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Investigation on two abnormal phenomena about thermal conductivity enhancement of BN/EG nanofluids.

Li Y, Zhou J, Luo Z, Tung S, Schneider E, Wu J, Li X - Nanoscale Res Lett (2011)

Bottom Line: The thermal conductivity of boron nitride/ethylene glycol (BN/EG) nanofluids was investigated by transient hot-wire method and two abnormal phenomena was reported.The chain-like loose aggregation of nanoparticles is responsible for the abnormal increment of thermal conductivity enhancement for the BN/EG nanofluids at very low particles volume fraction.And the difference in specific surface area and aspect ratio of BN nanoparticles may be the main reasons for the abnormal difference between thermal conductivity enhancements for BN/EG nanofluids prepared with 140- and 70-nm BN nanoparticles, respectively.

View Article: PubMed Central - HTML - PubMed

Affiliation: State Key Laboratory for Mechanical Behavior of Materials, School of Materials Science and Engineering, Xi'an Jiaotong University, Xi'an, Shanxi, 710049, China. lyj.xjtu@yahoo.com.cn.

ABSTRACT
The thermal conductivity of boron nitride/ethylene glycol (BN/EG) nanofluids was investigated by transient hot-wire method and two abnormal phenomena was reported. One is the abnormal higher thermal conductivity enhancement for BN/EG nanofluids at very low-volume fraction of particles, and the other is the thermal conductivity enhancement of BN/EG nanofluids synthesized with large BN nanoparticles (140 nm) which is higher than that synthesized with small BN nanoparticles (70 nm). The chain-like loose aggregation of nanoparticles is responsible for the abnormal increment of thermal conductivity enhancement for the BN/EG nanofluids at very low particles volume fraction. And the difference in specific surface area and aspect ratio of BN nanoparticles may be the main reasons for the abnormal difference between thermal conductivity enhancements for BN/EG nanofluids prepared with 140- and 70-nm BN nanoparticles, respectively.

No MeSH data available.


Thermal conductivity enhancement of BN/EG nanofluids.
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Figure 3: Thermal conductivity enhancement of BN/EG nanofluids.

Mentions: Some investigations reported in literature indicate that thermal conductivity enhancement will increase with the increment of volume fraction of nanoparticle [4,9,10]. That is to say that the thermal conductivity enhancement for nanofluids with low nanoparticle volume fraction must be lower than that of nanofluids with high-volume fraction of nanoparticle. But an absolutely different phenomenon was observed in current experiment. A 2.0% enhancement of thermal conductivity was obtained for 0.025 vol.% BN/EG nanofluids prepared by setting 1.25 vol.% BN (140 nm)/EG nanofluids for 216 days, which is much higher than a 0.8% increment for 0.2 vol.% BN (140 nm)/EG nanofluids prepared by a two-step method, as shown in Figure 3. To find the reason for this abnormal thermal conductivity enhancement, high-resolution TEM (HRTEM) observation of the nanoparticles suspended in the nanofluids was conducted.


Investigation on two abnormal phenomena about thermal conductivity enhancement of BN/EG nanofluids.

Li Y, Zhou J, Luo Z, Tung S, Schneider E, Wu J, Li X - Nanoscale Res Lett (2011)

Thermal conductivity enhancement of BN/EG nanofluids.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211862&req=5

Figure 3: Thermal conductivity enhancement of BN/EG nanofluids.
Mentions: Some investigations reported in literature indicate that thermal conductivity enhancement will increase with the increment of volume fraction of nanoparticle [4,9,10]. That is to say that the thermal conductivity enhancement for nanofluids with low nanoparticle volume fraction must be lower than that of nanofluids with high-volume fraction of nanoparticle. But an absolutely different phenomenon was observed in current experiment. A 2.0% enhancement of thermal conductivity was obtained for 0.025 vol.% BN/EG nanofluids prepared by setting 1.25 vol.% BN (140 nm)/EG nanofluids for 216 days, which is much higher than a 0.8% increment for 0.2 vol.% BN (140 nm)/EG nanofluids prepared by a two-step method, as shown in Figure 3. To find the reason for this abnormal thermal conductivity enhancement, high-resolution TEM (HRTEM) observation of the nanoparticles suspended in the nanofluids was conducted.

Bottom Line: The thermal conductivity of boron nitride/ethylene glycol (BN/EG) nanofluids was investigated by transient hot-wire method and two abnormal phenomena was reported.The chain-like loose aggregation of nanoparticles is responsible for the abnormal increment of thermal conductivity enhancement for the BN/EG nanofluids at very low particles volume fraction.And the difference in specific surface area and aspect ratio of BN nanoparticles may be the main reasons for the abnormal difference between thermal conductivity enhancements for BN/EG nanofluids prepared with 140- and 70-nm BN nanoparticles, respectively.

View Article: PubMed Central - HTML - PubMed

Affiliation: State Key Laboratory for Mechanical Behavior of Materials, School of Materials Science and Engineering, Xi'an Jiaotong University, Xi'an, Shanxi, 710049, China. lyj.xjtu@yahoo.com.cn.

ABSTRACT
The thermal conductivity of boron nitride/ethylene glycol (BN/EG) nanofluids was investigated by transient hot-wire method and two abnormal phenomena was reported. One is the abnormal higher thermal conductivity enhancement for BN/EG nanofluids at very low-volume fraction of particles, and the other is the thermal conductivity enhancement of BN/EG nanofluids synthesized with large BN nanoparticles (140 nm) which is higher than that synthesized with small BN nanoparticles (70 nm). The chain-like loose aggregation of nanoparticles is responsible for the abnormal increment of thermal conductivity enhancement for the BN/EG nanofluids at very low particles volume fraction. And the difference in specific surface area and aspect ratio of BN nanoparticles may be the main reasons for the abnormal difference between thermal conductivity enhancements for BN/EG nanofluids prepared with 140- and 70-nm BN nanoparticles, respectively.

No MeSH data available.