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Infrared thermometry study of nanofluid pool boiling phenomena.

Gerardi C, Buongiorno J, Hu LW, McKrell T - Nanoscale Res Lett (2011)

Bottom Line: The bubble departure frequency and NSD were found to be lower in nanofluids compared with water for the same wall superheat.Furthermore, it was found that a porous layer of nanoparticles built up on the heater surface during nucleate boiling, which improved surface wettability compared with the water-boiled surfaces.Using the prevalent nucleate boiling models, it was possible to correlate this improved surface wettability to the experimentally observed reductions in the bubble departure frequency, NSD, and ultimately to the deterioration in the nucleate boiling heat transfer and the CHF enhancement.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave,, Cambridge, MA 02139 USA. jacopo@mit.edu.

ABSTRACT
Infrared thermometry was used to obtain first-of-a-kind, time- and space-resolved data for pool boiling phenomena in water-based nanofluids with diamond and silica nanoparticles at low concentration (<0.1 vol.%). In addition to macroscopic parameters like the average heat transfer coefficient and critical heat flux [CHF] value, more fundamental parameters such as the bubble departure diameter and frequency, growth and wait times, and nucleation site density [NSD] were directly measured for a thin, resistively heated, indium-tin-oxide surface deposited onto a sapphire substrate. Consistent with other nanofluid studies, the nanoparticles caused deterioration in the nucleate boiling heat transfer (by as much as 50%) and an increase in the CHF (by as much as 100%). The bubble departure frequency and NSD were found to be lower in nanofluids compared with water for the same wall superheat. Furthermore, it was found that a porous layer of nanoparticles built up on the heater surface during nucleate boiling, which improved surface wettability compared with the water-boiled surfaces. Using the prevalent nucleate boiling models, it was possible to correlate this improved surface wettability to the experimentally observed reductions in the bubble departure frequency, NSD, and ultimately to the deterioration in the nucleate boiling heat transfer and the CHF enhancement.

No MeSH data available.


Related in: MedlinePlus

Forces due to surface tension, gravity, and momentum acting on bubble parallel to the surface. Adapted from Kandlikar [40].
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Figure 11: Forces due to surface tension, gravity, and momentum acting on bubble parallel to the surface. Adapted from Kandlikar [40].

Mentions: Kandlikar [40] considered the force balance on the left half of a single bubble at the moment where the force due to change in momentum from evaporation (or evaporation recoil force), FM, is higher than the sum of the hydrostatic pressure (FG) and surface tension forces (FS,1 and FS,2) holding the bubble in its spherical shape (see Figure 11). This causes the liquid/vapor interface to move rapidly outward along the heater surface, resulting in CHF. Kandlikar assumes that CHF occurs when the force due to the momentum change, FM, pulling the bubble interface away from the bubble center exceeds the sum of the forces holding the bubble intact, FS,1, FS,2, and FG. The force balance at this moment is:(10)


Infrared thermometry study of nanofluid pool boiling phenomena.

Gerardi C, Buongiorno J, Hu LW, McKrell T - Nanoscale Res Lett (2011)

Forces due to surface tension, gravity, and momentum acting on bubble parallel to the surface. Adapted from Kandlikar [40].
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211291&req=5

Figure 11: Forces due to surface tension, gravity, and momentum acting on bubble parallel to the surface. Adapted from Kandlikar [40].
Mentions: Kandlikar [40] considered the force balance on the left half of a single bubble at the moment where the force due to change in momentum from evaporation (or evaporation recoil force), FM, is higher than the sum of the hydrostatic pressure (FG) and surface tension forces (FS,1 and FS,2) holding the bubble in its spherical shape (see Figure 11). This causes the liquid/vapor interface to move rapidly outward along the heater surface, resulting in CHF. Kandlikar assumes that CHF occurs when the force due to the momentum change, FM, pulling the bubble interface away from the bubble center exceeds the sum of the forces holding the bubble intact, FS,1, FS,2, and FG. The force balance at this moment is:(10)

Bottom Line: The bubble departure frequency and NSD were found to be lower in nanofluids compared with water for the same wall superheat.Furthermore, it was found that a porous layer of nanoparticles built up on the heater surface during nucleate boiling, which improved surface wettability compared with the water-boiled surfaces.Using the prevalent nucleate boiling models, it was possible to correlate this improved surface wettability to the experimentally observed reductions in the bubble departure frequency, NSD, and ultimately to the deterioration in the nucleate boiling heat transfer and the CHF enhancement.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave,, Cambridge, MA 02139 USA. jacopo@mit.edu.

ABSTRACT
Infrared thermometry was used to obtain first-of-a-kind, time- and space-resolved data for pool boiling phenomena in water-based nanofluids with diamond and silica nanoparticles at low concentration (<0.1 vol.%). In addition to macroscopic parameters like the average heat transfer coefficient and critical heat flux [CHF] value, more fundamental parameters such as the bubble departure diameter and frequency, growth and wait times, and nucleation site density [NSD] were directly measured for a thin, resistively heated, indium-tin-oxide surface deposited onto a sapphire substrate. Consistent with other nanofluid studies, the nanoparticles caused deterioration in the nucleate boiling heat transfer (by as much as 50%) and an increase in the CHF (by as much as 100%). The bubble departure frequency and NSD were found to be lower in nanofluids compared with water for the same wall superheat. Furthermore, it was found that a porous layer of nanoparticles built up on the heater surface during nucleate boiling, which improved surface wettability compared with the water-boiled surfaces. Using the prevalent nucleate boiling models, it was possible to correlate this improved surface wettability to the experimentally observed reductions in the bubble departure frequency, NSD, and ultimately to the deterioration in the nucleate boiling heat transfer and the CHF enhancement.

No MeSH data available.


Related in: MedlinePlus