Annals of the Assembly for International Heat Transfer Conference 13
ISBN |
ARTICLE:
F. Liu D. R. Snelling Gregory J. Smallwood ABSTRACT Recent studies of using the laser-induced incandescence (LII) technique for the determination of the thermal accommodation coefficients of carbon black and flame-generated soot showed that these values vary over a wide range, from 0.07 in flame to 1 in argon. These studies were critically evaluated in terms of the heat conduction model used in the data analysis and the laser fluence used in the experiments. The heat conduction plays a very important role in the accuracy of the inferred value of thermal accommodation coefficient and must be modelled accurately in such applications. The Fuchs model remains accurate in the entire range of Knudsen number even at large particle-to-gas temperature ratios and is recommended for LII applications. Our currently poor capability of modelling carbon sublimation induced by a high fluence laser pulse causes significant uncertainty in the derived thermal accommodation coefficient through the uncertainty in the particle size at the end of sublimation. Low-fluence LII is recommended to avoid such uncertainty. This evaluation of the recent LII experimental data in the literature found that the thermal accommodation coefficient of soot falls in a relatively narrow range between 0.22 (in flame) and 0.45 (in argon). Using the most advanced low-fluence LII model developed recently for polydisperse primary particles and aggregates with the shielding effect accounted for, this study found that the thermal accommodation coefficient of soot in flame is 0.37. EXP-01 pages |
||||||
download article