Oh Dong-Wook, Kwon Ohmyoung, Lee Joon Sik
School of Mechanical and Aerospace Engineering, Seoul National University, Seoul 151-742, Korea.
J Nanosci Nanotechnol. 2008 Oct;8(10):4923-9. doi: 10.1166/jnn.2008.1178.
Nanofluid is a mixture of nanoscale particles of metal, metal oxide or carbon nanotube and heat transfer fluids such as water and ethylene glycol. This work presents the application of the 3-omega (3omega) method for measuring the colloidal stability and the transient thermal conductivity of multi-wall carbon nanotube (MWCNT), Al2O3 and TiO2 nanoparticles suspended in water or ethylene glycol. The microfabricated 3omega device is verified by comparing the measured thermal conductivities of pure fluids with the table values. After the validation, the transient thermal responses of the nanofluids are measured to evaluate the colloidal stability. All of Al2O3 nanofluid samples show a clear sign of sedimentation while the acid-treated MWCNT (tMWCNT) nanofluid and a couple of TiO2 nanofluids with pH control or surfactant addition are found to have excellent colloidal stability. The thermal conductivities of tMWCNT nanofluids in the de-ionized water and ethylene glycol are measured, which are found to be in good agreement with previous data.
纳米流体是金属、金属氧化物或碳纳米管的纳米级颗粒与水和乙二醇等传热流体的混合物。本文介绍了用3-ω（3omega）法测量悬浮在水或乙二醇中的多壁碳纳米管（MWCNT）、Al2O3和TiO2纳米颗粒的胶体稳定性和瞬态热导率。通过将纯流体的测量热导率与表格值进行比较，对微加工的3ω装置进行了验证。验证后，测量了纳米流体的瞬态热响应以评估胶体稳定性。所有Al2O3纳米流体样品都有明显的沉降迹象，而经酸处理的MWCNT（tMWCNT）纳米流体以及添加了pH调节剂或表面活性剂的几种TiO2纳米流体具有优异的胶体稳定性。测量了tMWCNT纳米流体在去离子水和乙二醇中的热导率，发现与先前数据吻合良好。
