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The Boiling Experiment Facility (BXF)  

  BXF Multimedia

BXF Status

The Boiling eXperiment Facility (BXF) was delivered to the International Space Station (ISS) aboard STS-133 in February, 2011. It was installed in the Microgravity Science Glovebox (MSG) research facility on Tuesday, March 22, and following experiment activation, functional and video checkouts, Microheater Array Boiling Experiment (MABE) and Nucleate Pool Boiling Experiment (NPBX) heater calibrations were performed. Science test point operations began on Tuesday, March 29.  Two weeks of science test point operation were conducted until April 11 when the BXF safety circuit trip due to a pressure reading and the BXF was shut down.
A troubleshooting plan was developed and executed on April 27 and revealed that the 24VDC bus 1 circuit had a fault.  Limited science operations for NPBX resumed on May 9 using only the 24 VDC bus 2 circuit.  Science operations ceased and the BXF was removed from the MSG Facility on May 13.  The BXF was returned on Space Shuttle Mission ULF-7 landing on July 21.
A Post-Flight Assessment Review (PFAR) Board was convened on July 18 and concluded in April 2012. It was determined that the 24VDC Bus 1 failure was due to excessive heating of one of the bulk fluid heaters that initiated an electrical short to ground.
In spite of the premature cessation of testing, BXF was able to complete 33% of the MABE test matrix thus meeting 70% of MABE science objectives.  BXF was able to complete 29% of original test matrix and 56% of the recovery test matrix for NPBX thus meeting 50% of NPBX science objectives.

BXF installed in MSG.

February 28, 2011- A nice online story about low-g boiling . . and a video of Prof. Jungho Kim in the ESA low-g aircraft . .  external link icon


The Boiling Experiment Facility (BXF) will accommodate two separate investigations, BXF–MABE (Microheater Array Boiling Experiment) and BXF–NPBX (Nucleate Pool Boiling Experiment), to examine fundamental boiling phenomena. BXF is planned for the Microgravity Science Glovebox (MSG) located in the U.S. Laboratory 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 the pool boiling curves.


Boiling efficiently removes large amounts of heat by generating vapor from liquid. It is used to produce steam to turn turbines in electrical power plants, cool high-powered electronic devices such as supercomputers, purify chemical mixtures, and even cook dinner. An upper limit, called the critical heat flux, exists where the heater generates so much vapor that the liquid can not reach the heated surface. Continued heating above this limit for prolonged periods can cause the heater to burn itself out. Determination of the critical heat flux in microgravity is essential for
designing cooling systems for space.

Pool boiling generates vapor bubbles by heating a stagnant body of liquid. It is a complex phase change process  here the hydrodynamics, heat transfer, mass transfer, and interfacial phenomena are tightly interwoven. By conducting tests in microgravity, it is possible to assess the effect of buoyancy on the overall boiling process and assess the relative magnitude of other effects and phenomena such as surface tension forces, liquid momentum forces, and microlayer evaporation.


Boiling is relevant to space-based hardware and processes such as heat exchangers, cryogenic fuel storage, and electronic cooling due to the large amounts of heat that can be removed with small increases in the temperature of the heat transfer fluid. This reduces the temperature difference between the heat source and radiator. For space applications, this reduction in the temperature difference equates to a higher radiator temperature which can reduce the radiator area and weight.

Pool boiling is an effective means for studying flow boiling. Some models that are used to predict flow boiling heat transfer coefficients consist of both pool boiling and liquid-phase forced flow convection terms. The liquid-phase term is well-quantified in all gravity environments. Pool boiling is also the limiting case of flow boiling whereby the flow becomes zero.

Science Objectives

The BXF uses normal-perfluorohexane as the test fluid and will operate between pressures of 60 to 244 kPa and temperatures of 35 to 60 °C. Pressure and bulk fluid temperature measurements will be made, and standard rate video will be acquired.

The objective of MABE is to determine the local boiling heat transfer mechanisms in microgravity for nucleate and transition boiling and the critical heat flux by examining the position of the liquid and vapor adjacent to the heater. MABE uses two 96-element microheater arrays, 2.7 by 2.7 mm and 7.0 by 7.0 mm in size, to measure localized heat fluxes while operating at a constant temperature. Most boiling experiments in the past have operated at constant wall heat flux with a much larger heater, allowing only time and space-averaged measurements to be made. Each heater is on the order of the bubble departure size in normal gravity, but significantly smaller than the bubble departure size in reduced gravity. A high speed video system will be used to visualize the boiling process through the bottom of the MABE heater arrays.

The other experiment, NPBX uses a 85-mm-diameter heater wafer that has been "seeded" with five individually controlled nucleation sites to study bubble nucleation, growth, coalescence and departure. The experiment will selectively activate these nucleation sites in order to understand bubble growth, detachment, and subsequent motion of single and large merged bubbles under reduced-gravity conditions.

Hardware Description

The BXF is currently scheduled to fly on Utilization Flight-5 to the ISS with facility integration into the MSG and operation during Increment 26.

The hardware consists of a boiling chamber mounted within a containment vessel. The boiling chamber has three science heaters (one for NPBX and two heater arrays for MABE), pressure and temperature measurement instrumentation, a bellows assembly for pressure control, and pumps for liquid conditioning. The containment vessel provides the second and third levels of containment for the test fluid in the event of a leak from the boiling chamber of the test fluid. Standard rate video cameras are mounted inside the chamber to provide two orthogonal side-view images of the vapor bubble during tests with the NPBX heater and a single side view of the vapor bubble during MABE testing. The high-speed video camera is mounted on the exterior of the containment vessel wall and acquires 4 seconds of images through the bottom of the MABE heater at 500 images per second.

An avionics box contains the data acquisition and control unit, removable hard drives, indicator panel, and the control unit for the high-speed video camera. The avionics box interfaces with the MSG mobile launch computer, the high-speed video camera, and the BXF-embedded controller boards within the containment vessel.


Contacts at NASA Glenn Research Center
BXF Project Manager: William Sheredy

MABE Project Scientist: John McQuillen


NPBX Project Scientist: Dr. David Chao


Principal Investigators (PI)
MABE PI: Prof. Jungho Kim, University of Maryland


NPBX PI: Prof. Vijay Dhir, UCLA


NPBX Bubbles video
Click image above for an NPBX sample video
NPBX Bubbles video
Click image above for an NPBX sample video
MABE colorized video
Click image above for an MABE sample video
MABE colorized video
Click image above for an MABE sample video
MABE colorized video
Click image above for an MABE sample video
MABE colorized video
Click image above for an MABE sample video
BXF chamber
BXF chamber
MABE heater array
MABE heater array of 96 individually
controlled heaters.

NPBX wafer
Top surface of NPBX wafer.

typical nucleation site
Scanning electron microscope
image of typical nucleation site
(10-µm-diameter hole).

MABE heater assembly
MABE heater assembly being prepared for calibration
vapor bubbles
High-speed time-lapse imagery documenting nucleation of three
separate vapor bubbles (top image), coalescence of the middle and right bubble (middle image), and finally after all the vapor bubbles have merged.
position of the vapor and liquid positions
High-speed video image that is colorized with heater power data. Correlating the position of the vapor and liquid positions with the heater power data provides insight into the heat transfer and phase change mechanisms.
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BXF Related Documents
small acrobat icon   BXF Overview Chart
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BXF Short Overview Presentation
small acrobat icon   BXF Presentations & Publications  
small acrobat icon   Journal Publications & Conference Proceedings  
small acrobat icon   BXF/NPBX SRD  
small acrobat icon   BXF/MABE SRD  
small acrobat icon   BXF/NPBX Publications & Presentations  
small acrobat icon   BXF/MABE Publications & Presentations  

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Tim Reckart
NASA Official: Thomas St. Onge
Last Updated: May 31, 2011
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