http://orcid.org/0000-0001-7991-155X
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ABSTRACT
The Direct Simulation Monte Carlo (DSMC) method is widely used to study the flow characteristics of subsonic flow in 2-D microchannels. It is seen from existing numerical studies that the temperature of the flow decreases towards the exit of the microchannel whereas such a drop has not been reported in experimental studies. To resolve this discrepancy, effect of flow parameters such as Knudsen number, aspect ratio and pressure ratio on temperature change is studied systematically using an in-house developed DSMC code. Based on the parametric analysis, a correlation for temperature drop is proposed which predicts the DSMC data within ±15%. A control volume analysis is further carried out to understand the reason for temperature drop in microchannels. The effect of mass diffusion is also modeled. It is found that accounting for mass diffusion improves prediction of mass flow rate but not temperature drop across the microchannel.
Nomenclature
| A | = | area |
| AR | = | aspect ratio |
| D | = | coefficient of diffusion |
| d | = | molecular diameter |
| H | = | height |
| h | = | enthalpy |
| kB | = | Boltzmann constant |
| Kn | = | Knudsen number |
| L | = | length |
| m | = | molecular mass |
| ṁ | = | mass flow rate |
| n | = | number density |
| P | = | pressure |
| PR | = | pressure ratio |
| R | = | specific gas constant |
| Re | = | Reynold’s number |
| T | = | temperature |
| ΔT | = | temperature drop |
| u | = | velocity in x direction |
| V | = | velocity |
| x | = | transverse to wall |
| y | = | normal to wall |
| Γ | = | diffusive flux |
| λ | = | mean free path |
| ρ | = | density |
| σ | = | tangential momentum accommodation coefficient |
| τ | = | shear stress |
| Subscripts | = | |
| c | = | cross sectional |
| g | = | gas |
| i | = | inlet |
| o | = | outlet |
| s | = | surface |
| w | = | wall |
Nomenclature
| A | = | area |
| AR | = | aspect ratio |
| D | = | coefficient of diffusion |
| d | = | molecular diameter |
| H | = | height |
| h | = | enthalpy |
| kB | = | Boltzmann constant |
| Kn | = | Knudsen number |
| L | = | length |
| m | = | molecular mass |
| ṁ | = | mass flow rate |
| n | = | number density |
| P | = | pressure |
| PR | = | pressure ratio |
| R | = | specific gas constant |
| Re | = | Reynold’s number |
| T | = | temperature |
| ΔT | = | temperature drop |
| u | = | velocity in x direction |
| V | = | velocity |
| x | = | transverse to wall |
| y | = | normal to wall |
| Γ | = | diffusive flux |
| λ | = | mean free path |
| ρ | = | density |
| σ | = | tangential momentum accommodation coefficient |
| τ | = | shear stress |
| Subscripts | = | |
| c | = | cross sectional |
| g | = | gas |
| i | = | inlet |
| o | = | outlet |
| s | = | surface |
| w | = | wall |
Acknowledgements
The authors are grateful to National PARAM Yuva II Supercomputing Facility (NPSF), Centre for Development of Advanced Computing (C-DAC), Pune, India.