问题 问答题 简答题

试述差压式流量计的测量原理?

答案

参考答案:

以能量守恒定律和流体连续性方程为基础,充满管道的流体流经管道内的节流装置,流束将在节流件处形成局部收缩,从而使流体的流速增加,静压力降低,于是在节流件前后产生了静压差。流体的流速越大,在节流前后的压差也越大,所以可以通过侧量差压来恒量流体流过节流装置时的流量大小。

阅读理解

Most Americans enjoy moving from place to place. For example, they often drive their cars 120 to 160 kilometres away just to have dinner with a friend or even fly to London or Paris just to watch a football match. In some states only one person in five lives in a place for more than five years. One may be born in one city, and go to school in another. He may finish his middle school in two or three cities, and then go to college far across the country. When he begins to work, he may possibly move from job to job. Moving from one job to another, which is called “job-hopping”, can be seen in many places in the United States.

Job-hopping does good to workers because every change of a job gives them a chance to get better pay. And job-hopping also gives bosses the chance to get new ideas and skills from him or her.

小题1:From this passage, we can see Americans often travel to _______________.

A.have dinner with their friends

B.go shopping

C.watch a football game

D.enjoy themselves小题2:Which of the following is true?

A.About 20% of the people stay in one place for over five years.

B.Children have to finish middle school in one place.

C.People go to the nearest college.

D.When people begin to work, they don’t move any more.小题3:Job-hopping means “_______________”.

A.looking for a job

B.having a job

C.changing jobs often

D.losing a job小题4:In the USA job-hopping _______________.

A.is very popular

B.helps young people go to college

C.helps workers in traveling

D.helps students begin to work小题5:The writer thinks job-hopping _______________.

A.does good only to the workers

B.does good only to the boss

C.must be stopped

D.is helpful

实验题