Trott Wayne M, Castañeda Jaime N, Torczynski John R, Gallis Michael A, Rader Daniel J
Engineering Sciences Center, Sandia National Laboratories, Albuquerque, New Mexico 87185-0826, USA.
Rev Sci Instrum. 2011 Mar;82(3):035120. doi: 10.1063/1.3571269.
An experimental apparatus has been developed to determine thermal accommodation coefficients for a variety of gas-surface combinations. Results are obtained primarily through measurement of the pressure dependence of the conductive heat flux between parallel plates separated by a gas-filled gap. Measured heat-flux data are used in a formula based on Direct Simulation Monte Carlo (DSMC) simulations to determine the coefficients. The assembly also features a complementary capability for measuring the variation in gas density between the plates using electron-beam fluorescence. Surface materials examined include 304 stainless steel, gold, aluminum, platinum, silicon, silicon nitride, and polysilicon. Effects of gas composition, surface roughness, and surface contamination have been investigated with this system; the behavior of gas mixtures has also been explored. Without special cleaning procedures, thermal accommodation coefficients for most materials and surface finishes were determined to be near 0.95, 0.85, and 0.45 for argon, nitrogen, and helium, respectively. Surface cleaning by in situ argon-plasma treatment reduced coefficient values by up to 0.10 for helium and by ∼0.05 for nitrogen and argon. Results for both single-species and gas-mixture experiments compare favorably to DSMC simulations.
已开发出一种实验装置，用于确定多种气体 - 表面组合的热适应系数。主要通过测量由充气间隙隔开的平行板之间传导热通量的压力依赖性来获得结果。测量的热通量数据用于基于直接模拟蒙特卡罗（DSMC）模拟的公式中，以确定系数。该组件还具有使用电子束荧光测量板间气体密度变化的补充功能。所研究的表面材料包括304不锈钢、金、铝、铂、硅、氮化硅和多晶硅。利用该系统研究了气体成分、表面粗糙度和表面污染的影响；还探索了气体混合物的行为。在没有特殊清洁程序的情况下，对于大多数材料和表面光洁度，氩气、氮气和氦气的热适应系数分别确定为接近0.95、0.85和0.45。通过原位氩等离子体处理进行表面清洁，氦气的系数值降低了高达0.10，氮气和氩气的系数值降低了约0.05。单物种和气体混合物实验的结果与DSMC模拟结果相比具有优势。
