Measurement of Key Pool BOiling Parameters in nanofluids for Nuclerar Applications

Conference · Mon Jan 01 04:00:00 EST 2007

OSTI ID:1026703

Bang, In C ^[1]; Buongiorno, Jdacopo ^[2]; Hu, Lin-wen ^[2]; Wang, Hsin ^[1]

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1. ORNL
2. Massachusetts Institute of Technology (MIT)

Nanofluids, colloidal dispersions of nanoparticles in a base fluid such as water, can afford very significant Critical Heat Flux (CHF) enhancement. Such engineered fluids potentially could be employed in reactors as advanced coolants in safety systems with significant safety and economic advantages. However, a satisfactory explanation of the CHF enhancement mechanism in nanofluids is lacking. To close this gap, we have identified the important boiling parameters to be measured. These are the properties (e.g., density, viscosity, thermal conductivity, specific heat, vaporization enthalpy, surface tension), hydrodynamic parameters (i.e., bubble size, bubble velocity, departure frequency, hot/dry spot dynamics) and surface conditions (i.e., contact angle, nucleation site density). We have also deployed a pool boiling facility in which many such parameters can be measured. The facility is equipped with a thin indium-tin-oxide heater deposited over a sapphire substrate. An infra-red high-speed camera and an optical probe are used to measure the temperature distribution on the heater and the hydrodynamics above the heater, respectively. The first data generated with this facility already provide some clue on the CHF enhancement mechanism in nanofluids. Specifically, the progression to burnout in a pure fluid (ethanol in this case) is characterized by a smoothly-shaped and steadily-expanding hot spot. By contrast, in the ethanol-based nanofluid the hot spot pulsates and the progression to burnout lasts longer, although the nanofluid CHF is higher than the pure fluid CHF. The presence of a nanoparticle deposition layer on the heater surface seems to enhance wettability and aid hot spot dissipation, thus delaying burnout.

• Research Organization: Oak Ridge National Laboratory (ORNL); High Temperature Materials Laboratory
• Sponsoring Organization: EE USDOE - Office of Energy Efficiency and Renewable Energy (EE)
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 1026703
• Country of Publication: United States
• Language: English

Related Subjects

22 GENERAL STUDIES OF NUCLEAR REACTORS
BOILING
BUBBLES
BURNOUT
COOLANTS
CRITICAL HEAT FLUX
DEPOSITION
ECONOMICS
ENTHALPY
ETHANOL
EVAPORATION
HEATERS
HOT SPOTS
HYDRODYNAMICS
NUCLEAR ENGINEERING
NUCLEATION
POOL BOILING
PROBES
SAFETY
SPECIFIC HEAT
TEMPERATURE DISTRIBUTION
THERMAL CONDUCTIVITY