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ABSTRACT
Thermal mixing phenomena of a coaxial jet with perforated obstacles are analyzed both experimentally and numerically. Perforated obstacles are used in front of a coaxial jet that has different temperatures of the fluid to control the thermal mixing behavior. An experimental set-up was constructed to perform several cases and all cases are simulated by using large eddy simulation (LES) turbulence model. Results of the study presented that inserting perforated obstacle affects the mixing performance positively and the best mixing performance is obtained in the case that the obstacle has the highest permeability. Experimental and computational results were compared and a good agreement was obtained.
Nomenclature
| = | Constant pressure specific heat (kJ/kg · K) | |
| = | Density of fluid (kg/m3) | |
| = | Enthalpy (kJ/kg) | |
| = | Gravitational body force (kg · m/s2) | |
| = | Pressure (Pa) | |
| = | Thermal conductivity (W/m · K) | |
| = | Deviatoric part of rate-of-strain tensor | |
| = | Distance to the closest wall (m) | |
| = | Effective thermal conductivity (W/m · K) | |
| = | Filtered velocity component | |
| = | Gravitational acceleration (m/s2) | |
| = | Mixing length for sub grid | |
| = | Molecular viscosity (kg/m · s) | |
| = | Reference density (kg/m3) | |
| = | Stress tensor (N/m2) | |
| = | Subgrid Prandtl number | |
| = | Subgrid-scale stress (N/m2) | |
| = | Turbulent subgrid viscosity (kg/m · s) | |
| = | Velocity component (m/s) | |
| = | Volume of the computational cell (m3) | |
| = | Von Karman constant | |
| = | WALE constant | |
| ΔT | = | Temperature difference between hot and cold fluid (K) |
| ṁ | = | Mass flow rate (kg/s) |
| n | = | Number of jet |
| St | = | Standard deviation of fluid temperature |
| T | = | Temperature of fluid (K) |
| t | = | Time (s) |
Subscript
| = | Direction index (i = x, y or z) | |
| = | Direction index (j = x, y or z) | |
| avg | = | Average |
| c | = | Cold flow |
| h | = | Hot flow |
Funding
Authors thank the Scientific and Technological Research Council of Turkey (TUBITAK) for their valuable financial support with a project number 114M584.