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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

SEM images (× 500) of ITO heater surface. After boiling in (a) DI water, (b) 0.01 vol.% diamond nanofluids, and (c) 0.1 vol.% silica nanofluids.
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Figure 9: SEM images (× 500) of ITO heater surface. After boiling in (a) DI water, (b) 0.01 vol.% diamond nanofluids, and (c) 0.1 vol.% silica nanofluids.

Mentions: SEM analysis of the heater surface during post-experimental analysis revealed that the surface was clean during pure water boiling (Figure 9a), but a porous layer built up during nanofluid boiling (Figure 9b,c). Energy-dispersive spectrometer analysis of the layer confirmed that it was made of the nanoparticle material. The presence of a porous nanoparticle layer due to particle deposition during nucleate boiling is now well known [18,21]. This particle layer was attached to the substrate well enough to not flake off during handling or when rinsed with a gentle water spray; however, the layer could be removed with moderate abrasion. Confocal microscopy confirmed that the surface roughness (SRa) and surface index (ratio of actual surface area due to peaks and valleys to the projected area viewed) were higher for nanofluid-boiled surfaces than for pure water-boiled surfaces. The measured surface roughness of the water-boiled heater (SRa = 132 nm) was slightly higher than the as-received heater (SRa = 30 nm), while it was significantly higher for the nanofluid-boiled surfaces (900 to 2,100 nm). The surface index for water-boiled surfaces was approximately 1.0 and for nanofluid-boiled surfaces ranged from 1.1 to 1.7. These values were smaller than expected given all of the peaks and valleys created by the nanoparticle deposits, but are consistent with other nanofluid results [26,30].


Infrared thermometry study of nanofluid pool boiling phenomena.

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

SEM images (× 500) of ITO heater surface. After boiling in (a) DI water, (b) 0.01 vol.% diamond nanofluids, and (c) 0.1 vol.% silica nanofluids.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 9: SEM images (× 500) of ITO heater surface. After boiling in (a) DI water, (b) 0.01 vol.% diamond nanofluids, and (c) 0.1 vol.% silica nanofluids.
Mentions: SEM analysis of the heater surface during post-experimental analysis revealed that the surface was clean during pure water boiling (Figure 9a), but a porous layer built up during nanofluid boiling (Figure 9b,c). Energy-dispersive spectrometer analysis of the layer confirmed that it was made of the nanoparticle material. The presence of a porous nanoparticle layer due to particle deposition during nucleate boiling is now well known [18,21]. This particle layer was attached to the substrate well enough to not flake off during handling or when rinsed with a gentle water spray; however, the layer could be removed with moderate abrasion. Confocal microscopy confirmed that the surface roughness (SRa) and surface index (ratio of actual surface area due to peaks and valleys to the projected area viewed) were higher for nanofluid-boiled surfaces than for pure water-boiled surfaces. The measured surface roughness of the water-boiled heater (SRa = 132 nm) was slightly higher than the as-received heater (SRa = 30 nm), while it was significantly higher for the nanofluid-boiled surfaces (900 to 2,100 nm). The surface index for water-boiled surfaces was approximately 1.0 and for nanofluid-boiled surfaces ranged from 1.1 to 1.7. These values were smaller than expected given all of the peaks and valleys created by the nanoparticle deposits, but are consistent with other nanofluid results [26,30].

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