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Enhancement of critical heat flux in nucleate boiling of nanofluids: a state-of-art review.

Kim H - Nanoscale Res Lett (2011)

Bottom Line: The purpose of this article is to provide an exhaustive review of these studies.Also, attempts to explain the physical mechanism based on available CHF theories are described.Finally, future research needs are identified.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Nuclear Engineering, Kyung Hee University, Yongin, Gyunggi 446-701, Republic of Korea. hdkims@khu.ac.kr.

ABSTRACT
Nanofluids (suspensions of nanometer-sized particles in base fluids) have recently been shown to have nucleate boiling critical heat flux (CHF) far superior to that of the pure base fluid. Over the past decade, numerous experimental and analytical studies on the nucleate boiling CHF of nanofluids have been conducted. The purpose of this article is to provide an exhaustive review of these studies. The characteristics of CHF enhancement in nanofluids are systemically presented according to the effects of the primary boiling parameters. Research efforts to identify the effects of nanoparticles underlying irregular enhancement phenomena of CHF in nanofluids are then presented. Also, attempts to explain the physical mechanism based on available CHF theories are described. Finally, future research needs are identified.

No MeSH data available.


Related in: MedlinePlus

Relation between CHF and surface characteristics. (a) CHF of pure water vs. contact angle of a water droplet on nanoparticle-deposited surfaces. SEM pictures (b) and maximum capillary wicking height of pure water (c) for surfaces boiled in 10-3% (A) and 10-1% (B) water-TiO2 nanofluids, with the same contact angles of ~20° [60].
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Figure 12: Relation between CHF and surface characteristics. (a) CHF of pure water vs. contact angle of a water droplet on nanoparticle-deposited surfaces. SEM pictures (b) and maximum capillary wicking height of pure water (c) for surfaces boiled in 10-3% (A) and 10-1% (B) water-TiO2 nanofluids, with the same contact angles of ~20° [60].

Mentions: where Rc and cosθ represent the microscopic structures and surface wettability of the nanoparticle layers, respectively. Capillary flow during boiling supplies fresh liquid to the dry region beneath the vapor bubbles, delaying the irreversible growth of hot spots and CHF. Kim and Kim [60] used capillarity to characterize a completely wetted nanoparticle-coated surface. They showed that the estimated heat-flux gain due to capillary liquid supply along the porous layer was of the same order of magnitude as that due to wettability enhancement (Figure 12). They concluded that the significant CHF enhancement of nanofluids during pool boiling is a consequence not only of increased surface wettability, but also of improved capillarity resulting from the surface deposition of nanoparticles.


Enhancement of critical heat flux in nucleate boiling of nanofluids: a state-of-art review.

Kim H - Nanoscale Res Lett (2011)

Relation between CHF and surface characteristics. (a) CHF of pure water vs. contact angle of a water droplet on nanoparticle-deposited surfaces. SEM pictures (b) and maximum capillary wicking height of pure water (c) for surfaces boiled in 10-3% (A) and 10-1% (B) water-TiO2 nanofluids, with the same contact angles of ~20° [60].
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211511&req=5

Figure 12: Relation between CHF and surface characteristics. (a) CHF of pure water vs. contact angle of a water droplet on nanoparticle-deposited surfaces. SEM pictures (b) and maximum capillary wicking height of pure water (c) for surfaces boiled in 10-3% (A) and 10-1% (B) water-TiO2 nanofluids, with the same contact angles of ~20° [60].
Mentions: where Rc and cosθ represent the microscopic structures and surface wettability of the nanoparticle layers, respectively. Capillary flow during boiling supplies fresh liquid to the dry region beneath the vapor bubbles, delaying the irreversible growth of hot spots and CHF. Kim and Kim [60] used capillarity to characterize a completely wetted nanoparticle-coated surface. They showed that the estimated heat-flux gain due to capillary liquid supply along the porous layer was of the same order of magnitude as that due to wettability enhancement (Figure 12). They concluded that the significant CHF enhancement of nanofluids during pool boiling is a consequence not only of increased surface wettability, but also of improved capillarity resulting from the surface deposition of nanoparticles.

Bottom Line: The purpose of this article is to provide an exhaustive review of these studies.Also, attempts to explain the physical mechanism based on available CHF theories are described.Finally, future research needs are identified.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Nuclear Engineering, Kyung Hee University, Yongin, Gyunggi 446-701, Republic of Korea. hdkims@khu.ac.kr.

ABSTRACT
Nanofluids (suspensions of nanometer-sized particles in base fluids) have recently been shown to have nucleate boiling critical heat flux (CHF) far superior to that of the pure base fluid. Over the past decade, numerous experimental and analytical studies on the nucleate boiling CHF of nanofluids have been conducted. The purpose of this article is to provide an exhaustive review of these studies. The characteristics of CHF enhancement in nanofluids are systemically presented according to the effects of the primary boiling parameters. Research efforts to identify the effects of nanoparticles underlying irregular enhancement phenomena of CHF in nanofluids are then presented. Also, attempts to explain the physical mechanism based on available CHF theories are described. Finally, future research needs are identified.

No MeSH data available.


Related in: MedlinePlus