问题 问答题 简答题

简述凝结水过冷却的主要原因?

答案

参考答案:

主要有三种原因:

1)汽器汽侧及存空气,使蒸汽压力下降,从而凝结水温度降低。

2)凝汽器水位高,淹没了一些冷却水管,形成凝结水过冷却。

3)凝汽器冷却水管排列不佳,或布置过密,使凝结水在冷却水管外形成水膜。水膜内层紧贴铜管外壁,所以水膜温度接近或等于冷却水温。当水膜变厚下垂成水滴时,水滴温度为水膜平均温度。这一平均温度低于凝汽器内压力下的蒸汽饱和温度,产生凝结水过冷却。

完形填空
完形填空。
     "This Friday we'll have the yearly Egg Drop Challenge," said our science teacher, Mr. baker. "You can
work alone or with a partner."
      My friend, Cassie, and I smiled at each other. We always worked on projets   1  .
     The   2   of the challenge was simple-to build a protective container to keep an egg from breaking when
  3    the stadium wall.
      I made my sandwich that afternoon while waiting for Cassie.   4   the butter-cream gave me an idea.
     "I have a brilliant design for our   5   container!"I said when Cassie arrived."We can   6   the egg with
some butter-cream."
     "Why not pit the egg in a basket with a parachute (降落伞)   7   ?" Cassie rolled her eyes. "The parachute
is better than that stupid idea."
      I couldn't believe it, Of course we'd had our little   8   in the past, but she'd never called any of my ideas"
   9   " before. "Then I'll build mine and you build yours!" 
       10   words had been out, our friendship was challenged. When Friday finally arrived, I had to   11   
Cassie's Egg Force One looked pretty good.  12 , my Egg-cellent Egg Cream didn't look quite scientific.
We kids carried our containers up three stadium steps and dropped them over the side wall. Those whose
eggs broke were out; those whose eggs survived   13   three more steps and dropped them again. This
would go on till the last egg broke.
     After four rounds, only Cassie and I were   14   . I let go of my box. I heard someone say"ew" after
seconds. Had my egg broken? I raced down the  15  . The side walk was dotted with egg shells (蛋壳)
from those
  16   drops. Finally I found my little Egg-cellent Egg Cream.
     "That looks like egg drop soup, Laura,"Cassie said. She was holding her Egg Force One. My   17 
 raced. Had she won? I looked at her basket.  18  . "My egg bounced  19   ,"she explained, pointing to a
broken shell. "A tie (平局),"Mr. Baker said. Cassie looked at me, and her glare   20   . I laughed. She smiled…
( )1.  A. patiently  
( )2.  A. function   
( )3.  A. rolled down
( )4.  A. Spreading  
( )5.  A. butter     
( )6.  A. protect    
( )7.  A. followed   
( )8.  A. ideas      
( )9.  A. wrong      
( )10.  A. Since     
( )11.  A. explain   
( )12.  A. Therefore 
( )13.  A. paced down
( )14.  A. left      
( )15.  A. steps     
( )16.  A. intended  
( )17.  A. eyes      
( )18.  A. Lost      
( )19.  A. around    
( )20.  A. returned  
B. silently      
B. goal           
B. pushed against 
B. Boiling        
B. sandwich       
B. replace        
B. covered        
B. fights       
B. stupid          
B. While          
B. deny          
B. Anyway       
B. turned around  
B. wanted        
B. way           
B. unexpected   
B. hands         
B. Dirty         
B. out            
B. remained   
C. together     
C. reason           
C. thrown at     
C. Baking         
C. cream           
C. carry         
C. attached        
C. worries       
C. brilliant       
C. But             
C. admit         
C. Otherwise        
C. walked up     
C. chosen        
C. wall             
C. failed        
C. feet           
C. Broken         
C. in              
C. increased
D. alone               
D. result                   
D. dropped over        
D. Holding               
D. egg                     
D. mix                  
D. supported              
D. challenges            
D. scientific          
D. And                    
D. prove                 
D. Besides                 
D. went back            
D. discovered           
D. sidewalk                
D. desired             
D. heart                 
D. Empty                 
D. down                    
D. softened         
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