Nusselt数在弯管对流换热中的作用

在工程应用中,管内Nu是一个非常重要的物理量,它反映了管内流体与外界的热交换特性。Nu可以分为周向Nup和平均Nu,周向Nup反映了壁面每个点上对流换热的强弱程度,而平均Nu反映的是管道整体的对流换热特性。数值研究表明:Gr数,Pr数以及Dn数较小的情况下,环形同心圆管道的换热效率最高,而当以上三个参数较大时,负偏心距时的换热效率最高。不管参数如何变化,正偏心距情况下的换热效率都最低。

The effect of Nusselt number on the heat convection in the curved pipes

The Nu in the pipes is very important in the project.It reflects the heat change characteristic between the fluid in pipes and the external environment.The Nu includes the mean Nu and the circumferentialNup.The circumferential Nup reflects strength level of heat exchange on every point in the wall.The mean Nup reflects the heat change characteristic of the whole pipes.The results show that if Gr number,Pr number,and Dn number is small,the heat transfer in curved concentric pipe is most efficiently.However,if the above-mentioned three dimensional variables become large,the efficiency of the heat transfer in minus eccentricity pipe is highest.Under any circumstances,the heat transfer in plus eccentricity pipe is the weakest one.