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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.


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Average wait time as measured by infrared thermometry. Uncertainty in wait time is ± 20%.
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Figure 5: Average wait time as measured by infrared thermometry. Uncertainty in wait time is ± 20%.

Mentions: By obtaining time- and space-resolved temperature data during bubble nucleation, the bubble departure diameter and frequency, growth and wait times, and nucleation site density were directly measured using the techniques detailed in Gerardi et al. [22] and Gerardi [23]. The bubble parameters for each individual nucleation event were tallied. Since boiling is essentially a random phenomenon, for each nucleation site and between nucleation sites, there was a distribution of the parameters; however, we observed that the parameters tend to be distributed narrowly about their mean for a given nucleation site (greater detail is given in the "Appendix"). Therefore, for comparative purposes, only the mean values of the parameters for all nucleation sites are shown in Figures 4,5,6,7,8. It can be seen that for a given wall superheat, the nanofluids have significantly lower bubble departure frequency, higher wait time, and lower nucleation site density with respect to pure water. The implications of these findings will be discussed in "Data interpretation."


Infrared thermometry study of nanofluid pool boiling phenomena.

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

Average wait time as measured by infrared thermometry. Uncertainty in wait time is ± 20%.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 5: Average wait time as measured by infrared thermometry. Uncertainty in wait time is ± 20%.
Mentions: By obtaining time- and space-resolved temperature data during bubble nucleation, the bubble departure diameter and frequency, growth and wait times, and nucleation site density were directly measured using the techniques detailed in Gerardi et al. [22] and Gerardi [23]. The bubble parameters for each individual nucleation event were tallied. Since boiling is essentially a random phenomenon, for each nucleation site and between nucleation sites, there was a distribution of the parameters; however, we observed that the parameters tend to be distributed narrowly about their mean for a given nucleation site (greater detail is given in the "Appendix"). Therefore, for comparative purposes, only the mean values of the parameters for all nucleation sites are shown in Figures 4,5,6,7,8. It can be seen that for a given wall superheat, the nanofluids have significantly lower bubble departure frequency, higher wait time, and lower nucleation site density with respect to pure water. The implications of these findings will be discussed in "Data interpretation."

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