Nucleate Pool Boiling eXperiment (NPBX)
Research Area: Fluid Physics
Expedition(s): 27 and 28
Principal Investigator(s): ● Vijay K. Dhir, PhD, University of California, Los Angeles, Los
Angeles, California
RESEARCH OBJECTIVES
Nucleate boiling is bubble growth from a heated surface and the subsequent detachment of the
bubble to a cooler surrounding liquid (bubbles in microgravity grow to different sizes than on
Earth). As a result, these bubbles can transfer energy through fluid flow; the Nucleate Pool
Boiling Experiment (NPBX) investigation provides an understanding of heat transfer and vapor
removal processes that take place during nucleate boiling in microgravity. This understanding is
needed for optimum design and safe operation of heat exchange equipment that uses nucleate
boiling as a way to transfer heat in extreme environments of the deep ocean (submarines) and
microgravity.
EARTH BENEFITS
The proposed research provides a fundamental understanding of bubble dynamics and heat
transfer during nucleate boiling in extreme conditions. Such an understanding optimizes the
design and safe operation of heat exchange equipment employing phase change for transfer of
heat in the environments of the deep ocean, extreme cold, and high altitudes.
SPACE BENEFITS
The experiments will give engineers
the capability to achieve cooling of
various components and systems used
in space in an efficient manner and
thereby lead to smaller and lighter
space exploration systems.RESULTS
In the Nucleate Pool Boiling
Experiment (NPBX) single bubble
dynamics (eg, inception and growth),
multiple bubble dynamics (lateral
merger and departure, if any),
nucleate pool boiling heat transfer,
and critical heat flux using Perfluoro-
n-hexane as the test liquid are
investigated.The results of the experiments show that a single bubble continues to grow to occupy the size
of the chamber without departing from the heater surface. During lateral merger of bubbles, at
high superheats (heating the surface beyond the boiling point) a large bubble may lift off from
Nucleate Pool Boiling eXperiment heater wafer. Polished
aluminum wafer (reflecting a black background) that was
manufactured with 5 nucleation cavities (~20 microns in
diameter) to initiate boiling at specific locations. NASA’s Glenn
Research Center image.