We consider combined temperature- and concentration-driven convection in air during evaporation of a substance with molar mass exceeding molar mass of air. It is shown that some substances (butanol, naphthalene) can exhibit both downward and upward convective flow, depending on the surface temperature. Using heat and mass transfer analogy in numerical modeling and for interpretation of experimental results, obtained with background oriented schlieren technique, is discussed. We show that if the analogy conditions are satisfied, it is possible to obtain temperature and vapor concentration fields in good agreement with simulation results. If analogy conditions are violated, e.g. if additional boundary conditions are present, temperature and concentration contributions to measured refractive index field can not be separated.
47.80.Jk Flow visualization and imaging
Chair of Molecular Processes and Extreme Matter States, Faculty of Physics, M.V.Lomonosov Moscow State University, Moscow 119991, Russia.
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