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>> Hello, my name is Brian Motil
and I'm the Principal Investigator
for the Packed Bed Reactor Experiment or PBRE.
>> And I'm Cathy Frey.
I'm in charge of developing the operations products for PBRE.
>> The goal of the PBRE is to conduct a fundamental study
of gas liquid flows through porous media
for the first time ever on the ISS.
Flow through porous materials are encountered in many places
in everyday life, both in technologies
such as chemical reactors and nature such as water,
gas and oil flow underground.
In space, specific applications include chemical reactors
for air and water revitalization as well as flows to deliver
and nutrients to plant systems.
Here are just some of the many current
and future applications for this technology.
These systems operate very differently
when in the microgravity environment, especially at low
to moderate flow rates.
Because the draining effect
of gravity no longer influences the flow distribution
and pressure drop.
Instead, the effects of the interfacial
or capillary forces along
with the viscous forces control flow dynamics.
The PBRE is designed to develop a basic understanding
of this important class of flows in the microgravity environment
for future space exploration.
Here is an example of how these other forces effect the flow.
At the very low gas flow rate,
the steady conditions are called bubble flow.
As you can see, gas bubbles flow around the fixed packing,
frequently getting momentarily trapped in a pore
until another bubble comes and merges
to make the bubble large enough to get swept downstream.
As a gas flow is increased, this effect broadens
across the column until an organized alternating pressure
or pulse flow can be measured as gas rich and liquid rich phases,
pass through the bed at velocities much higher
than the bulk flow rate would indicate.
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This is not just a curious hydrodynamic behavior,
it has important consequences on the operating conditions
and parameters for chemical reactors.
In fact, it is possible to operate a chemical reactor
of this type in microgravity at much higher efficiencies
than in normal gravity if the design
and operating parameters are properly selected.
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>> The space station experiment will provide a wide range
of water and air flows through two randomly packed test beds.
The packing will be three millimeter spherical beads
which are poured into the bed and then held in place
by spring loaded end caps.
This is what the experiment looks
like with the test column in the foreground.
The key diagnostics will include very sensitive pressure
and temperature measurements at points along the column as well
as two high speed and high resolution video cameras
to determine the flow conditions.
>> After the initial testing is complete,
the PBRE will be available for additional research.
The test section and diagnostics are replaceable for any type
of air water experiment within the envelope of 24 inches long
by 5 inches in diameter allowing for NASA or industry
to test almost any type of component or subsystem.
Water flow of up to 150 liters per hour in gas flow of up
to 3 kilograms per hour can be provided.