问题 问答题 简答题

过冷度存在有什么危害?

答案

参考答案:

由于过冷度的存在,使传给冷却水的热量增大,冷却水带走了额外的热量;凝集水过冷后,要提高凝结水温度,势必要多消耗抽汽,降低了汽轮机组的热经济性。此外,凝结水过冷后,将使凝结水中含氧量增加,虽然现代化电厂中都有除氧设备,但为了保证除氧前管道和低压加热器不被腐蚀,凝结水的含氧量应力求降低,因此消除过冷度不仅是为了提高经济性,而且也与安全性有关。

阅读理解

Jeff  Keith has only one leg. When he was 12 years old ,Jeff had cancer . Doctors had to cut off most of his right leg.

Every day Jeff puts on an artificial(人造的)leg. The leg is plastic. With the plastic leg Jeff can ski ,ride a bicycle ,swim and play soccer. He can also run.

Jeff made a plan with his friends who had plastic legs, too. They decided to run across America. They all wore special T-shirts. On it was “Run ,Jeff, Run ,Jeff Keith's Run Across America.”

When he was 22 years old,Jeff  Keith ran across the United States from the east to the west. He started running in Boston. Seven  months later ,he stopped running in Los Angeles . He ran 3200 miles. Jeff wore out 36 pairs of running shoes and five plastic legs. Jeff stopped in cities on the way to Los Angeles. In every city people gave Jeff money .The money was not for Jeff ,but for American Cancer Society .The Society used the money to know more about cancer .

On the way to Los Angeles Jeff talked to people about cancer. Jeff is disabled ,but he can do many things. He finished college and is studying to be a lawyer .Jeff says, “People can do anything they want to do .I want people to know that I ran not only for disabled people ,I ran for everybody.”

小题1:Jeff's right leg was cut off  because of  the______.        

A .TB        B. an accident           C. cancer           D. hurt

小题2:Jeff's friends ran across America with him .They all have no ______             

A.T-shirts

B.legs

C.shoes

D.bicycles小题3:The sentence “I ran for everybody ”means ______          

A.he wants to get more artificial legs

B.people can do anything they want to

C.some disabled men will become lawyers

D.disabled people can also run

综合