Experimental study on void fraction, pressure drop and flow regime analysis in a large ID piping system

An experimental study of the characteristics of air-water two-phase flow in a piping system with an inner diameter of 152.4 mm is presented. Both horizontal and vertical pipes (with the lengths of 15.09 m and 6.42 m) are included in the system and two 90-degree elbows are used for their connections. 71 flow conditions are performed in this experiment, covering plug, slug, pseudo slug, and stratified flow for the horizontal flow, and bubbly, cap bubbly, churn turbulent, and falling film/annular flow for the vertical flow. Detailed flow regime analysis for the flow regimes of the horizontal and vertical pipe flow and the effects of the elbow on the flow regime transition are discussed. The flow regime maps proposed generally agree with the existing maps. A significant flow regime shift in the vertical section is also observed and discussed. The area averaged void fraction development is presented and a sharp drop of void fraction in vertical downward test section is observed which results from the kinematic shock phenomenon. The result of the frictional pressure drop is discussed, and it agrees with the Kim et al.'s correlation. With the database, the drift flux model for Goda et al.'s vertical downward flow is evaluated. Large difference has shown at low void fraction which may indicate further modeling investigation. (C) 2018 Elsevier Ltd. All rights reserved.