Homogeneous nucleation rate measurements of 1-propanol in helium: The effect of carrier gas pressure

Abstract

Kinetics of homogeneous nucleation in supersaturated vapor of 1-propanol was studied using an upward thermal diffusion cloud chamber. Helium was used as a noncondensable carrier gas and the influence of its pressure on observed nucleation rates was investigated. The isothermal nucleation rates were determined by a photographic method that is independent on any nucleation theory. In this method, the trajectories of growing droplets are recorded using a charge coupled device camera and the distribution of local nucleation rates is determined by image analysis. The nucleation rate measurements of 1-propanol were carried out at four isotherms 260, 270, 280, and 290 K. In addition, the pressure dependence was investigated on the isotherms 290 K (50, 120, and 180 kPa) and 280 K (50 and 120 kPa). The isotherm 270 K was measured at 25 kPa and the isotherm 260 K at 20 kPa. The experiments confirm the earlier observations from several thermal diffusion chamber investigations that the homogeneous nucleation rate of 1-propanol tends to increase with decreasing total pressure in the chamber. In order to reduce the possibility that the observed phenomenon is an experimental artifact, connected with the generally used one-dimensional description of transfer processes in the chamber, a recently developed two-dimensional model of coupled heat, mass, and momentum transfer inside the chamber was used and results of both models were compared. It can be concluded that the implementation of the two-dimensional model does not explain the observed effect. Furthermore the obtained results were compared both to the predictions of the classical theory and to the results of other investigators using different experimental devices. Plotting the experimental data on the so-called Hale plot shows that our data seem to be consistent both internally and also with the data of others. Using the nucleation theorem the critical cluster sizes were obtained from the slopes of the individual isotherms and compared with the Kelvin prediction. The influence of total pressure on the observed isothermal nucleation rate was studied in another experiment, where not only temperature but also supersaturation was kept constant as the total pressure was changed. It was shown that the dependence of the nucleation rate on pressure gets stronger as pressure decreases.

Theoretical approaches to nucleation in the gas phase. With a glimpse at experiments and dust formation in astrophysics

“…For instance, most experiments have reported that the nucleation rate increases with decreasing total pressure, even if temperature and supersaturation ratios are both kept constant. This has been recently confirmed on measurements for the 1-propanol nucleation in helium gas [83], but is at variance with older experiments on n-butanol [87]. Needless to say, such effects induced by the environment should be taken into account when comparing experiment and theory, but they present significant additional difficulties.…”

“…(8), using appropriate values for the surface tension and liquid density. Remaining discrepancies of 20-40% in the critical size have been reported, depending on the nature of the fluid [81][82][83].…”

“…Many authors have addressed this issue, trying to get insight into the role of the carrier gas on the clustering process by varying the total pressure [83][84][85][86][87][88]. Unfortunately, pressure effects are far from being fully understood, and experimental results are somewhat contradictory.…”

Laboratory study of H₂SO₄/H₂O nucleation using a new technique – a laminar co-flow tube

“…According to Krejčí (2010), the saturators allow stable and repeatable saturated vapour generation in the range of parameters defined in Table 1. various devices is the mechanism used to achieve the supersaturated state of the system. The supersaturation can be reached by diffusion of the nucleating vapours (Ball et al, 1999;Benson et al, 2008;Benson et al, 2009;Berndt et al, 2010;Benson et al, 2011;Brus et al, 2011) or by cooling the vapours by either temperature gradient (Katz and Ostermier, 1967;Brus et al, 2005;Herrmann et al, 2010;Zollner et al, 2012;Travnickova et al, 2013) or adiabatic expansion (Wagner and Strey, 1981;Peters, 1982;Viisanen and Strey, 1994). The binary nucleation of H 2 SO 4 -H 2 O presents the most important atmospheric nucleation system (Benson et al, 2008).…”

Molecular dynamics of homogeneous nucleation in the vapor phase of Lennard-Jones. III. Effect of carrier gas pressure

“…However, the effect of the carrier-gas pressure on nucleation was not observed in previous experiments with the expansion cloud chambers. [6][7][8][9] Moreover, in some experiments the effect of the carrier gas pressure was shown to be negative, [1][2][3][4][5][10][11][12] that is, the carrier gas reduced the rate of nucleation, while in some other experiments the effect was shown to be positive. [13][14][15] The apparent conflicting results from different experiments called for more molecular-level investigations of the carrier-gas effect.…”