摘要
实验发现,与光管管束类似,随Re数增加圆翅片与椭圆翅片管束亦先后呈现3种不同的流态,即层流、混合流和紊流,相应的有3种不同的换热机制和规律。在低Re数时,换热由层流或混合流机制所控制。目前,工程中用紊流区的换热与阻力规律向下延伸,用于设计运行于低Re数工况的自然抽风空冷器将导致设计的失败。实验表明,在自然抽风空冷器操作条件下,对于同样的换热系数,椭圆翅片管的压降比国翅片管低45%左右,采用椭圆翅片管将取得较明显的经济效益。实验还发现,来流气流不均匀性对自然抽风空冷器的平均换热特性几乎没有影响,因此对吸风入口型线的设计可以大大放低要求。
Experimental results show that three flow patterns (laminar, mixture and turbulent flow) are ob-
served with increasing Re numbers. This is also reflected in the character of the heat transfer. In a
range of low Re numbers heat transfer is dominated by laminar or mixture flow. If the heat transfer
correlation in a range of turbulent flow is extented to design a natural convection air-cooled exchang-
er, the design will fail. Experimental results also show that the pressure drop of elliptical finned tube
banks is 45 percent lower than that of the circular finned tube banks at the same heat transfer coeffi-
cient. Therefore it will be favorable to use elliptical finned tube banks. So far it is found that nonuni-
formity of free stream has very little infulence on the average heat transfer coefficient, so that the
shape of entrance of natural convection air-cooled exchanger is not important in design.
出处
《西安交通大学学报》
EI
CAS
CSCD
北大核心
1992年第4期95-102,共8页
Journal of Xi'an Jiaotong University
关键词
传热性质
流动阻力
翅征管
Re数
heat transfer character
flow resistance
finned tubes
natural convection
air-cooled heat exchangers
