An experimental study of gas–liquid flow in a narrow conduit

This paper reports an experimental study of non-boiling air–water flows in a narrow conduit (diameter 1.95 mm). Results are presented for pressure drop characteristics and for local heat transfer coefficients over a wide range of gas superficial velocity (0.1–50 m s−1), liquid superficial velocity (0.08–0.5 m s−1) and wall heat flux (3–58 kW m−2). For a given liquid flow rate, the data exhibit sudden changes in pressure drop and, to a lesser extent, in heat transfer characteristics as the gas flow is increased. These events are believed to correspond to flow transitions, from bubbly, to intermittent slug, to annular flow. Overall, the pressure drops in these diabatic non-boiling two-phase flows can be estimated with good accuracy using correlations developed for adiabatic conditions. The heat transfer results are, on average, reasonably well described by the two-phase convective heat transfer components of flow-boiling correlations but there is considerable scatter in some cases.