对于附图所示的双层玻璃窗,试计算在一个黑暗的冬夜玻璃窗的散热损失。已知条件为:δg=4mm,δa=8mm;玻璃高1.5m,宽3m。在宽度方向离开玻璃2m处为墙角,有一股冷风沿着墙面从该墙角吹过窗子外表面。tfo=-10℃,tfi=20℃,玻璃的导热系数λ=0.78W/(m·K)。设对于波长大于3um的辐射能,玻璃的光谱吸收比ε(λ)=1。气体外略平板湍流边界层换热时,若加热段之前有一段非加热段l0,以非加热段起点到所研究地点的距离l作为Nu及Re的特征长度,而在加热段内的平均换热特征可按下式计算:
正确答案:
![](https://img.274949.com/Images/2020-04/04/dp0q5d72.jpg)
![](https://img.274949.com/Images/2020-04/04/5w8l27b7.jpg)
![](https://img.274949.com/Images/2020-04/04/658oh5dd.jpg)
![](https://img.274949.com/Images/2020-04/04/dp0q5d72.jpg)
![](https://img.274949.com/Images/2020-04/04/5w8l27b7.jpg)
![](https://img.274949.com/Images/2020-04/04/658oh5dd.jpg)
![](https://img.274949.com/Images/2020-04/04/l60bxmri.jpg)
答案解析:有
![](/editor/images/201705/qrcode_for_gh_573e2a458573_258.jpg)
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