Editing Mass transfer (section)

==Chemical engineering==

Mass transfer finds extensive application in [[chemical engineering]] problems. It is used in reaction engineering, separations engineering, heat transfer engineering, and many other sub-disciplines of chemical engineering like electrochemical engineering.<ref>Electrochimica Acta 100 (2013) 78-84. https://doi.org/10.1016/j.electacta.2013.03.134</ref>

The driving force for mass transfer is usually a difference in [[chemical potential]], when it can be defined, though other [[thermodynamics|thermodynamic gradients]] may couple to the flow of mass and drive it as well. A chemical species moves from areas of high chemical potential to areas of low chemical potential. Thus, the maximum theoretical extent of a given mass transfer is typically determined by the point at which the chemical potential is uniform. For single phase-systems, this usually translates to uniform concentration throughout the phase, while for multiphase systems chemical species will often prefer one phase over the others and reach a uniform chemical potential only when most of the chemical species has been absorbed into the preferred phase, as in [[liquid-liquid extraction]].

While thermodynamic equilibrium determines the theoretical extent of a given mass transfer operation, the actual rate of mass transfer will depend on additional factors including the flow patterns within the system and the [[mass diffusivity|diffusivities]] of the species in each phase. This rate can be quantified through the calculation and application of [[mass transfer coefficient]]s for an overall process. These mass transfer coefficients are typically published in terms of [[dimensionless quantities|dimensionless numbers]], often including [[Péclet number]]s, [[Reynolds number]]s, [[Sherwood number]]s, and [[Schmidt number]]s, among others.<ref name="basictext">{{cite book
|title=Fundamentals of momentum, heat, and mass transfer
|edition=2
|first1=James R.
|last1=Welty
|first2=Charles E.
|last2=Wicks
|first3=Robert Elliott
|last3=Wilson
|publisher=Wiley
|year=1976
|isbn=9780471022497
|url=https://books.google.com/books?id=hZxRAAAAMAAJ}}
</ref><ref name="BSL">{{cite book|title=[[Transport Phenomena (book)|Transport Phenomena]]|edition=2|first1=R.B.|last1=Bird|first2=W.E.|last2=Stewart|first3=E.N.|last3=Lightfoot|publisher=Wiley|year=2007}}</ref><ref name="TaylorKrishna">{{cite book|title=Multicomponent Mass Transfer|first1=R.|last1=Taylor|first2=R.|last2=Krishna|publisher=Wiley|year=1993}}</ref>