Investigation of Rayleigh-Marangoni-Benard Convection Instability in a Two-layer System of Vapor-liquid

摘要

Evaporative convection and instability give rise to both scientific and technological interests. Practically, many industrial applications such as thin film evaporators, boiling equipments and heat pipes are concerned about the evaporation process, i.e., the heat and mass transfer through the gas-liquid interface. From a physical viewpoint, one of interesting questions is the mechanisms of convection instability in thin-liquid layers induced by the coupling of evaporation phenomenon and Marangoni effect at the mass exchanged interface. Until now, available theories, such as Rayleigh's theory, referred to as Rayleigh-Benard convection, and Pearson's theory, referred to as Marangoni-Benard convection, are unable to explain completely the convection in an evaporating liquid layer. The mechanism of evaporation convection needs to be studied both theoretically and experimentally. In previous works, most researches on Marangoni-Benard instability were carried out for single liquid phase systems, and the gas phase adjacent to the liquid layer was considered as passive. Colinet and Legros proposed a one-sided model with an evaporation surface similar to Pearson's model, and obtained the neutral stability curves of critical Marangoni number versus wavenumber for different values of Biot number. Chai et al studied experimentally the effects of evaporating on Marangoni-Benard convection in thin liquid layers evaporating at room temperature. Zhang and Chao proposed a modified Marangoni number to gauge the convection stability status both in evaporating liquid layers and in the liquid layers without evaporation. Liu et al proposed recently a two-sided theoretical model for a two-layer Marangoni-Benard system with an evaporating interface, as shown schematically in Fig.1. In this paper, we will present the influences of evaporation on the Marangoni -Benard convective instability for both non-deformable and deformable perturbed vapor -liquid interface.