Characterization of horizontal air-water two-phase flow

This paper presents experimental studies performed to characterize horizontal air-water two-phase flow in a round pipe with an inner diameter of 38.1mm. A detailed flow visualization study is performed using a high-speed movie camera in a wide range of two-phase flow conditions. Two-phase flows are classified into bubbly, plug, slug, stratified, stratified-wavy, and annular flow regimes. While the transition boundaries identified in the present study compare well with the existing ones in general, some discrepancies are observed for the boundaries of bubbly-to-plug, bubbly-to-slug, and plug-to-slug flows. Two-phase frictional pressure loss analysis is performed using the Lockhart-Martinelli method. For the conditions studied in the present study, it is found that the coefficient C= 24 yields the best agreement with the data with the minimum average disagreement. Detailed local experiments are performed in a wide range of conditions in the bubbly flow regime using a four-sensor conductivity probe. An extensive database for local two-phase flow parameters is established, including void fraction, bubble velocity, interfacial area concentration and bubble Sauter mean diameter. Based on this database, functional relations for ((vg)) vs. (/'> and {a) vs. (jg)/(j) have been studied. It is found that ((vg))-(j) method predicts the bubble velocity and void fraction better compared to (a)-(jg)/(j) method. Additionally, the evolution of various local two-phase flow parameters in horizontal bubbly two-phase flow is studied by analyzing the measured local parameters along the flow field. Unlike vertical upward bubbly flow, the local void fraction and interfacial area concentration can reach 0.6 and 2000 1/m, respectively, in horizontal bubbly flow. It's noticed that bubbles begin to coalesce near the gas-liquid layer instead of in the highly packed region when gas volumetric flux increases.