Calculation of Equivalent Aerosol Particle Mobility in Different Mixtures of Gases Used to Study Convective Transport in Airways

ABSTRACT

Aerosol particles of minimal intrinsic mobility can be used to trace convective motion in a gaseous medium. Intrinsic panicle mobility is the combination of inertial motion and diffusion by Brownian motion. Mobility of particles in different gas mixtures depends on the values of viscosity, pressure, temperature, and the exact composition of the gas mixture. Equivalent particle mobility allows the direct comparison of particle transport through the intricate structure of the respiratory airways with different mixtures of gases. The geometric particle diameter for which mobility is equal in two different gas mixtures is calculated with consideration of the kinetic theory of gases. Size of the equivalent particle mobility diameter is very sensitive to the precision of variables, and the definitive formula of the calculation. A critical part of this calculation is the formulation of the mean free path. Different methods of this formulation can result in substantially different values. A method of calculation is presented as a proposed standard method of aerosol mobility calculation for studies of convective transport in airways of the lung and other conditions where empirical values of gas viscosity are known.