Experimental and theoretical studies of nanofluid thermal conductivity enhancement: a review

Abstract

Nanofluids, i.e., well-dispersed (metallic) nanoparticles at low- volume fractions in liquids, may enhance the mixture's thermal conductivity, knf, over the base-fluid values. Thus, they are potentially useful for advanced cooling of micro-systems. Focusing mainly on dilute suspensions of well-dispersed spherical nanoparticles in water or ethylene glycol, recent experimental observations, associated measurement techniques, and new theories as well as useful correlations have been reviewed.It is evident that key questions still linger concerning the best nanoparticle-and-liquid pairing and conditioning, reliable measurements of achievable knf values, and easy-to-use, physically sound computer models which fully describe the particle dynamics and heat transfer of nanofluids. At present, experimental data and measurement methods are lacking consistency. In fact, debates on whether the anomalous enhancement is real or not endure, as well as discussions on what are repeatable correlations between knf and temperature, nanoparticle size/shape, and aggregation state. Clearly, benchmark experiments are needed, using the same nanofluids subject to different measurement methods. Such outcomes would validate new, minimally intrusive techniques and verify the reproducibility of experimental results. Dynamic knf models, assuming non-interacting metallic nano-spheres, postulate an enhancement above the classical Maxwell theory and thereby provide potentially additional physical insight. Clearly, it will be necessary to consider not only one possible mechanism but combine several mechanisms and compare predictive results to new benchmark experimental data sets.

Thermal and rheological properties improvement of drilling fluids using functionalized carbon nanotubes

“…In a nutshell, the THW technique relies on determining the thermal conductivity, from calculating the slope of linear portion of temperature rise (DT) vs. the natural logarithm of the time evolution (ln(t)). Assuming the temperature at any time (t) and distance (r) from a hot-wire probe as Tðr; tÞ, the following relationship exists (Kleinstreuer and Feng 2011):…”

“…nano-particles, CNT) in a base fluid (nanofluid) has evolved over the past decade. The experiments have unveiled improvements in the rheological (Aladag et al 2012;Chen et al 2011;Jyothirmayee Aravind et al 2011;Lei et al 2008;Murshed et al 2008;Hobbie and Fry 2007;Vakili-nezhaad and Dorany 2009;Phuoc et al 2011;Liu et al 2005) as well as in the thermal (Ding et al 2006;Hwang et al 2006;Kalinina et al 2011;Ö zerinç et al 2010;Venkata Sastry et al 2008;Xie and Chen 2009;Kleinstreuer and Feng 2011;Choi et al 2001;Karthikeyan et al 2008;Xie et al 2002) properties of the nanofluid system, compared to its base fluid.…”

The effect of pressure on heat transfer during pool boiling of water-Al2O3 and water-Cu nanofluids on stainless steel smooth tube

“…Nanofluid is a suspension which consists of the base liquid and metallic or nonmetallic nanoparticles with a typical size less than 100 nm (Choi, 1995). The promise of nanofluids arises from the fact that relatively small concentration of nanoparticles, typically below 5% by volume, significantly enhances thermal conductivity of the fluid (Kleinstreuer, 2011). Though the augmentation of thermal conductivity of slurries is a well known fact, they have not been used due to problems associated with them such as sedimentation, erosion and fouling.…”

Моделирование Коэффициента Теплопроводности Наножидкости С Малыми Частицами Методом Молекулярной Динамики

“…Различные возможные причины обсуждались многими авторами. Возможно, наиболее систематически это было сделано в работах Кеблинского с коллега-ми [30,31] и в обзоре Кляйнстройера и Фенга [32]. В них анализировался вклад четырех возможных ме-ханизмов.…”