Energy transfer between an aerosol particle and gas at high temperature ratios in the Knudsen transition regime

Motivated by the Laser-Induced Incandescence (LII) technique for in situ si zing of submicron aerosols, non-continuum heat transfer between an isolated , motionless, highly overheated spherical particle and its cooler surroundi ng gas is studied using the Direct Monte Carlo Simulation (DSMC) technique for the 'calibration' case of a monatomic, hard-sphere gas. We find that ou r numerical DSMC results are adequately described by a variable property ex tension of Fuchs' two-layer theory, whereas other interpolation formulae fa il in the Knudsen transition regime when the particle/gas temperature ratio is large. On this basis, tractable equations are provided which will permi t accurate estimates of the transition regime heat transfer coefficient for a polyatomic ideal gas with arbitrary temperature-dependent heat capacity and Fourier conductivity. (C) 1999 Elsevier Science Ltd. All rights reserve d.