Physical interpretation of solids drying: An overview on mathematical modeling research

There are successive interests in developing various mathematic models for the solids drying process. Such efforts have been made for nearly three decades since Luikov's system and Whitaker's theory. This article gives some physical interpretations of solid drying by reviewing more than 70 published papers in the past decades based on studies done by researchers. Classical transport theory in porous media is sufficient for dealing with the solids drying process at a fundamental level. Current numerical technique and computer technology are able to solve problems for any material geometry. These advancements seem to go faster than one's understanding of processes and materials. Almost all available models for solids drying can only be used for a specific material system. Generality of a model still remains a major problem due to the lack of fundamental data. Measurements of unknown properties and experimental validation of models need to be improved. The design, operation, and optimization of industrial dryers call for a comprehensive mathematic model that gives attention to accuracy, generality, and complexity/simplicity.