P Paul Peeters

Nucleation at high pressure II: Wave tube data and analysis.

Nucleation rate data, obtained from expansion wave tube experiments, are reported for several vapor–gas mixtures at high pressure. Results are given for water–vapor in the presence of helium and nitrogen gas, and for n-nonane in helium and methane. For all these mixtures, carrier gas pressures of 10, 25, and 40 bar have been applied, with temperatures ranging from 230 to 250 K. An extended form of the nucleation theorem (in terms of the derivative of the nucleation rate with respect to carrier gas pressure) is derived, which appears to be very helpful in the interpretation of high pressure data. It can be used to obtain the carrier gas content of the critical nucleus directly from the pressure dependence of experimental nucleation rates. Combining this method with the theoretical considerations of part I of this paper [J. Chem. Phys. 111, 8524 (1999), preceding paper]: the nucleation behavior of water at high pressures of both helium and nitrogen can quantitatively be understood. For n-nonane in helium ou...

Transitional droplet growth and diffusion coefficients

The droplet growth models of Gyarmathy and Young, valid for arbitrary Knudsen numbers, are compared with experimental growth results obtained from expansion wave tube experiments. Growth experiments of n-pentanol in helium were performed at approximately 1 bar, resulting in growth curves stretching from the transition regime OKn11U to the continuum regimeOKn 1). Droplet growth experiments of water in helium and water in nitrogen were performed at elevated pressures, when the mean free path is small; hence, these growth curves are situated near the continuum regime. For Kn > 0.1, the Gyarmathy model appears to describe the experimental growth curves better than the Young model. However, for Kn < 0.02, the Young model gives the best results. For the water‐ helium and water‐nitrogen systems new experimental diAusion coeAcients are obtained, which are in good

The nucleation behavior of supercooled water vapor in helium

The nucleation behavior of supersaturated water vapor in helium is experimentally investigated in the temperature range of 200–240 K. The experiments are performed using a pulse expansion wave tube. The experimental results show a sharp transition in the nucleation rates at 207 K. We suggest that the transition is due to the transition of vapor/liquid to vapor/solid nucleation (ordered with decreasing temperature). A qualitative theoretical explanation is given based on the classical nucleation theory and the surface energy of ice.

Multi-component droplet growth. I. Experiments with supersaturated n-nonane vapor and water vapor in methane

Droplet growth rates of droplets suspended in methane gas and supersaturated water and/or n-nonane vapor are experimentally determined. The experiments are performed by applying the nucleation pulse principle using a modified shock tube. The droplets are optically detected using a combination of constant angle Mie scattering and light extinction measurements. From the analysis of the droplet growth rates in the binary systems the diffusion coefficients of water in methane and n-nonane in methane have been determined at two different conditions, being 11 bar and 242 K, and 44 bar and 247 K. The droplet growth rates in the ternary system have been determined at the same two conditions. From the analysis of these experiments it is evident that supersaturated water vapor does not condense onto n-nonane droplets while supersaturated n-nonane vapor does condense onto water droplets. This can be related to the wetting properties of liquid water on liquid n-nonane and vice versa.

Multi-component droplet growth. II. A theoretical model

A droplet growth model is formulated that describes the growth of homogeneous multi-component droplets suspended in a dilute gas–vapor mixture. The droplet is suspended in a real carrier gas, in which the vapors are diluted. The model is applicable for all Knudsen numbers. It is shown that the model can easily be extended to describe the growth of layered droplets. The model calculations are compared to the results of droplet growth experiments of supersaturated water and/or supersaturated n-nonane in methane. The model performs well for all the cases, except for the case when supersaturated n-nonane vapor is added to supersaturated water vapor in methane gas. In the latter case it is proposed that the discrepancies originate from the incomplete wetting of n-nonane on liquid water at the given conditions.

Homogeneous nucleation in high-pressure multi-component systems: Application to mixtures of N-alkanes

We present a new method of determining the formation energies of critical and near-critical clusters in multi-component systems and discuss the application to mixtures of n-alkanes, serving as a model of natural gas and derived mixtures.

Nucleation of water vapor in methane at high pressure

Preliminary experimental results of nucleation of water vapor in methane at high pressure are presented. The results are obtained by applying the nucleation pulse method, using a modified shock tube. The nucleation conditions were taken at two different temperatures (250 K and 240 K) and three different pressures (10 bar, 25 bar and 40 bar).