Presentations

Follow Up Nucleate Boiling On-Flight Experiment

Andrew Fassmann — Mon, 07 Nov 2011 08:27:42 PST

Gravitational Effects on Thin-Wire Subcooled Nucleate Boiling Dynamics

Justin Koeln et al. — Mon, 07 Nov 2011 08:24:19 PST

Surface Geometry and Heat Flux Effect on Thin Wire Nucleate Pool Boiling of Subcooled Water in Mictrogravity

Troy Munro et al. — Sun, 06 Nov 2011 15:53:03 PST

Effects of Heat Flux on Nucleate Boiling in Microgravity

Andrew Fassman — Sun, 06 Nov 2011 15:14:39 PST

The Design and Construction of a Microgravity Boiling Experiment

Troy Munro — Thu, 03 Nov 2011 14:08:01 PDT

Bubble Behavior in Nucleate Boiling Experiment Aboard the Space Shuttle

Justin Koeln et al. — Sun, 25 Sep 2011 16:05:57 PDT

Boiling dynamics in microgravity need to be better understood before heat transfer systems based on boiling mechanism can be developed for space applications. This paper presents the results of a nucleate boiling experiment aboard Space Shuttle Endeavor (STS-108). The experiment utilized nickel-chromium resistance wire to boil water in microgravity, and the data was recorded with a CCD camera and six thermistors. This data was analyzed to determine the behavior of bubble formation, detachment from the heating wire, and travel in the water with effects of drag on bubble movement. Bubbles were observed to be ejected from the wire, travel through and eventually stop in the unsaturated water. The data from this experiment is in good agreement with the results of theoretical equations used to model bubble-fluid dynamics in microgravity. The primary conclusion from this experiment is that a bubble can be ejected from a heated wire in the absence of gravity, instead of the creation of a single large vapor bubble. Further conclusions from this research could be applied to the development of safe and efficient heat transfer systems for microgravity and terrestrial applications.

Surface Geometry and Heat Flux Effect on Thin Wire Nucleate Pool Boiling of Subcooled Water in Microgravity

Troy Munro et al. — Sun, 25 Sep 2011 16:05:55 PDT

The motivation of this nucleate boiling research is to understand the effects of surface geometry and heat flux as applied to a thin wire heater. This will further the understanding of the fundamental behaviors of boiling onset, steady state heat transfer, and bubble dynamics with respect to nucleate boiling with the goal of creating efficient thermal management systems for future space applications. Using three different thin platinum wire geometries and five different power levels, subcooled water was boiled over a period of approximately 30 seconds for 15 parabolic arcs to simulate microgravity. To represent the trends in bubbles behavior across hundreds of frames of video in a single graph, a new method, named relative bubble area analysis, is introduced and used to analyze the results of the experiment. It was determined that the efficiency of steady state heat transfer via nucleate boiling in microgravity is comparable to, and in some cases more efficient than, steady state heat transfer in terrestrial applications. The three-wire geometry reduced the heat flux necessary to initiate boiling. Bubble dynamics show a transition from isolated bubbles to jets of small bubbles as heat flux increases. This can be confirmed both visually and with relative bubble area analysis. The implications of this research are that sustained convective heat transfer with subcooled water is possible in microgravity. A three-wire surface geometry was shown to initiate boiling at lower heat fluxes, which would provide minimal super heating of the surface, which is a result of the lack of convection, before boiling heat transfer could begin.