Implementation of the weighted sum of gray gases model to a narrow band: Application and validity
- Korea Advanced Inst. of Science and Technology, Kusong, Taejon (Korea, Republic of). Dept. of Mechanical Engineering
Modeling the nongray behavior of combustion gases, such as water vapor and carbon dioxide, is very important for calculating the radiative heat transfer in furnaces and boilers. Here, the weighted sum of gray gases model (WSGGM) is applied to narrow bands of water vapor for analyzing radiative heat transfer in nongray media. For a given narrow band, the band mean spectral emissivity is represented by a weighted sum of gray gas emissivities expressed in terms of absorption coefficients, weighting factors, absorbing gas density, and path length. Five types of temperature-versus-narrow band absorption coefficient relation are suggested, and comparisons between the modeled emissivity and that of the original narrow band model are made and shown at a few typical bands. Total and low-resolution spectral intensities at the boundary are obtained for uniform, parabolic, boundary-layer-type temperature and parabolic concentration profiles using the WSGGM with five gray gases. Results using the Curtis-Godson approximation are compared with the WSGGM computations for each narrow band. The results using the WSGGM show good agreement with the Curtis-Godson approximation results, and especially, two of the WSGGMs with wave number-dependent absorption coefficient show highly accurate results with a few percent error in the total wall heat flux. The WSGGMs with wave number-independent absorption coefficients are, however, more useful for total spectrum computation, with a slight sacrifice in the accuracy.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 419711
- Journal Information:
- Numerical Heat Transfer. Part B, Fundamentals, Journal Name: Numerical Heat Transfer. Part B, Fundamentals Journal Issue: 4 Vol. 30; ISSN 1040-7790; ISSN NHBFEE
- Country of Publication:
- United States
- Language:
- English
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