Paper presented at the 7th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Turkey, 19-21 July, 2010.
This paper deals with a study of enhanced critical heat flux
(CHF) and burnout heat flux (BHF) in pool boiling of water
with suspended silica nanoparticles using Nichrome wires and
ribbons. Previously our group and other researchers have
reported three-digit percentage increase in critical heat flux in
silica nanofluids. This study investigates the effect of various
heater surface dimensions and cross-sectional shapes on pool
boiling heat transfer characteristics of water and water-based
nanofluids. Our data suggest that the CHF and BHF decrease
as heater surface area increases. For concentrations from
0.1vol% to 2vol%, various properties such as viscosity, pH, and
surface tension as well as silica deposition on surface and
glowing length of ribbon are measured in order to study the
possible factors in the heat transfer behavior of nanofluids. The
deposition of the particles on the wire allows high heat transfer
through inter-agglomerate pores, resulting in a nearly 3-fold
increase in burnout heat flux at very low concentrations. As the
concentration is increased, the CHF and BHF each decrease
prior to increasing again at higher concentrations. Results
show a maximum of 270% CHF enhancement for ribbon-type
heaters. A trend is presented for the effect of concentration on
both CHF and BHF, and visualization of boiling experiments
aids with determination of bubble sizes, nucleation, and flow
regimes.
