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Title: Measurement of Key Pool BOiling Parameters in nanofluids for Nuclerar Applications

Abstract

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.more » 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.« less

Authors:
 [1];  [2];  [2];  [1]
  1. ORNL
  2. Massachusetts Institute of Technology (MIT)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); High Temperature Materials Laboratory
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
OSTI Identifier:
1026703
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Conference
Resource Relation:
Conference: 15th In'll Conf on Nuclear Engineering, Nagoya, Japan, 20070422, 20070426
Country of Publication:
United States
Language:
English
Subject:
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

Citation Formats

Bang, In C, Buongiorno, Jdacopo, Hu, Lin-wen, and Wang, Hsin. Measurement of Key Pool BOiling Parameters in nanofluids for Nuclerar Applications. United States: N. p., 2007. Web.
Bang, In C, Buongiorno, Jdacopo, Hu, Lin-wen, & Wang, Hsin. Measurement of Key Pool BOiling Parameters in nanofluids for Nuclerar Applications. United States.
Bang, In C, Buongiorno, Jdacopo, Hu, Lin-wen, and Wang, Hsin. Mon . "Measurement of Key Pool BOiling Parameters in nanofluids for Nuclerar Applications". United States. doi:.
@article{osti_1026703,
title = {Measurement of Key Pool BOiling Parameters in nanofluids for Nuclerar Applications},
author = {Bang, In C and Buongiorno, Jdacopo and Hu, Lin-wen and Wang, Hsin},
abstractNote = {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.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}

Conference:
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  • Artificial neural network (ANN) has the advantage that the best-fit correlations of experimental data will no longer be necessary for predicting unknowns from the known parameters. The ANN was applied to predict the pool boiling curves in this paper. The database of experimental data presented by Berenson, Dhuga et al., and Bui and Dhir etc. were used in the analysis. The database is subdivided in two subsets. The first subset is used to train the network and the second one is used to test the network after the training process. The input parameters of the ANN are: wall superheat {delta}T{submore » w}, surface roughness, steady/transient heating/transient cooling, subcooling, Surface inclination and pressure. The output parameter is heat flux q. The proposed methodology allows us to achieve the accuracy that satisfies the user's convergence criterion and it is suitable for pool boiling curve data processing. (authors)« less
  • A study of nucleate pool boiling heat transfer of TiO{sub 2}-water nanofluids is experimentally conducted. Nanofluids with various concentrations of 0.00005, 0.0001, 0.0005, 0.005, and 0.01 vol.% are employed. Horizontal circular plates made from copper and aluminium with different roughness values of 0.2 and 4 {mu}m are used as heating surfaces. The experiments are performed to explore the effects of nanofluids concentration as well as heating surface material and roughness on nucleate pool boiling characteristics and the heat transfer coefficient under ambient pressure. The results show that based on the copper heated surface which is tested with a concentration ofmore » 0.0001 vol.%, higher nucleate pool boiling heat transfer coefficient is obtained when compared with the base fluid. A 15% increase is obtained for the surface roughness of 0.2 {mu}m and a 4% increase is obtained for roughness of 4 {mu}m. For concentrations higher than 0.0001 vol.%, however, the higher the concentration, the lower the heat transfer coefficient. In the case of aluminium heated surface, the corresponding heat transfer coefficients are larger than for the copper surface by around 30% with a roughness of 0.2 {mu}m and around 27% with a roughness of 4 {mu}m. Moreover, the results also indicate that the heat transfer coefficient obtained based on a roughness of 4 {mu}m is higher than that for a roughness of 0.2 {mu}m by around 12% for aluminium and by around 13% for copper. (author)« less
  • No abstract prepared.
  • A collection of papers is presented on mixed convection, pool boiling, and flow boiling and two-phase flow. A unified similarity analysis is presented for turbulent convection next to vertical surfaces. Topics of interest include free-forced convection from a heated cone, decay of vertical buoyant jets in uniform environment, minimum heat flux during film boiling, and the dynamics of two-phase flow in a duct.