Homogeneous water nucleation in carbon dioxide–nitrogen mixtures: Experimental study on pressure and carrier gas effects

Abstract

New homogeneous nucleation experiments are presented at 240 K for water in carrier gas mixtures of nitrogen with carbon dioxide molar fractions of 5%, 15%, and 25%. The pulse expansion wave tube is used to test three different pressure conditions, namely, 0.1, 1, and 2 MPa. In addition, a restricted series of nucleation experiments is presented for 25% carbon dioxide mixtures at temperatures of 234 and 236 K at 0.1 MPa. As pressure and carbon dioxide content are increased, the nucleation rate increases accordingly. This behavior is attributed to the reduction in the water surface tension by the adsorption of carrier gas molecules. The new data are compared with theoretical predictions based on the classical nucleation theory and on extrapolations of empirical surface tension data to the supercooled conditions at 240 K. The extrapolation is carried out on the basis of a theoretical adsorption/surface tension model, extended to multi-component mixtures. The theoretical model appears to strongly overestimate the pressure and composition dependence. At relatively low pressures of 0.1 MPa, a reduction in the nucleation rates is found due to an incomplete thermalization of colliding clusters and carrier gas molecules. The observed decrease in the nucleation rate is supported by the theoretical model of Barrett, generalized here for water in multi-component carrier gas mixtures. The temperature dependence of the nucleation rate at 0.1 MPa follows the scaling model proposed by Hale [J. Chem. Phys. 122, 204509 (2005)].

Critical cluster composition from homogeneous nucleation data: application to water in carbon dioxide–nitrogen carrier gases

“…In , Luijten and van Dongen showed that nucleation phenomena of condensable vapors in a carrier gas can be considered as unary nucleation if x g,eq << (S − 1)∕S , with x g,eq the dissolved gas fraction in the bulk liquid. With a maximum carrier gas solubility x CO 2 ,eq < 0.038 in our experiments (see supplementary material of Campagna et al 2021), this condition was always fulfilled. For carrier gases with a much larger x g,eq , the full binary nucleation model applies (Looijmans et al 1995).…”

“…The experimental data (Campagna et al 2020a(Campagna et al , 2021 used for the analysis of the present work were carried out with the Pulse Expansion Wave Tube (PEWT). A schematic of the facility is reported in Fig.…”

“…In this way, knowing the thermodynamic conditions at the pulse (p and T), the supersaturation can be determined as S ≈ y 1 ∕y 1,eq , y 1,eq being dependent on (p, T, y 1 , y 2 , y 3 ) (Campagna et al 2021). A more extensive description of experimental methodology can be found in Campagna et al (2020aCampagna et al ( , b, 2021 For the analysis presented in this work, we use the homogeneous water nucleation experiments carried out in nitrogen and 0%, 5%, 15% and 25% of carbon dioxide, previously published by the authors (Campagna et al 2020a(Campagna et al , 2021. The tests were carried out at 240 K and three pressure conditions, 0.1 MPa, 1 MPa and 2 MPa.…”

“…3.2), which can be used in the case of unary as well as multi-component nucleation. Both methods will be applied to the experimental nucleation data of water-carbon dioxide-nitrogen mixtures at 240 K 1 and various pressures (0.1 MPa, 1 MPa and 2 MPa) and carbon dioxide molar fractions (0%, 5%, 15% and 25%) previously published by the authors (Campagna et al 2020a(Campagna et al , 2021. After careful parameterization of the nucleation data (Eqs.…”

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Knowledge on critical cluster composition is important for improving the nucleation theory. Thus, homogeneous water nucleation experiments previously carried out in nitrogen and 0%, 5%, 15% and 25% of carbon dioxide ( Campagna et al 2020a( Campagna et al , 2021 are analyzed. The tests were conducted at 240 K and 0.1 MPa, 1 MPa and 2 MPa.

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