Influence of Pore Size Distribution on Drying Behaviour of Porous Media by a Continuous Model

To my parents i Acknowledgements I would like to express my deepest gratitude to my principal supervisor Prof. Dr.-Ing. habil. Evangelos Tsotsas for his outstanding advices and support. I wish to express my deep thanks to my co-supervisor Dr. Thomas Metzger and his wife Mrs. Nicole Metzger not only for their very important guidance, constant encouragement to my scientific progress but also for the great help that I have received during the course of PhD work. for their very interesting documents and discussions about their model. I wish to express my sincere thanks to the president and members of the board for their comments and for agreeing to evaluate my thesis. for their help, support and encouragement. Thanks to all my friends, who I could not all mention by their name here, for their moral support and advice. Last but not least, I dedicate this work to my parents. I express my deep gratitude to my parents and my family members for their love, care and encouragement during the difficult time I was far away, which gave me determination to finish. ABSTRACT Being one of the most complex processes encountered in engineering, the drying of porous media has a vital role in many different industrial fields. In principle, the transport phenomena in the drying of porous media can be modeled using a continuous or discrete approach. The continuous approach is based on a description of the system as a fictitious continuum by using effective coefficients of heat and mass transfer. In the discrete approach the drying of porous media is represented by a network of pores and transport phenomena are directly described at the pore level. In developing a continuous drying model, the volume averaging technique can be used to derive a system of macroscopic transport equations from a set of basic transport laws at microscopic level for gas, liquid and solid phases. The derived system represents the conservation equations of mass, energy and momentum, in which the average state variables (moisture content, temperature and gas pressure) and a set of effective parameters are employed. These effective parameters have strong effects on the material drying characteristics and must be determined experimentally or must be modeled with a great care about the material microscopic structure. In general, the problem of determining the model effective parameters is yet to be solved and deserves careful attention. These parameters are capillary pressure curve, liquid …