Stable stratification alteration in a thermal diffusion cloud chamber

Abstract

Homogeneous nucleation rate measurements of 1-butanol in helium: A comparative study of a thermal diffusion cloud chamber and a laminar flow diffusion chamberThe influence of buoyant convection on the operation of the upward thermal diffusion cloud nucleation chamber J. Chem. Phys. 111, 8013 (1999); 10.1063/1.480274 Two-dimensional transport and wall effects in the thermal diffusion cloud chamber. II. Stability of operation J. Chem. Phys. 106, 624 (1997); 10.1063/1.473401 Two-dimensional transport and wall effects in the thermal diffusion cloud chamber. I. Analysis and operations criteriaThe formation of clouds resulting from the homogeneous condensation of vapor phase diluted in a background or carrier gas was studied numerically. The effect of the background gas on the nucleation process in a cloud chamber heated from below is discussed. The computations were performed using 1-propanol as the condensable gas and helium, hydrogen, nitrogen, and argon, respectively, as carrier gases. Results of the simulation conducted show that large differences appear in the cloud formation when operating with hydrogen or helium, and with argon or nitrogen for which the onset of convective motions are predicted. Therefore, the isothermal patterns and streamlines are similar to those obtained in the case of Rayleigh-Bénard instabilities. The influence of the thermal Rayleigh number on the nucleation process is also considered, and it is shown that supersaturation isolines exhibit complex distortions for supercritical thermal Rayleigh numbers. As a consequence, only small zones of important nucleation rate are observed.

Buoyancy-driven convective motion in a thermal diffusion cloud chamber using a water/helium mixture

“…However irregular roll patterns can be observed in a cylindrical container: the rolls arrange themselves naturally with their axis, whenever possible, perpendicular to the lateral boundary [21]. Indeed, Schaeffer et al [11] showed that the natural convection tends to increase maximum saturation. This is due to the fact that the Rayleigh-Bénard cells move the nucleation plane towards the upper plate.…”

“…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]). These effects have been examined numerically by Schaeffer et al [11] who used a 2D mass, heat and momentum numerical model to show that the choice of the carrier gas within the TDCC is of importance since an inappropriate choice can alter the nucleation processes. Quite recently, Ferguson et al [12] performed a similar analysis with lower molecular weight gases and with an emphasis on the effect of the total pressure on the TDCC operation.…”

Natural convection and wall condensation or evaporation in humid air-filled cavities subjected to wall temperature variations

“…It is shown that the mathematical model allows to properly predict the evolutions of the gas mixture properties from an initial state up to a well defined steady-state. However, these computations clearly display that too sharp increases or decreases in the wall temperature may lead to local supersaturations which are admissible provided they do not exceed the critical supersaturation corresponding to the local temperature within the cavity [21][22][23]. Table I.…”

Conjugate thermosolutal convection and condensation of humid air in cavities

“…Therefore, a numerical procedure based on a finite volume method could not converge properly in the framework of this assumption since the global mass conservation of the mixture is not satisfied. Dufour and Soret effects are assumed negligibly small and there is no fog formation inside the cavity [15]. There are no chemical reactions, heat dissipation or heat generation, and the radiative heat transfer in the cavity is neglected.…”