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首页> 外文期刊>International Journal of Heat and Mass Transfer >Non-gray radiative convective conductive modeling of a double glass window with a cavity filled with a mixture of absorbing gases
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Non-gray radiative convective conductive modeling of a double glass window with a cavity filled with a mixture of absorbing gases

机译：双层玻璃窗的非灰色辐射对流传导模型，其空腔填充有吸收性气体的混合物

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摘要

Coupled radiation and natural convection heat transfer occurs in vertical enclosures with walls at different temperatures filled with gas media. In glass window thermal insulation applications in hot climates, infrared absorbing gases appear as an alternative to improve their thermal performance. The thermal modeling of glass windows filled with non-gray absorbing gases is somewhat difficult due to the spectral variation of the absorption coefficients of the gases and the phenomena of natural convection. In this work, the cumulative wave-number (CW) model is used to treat the spectral properties of mixtures of absorbing gases and the radiative transport equation is solved using CW model and the discrete ordinates method. Due to the range of temperature variation, the mixture of gases is considered as homogeneous. The absorption coefficients were obtained from the database HITRAN. First, the natural convection in a cavity with high aspect ratio is modeled using a CFD code and the local and global Nusselt numbers are computed and compared with available empirical correlations. Also, the flow pattern for different Rayleigh numbers is analyzed. Then, the heat transfer in the gas domain is approximated by a radiative conductive model with specified heat flux at boundaries which is equivalent to convective transport at the walls surroundings. The energy equation in its two-dimensional form is solved by the finite volume technique. Three types of gas mixtures, highly absorbing, medium and transparent are investigated, to determinate their effectiveness in reducing heat gain by the gas ambient. Reflective glasses are also considered. The numerical method to solve radiative heat transport equation in gray and non-gray participant media was validated previously. The temperatures distributions in the gas and the glass domain are computed and the thermal performance of the gas mixtures is evaluated and discussed. Also, comparison with pure radiative conductive model is shown.
机译：辐射和自然对流的热传递耦合发生在垂直外壳中，在不同温度下的壁中充满了气体介质。在炎热气候下的玻璃窗隔热应用中，吸收红外线的气体似乎可以改善其热性能。由于气体吸收系数的光谱变化和自然对流现象，填充非灰色吸收气体的玻璃窗的热模型有些困难。在这项工作中，使用累积波数（CW）模型处理吸收气体混合物的光谱特性，并使用CW模型和离散坐标法求解辐射传输方程。由于温度变化的范围，气体混合物被认为是均匀的。吸收系数是从数据库HITRAN获得的。首先，使用CFD代码对高纵横比腔中的自然对流建模，并计算局部和全局Nusselt数，并将其与可用的经验相关性进行比较。同样，分析了不同瑞利数的流型。然后，通过辐射传导模型对气体域中的热传递进行近似，该模型在边界处具有指定的热通量，这等效于在壁环境中的对流传输。二维形式的能量方程通过有限体积技术求解。研究了三种类型的混合气体，即高吸收性，中等和透明的气体混合物，以确定它们在减少周围环境气体热量吸收方面的有效性。还考虑了反光眼镜。先前已经验证了求解灰色和非灰色参与介质中辐射热传递方程的数值方法。计算了气体和玻璃区域中的温度分布，并对气体混合物的热性能进行了评估和讨论。此外，还显示了与纯辐射传导模型的比较。

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