MEE Graduate Colloquium October 6, 2006

Nanofluids: New Frontiers in Nanoscale Thermophysics

Stephen U.S. Choi, Ph.D., Argonne National Laboratory

Abstract

Nanofluids are a new class of heat transfer fluid engineered by dispersing nanometer-size solid particles in traditional heat transfer fluids. They can be used to improve heat transfer and energy efficiency in thermal management systems for many applications, including transportation and microelectronics.

Work in our nanofluid group and other groups has discovered that the addition of a small amount (<1 vol. %) of nanoparticles to conventional heat transfer fluids increases the thermal conductivity of the base fluid by up to two fold.

Furthermore, nanofluids have strong temperature-dependent thermal conductivity, a nonlinear relationship between thermal conductivity and concentration, and a three-fold increase in critical heat flux. These unexpected, remarkable experimental discoveries in thermophysics have created a theoretical challenge to explain and model the observations.

Newly proposed mechanisms and models for thermal conduction in nanofluids will be discussed with emphasis on a new model that uses Brownian motion to account for the fundamental molecular and nanoscale nature of the dynamic interactions between liquid molecules and nanoparticles suspended in fluids, and is distinct from all previous models developed for micro- and meso-sized particles.

I will briefly address the latest advances in convection heat transfer of nanofluids. Finally, I will present some future directions for basic and applied nanofluid research including the need for new physics-based mechanisms for the significant conductivity and convective heat transfer enhancement.

Dr. Choi's Bio/CV

Dr. Choi joined Argonne National Laboratory (ANL) in 1983 and has conducted research in advanced fluids. He proposed the concept of nanofluids in 1993 and has led the nanofluids team to develop stable nanofluids that showed high thermal conductivities.

He currently serves as the principal investigator of the nanofluids team. His pioneering work created a new, active area of interdisciplinary research in the field of nanoscale thermal sciences. The nanofluid work was recognized as one of the top research accomplishments in the DOE Basic Energy Sciences Office in 2002.

Prior to ANL, Dr. Choi was a Staff Scientist at Lawrence Berkeley Laboratory. Dr. Choi received his Ph.D. in Mechanical Engineering from the UC, Berkeley. Recently Dr. Choi received the University of Chicago Distinguished Performance Award for pioneering scientific achievements in nanofluid research.

He is author or co-author of more than 100 technical publications and those most pertinent to the proposed research are listed below.