Two-phase upward flow 90° bend pressure loss model

Based on experimental pressure loss data during air-water flow in vertical 90° Plexiglass bends with an internal pipe diameter of 30 mm and a curvature radius of 120, 180, 240 and 300 mm a prediction model in the style of a two-phase flow multiplier is proposed. The underlying single-phase liquid flow pressure loss is calculated on the basis of the model by K.H. Beij, resp., D.S. Miller. The scatter of the logarithmic ratios made of the experimental and the predicted values amounts to about 25 % and is substantially lower than that obtained with selected models recommended in the literature. The new model includes physically consistent the usual design parameters and the limits of single-phase gas as well as liquid flow. Reasonable extrapolations with respect to bend dimensions, fluids and (subcritical) flow parameters should be possible.