Nanofluid – A New Concept for Advanced Heat Transfer Applications
Nanofluid, new class of heat transfer fluid comprising very low volume fraction (~ 1 vol.%) of ultrafine particles in a given fluid to form a stable colloid and offering a spectacular increase (> 100%) in thermal conductivity, is poised to revolutionize, if successfully implemented, the efficiency and heat management in several important technological applications including microelectronic or VLSI devices, automobiles, refrigerators, heat exchangers, and nuclear/thermal powder plants.
In the present talk, an overview of the experimental studies by this author and his colleagues on synthesis and characterization nano-metallic (Al70Cu30 and Al70Ag30) and ceramic (Al2O3, TiO2, ZrO2) dispersed (in 0.5-2.0 vol. %) water and ethylene glycol based nanofluids and measurement of thermal properties (conductivity and heat transfer coefficient) will be presented. The mechanically alloyed or as-received powders were characterized by XRD, TEM, SEM, EDS, DLS and BET. Thermal conductivity of the base fluid and nanofluid was measured using an indigenously developed thermal comparator set up. The measurements, calibrated using standard heat transfer fluid, showed up to 200% increase in conductivity ratio. Heat transfer coefficient, measured through closed loop tube-in-tube heat exchange experiments for evaporator assembly, recorded 5-10 % increase with only 0.1-0.5 vol.% loading of nanoparticles. Furthermore, an analytical study shows that shape factor and volume percent, besides composition and size of nanoparticles, exert significant influence on effective thermal conductivity of nanofluid. The talk will end with a discussion on the theoretical studies offering a possible explanation of this extraordinary thermal conductivity of nanofluid based on Brownian motion, near field interaction, etc.
Presentation: Invited at E-MRS Fall Meeting 2007, Acta Materialia Gold Medal Workshop, by Indranil Manna
See On-line Journal of E-MRS Fall Meeting 2007
Submitted: 2007-06-08 17:18 Revised: 2009-06-07 00:44