A review of methods used for rheological characterization of yield-power-law (YPL) fluids and their impact on the assessment of frictional pressure loss in pipe flow

Abstract

In this paper, we present a comprehensive review of the methods used for the rheological characterization of the yield-power-law (YPL) fluids. Ten different rheological characterization techniques have been evaluated, out of which seven of them use conventional rotational viscometer measurements, and the remaining three use advanced rheometer measurements. Results have shown that the YPL fluid characteristic determined by different techniques could vary significantly for the same fluid (flow behavior index (n): 0.2 to 0.68; consistency index (K): 1.02 to 11.48 Pa-s; and yield stress (τYS): 0.57–12.26 Pa).A sensitivity analysis is conducted to assess the effects of the variations in YPL fluid rheological properties (i.e., YPL model parameters estimated by using different rheological characterization techniques) on the predictions of frictional pressure loss in the pipe flow of YPL fluids. The friction pressure loss prediction model outlined in the API recommended practice (API-RP:13D) was used for the sensitivity analyses.Variations of the estimated YPL fluid rheological properties caused frictional pressure loss values for the laminar pipe flow of YPL fluids to alter within ± 12% of the median value. In turbulent pipe flow of YPL fluids, however, frictional pressure loss predictions fluctuated within the range of ± 5 to 35% of the median value depending on the methods used for determining YPL model parameters. Predictions of turbulent pressure drop were found to be very sensitive to small changes in flow behavior exponent (n) resulting from different rheological characterization methods.The results presented in this paper can help choose the most suitable rheological characterization method for determining YPL fluid rheological properties, which can then be used for a more realistic assessment of the frictional pressure losses associated with the flow of YPL fluids in pipes and annuli.