[nanoPost] Nanofluids for heat transfer applications

University USA

Nanoparticle suspensions (sometimes termed nanofluids) have emerged as an exciting new R&D area because of their unique wetting and transport properties. Nanofluids, for example, have been proposed as alternative coolants in heat transfer applications including transportation, MEMS, microelectronics and refrigeration systems.

Many industries from transportation to energy production to microelectronics require new, more efficient heat transfer fluids. Both coolants and lubricants used in today’s technology stand to benefit substanti-ally from more efficient heat transfer fluids.

Specific applications include heat transfer fluids (coolants) for automobiles, airplanes, refrigeration systems, micromachines including MEMS, electronics and instrumentation. Until recently nanofluids have been composed of nanoparticles (pristine or surface-modified) typically suspended into a solvent or a liquid. Depending on the type, size and surface chemistry of the nanoparticles, nanofluids with a range of properties and potential applications have been produced. In all these systems, however, a solid-like behaviour in the absence of a solvent is typical.

In the Department of Mechanical and Aerospace Engineering they have recently developed solvent-free nanoparticles with liquid-like behaviour and the ability to flow. Solvent-free nanofluids based on silica, titania and iron oxide have already been realized. The combination of fluidity in the absence of any solvent and low vapour pressure offer significant new scientific and technological opportunities.

The new nanofluids are inherently green and can circumvent environmental concerns associated with the presence of volatile solvents in conventional colloidal suspensions. In addition, they can provide new, unique opportunities as heat transfer media, fuels and lubricants.

They are also proposing to expand their effort to develop a series of new solvent-free nanofluids for heat transfer applications. The solvent-free nanofluids will provide better thermal conductivity, better wear resistance, low volatility and ability to flow in microchannels and other microfabricated environments.

Crucial to their program is the ability to systematically vary the size, shape, aspect ratio of nanoparticles as well as the nature of interactions between nanoparticles by varying the surface modification on the nanoparticles. To that end nanofluids of aluminium oxide, aluminium nitride, and copper oxide will be developed and evaluated. Exploiting their synthetic capability they will establish correlations between molecular/nanoscale properties and macroscopic transport properties (e.g. rheology, heat transfer), which will enable us to design and synthesize nanofluids for specific targeted applications. Samples will be delivered to the industrial sponsor for further testing and evaluation.