Preface

Mass transfer in the multiphase multicomponent systems represents one of the most important problems to be solved in chemical technology, both in theoretical as well as practical point of view. In libraries all over the world, many books and articles can be found related to the mass transfer. Practically, all textbooks devoted to the separation processes or reaction engineering contain chapters describing the basic principles of the mass (and heat) transfer. It would be impossible (and also meaningless) to make the list of them; however, the most fundamental works of Bird, Steward and Lightfoot [1] and Taylor, Krishna and Wesseling, [2, 3, 4] have to be mentioned.

Unfortunately, the application of sophisticated theory still requires use of advanced mathematical apparatus and many parameters, usually estimated experimentally, or via empirical or semi-empirical correlations. Solving practical tasks related to the design of new equipment or optimizing old one is often very problematic. Prof. Levenspiel in his paper [5] wrote: "...*In science it is always necessary to abstract from the complexity of the real world....this statement applies directly to chemical engineering, because each advancing step in its concepts frequently starts with an idealization which involves the creation of a new and simplified model of the world around us. ...Often a number of models vie for acceptance. Should we favor rigor or simplicity, exactness or usefulness, the \$10 or \$100 model?"* 

Presented book offers several "engineering" solutions or approaches in solving mass transfer problems for different practical applications: measurements of the diffusion coefficients, estimation of the mass transfer coefficients, mass transfer limitation in the separation processes like drying extractions, absorption, membrane processes, mass transfer in the microbial fuel cell design, and problems of the mass transfer coupled with the heterogeneous combustion.

I believe this book will provide its readers with interesting ideas and inspirations or with direct solutions of their particular problems. To conclude, let me quote professor Levenspiel again: "*May I end up by suggesting the following modeling strategy: always start* 

#### XII Preface

*by trying the simplest model and then only add complexity to the extent needed. This is the \$10 approach."* 

**Jozef Markoš** 

Institute of Chemical and Environmental Engineering, Slovak University of Technology in Bratislava, Slovak Republic

### **References**

