2014 Volume 56 Issue 175 Pages 67-73
Thermophoretic velocities in surrounding gas of argon, nitrogen, carbon dioxide, methane, or nitrous oxide are measured by means of microgravity experiments. Adopted particles are PMMA spheres with mean diameter of 2.91 µm. The temperature gradient is set at 10 K/mm while the pressure is set at several conditions in the range of 20 kPa to 100 kPa. Terminal velocities of particles suspended in a gas are individually measured. The residue values for all combination of accommodation coefficients are calculated from the obtained experimental results. Studies are made to determine the tangential momentum accommodation coefficient by assuming the thermal accommodation coefficient to be unity. Dependence of the coefficient on gas properties is investigated.
