Description of fluid dynamics and coupled transports in models of a laminar flow diffusion chamber

Abstract

The aim of this study is to assess how much the results of nucleation experiments in a laminar flow diffusion chamber (LFDC) are influenced by the complexity of the model of the transport properties. The effects of the type of fluid dynamic model (the steady state compressible Navier-Stokes system for an ideal gas/parabolic profile approximation) and the contributions of the coupled terms describing the Dufour effects and thermodiffusion on the predicted magnitude of the nucleation maxima and its location were investigated. This study was performed on the model of the homogeneous nucleation of an n-butanol-He vapor mixture in a LFDC. The isothermal dependencies of the nucleation rate on supersaturation were determined at three nucleation temperatures: 265 K, 270 K, and 280 K. For this purpose, the experimental LFDC data measured by A. P. Hyvärinen et al. [J. Chem. Phys. 124, 224304 (2006)] were reevaluated using transport models at different levels of complexity. Our results indicate that the type of fluid dynamical model affects both the position of the nucleation maxima in the LFDC and the maximum value of the nucleation rate. On the other hand, the Dufour effects and thermodiffusion perceptibly influence only the value of the maximal nucleation rate. Its position changes only marginally. The dependence of the maximum experimental nucleation rate on the saturation ratio and nucleation temperature was acquired for each case. Based on this dependence, we presented a method for the comparison and evaluation of the uncertainties of simpler models' solutions for the results, where we assumed that the model with Navier-Stokes equations and both coupled effects taken into account was the basis. From this comparison, it follows that an inappropriate choice of mathematical models could lead to relative errors of the order of several hundred percent in the maximum experimental nucleation rate. In the conclusion of this study, we also provide some general recommendations concerning the proper choice and setting of the mathematical model of transport processes in the LFDC.

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

“…3 (left) illustrates the schematic of a current design-the laminar flow diffusion chamber (LFDC). 149,150 In a LFDC (or the laminar flow reactor tube (LFRT) 145,146 ), a particle free carrier gas (N 2 , H 2 , He, Ar) first flows through a high temperature saturator, where the carrier gas is saturated with the condensable of interest. The condensable vapor -carrier gas mixture may then be heated further to ensure no vapor condenses before the flow enters the cold zone.…”

Temperature-Dependent Diffusion of H2SO4 in Air at Atmospherically Relevant Conditions: Laboratory Measurements Using Laminar Flow Technique

“…These equations and the general operating principles of FLUENT are described in detail in [30][31][32][33]. It has to be noted that unlike the earlier studies, this work did not include the Fine Particle Model (FPM).…”