http://orcid.org/0000-0003-0047-7696
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ABSTRACT
To evaluate the potential benefits of kerosene-based nanofluids as coolants for regenerative cooling system, a detailed numerical study of the turbulent heat transfer of copper/n-decane nanofluid flowing inside a miniature cooling tube at supercritical pressures has been conducted. Numerical results reveal that copper nanoparticles can significantly improve heat transfer performance in the entire cooling tube. This can be explained by the fundamental mechanism that within the near-wall turbulent flow region, the reduction of nanofluid kinematic viscosity leads to increased turbulent thermal conductivity and consequently causes heat transfer enhancement. Moreover, heat transfer deterioration phenomenon is delayed or weakened by nanoparticles, and the overall heat transfer performance of the base fluid has been improved. Results indicate potential advantages of kerosene nanofluids as coolants for regenerative engine cooling applications.
Nomenclature
| cp | = | constant-pressure heat capacity (J/kgK) |
| D | = | diameter of the cooling tube (mm) |
| et | = | total energy (J/kg) |
| f | = | friction factor |
| G | = | turbulent generation term |
| hc | = | convective heat transfer coefficient (W/m2K) |
| k | = | turbulent kinetic energy (J/kg) |
| Nu | = | Nusselt number |
| p | = | pressure (Pa) |
| qw | = | wall heat flux (W/m2) |
| r | = | radial coordinate (mm) |
| Re | = | Reynolds number |
| T | = | temperature (K) |
| u | = | velocity (m/s) |
| x | = | axial coordinate along the flow direction (mm) |
| Y | = | mass fraction |
| Greek symbols | = | |
| ρ | = | density (kg/m3) |
| τ | = | viscous stress (N/m2) |
| λ | = | thermal conductivity (W/mK) |
| ϕ | = | volume fraction of nanoparticles |
| μ | = | dynamic viscosity (kg/ms) |
| ν | = | kinematic viscosity (m2/s) |
| σ | = | turbulent Prandtl numbers |
| ε | = | turbulent dissipation rate (m2/s3) |
| Subscripts | = | |
| b | = | bulk parameter |
| bf | = | base fluid |
| eff | = | effective parameter |
| k | = | turbulent kinetic energy |
| nf | = | nanofluid |
| p | = | particle |
| pc | = | pseudo-critical value |
| t | = | turbulence |
| T | = | temperature |
| w | = | wall |
| ε | = | turbulent dissipation rate |
| 0 | = | inlet |
Nomenclature
| cp | = | constant-pressure heat capacity (J/kgK) |
| D | = | diameter of the cooling tube (mm) |
| et | = | total energy (J/kg) |
| f | = | friction factor |
| G | = | turbulent generation term |
| hc | = | convective heat transfer coefficient (W/m2K) |
| k | = | turbulent kinetic energy (J/kg) |
| Nu | = | Nusselt number |
| p | = | pressure (Pa) |
| qw | = | wall heat flux (W/m2) |
| r | = | radial coordinate (mm) |
| Re | = | Reynolds number |
| T | = | temperature (K) |
| u | = | velocity (m/s) |
| x | = | axial coordinate along the flow direction (mm) |
| Y | = | mass fraction |
| Greek symbols | = | |
| ρ | = | density (kg/m3) |
| τ | = | viscous stress (N/m2) |
| λ | = | thermal conductivity (W/mK) |
| ϕ | = | volume fraction of nanoparticles |
| μ | = | dynamic viscosity (kg/ms) |
| ν | = | kinematic viscosity (m2/s) |
| σ | = | turbulent Prandtl numbers |
| ε | = | turbulent dissipation rate (m2/s3) |
| Subscripts | = | |
| b | = | bulk parameter |
| bf | = | base fluid |
| eff | = | effective parameter |
| k | = | turbulent kinetic energy |
| nf | = | nanofluid |
| p | = | particle |
| pc | = | pseudo-critical value |
| t | = | turbulence |
| T | = | temperature |
| w | = | wall |
| ε | = | turbulent dissipation rate |
| 0 | = | inlet |