Two Phase Flow in a Microgravity Environment

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Two Phase Flow in a Microgravity Environment
Team Members
Dustin Schlitt Shem Heiple Jason Mooney Brian
Oneel Jim Cloer Academic Advisor Mark Weislogel
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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 NASAs KC-135.

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Two Phase Flow Over View
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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 ?gr2/s
is the ratio of the gravitational force and the
surface tension of the liquid, where ? density
of fluid, g the gravitational acceleration, r
the radius, s surface tension. When Bo gtgt
1, the gravitational force dominates fluid
behavior. For Boltlt 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.
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Bubbly Flow Normal Gravity vs. Micro-Gravity
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Slug Flow Normal Gravity vs. Zero Gravity
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Annular Flow Normal Gravity vs. Zero Gravity
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Design Requirements

• Because the apparatus was to be used in NASAs
  unique KC-135 test environment certain design
  criteria were imposed by NASAs 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.

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Performance
Customer Requirement Metric Importance
1 NASA The device is required to withstand hard landing loads. Forward 99.8 m/s2 Aft 39.8 m/s2 Down 69.8 m/s2 Lateral 29.8 m/s2 Up 29.8 m/s2 10
2 NASA The device is to withstand inadvertent contact loads that could exceed hard landing loads locally. 81.64 kg impacting the structure at a velocity of .6096 m/s. 556 N over a 5.08 cm radius 10
3 NASA The device must attain steady state operation within a short period of time. Because of the limited time available to take data the device must reach steady state within 25 seconds. 10
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Ergonomics
Customer Requirement Metric Importance
1 NASA The device must be easily transported on and off the air craft. For manual transport no one person shall carry more than 222.4 N. 10
Installation
Customer Requirement Metric Importance
1 NASA The apparatus must be secured to the floor of the aircraft The apparatus must not exceed the maximum floor loading of 9576 N/m2. The straps that will be used to secure the device to the floor of the air craft yield when 22241 N is applied, the device should not exceed this limit for any gravitational loading with less than a safety factor of 2 10
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Safety
Customer Requirement Metric Importance
1 NASA The device should not contain any sharp edges or points 10
2 NASA The device must have a kill switch for emergency shut down procedures The kill switch must de-energize all components in the system to a safe state. 10
3 NASA All electronic wiring and cabling must be installed to both the Johnson Space Center Safety and Health Handbook and the National Electronic Code Standards. 10
4 NASA Liquids approved for use in the air craft must be contained Non-hazardous liquids in volume greater than 177 ml must be doubly contained, and the containment method should be structurally sound and able to with stand the inadvertent contact loads described in the performance section of this document. 10
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Theory

• The testing apparatus employs the use of four
  transparent flexible tubes partially filled with
  a fluid of known properties ( viscosity (µ),
  surface tension (s), density (?) ). 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.

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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 ( Fs ). When these forces
balance a steady slug velocity develops.
V
Rrec
Radv
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Balancing forces yields,
From this force balance the governing
differential equation describing this flow is,
At steady state the governing differential
equation reduces to,
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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
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Our Design
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Our Design
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The Zero G Experience
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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
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Not Zero Gravitybut free fall
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Fluids in Reduced Gravity
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Reduced Gravity Fun
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Data Analysis
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Data Analysis

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

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Measuring Film Thickness
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Average Velocity
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Change In Slug Length
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Comparison of Data Against Previous Correlations
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Results

• Steady state flow 1
• Prediction match
• Errors
• Aircraft
• Apparatus
• Film thickness sensitivity