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ABSTRACT
Wavy-finned arrangement and nanofluid medium are applied to a heat sink for the purpose of achieving more efficient thermal hydraulic performance. Laminar forced convection of Al2O3/ethylene glycol–water nanofluid in a 3D wavy channel is considered. Computational Fluid Dynamics (CFD) simulations are conducted in a wide spectrum of nanoparticle volume concentrations (0.2% 0.3% 0.4% 0.5% 1% 2% 3% and 4%) with the Reynolds number varying between 400 and 1 200. Wavy channels are proved to dramatically improve the heat transfer performance compared with the plain channels of the same cross section. Utilizing nanofluid in a wavy channel further enhances the heat transfer but also brings additional flow resistance. Synthesizing wavy-finned arrangement and nanofluid technique achieves the highest overall thermal hydraulic performance factor of 1.74 for ϕ = 0.2% and Re = 600. In the wavy channel nanoparticle concentration is supposed to be less than 1.0% to provide a positive effect for the overall performance.
Nomenclature
| CP | = | specific heat, Jkg−1K−1 |
| Dh | = | hydraulic diameter, m |
| dp | = | diameter of nanoparticle, m |
| f | = | friction factor |
| g | = | gravity acceleration, Nm−2 |
| h | = | heat transfer coefficient, Wm−2K−1 |
| k | = | thermal conductivity, Wm−1K−1 |
| Lt | = | total length of the channel, m |
| Nu | = | Nusselt number |
| P | = | fluid pressure, Pa |
| Pr | = | Prandtl number |
| q | = | heat flux, W m−2 |
| Re | = | Reynolds number |
| St | = | Stanton number |
| T | = | temperature, K |
| TPF | = | thermal hydraulic performance factor |
| v | = | velocity component, m s−1 |
| β | = | thermal expansion coefficient, K−1 |
| μ | = | viscosity, Pa s |
| ρ | = | density, kg m−3 |
| φ | = | volume concentration |
| κ | = | Boltzmann constant |
| Subscripts | = | |
| avg | = | area average |
| bf | = | base fluid |
| eff | = | effective |
| lm | = | logarithmic mean |
| m | = | mixture |
| i | = | component (bf and p) index |
| nf | = | nanofluid |
| p | = | particle |
| syn | = | synthetic technology |
| 0 | = | reference value |
Nomenclature
| CP | = | specific heat, Jkg−1K−1 |
| Dh | = | hydraulic diameter, m |
| dp | = | diameter of nanoparticle, m |
| f | = | friction factor |
| g | = | gravity acceleration, Nm−2 |
| h | = | heat transfer coefficient, Wm−2K−1 |
| k | = | thermal conductivity, Wm−1K−1 |
| Lt | = | total length of the channel, m |
| Nu | = | Nusselt number |
| P | = | fluid pressure, Pa |
| Pr | = | Prandtl number |
| q | = | heat flux, W m−2 |
| Re | = | Reynolds number |
| St | = | Stanton number |
| T | = | temperature, K |
| TPF | = | thermal hydraulic performance factor |
| v | = | velocity component, m s−1 |
| β | = | thermal expansion coefficient, K−1 |
| μ | = | viscosity, Pa s |
| ρ | = | density, kg m−3 |
| φ | = | volume concentration |
| κ | = | Boltzmann constant |
| Subscripts | = | |
| avg | = | area average |
| bf | = | base fluid |
| eff | = | effective |
| lm | = | logarithmic mean |
| m | = | mixture |
| i | = | component (bf and p) index |
| nf | = | nanofluid |
| p | = | particle |
| syn | = | synthetic technology |
| 0 | = | reference value |