Water holdup estimation from pressure drop measurements in oil-water two-phase flows by means of the two-fluid model

The Two-Fluid Model (TFM) has been applied to determine water holdup from pressure drop measurements for core-annular flows in horizontal pipes. The fluids are Milpar 220 oil (rho(o)=890 kg/m(3), mu(o)=0.832 Pa.s at 20 degrees C) and tap water (mu(w)=1.026x10(-3) Pa.s at 20 degrees C). The investigated volume flow rates range from 2 to 6 m(3)/h, for water, and from 1 to 3.5 m(3)/h, for oil, respectively. The results are in very good agreement with available experimental data from the literature and a simple correlation between water holdup and water input fraction has been benchmarked to the overall data set. Eventually, the TFM endowed with the holdup correlation has been adopted to predict the pressure drop with quite satisfactory results: 98% of data fall within a percentage error of +/- 10%, 99% of the data fall within +/- 15%, and all the data are predicted within +/- 20%. On the other hand, the mean absolute relative error for the pressure drop reduction factor is 5.5%.