管壁特性与摩阻关系

对憎液表面的水力摩阻特性进行了试验研究,实验中憎液表面材料采用聚四氟乙烯,试验工质采用水和7号机械油。试验结果表明,内衬聚四氟乙烯管较普通钢管具有一定的减阻效果,对工质水而言,其减阻效果大约为12％,对7号机械油而言,其减阻效果为6％左右,减阻效果取决于壁面材料对介质的憎液程度,即聚四氟乙烯对水的憎液性能比对7号机械油的好。通过对憎液表面流动机理的理论分析表明,表面经憎液处理后,由于降低了表面能级,使得固壁对液体分子的吸引力小于液体分子间的吸引力,壁面部分流体产生滑移现象,从而达到了一定的减阻效果。

The Relation Between the Nature of Pipe Wall and Frictional Drag.

Experimental study is conducted on the characteristics of hydrolic frictional drag for lyophobic surface, with the surface consisting of polytetrafluoroethylene and the working media being water and 7# machine oil. The test results indicate that, depending on the lyophobic performance of the lining material, the pipes lined with polytetrafluoroethylene have a better drag reducing effect than conventional steel pipes. A drag reduction of about 12% or 6% is achieved with the working medium being water and 7#machine oil respectively, that is to say, polytetrafluoroethylene has a higher lyophobic performance against water than against 7# machine oil. The theoretical analysis made on the flow mechanism of lyophobic surface shows that surface lyophobic treatment, which can lower the surface energy level to such a degree that the attraction of the solid wall on liquid molecules becomes weaker than the liquid molecular absorption, gives rise to gliding flow adjacent to the pipe wall, thus reducing the drag to a certain extent.