Characterization of Horizontal Air-water Two-phase Flow in Different Pipe Sizes

Ran Kong, Purdue University

Abstract

The highly asymmetric void distribution in horizontal two-phase flow due to buoyancy adds further complications to the study of horizontal flow, both experimentally and analytically. As such, there has been limited research on horizontal two-phase flow, comparing with the extensively studied vertical two-phase flow. However, understanding of horizontal two-phase flow is essential to the correct simulation of two-phase flow in engineering systems such as nuclear power plant. With this in mind, the current work characterizes the horizontal air-water two-phase flow in straight pipes of different pipe sizes. An extensive experimental database is established for both global and local two-phase flow parameters in 38.1 mm and 101.6 mm ID pipes, using high-speed video camera, pressure transducer and local four-sensor conductivity probe. A specially designed instrumentation port is employed for local probe measurements by considering the asymmetric gas distribution. A wide range of flow regimes is investigated including horizontal bubbly, plug and slug flows. Some of the major characteristic two-phase flow phenomena of interest include flow regime transitions, two-phase frictional pressure drop, local interfacial structures, and one-dimensional drift-flux analysis. Considering that the bubble size to pipe diameter ratio may govern the asymmetry of the gas distribution, the effects of pipe size on flow regime transitions are investigated. The flow regime maps for horizontal two-phase flow in reactor system analysis codes TRACE and RELAP are evaluated and improvements are suggested. Effects of pipe size on local two-phase flow parameters and further on the flow regime transition are observed. Due to the importance of pressure drop in the engineering system design, a systematic study is performed to investigate the effects of pipe size, flow regime, and flow orientation on two-phase frictional pressure drop analysis in straight pipes. Various modeling approaches are evaluated and methods with the best performance are recommended. Finally, the one-dimensional one-group IATE for horizontal air-water bubbly flow applicable to different pipe sizes is developed. The closure relations are developed based on the more comprehensive experimental database. As a result, the IATE for horizontal bubbly flow can predict measured <ai