Multiphase Flows in Small Scale Pipes

Wegmann A.

This study presents results of multi-phase flows in small scale pipes. Experiments are carried out for water-air, paraffin-air, water-paraffin and water-paraffin-air flows in pipes with inner diameters of 5.6 mm and 7.0 mm, respectively. Deionized water, compressed dried air and a very low viscosity paraffin oil with a density of and a viscosity ◄ at 20º ♫C are used as working fluids. The flow test facility was especially designed to provide steady volume flows without any pulsation even for very small volume flow rates. This is achieved through the use of pressurized storage vessels for the three fluids instead of rotational pumps. The flow rates of the two liquids are controlled by state-of-the-art mass flow controllers, whose measuring principle is based on the coriolis effect. The flow rate of the gas is controlled by three thermal mass flow controllers corresponding to different flow rate capacities. The experiments are conducted with respect to the developing flow patterns and the pressure drops caused by the flow. High accuracy glass pipes are used, concerning outer diameter and wall thickness. The flow is illuminated on the one hand by a stroboscope, brightening the whole pipe volume and on the other hand by a laser sheet, brightening a vertical plane that cuts through the axis of the pipe. A comprehensive simulation of the light distortion caused by the different refraction indices of the fluids and the curved pipe surfaces shows that pictures taken directly from the pipe exhibit tremendous distortions. These are reduced by the use of compensation boxes containing water or paraffin, corresponding to the continuous phase inside the pipe. This reduces the distortion to a marginal area.The resulting flow pattern data are presented analogous to presentations of corresponding data in literature. The comparison of the flow pattern maps with literature data shows that a variation in pipe diameters in the range of several centimeters to several millimeters causes an essential change in the flow pattern transitions. Especially the Bond number which represents the ratio of gravitational forces to surface tension forces, reaches the order of O(1) if gas is present in the flow. For Bond numbers , surface tension forces are dominant. This is proven by the fact that almost no stratified flow was observed in the 7.0 mm pipe. In the 5.6 mm pipe, absolutely no stratification was observed. The dominance of surface tension results in intermittent flows being the flow pattern most frequently observed in liquid-gas and liquidliquid-gas flows. In liquid-liquid flows, the same effect of the reduction in pipe diameter is discovered. However, intermittent flow is no longer the dominant flow pattern as annular flow patterns occur for wide ranges of flow conditions. Flow pattern prediction methods are tested for their ability to predict the experimental results. No precise agreement was found, but some models show trends corresponding to the experiments.The experimental pressure drop shows comparable behavior to results from other authors published in literature. The ability of theoretical pressure drop calculation methods to predict the experimental values has been tested. For liquid-gas and liquid-liquid flows, several applicable models are found. By contrast, the only model explicitly developed for the use with liquid-liquid-gas flows, predicts values that are far too low.

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Table of contents :
Vorwort……Page 5
Summary……Page 7
Table of Contents……Page 9
Nomenclature……Page 17
1 Introduction……Page 21
1.1.1 Transport Facilities……Page 22
1.1.2 Tubular Reactors……Page 23
1.2.1.1 Liquid-Gas Flows……Page 28
1.2.1.2 Liquid-Liquid Flows……Page 30
1.2.1.3 Liquid-Liquid-Gas Flows……Page 31
1.2.2 Pressure Drop……Page 33
1.2.2.1 Liquid-Gas Flows……Page 34
1.2.2.2 Liquid-Liquid Flows……Page 37
1.2.2.3 Liquid-Liquid-Gas Flows……Page 38
1.4 Structure of the Thesis……Page 40
2 Experimental Setup, Measurement Methods……Page 42
2.1 Description of the flow test facility……Page 43
2.2 Optical Devices……Page 46
2.2.1 The Problem of Light Distortion……Page 48
2.2.2 Multiple Distortion……Page 55
2.4 Measurement Accuracy……Page 60
2.5 Reproducibility of Measurements……Page 61
2.6 Limitations of the Experimental Setup……Page 64
3 Two-Phase Liquid-Gas Systems……Page 66
3.1.2 Transitions Between Flow Regimes……Page 67
3.1.3.1 Types of models……Page 70
3.1.3.2 Closure Relationships……Page 72
3.1.3.3 The Taitel Dukler Model……Page 74
3.1.3.4 The Weisman Model……Page 79
3.1.3.5 The Zhang Model……Page 81
3.1.3.6 The Petalas Model……Page 88
3.1.4.1 The Method of Lockhart and Martinelli……Page 91
3.1.4.2 The Method of Storek and Brauer……Page 94
3.2.1 Flow Pattern Maps……Page 96
3.2.1.1 Comparison to the Flow Map of Baker……Page 100
3.2.1.2 Comparison to the Flow Map of Mandhane……Page 105
3.2.1.3 Comparison of the Taitel Model with the Experimental Data……Page 110
3.2.1.4 Comparison of the Weisman Model with the Experimental Data……Page 114
3.2.1.5 Comparison of the Zhang Model with the Experimental Data……Page 115
3.2.1.6 Comparison of the Petalas Model with the Experimental Data……Page 116
3.2.1.7 Summary on Models Predicting Liquid-Gas Flows……Page 117
3.2.2.1 Experimental Results……Page 118
3.2.2.2 Comparison with Models……Page 119
4 Two-Phase Liquid-Liquid Systems……Page 122
4.1.1 Transitions Between Flow Regimes……Page 123
4.1.2 Flow Pattern Prediction Models……Page 126
4.1.2.1 The Brauner Model……Page 127
4.1.3.1 The Homogeneous Dispersed Model……Page 134
4.1.3.2 The Method of Brauner……Page 136
4.2.1 Observed Flow Patterns……Page 140
4.2.2 Flow Pattern Maps……Page 144
4.2.2.1 Comparison of the Brauner Model with the Experimental Data……Page 151
4.2.3 Pressure Drop……Page 153
4.2.3.1 Comparison with Models……Page 154
5 Three-Phase Liquid-Liquid-Gas Systems……Page 157
5.1.2 The Flow Pattern Prediction Model by Taitel……Page 158
5.1.3 The Pressure Drop Correlation by Millies……Page 161
5.2.1 Observed Flow Patterns……Page 164
5.2.2 Flow Pattern Maps……Page 166
5.2.3 Comparison with Literature Data……Page 171
5.2.3.1 Comparison with the Flow Map of Acikgoz et al…….Page 173
5.2.3.2 Comparison of the Brauner Model with the Experimental Data……Page 174
5.2.4 Pressure Drop……Page 175
5.2.5 Comparison with the Model of Millies……Page 176
6 Conclusions and Outlook……Page 179
6.1 Liquid-Gas Flows……Page 180
6.2 Liquid-Liquid Flows……Page 181
6.3 Liquid-Liquid-Gas Flows……Page 182
6.5 Application of -PIV……Page 184
A Pressure Drop Data: Additional Graphs……Page 188
B Flow Pattern Data: Additional Graphs……Page 192
C.1.1 Flow Patterns of Water-Air Flows in the 5.6 mm Pipe……Page 202
C.1.2 Flow Patterns of Paraffin-Air Flow in the 5.6 mm Pipe……Page 206
C.1.3 Flow Patterns of Water-Air Flow in the 7.0 mm Pipe……Page 209
C.1.4 Flow Patterns of Paraffin-Air Flow in the 7.0 mm Pipe……Page 213
C.1.5 Pressure Drop of Water-Air Flows in the 5.6 mm Pipe……Page 217
C.1.6 Pressure Drop of Paraffin-Air Flows in the 5.6 mm Pipe……Page 218
C.1.7 Pressure Drop of Water-Air Flows in the 7.0 mm Pipe……Page 219
C.1.8 Pressure Drop of Paraffin-Air Flows in the 7.0 mm Pipe……Page 221
C.2.1 Flow Patterns of Paraffin-Water Flow in the 5.6 mm Pipe……Page 223
C.2.2 Flow Patterns of Paraffin-Water Flow in the 7.0 mm Pipe……Page 230
C.2.3 Pressure Drop of Paraffin-Water Flows in the 5.6 mm Pipe……Page 234
C.2.4 Pressure Drop of Paraffin-Water Flows in the 7.0 mm Pipe……Page 238
C.3.1 Paraffin-Water-Air Flow in the 5.6 mm Pipe……Page 242
References……Page 249
Curriculum Vitae……Page 254