Average Physical Parameters in an Air-Water Two-Phase Flow in a Small, Square-Sectioned Channel

Abstract

This experimental study focuses on an adiabatic two-phase air-water flow generated in a small, horizontal, 6.35 mm square channel. Pressure and temperature were near standard conditions. Experimental data and correlations available in the literature, generally, do not consider the full range of concentration, small cross-sectional areas and direct physical parameters, such as concentration (void fraction) and/or phase velocities. Based on the direct measurement of in-situ spatial concentration (in a full range of concentrations, including gas and liquid phases only), and flow-pattern determination, the experimental data from the study are compared with data from the literature and with prediction by the generally accepted Lockhart-Martinelli’s and Chen’s models. Spatial concentration measurements were made with a computer-based system developed and built by the authors. Pressure drop over a length of the channel was also measured with pressure transducers. These measurements were made for a variety of flow conditions which encompassed bubble, slug, plug, and annular flow regimes. Flow patterns were established, and both mean and fluctuating components of the concentration measurements were used to objectively identify the flow patterns. These results, together with visual enhanced observation (stroboscope) supplemented with a high-speed CCD camera recording enhanced with dye injection, were used to obtain flow-pattern maps and compared with the literature. Spatial concentration is shown to be a key physical parameter in describing the state of the mixture in two-phase flow.