Effects of Background Gases on the Homogeneous Nucleation of Vapors. 2

Heist, Richard H.; Ahmed, Junaid; Janjua, M. B. I.

doi:10.1021/j100001a056

Cited by 45 publications

(62 citation statements)

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“…Operating at total pressures as high as 40 bars, Heist and co-workers reported that S crit increased significantly with pressure and that the rate of increase depended on the carrier gas (H 2 , He, N 2 , Ar). 64,[226][227][228] Other experiments reported more modest effects for pressures at or below 1 atm. 229 These contradictory results spurred careful two-dimensional modeling studies of TDCCs 230,231 to determine the limits of stability within the chamber and to understand more fully the effect convection has on the derived values of S and T. Models show that high pressures in a TDCC can lead to buoyancy driven flow.…”

Section: What Is the Role Of The Carrier Gas?mentioning

confidence: 95%

Overview: Homogeneous nucleation from the vapor phase—The experimental science

Wyslouzil

Wölk

2016

The Journal of Chemical Physics

132

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Homogeneous nucleation from the vapor phase has been a well-defined area of research for ∼120 yr. In this paper, we present an overview of the key experimental and theoretical developments that have made it possible to address some of the fundamental questions first delineated and investigated in C. T. R. Wilson’s pioneering paper of 1897 [C. T. R. Wilson, Philos. Trans. R. Soc., A 189, 265–307 (1897)]. We review the principles behind the standard experimental techniques currently used to measure isothermal nucleation rates, and discuss the molecular level information that can be extracted from these measurements. We then highlight recent approaches that interrogate the vapor and intermediate clusters leading to particle formation, more directly.

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Section: What Is the Role Of The Carrier Gas?mentioning

confidence: 95%

Overview: Homogeneous nucleation from the vapor phase—The experimental science

Wyslouzil

Wölk

2016

The Journal of Chemical Physics

132

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“…In diffusion cloudchamber experiments, [1][2][3][4][5] for example, marked effects of carrier-gas pressure on the rate of nucleation and the critical supersaturation were seen. For a water/nitrogen system, however, a recent experiment 6 using a high pressure pulseexpansion wave tube demonstrated that when the nucleation rate is plotted as a function of conventional supersaturation ͑i.e., the ratio of the partial vapor pressure of the supersaturated vapor to the equilibrium vapor pressure of the pure component͒, the carrier-gas pressure effect is hardly discernible.…”

Section: Introductionmentioning

confidence: 99%

Effect of carrier-gas pressure on barrier to nucleation: Monte Carlo simulation of water/nitrogen system

Zeng

2001

The Journal of Chemical Physics

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Carrier gases are used in most nucleation experiments for releasing the latent heat generated during vapor condensation. In the analysis of experimental data it is often assumed that the carrier gas is inert and would not participate in the nucleation process of the target gas. Several recent nucleation experiments show that the influence of carrier gases to nucleation rate is not negligible under certain conditions. To gain more insight into the carrier-gas effect, we carry out Monte Carlo simulation to compute the free energy of formation of water clusters in the presence of a nitrogen carrier gas. At fixed temperature ͑240 K͒ and chemical potential, it is found that the barrier height to nucleation increases with the carrier-gas pressure. This barrier enhancement is attributed to the increase of equilibrium vapor pressure of water in the presence of carrier gas, which results in a decrease of supersaturation. It is also found that the simulation results are consistent with the binary-nucleation theorem.

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“…a TDCC with respect to buoyancy-driven convective motion, since it may finally yield a misleading rendering of the experimental results. Indeed, Heist et al [8,9] have shown that the presence of a non-condensable component (carrier gas) influences the clustering process, that the use of heavy carrier gases in a TDCC may influence the stable stratification of the vapor gas mixture with the non-condensable gas and may therefore lead to convection. Moreover, the heated chamber wall (the wall is heated to be kept clean of condensate) may cause a buoyancy driven convection that can propagate towards the center of the chamber and cause a motion of the gas mixture (Ferguson and Nuth [10]).…”

Section: Introductionmentioning

confidence: 99%