The drying process of the wet material, especially the thermal drying process, is essentially a coupled transfer of heat and mass. On the one hand, the material absorbs heat from the drying medium, ie the heat is transferred from the outside to the inside of the wet material; on the other hand, the moisture inside the wet material is transferred from the inside to the outside until the moisture content of the wet material is reduced to meet the process requirements. . Therefore, the heat and mass transfer process in the boundary layer of the fluid inside and around the solid material is one of the most important issues in the study of the drying process.
According to the division of Luikov, the dried wet solids can be divided into three categories, namely: typical colloids, typical capillary porous media and colloidal capillary porous media. Porous media are widely found in various fields of the national economy. Rocks, minerals, ceramics, building materials, insulation materials, catalysts, roots and leaves of plants, and various agricultural products and foods are all categories of porous media. It can be said that porous media is the main object facing industrial drying technology.
It is necessary to pay attention that the theory and development history of the wet migration of solid materials in the drying process and the main theories and models of the moisture transfer in solid materials are becoming the supporting systems for the development of drying technologies, including the traditional continuous medium hypothesis model. And in order to overcome their deficiencies in the description of the characteristics of mesostructures, the volume average theory applied to porous media was established. In addition, the trend of drying theory research for more than a decade, especially the use of the results of neighboring disciplines to reveal the main viewpoints and respective characteristics of various continuum hypothesis models for the migration of solids during the drying process, Pointed out the shortcomings and defects of the continuum hypothesis theory, which also includes the pore network model, multi-scale methods, and the application prospect of the fractal theory in the process of moisture migration in dry and wet porous media. These studies are crucial to the development of the drying industry. .
Compared with the assumption of continuous medium migration theory, the pore network model method can be said to be a revolution in the theory of drying theory. It aims at the mesoscale structure of porous media and seeks to explore the relationship between the microstructural characteristics of porous media and macroscopic transmission phenomena. With the deepening of research, the Kongdao network method will also play a greater role. The multi-scale method has been applied in many fields, especially in the solution of complex system problems with other methods incomparable advantages. Based on the analysis of the morphological characteristics and internal thermal mass transfer characteristics of porous media, the author believes that it is feasible to introduce a multi-scale method for drying porous media. Dry multi-scale research should be based on the classification of scales and the representative methods on each scale, using a scale synthesis method, with multi-scale information fusion as the ultimate goal. The pore network theory and fractal theory will be an effective method for scale synthesis. Fractal geometry is also a new method that has made great achievements in many fields of application. It also has a broad application prospect in the field of porous media drying.
According to the division of Luikov, the dried wet solids can be divided into three categories, namely: typical colloids, typical capillary porous media and colloidal capillary porous media. Porous media are widely found in various fields of the national economy. Rocks, minerals, ceramics, building materials, insulation materials, catalysts, roots and leaves of plants, and various agricultural products and foods are all categories of porous media. It can be said that porous media is the main object facing industrial drying technology.
It is necessary to pay attention that the theory and development history of the wet migration of solid materials in the drying process and the main theories and models of the moisture transfer in solid materials are becoming the supporting systems for the development of drying technologies, including the traditional continuous medium hypothesis model. And in order to overcome their deficiencies in the description of the characteristics of mesostructures, the volume average theory applied to porous media was established. In addition, the trend of drying theory research for more than a decade, especially the use of the results of neighboring disciplines to reveal the main viewpoints and respective characteristics of various continuum hypothesis models for the migration of solids during the drying process, Pointed out the shortcomings and defects of the continuum hypothesis theory, which also includes the pore network model, multi-scale methods, and the application prospect of the fractal theory in the process of moisture migration in dry and wet porous media. These studies are crucial to the development of the drying industry. .
Compared with the assumption of continuous medium migration theory, the pore network model method can be said to be a revolution in the theory of drying theory. It aims at the mesoscale structure of porous media and seeks to explore the relationship between the microstructural characteristics of porous media and macroscopic transmission phenomena. With the deepening of research, the Kongdao network method will also play a greater role. The multi-scale method has been applied in many fields, especially in the solution of complex system problems with other methods incomparable advantages. Based on the analysis of the morphological characteristics and internal thermal mass transfer characteristics of porous media, the author believes that it is feasible to introduce a multi-scale method for drying porous media. Dry multi-scale research should be based on the classification of scales and the representative methods on each scale, using a scale synthesis method, with multi-scale information fusion as the ultimate goal. The pore network theory and fractal theory will be an effective method for scale synthesis. Fractal geometry is also a new method that has made great achievements in many fields of application. It also has a broad application prospect in the field of porous media drying.
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