Abstract
This experimental study examines the two phase flow structures of airflow pressures for annular flow through a 900 bend, with and without, a vortex fin for drainage applications. The superficial liquid flow characteristics: Reynolds number (ReL) and air-to-water flow volume ratio (AW) in the ranges of 11200-20000 and 1.1 - 9.6 respectively were selected as the control parameters throughout the specified tests. At each test condition the flow structures observed by the computerized videography were also synchronized to the airflow pressure measurements. Particular dependence on ReL and AW, the interfacial air-water flow behaviour through the 900 bend with and without a vortex fin varied periodically, to generate a variety of two-phase patterns which signified the temporal airflow pressure variations. The associated flow physics of the dynamic processes of airflow pressure variations were then revealed. In the 900 bend with fin, the down- flow water screen was discontinuous, leading to a reduction of positive airflow pressure. The empirical correlations observed permitted the individual interdependent evaluation of ReL and AW impact on the time-mean airflow pressures in the 900 bend with and without a vortex fin were derived to assist the design performance.
