题目内容
水在圆管中强制湍流时的对流传热系数αi为 1000 W/m2.℃，若将水的流量增加一倍，而其他条件有变，则αi为（ ）W/m2.℃
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对间壁两侧流体一侧恒温、另侧变温的传热过程，逆流和并流时△tm大小为( )。
利用水在逆流操作的套管换热器中冷却某物料，要求热流体温度T1，T2及流量Wh不变，今因冷却水进口温度t1增高，为保证完成生产任务，提高冷却水的流量Wc，其结果是（）。
一套管换热器采用逆流操作，热流体的进、出口温度分别为350K、300K，冷流体的进、出口温度分别为250K、300K，此时的对数平均温度差Δtm为（）℃。
Unit 4-Exercise 2: Who invented popcorn? P49Listen to the conversation and fill in the missing information in the notes below.[音频]Popcorn is a delicacy that was developed by the 1. ___________ of North America, dating back 2. ____________ years. Besides eating popped corn, the Indians also used popped corn in 3. ____________ necklaces and in 4. __________ ceremonies. According to most sources, a deerskin bag full of 5. ______________ was served at the first 6. ______________ dinner at Plymouth Rock in 7. ______________.Popcorn’s popularity grew during the Depression of the 8. ______________ when people realized that a little popcorn could go 9. ______________. But its success was clinched when movie10. ______________ across the continent started serving the snack. By 1947, 11. ______________ movie houses were selling popcorn at their concession stands.
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