ɸ50×5的不锈钢管,导热系数λ1为16W/m·K,外包厚30mm的石棉,导热系数λ2为0.2W/m·K。若管内壁温度为350℃,保温层外壁温度为100℃,试计算每米管长的热损失。
A. 396.9
B. 366.9
C. 285.9
D. 258.9
查看答案
在圆筒壁的一维稳态导热速率方程中，传热面积应为（ ）。
A. 圆筒壁的外表面积
B. 圆筒壁的内表面积
C. 圆筒壁内、外表面积的对数平均值
D. 圆筒壁内、外表面积的几何平均值
在多层圆筒壁一维稳态热传导过程中，通过各层壁面的传热速率和热通量均相同
A. 对
B. 错
Why was Tilly Smith awarded Child of the Year?
A. She saved people’s lives in Thailand.
B. She wrote a report about tsunamis.
C. She won a contest in geography.
D. She helped to clean up the beach.
Where did Tilly Smith learn about tsunamis?
A. From a magazine article.
B. From a TV program.
C. From her parents.
D. From her teacher.
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