Nanofluids—The Cooling Medium of the Future

SARIT K. DAS
Department of Mechanical Engineering, Indian Institute of Technology-Madras, India

Heat transfer technology stands at a critical juncture today when the cooling needs of cutting edge technologies are demanding a paradigm shift in approach. Probably the most talked about area among these is that of electronic cooling. Rapid miniaturization,
the multiplication of speed of operation and data transfer,
and the use of high-energy density in laser and optical fibers have already pushed the conventional air and water cooling to their limits. However, the challenge does not only lie at the micro but also in the mega level. Large transport vehicles, high and medium temperature fuel cells and precisely controlled bioreactors do pose similar challenges to heat transfer technology.
All the efforts to improve cooling technology in the past are,
in a sense, “penny wise and pound foolish,” due to the fact that while every effort to improve transport processes (e.g., turbulence, boundary layer interruption) have been tried, very little attention has been paid to the fact that the fluids themselves are very poor conductors of heat (setting aside liquid metals, which cannot be used at usual temperatures). This inherent inadequacy of cooling fluids gives a hope that the present level of heat removal can be enhanced significantly by designing fluids that are better conductors. Nano-fluids, which are nano-sized particles suspended in liquids, have emerged as a potential candidate for this. The study by a group at Argonne National Laboratory [1] showed that these fluids enhance thermal conductivity of the base liquid enormously, which is beyond the explanation of any theory on suspensions.