题目内容

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（）℃。

A. 30
B. 40
C. 45
D. 50

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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.

Unit 4-Exercise 7 Koala P52-53Listen to the talk and write down the missing information in the notes below.[音频]Koala is the Australian teddy bear. It is 1. feet long, with 2. seeming as if they were stuck on, and it has beady eyes but no 3. . The fur is 4. in color. They are pouched mammals, not bears at all.Koalas spend almost all their lives in the eucalyptus trees and eat the 5. . All the toes are armed with 6. claws, and the 7. are divided into two groups. The great 8. is thumb-like. All of these features aid in climbing. Koalas are able to spring from one upright branch to another with 9. skill.The baby is carried in the 10. at first, then it clings to the fur of the mother’s 11. until it is almost as large as the mother. Koalas become quite tame and they are great 12. __ at the Australian zoos and parks.

Unit 4-Exercise 11 Inventor of the telephone (1) P54-55Listen to the first part of the talk about the inventor of the telephone. As you listen to the talk, write down the missing information in the notes below.[音频]The man who invented the telephone was Alexander Graham Bell. He was born in Edinburgh,Scotland, in 1. _______· His father and grandfather had both been teachers of 2. _. His father had worked out a system of “Visible Speech”, that is, a system by which a deaf person can “see” what people say by reading 3. _. Bell learned this system and soon he 4. _ a teacher of the deaf too, and he opened his 5. _ school for the deaf people in Canada.Through his teaching, Bell became interested in the 6. _ of the human voice. He thought that it should be possible to 7. _ sound across a distance. He worked very hard with his assistant Thomas A. Watson day and night on this idea. They made some 8. _______and tried again after each failure.