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Multiphase Flows with Droplets and Particles
Published in Greg F. Naterer, Advanced Heat Transfer, 2018
Another important process during droplet evaporation is called Stefan flow. Although it will be neglected in this analysis, Stefan flow becomes significant at high evaporation rates. It can be included by adding it to above equation and/or correcting the heat and mass transfer coefficients. Stefan flow is a transport process involving the movement of chemical species by the gas flow due to production or removal of species at an interface. The Stefan flux is different than Fick's law (Chapter 1) but has the same dependence on a concentration gradient in the gas stream. When some of the liquid droplet evaporates into vapor at the surface of the droplet, it flows away from the droplet when it is displaced by additional vapor evaporating from the droplet. At high evaporation rates, the total transport of species during the evaporation process is a sum of both Fickian diffusion and Stefan flow.
Heat and Mass Transfer
Published in Raj P. Chhabra, CRC Handbook of Thermal Engineering Second Edition, 2017
Robert F. Boehm, Swati A. Patel, Raj P. Chhabra, George D. Raithby, K.G. Terry Hollands, Anoop K. Gupta, N.V. Suryanarayana, Thomas F. Irvine, Massimo Capobianchi, Michael F. Modest, Van P. Carey, John C. Chen, Vasilios Alexiades, Jan Kośny, Anthony F. Mills
Net mass transfer across a surface results in a velocity component normal to the surface, and an associated convective flux in the direction of mass transfer. This convective flow is called a Stefan flow. The solutions of a number of mass transfer problems, involving a Stefan flow induced by the mass transfer process itself, follow. When necessary to obtain an analytical result, properties are assumed constant. Thus, use of these results requires evaluation of properties at a suitable reference state.
Preliminary Modeling of Chloride Deposition on Spent Nuclear Fuel Canisters in Dry Storage Relevant to Stress Corrosion Cracking
Published in Nuclear Technology, 2022
Philip J. Jensen, Sarah Suffield, Christopher L. Grant, Casey Spitz, Brady Hanson, Steven Ross, Sam Durbin, Charles Bryan, Sylvia Saltzstein
Stefan flow acts similarly to diffusiophoresis in that it arises from a concentration gradient. Stefan flow is an additional case when diffusion is concerned with the transfer of a condensable vapor through a noncondensable gas toward a condensing surface or away from an evaporating surface. Under such circumstances, a secondary macroscopic flow is established within the gas, known as Stefan flow, which arises from a subtle mass balance between the diffusive flows of the gas and the water vapor. The direction of Stefan flow is always away from an evaporating surface or toward a condensing surface. Therefore, the motion of the particles is determined by the combined action of Stefan flow and diffusiophoresis.14,21 Since this mechanism can act in opposition to thermophoresis and diffusiophoresis, it may be considered important in ISFSI deposition modeling. Both diffusiophoresis and Stefan flow should be considered for ISFSI deposition modeling, but further analysis into particle distributions, as well as condensation and evaporation expectations within a dry storage system, could determine that these two mechanisms are less prevalent than others.