An investigation of low liquid loading gas-liquid stratified flow in near-horizontal pipes.

摘要

Low liquid loading gas-liquid two-phase flow was studied both experimentally and theoretically. Two sets of facilities with different diameters were used to conduct experiments with air and water as working fluids. On the 50.8-mm ID flow loop, the superficial gas velocity changed from 5 to 25 m/s, and the superficial liquid velocity changed from 0.00025 to 0.03 m/s. The pipe inclination angle varied from -2° to 2° from horizontal with an increment of 1°. Stratified-smooth flow, stratified-wavy flow and annular flow were encountered. On the 149.6-mm ID flow loop, the superficial gas velocity ranged from 7.5 to 21 m/s, and the superficial liquid velocity ranged from 0.005 to 0.05 m/s. The pipe inclination angle was -2°, 0°, and 2° from horizontal. Stratified-smooth flow and stratified-wavy flow were covered. The measured parameters included gas flow rate, liquid flow rate, pressure, temperature, pressure gradient, liquid holdup, wetted wall perimeter, liquid entrainment fraction, liquid film thickness, and interfacial velocity. A total of 351 data points was collected in the present study.; A mechanistic two-fluid model with new closure relationships was developed to better predict low liquid loading gas-liquid two-phase flow characteristics. New correlations for wetted wall fraction, liquid-wall friction factor and interfacial friction factor are proposed. An iterative calculation procedure is given to solve for pressure gradient and liquid holdup for given operation conditions, pipe geometry and fluid properties. A calculation program was written in FORTRAN language.; The TUFFP databank, the Espedal (1998) data, and the present study data were used to evaluate the proposed model and existing models and correlations, including the Hart et al. (1989) model, the Zhang et al. (2003) unified model, and the Beggs and Brill (1973) correlation. A screening process was applied to the TUFFP databank before it was used to do the evaluation. The evaluation showed that the proposed model gave the best predictions for both liquid holdup and pressure gradient.