Latent-To-Sensible Heat Conversion Kinetics During Nanoparticle Coalescence

ABHILASH OJHA, Tomoya Tamadate, Christopher J. Hogan, University of Minnesota

     Abstract Number: 70
     Working Group: Aerosol Physics

Abstract
Coagulational growth in aerosols is a multi-step process involving collision followed by coalescence. Previous studies have explored coalescence kinetics using atomistic simulations of nanoclusters, often assuming the process to be completely isothermal or at constant energy. However, during coalescence, new bonds form, which lowers the potential energy and increases the kinetic energy. The evolution of this internal kinetic energy depends not only on the coalescence itself but also on heat transfer to the surrounding gas.

In this work, we develop and validate a model that predicts the evolution of internal kinetic energy in nanoclusters formed by collisions in the presence of a background gas. We show that the dynamics of kinetic energy follow a power-law relationship that links latent heat release to sensible heating and involves a modified thermal accommodation coefficient. We tested the model against atomistic simulations of $1.5text{–}3.0$ $nm$ gold nanocluster coalescence in argon and helium environments. The model shows excellent agreement with the simulations across all tested conditions. Our results reveal that nanocluster temperatures can rise by several hundred Kelvin due to coalescence. However, the rate and extent of kinetic energy changes depend strongly on the surrounding gas. Finally, we use this model to predict how temperature evolves during sintering for different cluster sizes and to estimate the thermal accommodation coefficient in various gas environments.