A Study on Flow Regime Identification in Microgravity Gas-Liquid Flows Using a Capacitance Sensor
The first objective of this study was to design, build, and test a void fraction sensor for measuring micro gravity two-phase flows. To this end, a capacitance type sensor was built. It has a two tube diameter sensing length as a compromise between obtaining a local measurement and the greater sensitivity achieved with a longer sensor. Calibration of the sensor was done using quick closing valves.
Void fraction data was collected for water-air two-phase flow in a 3/8 in. (9.525 mm) tube on board the NASA Lewis DC-9 microgravity aircraft. Void fraction data was compared against that of Elkow (1995) and Bousman (1995), and was found to be in excellent agreement.
The microgravity void fraction data was used in the form of probability density functions to determine a more objective method of identifying the flow regimes and their transitions than what is possible from examining video images. This, in turn, minimizes the errors and complexity associated with the use of subjective methods such as two dimensional video images.
Once the flow regimes were identified, the data was compared against microgravity flow regime transition models in the literature. The Drift-Flux model, originally developed by Zuber and Findlay (1965) and later modified for micro gravity flows by Bousman (1995), separated the bubbly and slug flow regimes well when evaluated with the transition void fraction determined from this data set. The slug-to-annular transition model suggested by Bousman (1995) resulted in a transition line which fell in the transitional flow region. The Weber number model for the transition from slug to transitional and from transitional to annular flow, originally suggested by Zhao and Rezkallah (1993), separated the slug and transitional flows perfectly. The transitional-to-annular boundary was slightly over-predicted. It was concluded that the Weber number model is of more use than the slug-to-annular transition model suggested by Bousman (1995) since it delineates both the slug-to-transitional and transitional-to-annular flow regime boundaries.
Advisor:Watson, Lyle Glen; Bugg, James Donald; Rezkallah, Kamiel, S.
School:University of Saskatchewan
School Location:Canada - Saskatchewan
Source Type:Master's Thesis
Date of Publication:05/08/2009