螺旋扁管管内传热强化及流阻性能

以水为介质,研究了不同截面短长轴比B/A (B/A＝0.3-0.5)和导程与直径比S/de (S/de=17-50)的螺旋扁管管内传热和流阻性能.实验结果表明:管内Nu和f值均随均随B/A值和S/de值的增大而减小,但随B/A值的增加而减小得更快,B/A值对螺旋扁管管内传热与流阻性能影响更大;在相同Re和Pr下,螺旋扁管管内Nu数为光滑管的1.3～2.5倍;阻力系数f是光滑管的1.2～1.5倍.通过多元线性回归法对实验数据进行归纳与整理,提出螺旋扁管管内努塞尔数和阻力系数的准数方程式,其最大误差分别是12%和6%,可为螺旋扁管换热器的工程设计提供依据.

Tube-side heat transfer enhancement and flow resistance properties of single spiral-flat tubes

In this paper, water is used as working medium, the heat transfer and flow resistance performance inside single spiral-flat tubes with different B/A (B/A=0.3~0.5) and S/de (S/de=17~50) are studied experimentally. The experimental results indicate that, over a ranger of tube side Reynolds number and Prandtl number (Re=4000~20000, Pr=6~7.5), the internal Nusselt number and friction factor of spiral-flat tube increased by 30%-150% and 20%-50% respectively compared with smooth tube at the same Re and Pr. The value of friction factor decreases with increasing the value of B/A as well as increasing that of S/de, and the same phenomena can also be observed for Nusselt number. Through multiple linear regression method, the correlations of Nusselt number and friction factor which can be applied to the design of spiral-flat-tube heat exchanger are also proposed with deviations of 12%、6% respectively.