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The gas, oil and water co-current flow in pipes either flow in separate layers or in the form of a mixture. Other than gas, the liquid mixtures are common during the transportation of oil. In liquid mixtures, one liquid acts as a continuous phase and the other liquid dispersed in it. The phase inversion in three-phase flow majorly depends on the superficial velocity of individual phases, the volume fraction of liquid phases in total liquid and the internal diameter of the pipe. Pipe bends and fittings are commonly used in pipe networks for the diversion and distribution of flow. The 90° elbow bends are commonly used in such systems, where they change the flow direction from horizontal to vertical and vice versa. For the case of horizontal to upward vertical flow, the bend offers restriction to the flow compared to the straight pipe. Therefore, the process of phase inversion gets effected upstream 90° bend. In the current work, the phase inversion process during three-phase horizontal flow upstream 90° bend has been studied. The internal diameter of the pipe was 0.1524 m and the bend radius to diameter ratio (r/d) was 1. The range of superficial velocities are 0.5-5, 0.08-0.4, and 0.08-0.4 for oil-gas and water respectively. The continuous liquid phase and its effect on pressure drop have been studied at various oil to liquid volume ratios (fo). The results show the different oil-water relationships and the liquid holdup occurred due to the bend.

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The use of 90° bend is common in pipeline networks to connect the horizontal and vertical pipes in different orientations. The gas–oil–water flow pattern experiences a significant change while flowing through the bend. The centrifugal and gravitational forces influence the upstream flow pattern and transform it into a different type in the downstream pipe. An experimental study is conducted to identify flow pattern transformation in horizontal to vertical upward bend having an (R/d) ratio of 1. Each phase velocity affects the flow patterns; hence, the superficial velocities have been varied in the range of 0.5–5, 0.08–0.36, and 0.08–0.36 m/s for gas, oil, and water, respectively. The three-phase flow patterns in the bend’s horizontal and vertical legs have been identified and discussed in detail. Flow regime transition maps are plotted, and the variation in flow patterns with the change in superficial velocities of fluids has been analyzed. The pressure drop has been analyzed, and the prediction model for total pressure drop across the bend has been developed. The comparison of the experimental and predicted results showed close agreement.