A computational investigation of noncontinuum gas-phase heat transfer between a heated microbeam and the adjacent ambient substrate
| Autor: | Michail A. Gallis, John Robert Torczynski, Daniel J. Rader |
|---|---|
| Rok vydání: | 2007 |
| Předmět: |
Argon
Metals and Alloys chemistry.chemical_element Thermodynamics Microbeam Mechanics Condensed Matter Physics Nitrogen Surfaces Coatings and Films Electronic Optical and Magnetic Materials chemistry Heat transfer Thermal Boundary value problem Direct simulation Monte Carlo Electrical and Electronic Engineering Instrumentation Microscale chemistry |
| Zdroj: | Sensors and Actuators A: Physical. 134:57-68 |
| ISSN: | 0924-4247 |
| DOI: | 10.1016/j.sna.2006.05.003 |
| Popis: | Noncontinuum gas-phase heat transfer in two microscale geometries is investigated computationally. The motivation is microscale thermal actuation produced by heating-induced expansion of a near-substrate microbeam in air. The first geometry involves a 1-μm microgap filled with argon or nitrogen and bounded by parallel solid slabs. The second geometry involves a heated I-shaped microbeam 2 μm from the adjacent ambient substrate, with nitrogen in between. Two computational methods are applied to the above. The Navier–Stokes slip-jump (NSSJ) method uses continuum heat transfer in the bulk gas and temperature jumps at the boundaries to treat noncontinuum effects. The Direct Simulation Monte Carlo (DSMC) method uses computational molecules to simulate noncontinuum gas behavior more rigorously. For the microgap, the heat-flux values from both methods are in good agreement for all pressures and accommodation coefficients except for intermediate pressures and near-unity accommodation coefficients, where differences up to 8% are observed. For the microbeam, both methods are in good agreement except for low pressures and near-unity accommodation coefficients, where differences up to a factor of 2 are observed in the heat-flux values. The causes of these discrepancies are explained in terms of noncontinuum gas behavior in the vicinity of solid surfaces, and modifications to the NSSJ temperature-jump boundary condition that improve agreement are presented. DSMC simulations of the microbeam are presented that show the steady gas motion produced by noncontinuum stresses in gases with nonparallel isotherms. |
| Databáze: | OpenAIRE |
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