(An) experimental investigation of interfacial friction factor for countercurrent stratified two-phase flow in horizontal and inclined pipes

Abstract

To investigate the interfacial friction factor for the countercurrent stratified two-phase flow, a series of experiments have been performed in horizontal and inclined pipes with the inner diameter of 0.05m. The length of pipes are 2m and 4m, and the pipe inclination angles are 0°, 1°, and 2°. The air and water at room temperature and at atmospheric pressure are used as working fluids. The instantaneous local void fractions are measured by the parallel wire conductance probes located at L/D=1.2, 21.5, and 22.1 for 2m-tests, and 41.4, 42.0, and 62.0 for 4m-tests from the inlet of water flow, respectively. The superficial water velocity ranges from 0.0127 to 0.1358m/s and the range of superficial air velocity is from 0.679m/s to the value of slug occurrence. The interfacial friction factor has been determined from the measurements of air and water flow rates, pressure drop, and void fractions. From the present experiment, it is found that the value of $(f_{i}/ f_{g})_{exp}$ is strongly sensitive to the existence of the hydraulic jump where two distinct water levels contact and the range of its value increases with the inclination angle. The comparison of the present experimental data with Lees correlation for the interfacial friction factor has resulted in a good agreement in three-dimensional wave regime. It should be noted here that the measurement point of the void fraction is important in analyzing the onset of slugging, because the relative difference in the void fractions measured at different locations varies as large as 65% at the condition of the slug occurrence. A comparison with the cocurrent flow pattern map shows that there is a large difference from the present experimental data. Therefore, it is necessary to develop the countercurrent flow pattern map including several important variables, such as pipe length, inclination angle and others.