Modified multi-component gas transport formulation with phoretic effects

Abstract

The understanding of multicomponent mass transport processes is essential for modeling and optimization of many systems, such as fuel cells. The understanding of individual species behavior becomes quite significant at micro-nano scales, where average mixture models are not very accurate. Also at micro-nano scales, additional phoretic transport is present due to strong local temperature and pressure gradients, which is discussed by Chakraborty and Durst (Phys Fluids 19(8):088104-01–088104-04, 2007). To account for multicomponent mass transport, recently proposed mass transport model by Kerkhof and Geboers (AIChE J 51(1):79–121, 2005), provides a way to look into individual components. This article presents extended multicomponent mass transport equations for micro-nano scales within continuum region. The Kerkhof–Geboers theory and the modifications suggested by Chakraborty and Durst (2007) have been combined together to form a new set of equations. An extensive order of magnitude analysis has been done on the modified equations. The application of new equations to different problem situations has also been discussed. It is shown that at very small length scales and for highly diffusive transport, the phoretic transport dominates the system, thus rendering the conventional equations erroneous.