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

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 0.4to 1.4and 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.