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CVB Status
June 2010 - Two of the four Constrained Vapor Bubble (CVB) science
modules were returned from ISS on ULF-4 on May 26, 2010. The 30mm
pentane and the dry calibration modules will be used for additional
ground testing for the science investigation team. This experiment
is expected to produce multiple scientific journal articles.
May 2010 - The STS-132, ULF-4, is scheduled to return two of
the completed CVB modules on May 26. The 30mm Pentane and the
Dry calibration/control modules have successfully complete science operations
and will be used to verify preflight ground testing. To date three
journal articles are planned for these results. The 30mm module
may be refurbished with a mixed fluid to be a reflight experiment in
2012.
* The Constrained Vapor Bubble (CVB) 40 mm dry module was operated
on the International Space Station (ISS) from April 26 to April 30,
2010. In the approximately 112 hours of operation, all the science
objectives were fulfilled. The original test matrix was completed
and an additional run was performed giving us excellent calibration
characteristics.
April 2010 - The Constrained Vapor Bubble (CVB) 30-mm Pentane
module was removed from the Light Microscopy Module (LMM) on April 16,
2010 and replaced with the Dry Calibration/Control Module. Operations
will continue with the Dry Module on April 26, 2010. Both the
30 mm and dry module will be returned on ULF-4 in August 2010. Below
is an image from the video downlink.
CVB Module Installation
• Fluids Integrated Rack/Light Microscopy
Module/Constrained Vapor Bubble (FIR/LMM/CVB) operations are on-going
through day 091. We have completed over 90% of the extended test
matrix. We are presently collecting data by holding the heater
temperature constant and changing (raising) the cooler temperature. We
have also collected video data of lateral oscillations. We are looking
forward to starting operations with the dry/calibration module.
Overview
The use of interfacial free energy gradients to control
fluid flow naturally leads to simpler and lighter heat transfer systems
because of the absence of mechanical pumps. Therefore, “passive” engineering
systems based on this principle are ideal candidates for the space
program. In this context, “passive” refers to the natural
pressure field for fluid flow due to changes in the intermolecular
force field under an imposed nonisothermal temperature field. This
force field is a function of the shape, temperature, and composition
of the system. For example, heat pipes which rely on these forces
have been proposed frequently to optimize heat transfer under microgravity
conditions. However, the basic thermophysical principles controlling
these systems are not well understood and, as a result, they have
under performed. In general, the full potential of interfacial forces
has not been realized in transport phenomena.
Therefore, the basic experimental and
theoretical studies of the constrained vapor bubble (CVB) under microgravity
conditions to help remedy this undesirable situation. The proposed
use of a transparent glass cell and related optical measurements will
increase the understanding of transport systems controlled by interfacial
phenomena because the system is viewed directly. Relatively large
systems with high heat fluxes and small capillary pressure levels
set in the condenser will be emphasized.
In particular, we are concerned with
the experimental study of the CVB for a completely wetting system,
the liquid will coat all the walls of the chamber. Since in
microgravity the bubble will tend to travel in the middle of the constraining “pipe”.
The first CVB flight unit is presently
under construction (March 2007). Five flight units will be launched
with LMM on ULF 1. With the following samples:
- Pentane Cell 1: bubble length of 20 mm ±5%
at 20°C
- Pentane Cell 2: bubble length of 30 mm ±5%
at 20°C
- Pentane Cell 3: bubble length of 40 mm ±5%
at 20°C
- Ethanol Cell 4: bubble length of
25 mm ±5% at 20°C
- Dry cell: evacuated to 5 torr
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LMM/CVB Qualification
Model #2 |
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