2pm on August 26, 2008 (Tuesday)
Howey Physics, Room N110

"Heat transfer enhancement in dense suspensions of agitated solids: theory, experiments and implications for nanofluids"

Michel Louge
Mechanical and Aerospace Engineering
Cornell University

We predict heat transfer enhancement through dense homogeneous suspensions of agitated solids in conductive fluids. The enhancement is governed by a Damkohler number demarcating an "exchange limit" where the two phases have distinct temperatures, and a "diffusion limit" set by the ability of agitated particles to self-diffuse. We test the theory in the exchange limit by vibrating acrylic spheres in a box.  We illustrate the diffusion limit by considering nanofluids. Because nanoparticles are agitated by Brownian motion, their self-diffusivity is modest, the fluid and solid phases share the same temperature, and mixture theory should predict enhancement of the effective suspension conductivity. To inform a debate on anomalous thermal conductivity of nanofluids, we also analyze the response of hot-wire thermal conductimetry to thermophoresis and particle resuspension.