with an attendant more rapid drop in gas mean temperature. Gas radiation is seen to increase the local convective and total (radiative plus convective) Nusselt number for increasing radiating species mole fraction for both H2O and CO2, and for increasing gas inlet temperature. The influence of gas radiation on the thermal development is lower for CO2 than for H2O. An apparent thermally fully-developed condition may exist for this combined convection-radiation problem with real gases in the gas cooling scenario, and radiation has the effect of significantly extending the thermally developing region. Combined hydrodynamic and thermal development yields higher heat transfer than the thermally developing condition. Smaller channel wall spacing results in lower radiative heat transfer, and the aforementioned radiation effects are diminished. Local convective and radiative flux, and thermal entry length also increase with elevated gas total pressure.

https://asmedigitalcollection.asme.org/heattransfer/article-pdf/145/5/052801/7000125/ht_145_05_052801.pdf

Combined Radiation and Convection in Developing Flow in a Parallel Plate Channel with Real Gas Behavior: The Case of Gas Cooling

The problem of energy transfer in a thermally developing, radiating and conducting medium is studied. In particular, laminar flow of carbon monoxide is considered although the results may be interpreted more generally as referring to any infra red radiating diatomic gas. The effects of radiation and conduction on the temperature profile and the Nusselt number are presented for slug flow and for the parabolic velocity distribution.

D. M. McEligot

Papers

Thermally developing laminar flows with radiative interaction using the total band absorptance model