Limits...
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 vs. volume fraction for BN/EG nanofluids with different size of BN nanoparticles.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3211862&req=5

Figure 5: Thermal conductivity enhancement vs. volume fraction for BN/EG nanofluids with different size of BN nanoparticles.

Mentions: Size of nanoparticles is an important factor influencing thermal conductivity of nanofluids because shrinking it down to nanoscale not only increases the surface area relative to volume but also generates some nanoscale mechanisms in the suspensions [18,24]. Theoretical evidence [18,24,35] indicate that the effective thermal conductivity of nanofluids increases with decreasing particle size. Some experimental research [36-39] showed that as the nanoparticle diameter is reduced, the effective thermal conductivity of nanofluids becomes larger. The reason for this phenomenon was interpreted as the high specific surface area of small nanoparticles and intensified micro-convection provoked by small nanoparticles. While in present study, thermal conductivities of BN/EG nanofluids synthesized with 140- and 70-nm BN nanoparticles were measured and a different phenomenon was observed, as shown in Figure 5. It can be found that the thermal conductivity enhancement of nanofluids synthesized with large size (140 nm) BN nanoparticles is higher than that synthesized with small size (70 nm) BN nanoparticles. Hong [4] and Xie [9] also found similar phenomenon. This phenomenon is much different from the normal rule. What was the reason for this abnormal difference in thermal conductivity enhancement? The author believed that it can be ascribed to the difference in shape of the BN nanoparticles by x-ray diffraction (XRD) analysis, HRTEM images, and specific surface area of the BN nanoparticles.


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 vs. volume fraction for BN/EG nanofluids with different size of BN nanoparticles.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 5: Thermal conductivity enhancement vs. volume fraction for BN/EG nanofluids with different size of BN nanoparticles.
Mentions: Size of nanoparticles is an important factor influencing thermal conductivity of nanofluids because shrinking it down to nanoscale not only increases the surface area relative to volume but also generates some nanoscale mechanisms in the suspensions [18,24]. Theoretical evidence [18,24,35] indicate that the effective thermal conductivity of nanofluids increases with decreasing particle size. Some experimental research [36-39] showed that as the nanoparticle diameter is reduced, the effective thermal conductivity of nanofluids becomes larger. The reason for this phenomenon was interpreted as the high specific surface area of small nanoparticles and intensified micro-convection provoked by small nanoparticles. While in present study, thermal conductivities of BN/EG nanofluids synthesized with 140- and 70-nm BN nanoparticles were measured and a different phenomenon was observed, as shown in Figure 5. It can be found that the thermal conductivity enhancement of nanofluids synthesized with large size (140 nm) BN nanoparticles is higher than that synthesized with small size (70 nm) BN nanoparticles. Hong [4] and Xie [9] also found similar phenomenon. This phenomenon is much different from the normal rule. What was the reason for this abnormal difference in thermal conductivity enhancement? The author believed that it can be ascribed to the difference in shape of the BN nanoparticles by x-ray diffraction (XRD) analysis, HRTEM images, and specific surface area of the BN nanoparticles.

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.