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ABSTRACT
Laminar flow and heat transfer of three different types of nanofluids; Al2O3, CuO, and SiO2 suspended in ethylene glycol, in a triangular duct using delta-winglet pair of vortex generator are numerically simulated in three dimensions. The governing equations of mass, momentum and energy are solved using the finite volume method. The effects of types, concentrations, and diameter of solid nanoparticles and Reynolds number on thermal and hydraulic performance of triangular duct are examined. The range of Reynolds number, volume fraction and nanoparticles diameters is 100–1200, 1–4%, and 25–85 nm, respectively. The results indicate that the average Nusselt number increases with the particles volume fraction and Reynolds number associated with an increase in the pressure drop. The heat transfer enhancement and pressure drop penalty reduce with increasing the particles diameters. However, a reduction in the pumping power required is observed to force the nanofluids when the volume fraction increases, assuming the heat transfer coefficient remains constant.
Nomenclature
| a | = | distance between the tips of the vortex generator (m) |
| A | = | cross-sectional area of the flow (m2) |
| cp | = | Specific heat capacity (J/kg.K) |
| Dh | = | hydraulic diameter (m) |
| dbf | = | diameter of the base fluid (m) |
| dp | = | solid particle diameter (m) |
| DWP | = | delta-winglet pair |
| E% | = | ratio of heat transfer augmentation |
| EG | = | Ethylene glycol |
| f | = | Darcy Friction factor |
| h | = | height of the vortex generator (m) |
| h | = | convective heat transfer coefficient (W/m2.K) |
| H | = | height of the duct (m) |
| k | = | thermal conductivity (W/m.K) |
| κ | = | Boltzmann constant (κ = 1.3807 × 10−23 J/K) |
| L | = | length of the channel (m) |
| l | = | length of vortex generator (m) |
| M | = | molecular weight (kg/mol) |
| = | mass flow rate (kg/s) | |
| N | = | Avogadro number (N = 6.02214179 × 1023 mol−1) |
| Nu | = | Nusselt number (Nu = h Dh / k) |
| ΔP | = | difference of the pressure drop (pa) |
| P.P | = | pumping power (W) |
| Pr | = | Prandtl number, (Pr = cp µ / k) |
| Re | = | Reynolds number (Re = ρ u Dh / µ) |
| T | = | temperature (K) |
| To | = | reference temperature, 273K |
| t | = | thickness of the vortex generator (m) |
| u, v, w | = | velocity components (m/s) |
| U, V, W | = | dimensionless velocity components in x, y, z direction, respectively |
| VG | = | vortex generator |
| W | = | width of the duct (m) |
| WP | = | wetted perimeter of the flow (m) |
| x, y, z | = | 3-D Cartesian coordinates (m) |
| Z | = | dimensionless of (L / Dh) / (Re Pr) |
Greek symbols
| β | = | attack angle of vortex generator |
| ϕ | = | function of liquid volume (dimensionless) |
| φ | = | volume fraction |
| µ | = | dynamic viscosity (kg/m.s) |
| ϑ | = | kinematic viscosity (m2/s) |
| ρ | = | density (kg/m3) |
| θ | = | dimensionless temperature |
Subscript
| avr | = | average |
| eff | = | effective |
| bf | = | base fluid |
| in | = | inlet |
| m | = | mean |
| max | = | maximum |
| min | = | minimum |
| nf | = | nanofluid |
| out | = | outlet |
| p | = | particle |
| swa | = | spanwise average |
| w | = | wall |
| x | = | local |
Additional information
Notes on contributors
Hamdi E. Ahmed
Hamdi E. Ahmed was awarded the Bachelor of Science in Mechanical Engineering, from the University of Anbar, Anbar, Iraq in 2002. Then he received the master degree in Mechanical Engineering at the same university in 2005. He received the Ph.D. degree in Mechanical Engineering from the Universiti Tenaga Nasional, Malaysia in 2014. He is interested in optimization of hydrothermal design of macro- and micro-channels using conventional- and nano-fluids. His research works have been published in many international peer reviewed journals in the field of heat transfer and fluid flow.
Mohd Z. Yusoff
Mohd. Z. Yusoff obtained his Ph.D. from University of Birmingham, UK, specializing in the computational fluid dynamics (CFD) modelling of high speed condensation in low pressure steam turbine. He is currently the Deputy Vice Chancellor at the Universiti Tenaga Nasional (UNITEN), Malaysia. Previously, he was Head of Mechanical Engineering Department and Dean of the College of Engineering at UNITEN. His research interest is in CFD, high speed compressible flows, steam condensation and heat transfer. He was the founder of the Centre of Fluid Dynamics at UNITEN.