Molecular dynamics (MD) simulations are performed to investigate the thermal and mass accommodation
coefficients (TAC and MAC, respectively) for the combination of iron(-oxide) and air. The obtained values
of TAC and MAC are then used in a point-particle Knudsen model to investigate the effect of chemisorption and the Knudsen transition regime on the combustion behavior of (fine) iron particles. The thermal
accommodation for the interactions of Fe with N2 and FexOy with O2 is investigated for different surface
temperatures, while the mass accommodation coefficient for iron(-oxide) with oxygen is investigated for
different initial oxidation stages ZO, which represents the molar ratio of O/(O + Fe), and different surface
temperatures. The MAC decreases fast from unity to 0.03 as ZO increases from 0 to 0.5 and then diminishes as ZO further increases to 0.57. By incorporating the MD-informed accommodation coefficients
into the single iron particle combustion model, the oxidation beyond ZO = 0.5 (from stoichiometric FeO
to Fe3O4) is modeled. A new temperature evolution for single iron particles is observed compared to
results obtained with previously developed continuum models. Specifically, results of the present simulations show that the oxidation process continues after the particle reaching the peak temperature, while
previous models predicting that the maximum temperature was attained when the particle is oxidized
to ZO = 0.5. Since the rate of oxidation slows down as the MAC decreases with an increasing oxidation
stage, the rate of heat loss exceeds the rate of heat release upon reaching the maximum temperature,
while the particle is not yet oxidized to ZO = 0.5. Finally, the effect of transition-regime heat and mass
transfer on the combustion behavior of fine iron particles is investigated and discussed.