幂律流体管内紊流摩阻系数计算式评价

New Evaluation of Correlations Calculating Friction Factors for Power Law Fluids in Turbulent Pipe Flow

幂律流体是最常见的非牛顿流体,其管内紊流摩阻系数的计算方法较多,但远没有牛顿流体的成熟。对搜集的国内外已公开报道的14个幂律流体管内紊流摩阻系数的计算式,通过计算机程序计算了Fanning摩阻系数f,对计算结果以图表形式进行了相对偏差评价。结果表明,相对于其他计算公式,Dodge-Metzner式计算结果的总平均相对偏差最小,因而该公式适用于幂律流体管内紊流摩阻系数的计算。

The power law fluid is one of the most typical non-Newtonian fluids. Although the correlations are abundant for calculating friction factors for turbulent pipe flow of the power law fluids, those are not grea-tly accurate and are still being developed. As well,there is no consensus at present to confirm the most practicable approach among them. This paper collects fourteen published correlations calculating the friction factors for power law fluids in turbulent pipe flow from 1959 to 2003. According to those methods the Fanning friction factor,f,is computed. The correlations are then evaluated by plotting the curves of the calculated values and by listing the special relative deviation table of the calculated values. Separate investigation is conducted on the relationship of the calculated value of f and ReMR (Metzner-Reed Reynolds number) when setting a given rheological behavior index, n, and the one between the calculated value of f and n when setting a given ReMR. In the study, ranging of n from 0. 4 to 1. 4 and ReMR from 4 000 to 100 000,and according to the same combination, (n,ReMR) ,the f value calculated from each correlation is compared with the mean value of all the f values calculated from the 14 correlations,. It shows that the overall mean relative deviation (OMRD) of the Dodge-Metzner correlation is the minimum,1.5%,followed by the OMRD of the Shenoy correlation, 1. 9%. Based on the evaluation from the statistical significance, this paper recommends the Dodge-Metzner correlation for predicting the friction factors for the turbulent pipe flow of the power law fluids.