<p>Two-phase gas-liquid flow in pipes is of great practical importance in the nuclear and petroleum industries, etc. Currently, in thermalhydraulic analysis which requires modelling of a two-phase flow medium, such as boiling liquids, condensing vapors, etc., a variety of computer codes are employed to solve the time dependent mass and momentum equations in different parts of the flow system. To improve the numerical simulations, more detailed experimental knowledge of two-phase flow is required. Most instrumentation available today provides some of the required information but have various disadvantages ranging from poor sensitivity to geometrical limitations.</p> <p>This work focuses on the design of a High Speed Ultrasonic Pulse-Echo system for two-phase flow parameter measurement. The ultrasonic system utilizes four ultrasonic (10 MHz frequency) transducers positioned in the axial direction on the surface of a 2.1 cm diameter cylindrical pipe, operating in pulse-echo mode. Two of the transducers are placed on the top of the pipe and the other two on the bottom of the pipe to measure the liquid level or film thickness. The liquid and gas superficial velocities studied in this work ranged from U<sub>ls</sub>=0.019 m/s to U<sub>Is</sub>=0.14 m/s and from U<sub>gs</sub>=0.24 m/s to U<sub>gs</sub>=4.33 m/s respectively, at standard conditions (1 bar, 20°C). This system was designed to acquire the data in real time 170 frames/s (A-scans/s) and the sampling rate was 2μs displaying the data at every 6msec with a spatial resolution of 0.0071 mm.</p> <p>The theoretical basis for obtaining liquid level measurements, which can be used to determine the two-phase flow parameters, such as two-phase flow pattern characterization, void fraction measurements, plug, bubble and slug velocities as well as wave amplitude and frequency for a stratified wavy and annular flow regime are discussed. The Ultrasonic System hardware and analysis software is also presented.</p> <p>The High Speed Ultrasonic Pulse-Echo System can characterize accurately each different flow regime and flow regime map can be established where the flow regime map obtained in the present work is in good agreement with the previous theoretical and experimental works. The High Speed Ultrasonic Pulse-Echo System also proved to give accurate results for the determination of the liquid level within ± 1.5% and the time averaged liquid level measurements performed in the present work agree within ±10% with the theoretical models. Time averaged void fraction measurements for a stratified smooth flow, stratified wavy, plug flow and annular flow qualitatively agree with the theoretical predictions. Liquid plug and bubble velocities measurements for gas superficial velocities lower than 0.48 m/s qualitatively and quantitatively agree with the correlations, while for higher gas superficial velocities it was proved that there is only qualitative agreement between the results due to the inability of the correlations to predict accurately. For slug velocity there is only qualitative agreement with the correlations, where the discrepancy is likely due to limitations in the correlations. Finally, wave height and frequency for a stratified wavy and annular flow were determined.</p> / Master of Applied Science (MASc)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/13113 |
| Date | 11 1900 |
| Creators | Masala, Tatiana |
| Contributors | Harvel, Glenn, Chang, J. S., Engineering Physics |
| Source Sets | McMaster University |
| Detected Language | English |
| Type | thesis |
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