Abstract The accuracy of the gray gas (GG) assumption for modeling the radiative transfer in fire simulations is studied for a closed compartment, an open environment, and a compartment with an opening. The liquid fuels used for each case are ethanol, heptane and methanol, respectively. Three different GG formulations, implemented on the solver Fire Dynamics Simulator (FDS), are tested and compared to experimental data. Transient, large eddy simulations (LES) are carried out in FDS, where the radiative transfer is solved coupled to the fluid flow and combustion processes. For each fire configuration, the GG formulations are compared to each other and to experimental data. The mean radiative heat flux computed in the simulations showed a good correspondence to measurements, especially for the ethanol and heptane flames, with average deviations ranging between 7% and 21%, which indicates that the GG assumption is adequate even for these weakly-sooting fuels. Among the GG models tested, the default formulation employed by FDS and the one based on a weighted-sum-of-gray-gases estimation of the medium emittance performed similarly, both providing in general more accurate results than the approach using the Planck-mean absorption coefficient.

中文翻译：

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火灾模拟中的辐射传输计算：使用 FDS 软件评估不同的灰色气体模型

摘要 针对封闭隔间、开放环境和有开口的隔间，研究了用于模拟火灾模拟中的辐射传递的灰气 (GG) 假设的准确性。每种情况下使用的液体燃料分别是乙醇、庚烷和甲醇。在求解器 Fire Dynamics Simulator (FDS) 上实现的三种不同的 GG 公式经过测试并与实验数据进行比较。瞬态大涡模拟 (LES) 在 FDS 中进行，其中辐射传递与流体流动和燃烧过程耦合求解。对于每种火灾配置，GG 配方相互比较并与实验数据进行比较。模拟中计算的平均辐射热通量显示出与测量值的良好对应，特别是对于乙醇和庚烷火焰，平均偏差在 7% 到 21% 之间，这表明 GG 假设即使对于这些弱碳烟燃料也是足够的。在测试的 GG 模型中，FDS 采用的默认公式和基于中等发射率的灰色气体加权总和估计的公式执行相似，两者通常提供比使用普朗克均值的方法更准确的结果吸收系数。