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Two Phase Flow in a Microgravity Environment

Two Phase Flow in a Microgravity Environment. Dustin Schlitt Shem Heiple Jason Mooney Brian Oneel Jim Cloer Academic Advisor Mark Weislogel. Team Members:. Mission.

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Two Phase Flow in a Microgravity Environment

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  1. Two Phase Flow in a Microgravity Environment Dustin Schlitt Shem Heiple Jason Mooney Brian Oneel Jim Cloer Academic Advisor Mark Weislogel TeamMembers:

  2. Mission While Two-Phase flow cycles are more efficient in the transfer of heat energy, they have been avoided in low gravity applications due to the lack of experimental data describing the behavior of the flow regimes. It was the goal of the Portland State Team to develop a reliable, inexpensive testing apparatus that would reproduce a steady slug flow regime that could be easily employed in ground based micro-gravity test facilities, such as NASA’s KC-135.

  3. Two Phase Flow Over View

  4. Micro-Gravity vs. Normal Gravity Fluid flows in which the effect of surface tension is significant are called capillary flows. Generally in normal gravity such flows are limited to small channels less than a few millimeters in diameter. The Bond number, Bo = ρgr2/σ is the ratio of the gravitational force and the surface tension of the liquid, where ρ = density of fluid, g = the gravitational acceleration, r = the radius, σ = surface tension. When Bo >> 1, the gravitational force dominates fluid behavior. For Bo<< 1, surface tension plays a significant role in the behavior of the fluid. In the absence of gravity Bond numbers for large radius tubes can remain extremely small allowing flow patterns that are totally unique and unable to attain in normal gravity.

  5. Bubbly Flow: Normal Gravity vs. Micro-Gravity

  6. Slug Flow: Normal Gravity vs. Zero Gravity

  7. Annular Flow: Normal Gravity vs. Zero Gravity

  8. Design Requirements • Because the apparatus was to be used in NASA’s unique KC-135 test environment certain design criteria were imposed by NASA’s Reduced Gravity Flight Office. These deign criteria along with a weighing factor enabled the evaluation of various designs to a common metric. • The design criteria provided by NASA were broken down into the following categories: Performance, Ergonomics, Installation, and Safety. The following table highlights the design specifications.

  9. Performance

  10. Ergonomics Installation

  11. Safety

  12. Theory The testing apparatus employs the use of four transparent flexible tubes partially filled with a fluid of known properties ( viscosity (μ), surface tension (σ), density (ρ) ). These tubes are made to rotate around two drums. The drums in turn are mounted on a large rotating disk. As the large disk rotates the liquid slugs in the tubes experience a centripetal acceleration. This centripetal acceleration is sufficient enough to drive the fluid motion while maintaining a capillary dominated flow. As the large disk is rotated the drums are made to rotate dragging the fluid from the outer edge of the drum to the linear portion of the tube path shown.

  13. Theory A force balance in the linear path can be obtained between the acceleration force ( Fa ), the viscous dissipation force( Fμ), and the surface tension force ( Fσ ). When these forces balance a steady slug velocity develops. V Rrec Radv

  14. Balancing forces yields, From this force balance the governing differential equation describing this flow is, At steady state the governing differential equation reduces to,

  15. Our Design 1. Aluminum Frame 2. Mounting Plate 3. Motor/Gear Box ( Large Disk ) 4. Motor/Gear Box ( Drums ) 5. Drum Pack Assembly 6. Counter Weight 7. Digital Video Camera 8. Large Disk Rotational Velocity Display 9. Back Light Switch 10.DV Monitor 11.Speed Controls ( Large Disk, Drum ) 12.Power Supply 13.Outreach Experiment Controls 14.Outreach Experiment Housing 8. Large Disk Rotational Velocity Display 9. Back Light Switch 10.DV Monitor 11.Speed Controls ( Large Disk, Drum ) 12.Power Supply 13.Outreach Experiment Controls 14.Outreach Experiment Housing

  16. Our Design

  17. Our Design

  18. The Zero G Experience

  19. KC135 Reduced Gravity Aircraft Number of Parabolas: 32 Top of Parabola : 32,000 ft Free Fall Time : 21 seconds Bottom of Parabola : 24,000 ft

  20. Not Zero Gravity…but free fall

  21. Fluids in Reduced Gravity

  22. Reduced Gravity Fun

  23. Data Analysis

  24. Data Analysis • Steady state slug velocity. • Steady slug length. • At least one revolution of the tube loop during steady state.

  25. Measuring Film Thickness

  26. Average Velocity

  27. Change In Slug Length

  28. Comparison of Data Against Previous Correlations

  29. Results • Steady state flow ± 1% • Prediction match • Errors • Aircraft • Apparatus • Film thickness sensitivity

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