Measurements of the temperature dependent diffusion coefficient of nanoparticles in the range of 295–600K at atmospheric pressure

Annular flow configuration with high deposition efficiency for the experimental determination of thermophoretic diffusion coefficients

“…(12)) have been chosen respectively as: 1.257, 0.40, and 0.55 (Friedlander, 2000), evaluated at room temperature. Recent studies (Rudyak, Dubtsov, & Baklanov, 2008;Rudyak, Dubtsov, & Baklanov, 2009) have shown that these coefficients, in the Cunningham-Millikan-Davies correlation, do not give satisfactory results beyond 350 K (77 1C). It should be noted, however, that under our experimental conditions, the thermophoretic migration takes place in the boundary layer of the cold wall (with temperature T c close to 5 1C), while the inlet/outlet average gas temperature remains lower than 56 1C.…”

Sulfur isotope fractionation during oxidation of sulfur dioxide: gas-phase oxidation by OH radicals and aqueous oxidation by H<sub>2</sub>O<sub>2</sub>, O<sub>3</sub> and iron catalysis

“…Nanoparticles in the size range of 2 nm will follow Brownian motion, like the sulfuric acid gas molecules, thus the wall loss calculation can be extended to estimate the loss of these ultrafine particles. The diffusion coefficient for 2 nm particles is ∼0.035 cm 2 s −1 (extrapolated from Rudyak et al (2009)), so the predicted wall loss will be >97 % in the two condensers. The actual wall loss will be considerably higher than predicted as turbulence and electrostatic attraction in the system will increase the frequency of collisions with the walls.…”

Reply to the comments on “Measurement of the temperature dependent diffusion coefficient of nanoparticles in the range of 295–600K atmospheric pressure”

“…Neglecting of polydispersity in Rudyak, Dubtsov, and Baklanov (2009) resulted in overestimation in the reported diffusion coefficient values by 10-15%. This difference, however, does not depend on the temperature in the range 300-600 K. However this decrease does not exceed the experimental error and, most importantly, the exponent of the T dependence remains almost unchanged.…”

“…The cited paper by Rudyak, Dubtsov, and Baklanov (2009) offers a new approximation function for the temperature dependence of the particle diffusion coefficient, based on systematic measurements with slightly polydispersed WO x and Pt nanoparticles of many different sizes (3.5, 4.4, 6.2, 6.5, 7.6, 8.7, 10.0, 18.0, 35, and 84 nm) in air or nitrogen at atmospheric pressure. The data show that neither the Cunningham-Maxwell-Davis (CMD) correlation nor the correlation given by Baron and Willeke (2001) describe the observed temperature dependence of the diffusion coefficient.…”

“…Note that the lognormal distributions shown in Fig. 3 of the original paper by Rudyak et al (2009) were for illustration only. One can see that the distributions were fairly narrow with a geometric standard deviation on the order of about 1.2 70.1.…”