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Round-robin test on thermal conductivity measurement of ZnO nanofluids and comparison of experimental results with theoretical bounds.

Lee WH, Rhee CK, Koo J, Lee J, Jang SP, Choi SU, Lee KW, Bae HY, Lee GJ, Kim CK, Hong SW, Kwon Y, Kim D, Kim SH, Hwang KS, Kim HJ, Ha HJ, Lee SH, Choi CJ, Lee JH - Nanoscale Res Lett (2011)

Bottom Line: Ethylene glycol (EG)-based zinc oxide (ZnO) nanofluids containing no surfactant have been manufactured by one-step pulsed wire evaporation (PWE) method.Round-robin tests on thermal conductivity measurements of three samples of EG-based ZnO nanofluids have been conducted by five participating labs, four using accurate measurement apparatuses developed in house and one using a commercial device.The results have been compared with several theoretical bounds on the effective thermal conductivity of heterogeneous systems.

View Article: PubMed Central - HTML - PubMed

Affiliation: Mechanical and Industrial Engineering Department, University of Illinois at Chicago, Chicago, IL, USA. suschoi@uic.edu.

ABSTRACT
Ethylene glycol (EG)-based zinc oxide (ZnO) nanofluids containing no surfactant have been manufactured by one-step pulsed wire evaporation (PWE) method. Round-robin tests on thermal conductivity measurements of three samples of EG-based ZnO nanofluids have been conducted by five participating labs, four using accurate measurement apparatuses developed in house and one using a commercial device. The results have been compared with several theoretical bounds on the effective thermal conductivity of heterogeneous systems. This study convincingly demonstrates that the large enhancements in the thermal conductivities of EG-based ZnO nanofluids tested are beyond the lower and upper bounds calculated using the models of the Maxwell and Nan et al. with and without the interfacial thermal resistance.

No MeSH data available.


Comparison of experimental thermal conductivity enhancement of 5.5 vol.% ZnO nanofluids with theoretical bounds of H-S and Maxwell models.
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Figure 7: Comparison of experimental thermal conductivity enhancement of 5.5 vol.% ZnO nanofluids with theoretical bounds of H-S and Maxwell models.

Mentions: Figures 6 and 7 show comparisons of experimental thermal conductivity enhancements of 3.0 vol.% and 5.5 vol.% ZnO nanofluids with the three theoretical bounds of Hashin and Shtrikman and Maxwell models. The properties, such as the thermal conductivities of EG [49] and ZnO nanoparticles [51], used for calculating the theoretical bounds are summarized in Table 2. The upper bound of Hashin and Shtrikman, which was used by Eapen et al. [27] and Kelbinski et al. [29], dramatically overestimates the thermal conductivity of ZnO nanofluids. The H-S upper bound corresponds to large pockets of fluid separated by linked chain-forming or clustered nanoparticles [29]. The long wire-like structures made of perfectly aligned nanoparticles are not realizable with dilute nanofluids with well-dispersed nanoparticles. Furthermore, it is almost impossible to separate fluid by nanoparticle chains in nanofluids, although nanoparticles can be partially aggregated in nanofluids. Therefore, the upper bound given by the H-S model is not applicable to nanofluids. More realistic upper and lower bounds for nanofluids having low concentration of well-dispersed nanoparticles are given by Buongiorno et al. [34]. It is clear from Figures 6 and 7 that the thermal conductivity enhancements of EG-based ZnO nanofluids are larger than the upper bound of the Maxwell model.


Round-robin test on thermal conductivity measurement of ZnO nanofluids and comparison of experimental results with theoretical bounds.

Lee WH, Rhee CK, Koo J, Lee J, Jang SP, Choi SU, Lee KW, Bae HY, Lee GJ, Kim CK, Hong SW, Kwon Y, Kim D, Kim SH, Hwang KS, Kim HJ, Ha HJ, Lee SH, Choi CJ, Lee JH - Nanoscale Res Lett (2011)

Comparison of experimental thermal conductivity enhancement of 5.5 vol.% ZnO nanofluids with theoretical bounds of H-S and Maxwell models.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211320&req=5

Figure 7: Comparison of experimental thermal conductivity enhancement of 5.5 vol.% ZnO nanofluids with theoretical bounds of H-S and Maxwell models.
Mentions: Figures 6 and 7 show comparisons of experimental thermal conductivity enhancements of 3.0 vol.% and 5.5 vol.% ZnO nanofluids with the three theoretical bounds of Hashin and Shtrikman and Maxwell models. The properties, such as the thermal conductivities of EG [49] and ZnO nanoparticles [51], used for calculating the theoretical bounds are summarized in Table 2. The upper bound of Hashin and Shtrikman, which was used by Eapen et al. [27] and Kelbinski et al. [29], dramatically overestimates the thermal conductivity of ZnO nanofluids. The H-S upper bound corresponds to large pockets of fluid separated by linked chain-forming or clustered nanoparticles [29]. The long wire-like structures made of perfectly aligned nanoparticles are not realizable with dilute nanofluids with well-dispersed nanoparticles. Furthermore, it is almost impossible to separate fluid by nanoparticle chains in nanofluids, although nanoparticles can be partially aggregated in nanofluids. Therefore, the upper bound given by the H-S model is not applicable to nanofluids. More realistic upper and lower bounds for nanofluids having low concentration of well-dispersed nanoparticles are given by Buongiorno et al. [34]. It is clear from Figures 6 and 7 that the thermal conductivity enhancements of EG-based ZnO nanofluids are larger than the upper bound of the Maxwell model.

Bottom Line: Ethylene glycol (EG)-based zinc oxide (ZnO) nanofluids containing no surfactant have been manufactured by one-step pulsed wire evaporation (PWE) method.Round-robin tests on thermal conductivity measurements of three samples of EG-based ZnO nanofluids have been conducted by five participating labs, four using accurate measurement apparatuses developed in house and one using a commercial device.The results have been compared with several theoretical bounds on the effective thermal conductivity of heterogeneous systems.

View Article: PubMed Central - HTML - PubMed

Affiliation: Mechanical and Industrial Engineering Department, University of Illinois at Chicago, Chicago, IL, USA. suschoi@uic.edu.

ABSTRACT
Ethylene glycol (EG)-based zinc oxide (ZnO) nanofluids containing no surfactant have been manufactured by one-step pulsed wire evaporation (PWE) method. Round-robin tests on thermal conductivity measurements of three samples of EG-based ZnO nanofluids have been conducted by five participating labs, four using accurate measurement apparatuses developed in house and one using a commercial device. The results have been compared with several theoretical bounds on the effective thermal conductivity of heterogeneous systems. This study convincingly demonstrates that the large enhancements in the thermal conductivities of EG-based ZnO nanofluids tested are beyond the lower and upper bounds calculated using the models of the Maxwell and Nan et al. with and without the interfacial thermal resistance.

No MeSH data available.