This article reports on the International Nanofluid Property Benchmark Exercise, or INPBE, in which the thermal conductivity of identical samples of colloidally stable dispersions of nanoparticles or “nanofluids,” was measured by over 30 organizations worldwide, using a variety of experimental approaches, including the transient hot wire method, steady-state methods, and optical methods. The nanofluids tested in the exercise were comprised of aqueous and nonaqueous basefluids, metal and metal oxide particles, near-spherical and elongated particles, at low and high particle concentrations. The data analysis reveals that the data from most organizations lie within a relatively narrow band (±10% or less) about the sample average with only few outliers. The thermal conductivity of the nanofluids was found to increase with particle concentration and aspect ratio, as expected from classical theory. There are (small) systematic differences in the absolute values of the nanofluid thermal conductivity among the various experimental approaches; however, such differences tend to disappear when the data are normalized to the measured thermal conductivity of the basefluid. The effective medium theory developed for dispersed particles by Maxwell in 1881 and recently generalized by Nan et al. [J. Appl. Phys. 81, 6692 (1997)], was found to be in good agreement with the experimental data, suggesting that no anomalous enhancement of thermal conductivity was achieved in the nanofluids tested in this exercise.

A Benchmark Study on the Thermal Conductivity of Nanofluids

This paper explores the recent research developments in high-heat-flux thermal management. Cooling schemes such as pool boiling, detachable heat sinks, channel flow boiling, microchannel and mini-channel heat sinks, jet-impingement, and sprays, are discussed and compared relative to heat dissipation potential, reliability, and packaging concerns. It is demonstrated that, while different cooling options can be tailored to the specific needs of individual applications, system considerations always play a paramount role in determining the most suitable cooling scheme. It is also shown that extensive fundamental electronic cooling knowledge has been amassed over the past two decades. Yet there is now a growing need for hardware innovations rather than perturbations to those fundamental studies. An example of these innovations is the cooling of military avionics, where research findings from the electronic cooling literature have made possible the development of a new generation of cooling hardware which promise order of magnitude increases in heat dissipation compared to today's cutting edge avionics cooling schemes.

Assessment of high-heat-flux thermal management schemes

▪ Abstract This review examines recent advances made in predicting boiling heat fluxes, including some key results from the past. The topics covered are nucleate boiling, maximum heat flux, transition boiling, and film boiling. The review focuses on pool boiling of pure liquids, but flow boiling is also discussed briefly.

Boiling heat transfer

Advances and challenges in explaining fuel spray impingement: How much of single droplet impact research is useful?

The extremely high rates of heat transfer obtained by employing microchannels makes them an attractive alternative to conventional methods of heat dissipation, especially in applications related to the cooling of microelectronics. A compilation and analysis of the results from investigations on fluid flow and heat transfer in micro- and mini-channels and microtubes in the literature is presented in this review, with a special emphasis on quantitative experimental results and theoretical predictions. Anomalies and deviations from the behavior expected for conventional channels, both in terms of the frictional and heat transfer characteristics, are discussed.

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A Comparative Analysis of Studies on Heat Transfer and Fluid Flow in Microchannels

Burnout in highly subcooled water flow boiling in small diameter tubes

Assessment of correlations and models for the prediction of CHF in water subcooled flow boiling

The results of an experimental study on the effects of the flow of nanofluids (water-based suspensions of nanometer-sized solid particles) on metal surfaces are presented. Either different nanofluids (containing TiO2, Al2O3, ZrO2, and SiC, respectively) and different target materials (aluminum, copper, stainless steel) have been investigated, under similar operating conditions. Different behaviors were observed depending on the specific combination nanofluid-target material, which in some cases led to severe damaging of the tested target, thus highlighting the need for an adequate preliminary investigation of the possible interactions between the selected nanofluid and the apparatus materials, before its adoption as heat transfer fluid.

Experimental results of nanofluids flow effects on metal surfaces

Influence of channel diameter on subcooled flow boiling burnout at high heat fluxes

The behaviour of one drop impinging on a hot surface by varying the surface temperature, the drop velocity and the position of the surface (horizontal and a inclined 45°) both at a temperature below and above the Leidenfrost temperature has been experimentally evaluated, estimating the temperature at which the drop rebounds. A large influence on the drop velocity has been evidenced. The inclination of the surface decreases the critical value of the temperature above which the surface is not rewetted.

Andrea Mariani

Papers

Burnout in highly subcooled water flow boiling in small diameter tubes

Assessment of correlations and models for the prediction of CHF in water subcooled flow boiling

Experimental results of nanofluids flow effects on metal surfaces

Influence of channel diameter on subcooled flow boiling burnout at high heat fluxes

Visualization of the impact of water drops on a hot surface: effect of drop velocity and surface inclination