Pressure dependence of nucleation rates in binary systems

Abstract

The influence of carrier gas pressure on nucleation rates is not very well known. Diffusion cloud chamber experiments have shown that for the mixtures 1-propanol/helium and 1-propanol/hydrogen, nucleation rates depend on the pressure of the carrier gas in a nontrivial manner. Looijmans have studied the systems methane/n-nonane and methane/n-octane both theoretically and experimentally. They concluded that such systems have to be considered as binary, in the sense that both components actively contribute to the nucleation process. This chapter presents the new results that are obtained with the pulse-expansion wave tube designed by Looijmans. The technique is based on the nucleation pulse method. The tube can be operated at nucleation pressures in between 1 and 50 bar. Therefore, it can perfectly be used to study ambient pressure influence on nucleation behavior. It uses water/nitrogen as a model system to do so. A comparison is made between nucleation rates at pressures below 1 bar and higher pressures of 10, 25, and 40 bar, respectively. The nucleation rates obtained are compared with the predictions of classical nucleation theory.