http://orcid.org/0000-0003-2573-6789
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ABSTRACT
Oscillatory mixed convection in the jet impingement cooling of a partially heated horizontal surface immersed in a nanofluid-saturated porous medium is simulated and discussed in this study. This situation appears when the jet flow and the flow due to buoyancy have opposing effects and are in conflict for domination. The aim of the present contribution is to explore how governing parameters may alter these oscillations and the resulting heat exchange. It is demonstrated that the final steady or oscillatory flow response depends on the values of the Reynolds number, the Grashof number, and the Darcy number but not influenced by the medium porosity and the nanoparticles fraction.
Nomenclature
| C | = | specific heat [J/(kg · K)] |
| d | = | half of the width of the jet inlet (m) |
| Da | = | Darcy number, κ/L2 |
| g | = | gravitational acceleration (m/s2) |
| Gr | = | Grashof number, |
| h | = | heat transfer coefficient [W/(m2 · K)] |
| k | = | thermal conductivity [W/(m · K)] |
| L | = | jet-to-plate spacing and half of the heat source length (m) |
| Nu | = | local Nusselt number, Nu = hL/kf |
| = | space-averaged Nusselt number | |
| = | time-space-averaged Nusselt number | |
| p | = | pressure (Pa) |
| P | = | dimensionless pressure, |
| Pr | = | Prandtl number, |
| Re | = | Reynolds number, |
| t | = | time (s) |
| T | = | temperature (K) |
| u, v | = | velocity components along x- and y-axes, respectively (m/s) |
| U, V | = | dimensionless velocity components, u/V0, v/V0 |
| V0 | = | jet velocity (m/s) |
| w | = | half of the width of the solution domain |
| x, y | = | Cartesian coordinates (m) |
| X, Y | = | dimensionless Cartesian coordinates, x/L, y/L |
| Greek symbols | = | |
| β | = | thermal expansion coefficient (1/K) |
| θ | = | dimensionless temperature, |
| κ | = | permeability (m2) |
| μ | = | dynamic viscosity (Pa · s) |
| ρ | = | density (kg/m3) |
| τ | = | dimensionless time, |
| φ | = | porosity |
| χ | = | nanoparticles fraction |
| ψ | = | dimensionless stream function, |
| Ω | = | dimensionless vorticity, |
| Subscripts | = | |
| C | = | cold |
| f | = | base fluid |
| H | = | hot |
| nf | = | nanofluid |
| p | = | nanoparticle |
| s | = | solid matrix |
| stag | = | stagnation point |
Nomenclature
| C | = | specific heat [J/(kg · K)] |
| d | = | half of the width of the jet inlet (m) |
| Da | = | Darcy number, κ/L2 |
| g | = | gravitational acceleration (m/s2) |
| Gr | = | Grashof number, |
| h | = | heat transfer coefficient [W/(m2 · K)] |
| k | = | thermal conductivity [W/(m · K)] |
| L | = | jet-to-plate spacing and half of the heat source length (m) |
| Nu | = | local Nusselt number, Nu = hL/kf |
| = | space-averaged Nusselt number | |
| = | time-space-averaged Nusselt number | |
| p | = | pressure (Pa) |
| P | = | dimensionless pressure, |
| Pr | = | Prandtl number, |
| Re | = | Reynolds number, |
| t | = | time (s) |
| T | = | temperature (K) |
| u, v | = | velocity components along x- and y-axes, respectively (m/s) |
| U, V | = | dimensionless velocity components, u/V0, v/V0 |
| V0 | = | jet velocity (m/s) |
| w | = | half of the width of the solution domain |
| x, y | = | Cartesian coordinates (m) |
| X, Y | = | dimensionless Cartesian coordinates, x/L, y/L |
| Greek symbols | = | |
| β | = | thermal expansion coefficient (1/K) |
| θ | = | dimensionless temperature, |
| κ | = | permeability (m2) |
| μ | = | dynamic viscosity (Pa · s) |
| ρ | = | density (kg/m3) |
| τ | = | dimensionless time, |
| φ | = | porosity |
| χ | = | nanoparticles fraction |
| ψ | = | dimensionless stream function, |
| Ω | = | dimensionless vorticity, |
| Subscripts | = | |
| C | = | cold |
| f | = | base fluid |
| H | = | hot |
| nf | = | nanofluid |
| p | = | nanoparticle |
| s | = | solid matrix |
| stag | = | stagnation point |