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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

Effect of pressure on the maximum CHF enhancement in nanofluids. The used heater geometries are 40 × 40 mm2 [20,27] and 10 × 10 mm [5,22,28,29].
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Figure 6: Effect of pressure on the maximum CHF enhancement in nanofluids. The used heater geometries are 40 × 40 mm2 [20,27] and 10 × 10 mm [5,22,28,29].

Mentions: Figure 6 shows the pressure dependency of CHF enhancement in nanofluids. It is of interest that the CHF enhancement apparently decreases with increasing the pressure. This pressure effect cannot be simply explained by traditional boiling CHF theory, but however, some insight can be given based on a comparison of behaviors of dry patches, whose irreversible growth can cause CHF [26,30], under different pressure conditions. Van Ouwerkerk [31] found that when the CHF is approached, the mechanism of formation of dry areas is different for atmosphere and low-pressure conditions: the large dry patch is created by coalescence of small vapor bubbles that forms at atmospheric pressure but underneath are individual bubbles growing to immense size at low pressure. This different mechanism of formation of dry patches under atmospheric and low-pressure conditions suggests that the pressure in nanofluid boiling can have strong impact on the CHF enhancement. In addition, if the use of nanofluids alters local properties of individual bubbles growing on the heating surface, such as wetting ability, its impact on the CHF value can be more significant in low-pressure condition where a dry patch underneath a single bubble plays a key role in triggering CHF.


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

Kim H - Nanoscale Res Lett (2011)

Effect of pressure on the maximum CHF enhancement in nanofluids. The used heater geometries are 40 × 40 mm2 [20,27] and 10 × 10 mm [5,22,28,29].
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 6: Effect of pressure on the maximum CHF enhancement in nanofluids. The used heater geometries are 40 × 40 mm2 [20,27] and 10 × 10 mm [5,22,28,29].
Mentions: Figure 6 shows the pressure dependency of CHF enhancement in nanofluids. It is of interest that the CHF enhancement apparently decreases with increasing the pressure. This pressure effect cannot be simply explained by traditional boiling CHF theory, but however, some insight can be given based on a comparison of behaviors of dry patches, whose irreversible growth can cause CHF [26,30], under different pressure conditions. Van Ouwerkerk [31] found that when the CHF is approached, the mechanism of formation of dry areas is different for atmosphere and low-pressure conditions: the large dry patch is created by coalescence of small vapor bubbles that forms at atmospheric pressure but underneath are individual bubbles growing to immense size at low pressure. This different mechanism of formation of dry patches under atmospheric and low-pressure conditions suggests that the pressure in nanofluid boiling can have strong impact on the CHF enhancement. In addition, if the use of nanofluids alters local properties of individual bubbles growing on the heating surface, such as wetting ability, its impact on the CHF value can be more significant in low-pressure condition where a dry patch underneath a single bubble plays a key role in triggering CHF.

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