Abstract
Forced convective heat transfer is exptl. investigated using aq. and ethylene glycol-based spherical titania nanofluids, and aq.-based titanate nanotubes, carbon nanotubes and nano-diamond nanofluids. These nanofluids are formulated from dry nanoparticles and pure base liqs. to eliminate complications due to unknown soln. chem. All the formulated nanofluids show a higher effective thermal cond. than that predicted by the conventional theories. Except for the ethylene glycol-based titania nanofluids, all other nanofluids are found to be non-Newtonian. For aq.-based titania and carbon and titanate nanotube nanofluids, the convective heat transfer coeff. enhancement exceeds, by a large margin, the extent of the thermal conduction enhancement. However, deterioration of the convective heat transfer is obsd. for ethylene glycol-based titania nanofluids at low Reynolds nos. and aq.-based nano-diamond nanofluids. Possible mechanisms for the obsd. controversy are discussed from both microscopic and macroscopic viewpoints. The competing effects of particle migration on the thermal boundary layer thickness and that on the effective thermal cond. are suggested to be responsible for the exptl. observations. [on SciFinder (R)]
Original language | English |
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Pages (from-to) | 813-824 |
Number of pages | 12 |
Journal | Advanced Powder Technology |
Volume | 18 |
Issue number | 6 |
Publication status | Published - 2007 |
Keywords
- Rheology
- Thermal conductivity (forced convective heat transfer of nanofluids)
- heat transfer nanofluid thermal cond rheol
- Nanofluids
- Reynolds number
- Heat transfer