Microheater Array Boiling Experiment (MABE) - 01.09.14
Science Objectives for Everyone
Boiling efficiently removes large amounts of heat by generating vapor from liquid; this process is currently being used in many power plants to generate electricity. An upper limit, called the critical heat flux, exists where the heater is covered with so much vapor that liquid supply to the heater begins to decrease, potentially destroying the heater. Microheater Array Boiling Experiment (MABE) determines the critical heat flux during boiling in microgravity to design optimal cooling systems for future space exploration vehicles as well as on Earth.
Science Results for Everyone
A watched pot does boil, even in space. Researchers conducted tests on the International Space Station to improve our understanding of how microgravity affects boiling mechanisms and heat transfer. This knowledge will contribute to proper design of equipment used to remove heat in space. Data from the boiling tests agreed with predictions, which included the effects of spacecraft vibrations, known as g-jitter. The data were used to modify models, which were primarily based on parabolic flight experiments, for how gravity affects heat flux. These revised models more accurately predict low gravity heat transfer.
Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)
Human Exploration and Operations Mission Directorate (HEOMD)
ISS Expedition Duration:
September 2010 - September 2011
Previous ISS Missions
MABE is a unique investigation, nothing like this has flown in space before. It measures local heat transfer coefficient with finer temporal and spatial fidelity than any previous pool boiling experiment.
- Microheater Array Boiling Experiment (MABE) is one of two investigations scheduled to operate in the Boiling eXperiment Facility (BXF). The other investigation is Nucleate Pool Boiling Experiment (NPBX).
- Understanding of microgravity effects on boiling mechanisms is critical to the proper design of heat removal equipment for use in space-based applications.
Boiling heat transfer is a method whereby large amounts of heat can be removed from a material. This process is being used in electric power plants, electronic cooling and purification and separation of chemical mixtures. An upper limit, called the critical heat flux, exists where the heater is covered with so much vapor that liquid supply to the heater begins to decrease. Supplying constant power above this limit for prolonged periods can increase the heater temperature to the point whereby the heater is destroyed. Determination of critical heat flux in microgravity is essential for designing cooling systems for space. In this experiment, scientists study boiling of fluorocarbons to increase the effectiveness of cooling in space.
Boiling of n-perfluorohexane is studied in MABE. n-perfluorohexane is the main ingredient in FC-72. FC-72 is used by the electronic industry for cooling and by a wide cadre of boiling researchers because of its inertness, low boiling point and low heat of vaporization.
The Boiling eXperiment Facility (BXF) houses two separate investigations, Microheater Array Boiling Experiment (MABE) and Nucleate Pool Boiling Experiment (NPBX). BXF is planned for the Microgravity Science Glovebox (MSG) located in the US Lab on the International Space Station (ISS). The purpose of the BXF is to validate models being developed for heat transfer coefficients, critical heat flux and pool boiling curves.
BXF-MABE provides localized, time-dependent, heat transfer coefficients that will be correlated against known positions of vapor and liquid above the heater array to determine the mechanisms by which heat is removed through boiling in the absence of gravity.
In microgravity, a bubble can cover an entire heater array instead of just a small area, resulting in burnout of components if local hot spots are present. The increased spatial resolution of these measurements will enable the extent of the dry spot to be measured along with the heat transfer from the liquid surrounding the dry spot. This technique can be applied to other areas including spray cooling, turbulence measurements and flow boiling.
The proposed research has shown that transient conduction is the dominant heat transfer mechanism in boiling of refrigerants-like fluids. This research will provide insight into creating more efficient cooling systems on Earth.
MABE utilizes two heater arrays ( (7 mm x 7 mm and 2.7 mm x 2.7 mm), each heater array consisting of 96 individually controlled heaters. The heaters are operated at a constant temperature, enabling measurements to be made at critical heat flux and beyond. A group of experiments is run with each microheater array. Each group contains a set of individual experiments with the initial starting point at a specific bulk fluid temperature and pressure. For each experiment, the temperature of the selected microheater array is increased to the desired temperature and the heat transfer distribution during boiling is measured. During the experiments, video is recorded using the MSG cameras and stored on a hard drive. If Ku band is available, video data will be downlinked from ISS to the Glenn Research Center TeleScience Center in Cleveland, OH. The heater data will be overlaid onto the high-speed video data to correlate vapor and liquid position on the heater array. These results will be used to validate and test theoretical models of boiling mechanisms.
MABE will require crew time to set up the hardware to perform 40 test sessions. The data from the test sessions will be captured on videotapes and hard drives that will be changed out by the crew. The hard drive and videotapes will be stowed for later return to Earth for analysis by the investigator.
This investigation requires the crew to set up the BXF hardware in the Microgravity Science Glovebox. Once activated, a ground-based crew controls the BXF. BXF-MABE runs for 28 hours and performs a total of 40 test sessions. The crew performs hard drive and videotape changes at specific intervals throughout the sessions. After the session is completed the crew deactivates, labels and stows the BXF hardware.
MABE completed over two hundred pool boiling tests onboard the ISS between March and April 2011. In the ISS microgravity environment, the heat transfer mechanisms during bubble formation can be determined more accurately since the level of g-jitter (i.e. vibrations from the spacecraft, onboard machinery, and crew) is much less than with short-duration experiments using sounding rockets or drop towers. Surface tension dominated boiling (SDB), characterized by the formation of a non-departing coalesced bubble, occurs on small heaters in microgravity. It is found that once a stationary, coalesced bubble covers the heater, a small change in the gravity level would only change the bubble shape without significantly affecting the steady state value of heat transfer. By comparison, if the gravity levels continuously fluctuate as is the case in parabolic flights where the g-jitter values are relatively large, the resulting continuous adjustments in bubble shape can produce flow around the bubble increasing the heat transfer. In essence, the fluctuation in acceleration (g-jitter) affects heat transfer more than the absolute value of acceleration in the SDB case. Microgravity heat transfer predictions based on modified scaling law and taking into account g-jitter effects were shown to be in excellent agreement with experimental data. This is one of the most significant findings of the current work performed under space microgravity environments and may address the widely discussed problem of the effect of g-jitter on pool boiling studies (Rishi et al. 2012).
Raj R, Kim J, McQuillen JB. Pool Boiling Heat Transfer on the International Space Station: Experimental Results and Model Verification. Journal of Heat Transfer. 2012; 134(10).
Ground Based Results Publications
Kim J, McQuillen JB, Balombin J. Microheater Array Boiling Experiment. NASA Technical Memorandum; 2002.
Henry CD, Kim J, McQuillen JB. Dissolved Gas Effects on Thermocapillary Convection During Boiling in Reduced Gravity Environments. Heat and Mass Transfer. 2006; 42: 919-928.
Henry CD, Kim J. Heater size, subcooling, and gravity effects on pool boiling heat transfer. International Journal of Heat and Fluid Flow. 2004; 25(2): 262-273.
Demiray F, Kim J. Microscale Heat Transfer Measurements During Pool Boiling of FC-72: Effect of Subcooling. International Journal of Heat and Mass Transfer. 2004; 47: 3257-3268.
Henry CD, Kim J. Thermocapillary Effects on Low-G Pool Boiling From Microheater Arrays of Various Aspect Ratio. Microgravity Science and Technology. 2005; 16(1-4): 170-175. DOI: 10.1007/BF02945970.
Yin Z, Prosperetti A, Kim J. Bubble Growth on an Impulsively Powered Microheater. International Journal of Heat and Mass Transfer. 2004; 47(5): 1053-1067. DOI: 10.1016/j.ijheatmasstransfer.2003.07.015.
Henry CD, Kim J, Chamberlain B, Hartmann TG. Heater aspect ratio effects on pool boiling heat transfer under varying gravity conditions. Experimental Thermal and Fluid Science. 2005; 29(7): 773-782.
Myers JG, Yerrramilli VK, Hussey SW, Yee GF, Kim J. Time and space resolved wall temperature and heat flux measurements during nucleate boiling with constant heat flux boundary conditions. International Journal of Heat and Mass Transfer. 2005; 48(12): 2429-2442.
Image of liquid boiling on a heater array during the low gravity produced by NASA's KC-135 aircraft. Blue regions indicate regions of low heat transfer. Courtesy of University of Maryland.
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