Study Investigates Multiphase Flow in Circular and Triangular Pipes
Authors: Carpenter Chris 
Published: January 2023

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This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 208101, “Multiphase Flow in Circular and Triangular Pipes: Examining Flow Characteristics, Sand Erosion, and Heat Transfer Through Computational Fluid Dynamics and Experimental Work,” by Ronald E. Vieira, Thiana A. Sedrez, and Siamack A. Shirazi, SPE, The University of Tulsa, et al. The paper has not been peer reviewed.

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The authors present a survey of air/water and air/water/sand flow through circular and triangular pipes. The main objective of this investigation is to study the potential effects of triangular pipe geometry on flow patterns, slug frequency, sand erosion in elbows, and heat transfer in multiphase flow.

Introduction
The complete paper summarizes several important benefits of triangular pipes as compared with circular pipes in multiphase flow. First, a survey of horizontal multiphase air/water flow through circular and triangular pipes is presented. Second, the erosion patterns in triangular elbow geometry are examined experimentally and predicted computationally using existing erosion models. The results are compared with circular elbows for steel materials. Initially, an experimental investigation was performed using flow visualization with a paint-removal study to determine the location where particles impinge and lead to erosion. Erosion-measurement experiments are also conducted in a flow loop containing liquid and 300-µm sand particles. The experimental studies were followed by computational fluid dynamics (CFD) erosion modeling for liquid/sand and liquid/gas/sand flows in circular and triangular elbows. Third, an attempt is made to analyze the effect of circular and triangular pipe configurations on heat transfer at constant wall temperature and under the influence of different Reynolds number values. The analysis was performed numerically using CFD for turbulent and laminar flow with water at two different viscosities.

Experimental Setups
The main objective of the first set of experiments was to study the potential effects of triangular pipe geometry on flow patterns and slug frequency in gas/liquid flows. The experimental facility and methodology are detailed in the complete paper.
The setup consisted mainly of a pump, tank, separator, and test-loop section (pipes). The water flow rate (containing particles) was measured by timing the liquid volume loss from the tank. Measurements were repeated three times, and the averaged measured time was used. The gas-flow rate was measured using a digital vortex flowmeter. Experiments were performed horizontally and near atmospheric pressure conditions.
The circular test section consisted of a 2-in.-inner diameter, 28-ft-long clear acrylic pipe. The triangular test section was formed from three 7-ft-long, 2.7-in.-wide sheets of cast acrylic.
The effect of corners of the triangular pipe on the liquid distribution compared with round tubes was investigated using two different orientations of triangular pipe, apex upward and downward. Detailed videos and slug-frequency measurements were collected for horizontal air/water flow through the round and the triangular clear pipes to identify flow patterns. The slug frequency was measured by analyzing the videos.