Combined non-gray radiative and conductive heat transfer in solar collector glass cover
Combined non-gray radiative and conductive heat transfer in solar collector glass cover
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太阳能集热器玻璃罩中的非灰辐射和传导传热相结合
DOI：
10.1016/j.solener.2003.08.027
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发表时间：
2003
期刊：
影响因子：
6.7
通讯作者：
M. Behnia
中科院分区：
文献类型：
--
作者：
M. Khoukhi;S. Maruyama;S. Sakai;M. Behnia
提出了一种严谨的太阳能集热器玻璃辐射传热分析方法。该模型可以更准确地预测太阳能集热器系统的热性能。采用射线发射模型（REM by REM）的辐射单元法，分析了玻璃材料在一维情况下受太阳和热辐射的非灰色平面平行介质。该方法用于分析玻璃介质中非灰色对流、导电和辐射组合传热。玻璃的边界表面是镜面。考虑了玻璃相关辐射特性（即镜面反射率、折射角和吸收系数）的光谱依赖性。采用Bird和Riordan提出的光谱太阳模型对边界表面进行准直照射和漫射照射。采用了一种商用普通透明玻璃材料的光学常数。这些玻璃材料复折射率实部和虚部的光学常数（100个值）涵盖了计算通过太阳能集热器玻璃盖的太阳和热辐射传热的兴趣范围。该模型可以计算玻璃层内的稳态热流密度和温度分布。研究了热传导和辐射对传热过程的影响。复折射率的实部和虚部对层温分布有很大的影响。对于具有100个n和k值的非灰色情况，预测该系统的联合传热计算时间很长。因此，提出了一个具有10个n和k值的简化非灰色模型和两个半灰色模型，以实现快速计算。将所提出的模型与参考的非灰色案例进行了比较。结果表明，10个带宽可以用于快速计算，并且具有很高的精度。
A rigorous approach for the radiative heat transfer analysis in solar collector glazing is developed. The model allows a more accurate prediction of thermal performance of a solar collector system. The glass material is analysed as a non-gray plane-parallel medium subjected to solar and thermal irradiations in the one-dimensional case using the Radiation Element Method by Ray Emission Model (REM by REM). This method is used to analyse the combined non-gray convective, conductive and radiative heat transfer in glass medium. The boundary surfaces of the glass are specular. The spectral dependence of the relevant radiation properties of glass (i.e. specular reflectivity, refraction angle and absorption coefficient) are taken into consideration. Both collimated and diffuse incident irradiation are applied at the boundary surfaces using the spectral solar model proposed by Bird and Riordan. The optical constants of a commercial ordinary clear glass material have been used. These optical constants (100 values) of real and imaginary parts of the complex refractive index of the glass material cover the range of interest for calculating the solar and thermal radiative heat transfer through the solar collector glass cover. The model allows the calculation of the steady-state heat flux and temperature distribution within the glass layer. The effect of both conduction and radiation in the heat transfer process is examined. It has been shown that the real and imaginary parts of the complex refractive index have a substantial effect on the layer temperature distribution. The computational time for predicting the combined heat transfer in such a system is very long for the non-gray case with 100 values of n and k. Therefore, a simplified non-gray model with 10 values of n and k and two semi-gray models have been proposed for rapid computations. A comparison of the proposed models with the reference non-gray case is presented. The result shows that 10 bandwidths could be used for rapid computation with a very high level of accuracy.