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 |