chapter  6
20 Pages

- Modeling Thermal Processing Using Computational Fluid Dynamics (CFD)

In the food industry, thermal processing normally refers the processes that heat, hold, and cool a product sequentially, which is required to be free of food-borne illness for a desired period of time. There are many types of thermal processes; among them, pasteurization is a typical one, which reduces the potential of contamination of a special pathogenic microorganism to a predesigned extent. The product will still need to be refrigerated; otherwise, it will not be shelf stable. Sterilization is another example of thermal processes that leads to shelf-stable products in

6.1 Introduction .......................................................................................................................... 131 6.2 Basic Thermal Processing Parameters ................................................................................. 132

6.2.1 Decimal Reduction Time D ...................................................................................... 132 6.2.2 Thermal Resistance Constant Z ................................................................................ 133 6.2.3 Thermal Death Time F ............................................................................................. 134 6.2.4 Relationships between Chemical Kinetics and Thermal Processing Parameters ...... 134

6.3 Fundamental Conservation Equations for Computational Fluid Dynamics ........................ 134 6.3.1 Cartesian Coordinate System ................................................................................... 134 6.3.2 Cylindrical Coordinate System ................................................................................ 135

6.4 Boundary and Initial Conditions .......................................................................................... 136 6.4.1 Velocity Boundary Conditions ................................................................................. 136 6.4.2 Thermal Boundary Conditions ................................................................................. 136 6.4.3 Mass Transfer Boundary Conditions ........................................................................ 137

6.5 Solution Methods .................................................................................................................. 138 6.6 Worked Examples ................................................................................................................. 138 6.7 Recent CFD Applications in Thermal Processing ............................................................... 142

6.7.1 Drying Process ......................................................................................................... 143 6.7.2 Baking Process ......................................................................................................... 143 6.7.3 Ohmic Heating .......................................................................................................... 144 6.7.4 Other Applications .................................................................................................... 144

6.8 Conclusion ............................................................................................................................ 145 Nomenclature ................................................................................................................................. 145 Acknowledgment ........................................................................................................................... 146 References ...................................................................................................................................... 146

cans, soft containers, or bottles [1]. This process usually employs a much greater temperature than pasteurization.