Increase in thermophoretic velocity of carbon aggregates as a function of particle size

• We use a new device for measuring carbon aggregates׳ thermophoresis.
• Results show an increase in thermophoretic velocity with aggregate size.
• Results show discrepancy in comparison with spherical particles.
• Thermophoresis of aggregates is correlated with the number of primary particles.
• Results confirm for the first time Mackowski׳s Monte-Carlo simulations.

The Radial Flow Thermophoretic Analyser developed by Brugière et al. (2013) is used to measure the thermophoretic velocity of carbon nanoparticle aggregates produced by combustion with a propane/air diffusion flame. This work is carried out within the scope of the evaluation of aerosol deposition by thermophoresis for nuclear power plant fire risk assessment purposes.Thermophoretic velocity measurements are performed on monodisperse particles with electrical mobility diameters ranging from 30 nm to 600 nm and for a temperature gradient equal to 50 750 K/m. The results obtained show an increase in thermophoretic velocity as a function of the mobility diameter, contrary to what is observed for spherical particles in the transition regime.When the thermophoretic velocity is expressed as a function of the number of primary particles making up the aggregates, a good agreement is found with the experimental results of Messerer et al. (2003). Measurements performed with the Radial Flow Thermophoretic Analyser show, for the first time, an increase in the thermophoretic velocity of carbon aggregates as a function of the number of primary particles, in qualitative agreement with the Monte Carlo simulation results of Mackowski (2006).