A study of two-phase flow in a large diameter horizontal pipeline and the measurement of interfacial level gradient in smooth stratified flow conditions
This study investigates the behaviour of two-phase flow in large diameter horizontal pipelines. The study was divided into two main parts: (i) General two-phase flow in 203 mm diameter pipeline, where the pressure drop and void fraction were measured. The pressure drop was measured using 23 bottom tapping points along a 34 m test section. The results were compared with six well known pressure drop models; these models did not allow for diameter size effect, it was therefore not surprising that good agreement was not achieved. A traversing y-ray apparatusw as designed and constructed for the measurements of void fraction. Void fraction measurements were compared with geometrical void fraction calculation, and very satisfactory agreements were obtained. The apparatus was also tested under a different number of chordal positions (steps) to determine the influence of the number of steps on the accuracy of the results. The void fraction results were compared with nine correlations foun d in the literature; the effect of pipe size was clear. A flow pattern map was also drawn for a 203 mm pipeline, which covered all the possible flow patterns (annular flow could not be obtained in this size of pipe, with the available air supply), and compared with three well known flow pattern maps, where a little agreement was found. (ii) The measurement of interfacial level gradient in the smooth stratified flow conditions. Two depth gauges (probes) were designed, constructed and calibrated for the measurement of the water level change along the test section. The two probes were placed 12 metres apart in the test section, where the flow conditions considered settled. The measurement accuracy of the probes was within 1 mm of liquid height, i. e. less than 1%. Two theoretical models in the field of stratified flow were tested and then modified to improve their ability to predict the present data, and perhaps 11 other data obtained from large diameter pipelines. A model based on the present set of data, following Bishop et. al (1986) approach was proposed, which predicts the present data within RMS of 8%.