题目内容
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( )。
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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.
Unit 4-Exercise 6 How crossword puzzles are created P51Listen to the conversation and fill in the information in the notes below.[音频]The crossword puzzle was introduced in the Sunday supplement of the New York World newspaper in 1. __________________. The designer of crossword, Arthur Wynne, was inspired by 2. __________________ Square, a children’s word game in which words are 3. __________________ vertically and horizontally. Wynne added empty squares and some clues. By the early 1920s, crossword puzzles were 4. __________________ features of almost every American newspaper. In 1924, four puzzle books were on the 5. __________________ lists. Today, crossword puzzle makers each have their own techniques to 6. __________________ the skills of their players. Eugene Waleska is a creator of the New York Times crossword puzzle. He begins with a 7. __________________ and lists as many words as he can think of that loosely fit the theme. Then Waleska starts to fill in the grid with the 8. __________________ first, avoiding words ending in J or beginning with X. He works first in the lower right corner of the grid, since it is 9. __________________ to find a word that ends with a certain letter. Waleska says that when he started in this business, it took him 10. __________________ to fit the words into a 15*15 square grid. Now it takes less than an hour.
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