问题 问答题 简答题

黄铜表面式凝汽器与铜管钢片空冷塔相结合的空冷循环水系统有哪些特点?对水质有哪些要求?

答案

参考答案:

黄铜管表面式凝汽器与钢管片空冷塔相合的间接空冷循环水系统,一般采用二级除盐水作为循环冷却水。由于系统中存在着铁、铜两种不同材质,且这两种材质的电化学性质存在着差异,因而它们对水质的要求也就不同。为此需要研究适应铁,铜的最佳化学工况及水质指标,既保证钢制散热器有足够长的耐蚀寿命,又要使铜的腐蚀速率控制在工程上允许的范围之内,从而保护机组的长期安全运行。

阅读理解

Once there was a huge apple tree. A little boy loved to come and play around it every day. He loved the tree and the tree loved to play with him.

Time went by …The little boy had grown up and he no longer played around the tree every day. One day, the boy came back to the tree and he looked sad , " Come and play with me," the tree asked the boy. "I'm no longer a kid. I wouldn't play around the tree any more. " The boy replied.  "I want toys. I need money to buy them. " " Sorry, I don't have money. But you can pick all my apples and sell them. So you will have money. " The boy picked all the apples on the tree and left happily. The boy never came back after he picked the apples.

One day, the boy returned and the tree was so excited. "Come and play with me, " the tree said.  "I don't have time to play. I have to work for my family. We need a house for shelter. Can you help?" " Sorry ,  I don't have a house. But you can cut off my branches(树枝)to build your house. " So the boy cut all the branches off the tree and left happily. The tree was glad to see him happy but the boy never came back since then. The tree was again lonely and sad.

One hot summer day, the boy returned and the tree was pleased. " Come and play with me ! " the tree said. "I am sad and getting old. I want to go sailing to relax myself. Can you give me boat?" " Use my trunk(树干)to build your boat. You can sail far away and be happy. " So the boy cut the tree trunk to make a boat. He went sailing and never showed up for a long time.

Finally, the boy returned after he left for so many years. " Sorry, my boy. But I don't have anything for you any more. The only thing left is my dying root(树根).” The tree said with tears. “I don't need much now, just a place to rest. I'm tired after all these years," the boy replied.

"Good! Old tree root is the best place to lean on and rest. Come and sit down with me and rest. " The boy sat down and the tree was glad and smiled with tears.

小题1:-When did the boy come back to the apple tree?

-He came back___________.

A.whenever he was happy

B.if he missed the apple tree

C.when he was in times of difficulty

D.as soon as he was free小题2:-What did the boy want at last?

-He wanted ___________.        .

A.to have a house to live in

B.nothing except a place to rest

C.the root of the apple tree

D.anything that the apple tree had小题3:-What can we learn from the story?

-We should ___________.

A.plant more apple trees

B.learn from the boy

C.always stay at home

D.be thankful to our parents小题4:According to the passage , which of the following statements is NOT true?

A.The phrase " with tears① " means that the apple tree was sad because the boy asked for too much.

B.The phrase " with tears② " means that the apple tree was still happy because she could help the boy for the last time.

C.Each time the boy asked the apple tree for help, the tree tried her best to satisfy him.

D.After reading the passage, we can easily think of the old Chinese saying “ Parents love is universal !”

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