Dense carrier gas effect in vapor phase nucleation

Новіков, В. М.; Васильев, О.В.; Reiss, Howard

doi:10.1103/physreve.55.5743

Cited by 15 publications

(12 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This can be explained by a large increase of the cross section for capture of molecules from the vapor due to the diffuse nature of the outer layer of the cluster and also as a result of its attractive potential. [39][40][41] This result re- emphasizes the fact that one should not expect an n 2/3 law for the ␥'s, but rather a linear increase of magnitude with n.…”

Section: Multimolecule Events Involve Clusters Evaluation Ofmentioning

confidence: 67%

Simulative determination of kinetic coefficients for nucleation rates

Schaaf

Senger

Voegel

et al. 2001

The Journal of Chemical Physics

View full text Add to dashboard Cite

A unimolecular evaporation model for simulating argon condensation flows in direct simulation Monte Carlo Phys. Fluids 21, 036101 (2009); 10.1063/1.3094957 Evaluating nucleation rates in direct simulationsNucleation kinetics can be formulated generally and rigorously as a set of master equations that govern the time evolution of the cluster distribution that underlies the observable rate process. However, this general formulation is only useful if the magnitudes of the coefficients that describe the loss and gain ͑evaporation and condensation͒ of molecules by a cluster are quantitatively known. Moreover, these coefficients can refer to multiple losses and gains of molecules ͑several molecules in a single step͒. In order to measure these coefficients accurately and efficiently, we have devised a molecular dynamics ͑MD͒ simulation that follows the development and equilibration of a single cluster in a small container ͑volume͒ that involves only a small number of molecules ͑in our case 216͒. There is evidence that such a system can provide a reliable picture of the behavior of a cluster in a larger system. This approach has been applied to supersaturated argon vapor at 85 K. In particular, we have been able to study the fluctuation in the size of the ''equilibrium'' cluster that develops in the small volume and, from these observations, to determine the evaporation and condensation coefficients. Besides yielding the values of these coefficients, the study has allowed us to establish several points, including the validity of detailed balance within the simulation, the importance of multimolecular losses and gains of molecules, and the intrinsic nature ͑nonimportance of the surrounding vapor͒ of the evaporation coefficients. Also, it is shown that the clusters disappear by a first order decay law, thus establishing the relevance of the linear form of the set of master equations that can be used to describe the nucleation process. It is also established, by our first estimates of the condensation coefficients, that they are an order of magnitude larger than those predicted by the simple molecular kinetic theory used in classical nucleation theory ͑CNT͒, suggesting the effects of the diffuse outer layers of the actual physical cluster and the role of the cluster's attractive potential. In addition, we have performed an analysis, involving the statistics of correlation, that strongly supports the idea that multimolecule losses and gains experienced by a cluster are chiefly due to the departure and arrival of smaller ''clusters.'' Finally, we have modeled the nucleation process in the small system, using CNT, and have found that in many respects CNT provides a good account of the phenomena observed by means of MD. Because of the ''intrinsic nature'' of the evaporation coefficient, it is possible to perform the simulations at quite high levels of supersaturation, thereby accelerating the approach to equilibrium, and requiring less computer capacity. The evaporation coefficient of the ''equilibrium cluster'' that forms the ...

show abstract

Section: Multimolecule Events Involve Clusters Evaluation Ofmentioning

confidence: 67%

Simulative determination of kinetic coefficients for nucleation rates

Schaaf

Senger

Voegel

et al. 2001

The Journal of Chemical Physics

View full text Add to dashboard Cite

show abstract

“…Kane and El-Shall 8 found that the carrier-gas effect observed in diffusion cloud chamber experiments arises from the slowdown of the dynamics of growth of the nuclei into detectable droplets. Reiss and co-workers [9][10][11] suggested that the carrier-gas effect may be due to the screening effect of a kinetic origin by which the drop's attractive potential is weakened by encounters of incoming molecules with other vapor or carrier-gas molecules.…”

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

View full text Add to dashboard Cite

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.

show abstract

“…As shown in Itkin and Kolesnichenko (1997) MNT succeeds in reproducing the difference in the nucleation rate for pure water vapor and moist air in the above mentioned experiments (Gorbunov et al 1984;Binnie and Woods 1938). Other authors try to associate the discussed phenomenon with nonisothermal effects (Ford 1992), the in uence of the background gas on the capture of vapor molecule by a drop (Novikov et al 1997), and some others. A group of researchers associate the in uence of the carrier gas with the transport processes in DCC.…”

Section: Introductionmentioning

confidence: 75%

“…It can be shown (see discussion at the end of this paper) that such a model predicts the in uence of the carrier gas pressure on the critical supersaturation in DCC, but the form of this dependence is far from the linear one observed in experiments. ² Another problem is concerned with the work of Novikov et al (1997). The authors of this paper take into account details of interaction between a droplet and a vapor molecule that results, in particular, in the disturbance of the Maxwell distribution of molecules over the ve-locity in the vicinity of the drop.…”

Section: Introductionmentioning

confidence: 99%

“…However, the steady state rate of nucleation which is used to estimate the effect of this interaction on the nucleation rate could be derived from the respective kinetic equation only under the assumption made that the distribution of both clusters and monomers is Maxwellian. Otherwise, it is also possible to present the steady nucleation rate in the usual form, as in Novikov et al (1997), but the rate constants now depend on the concentrations of monomers in a rather complex and, more importantly, implicit way. For instance, one can introduce a small correction to the Maxwell distribution, as is usually done when describing the Knudsen layer, and further try to solve analytically the corresponding kinetic equation in order to reveal an explicit form of the quasisteady equations for concentrations and the steady state rate of nucleation.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Kinetic Model of Effect of a Carrier Gas on Nucleation in a Diffusion Chamber

Itkin¹

2001

Aerosol Science and Technology

View full text Add to dashboard Cite

For the rst time a model of nucleation when a transport of condensing molecules to the cluster surface is determined by their diffusion through a carrier gas is proposed. The approach in use is strongly based on the microscopic theory of nucleation put forward by the author and allows an analytical representation of the cluster's concentrations through supersaturation, gas temperature, and carrier gas pressure, which is quite new. It is shown that usual conditions of experiments in diffusion cloud chambers meet the requirements of the model validity that means this model can be used to explain a mechanism of the carrier gas pressure in uence on the nucleation kinetics observed in experiments.

show abstract

Dense carrier gas effect in vapor phase nucleation

Cited by 15 publications

References 23 publications

Simulative determination of kinetic coefficients for nucleation rates

Simulative determination of kinetic coefficients for nucleation rates

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

Kinetic Model of Effect of a Carrier Gas on Nucleation in a Diffusion Chamber

Contact Info

Product

Resources

About