Drying System Designs: Global Balance and Costs

Abstract

When designing drying systems, heat and mass balance should be studied as well as constructing and operating costs. These designs, which differ by type of dryer, depend on the heat‐mass relationship. The heat and mass balance on drying systems depend on the type of dryer, the drying process and the drying rate. One of the biggest problems involving dryers’ selection consists in obtaining the required quality of the product with a great variety of drying equipments and processes. Many methods are presented in literature, those based on phenomenological concepts and those based on cost aspects. Consequently the criteria to classify and design dryers are also in a large number and different for each drying system. Drying system simulation models can also be used to design the dryer. Equations for dryer designs and the costs and area calculations are presented to help food engineers. The case study with specific software using these equations will be presented in future articles. PRACTICAL APPLICATIONS In order to increase the aggregate value of food products, research in the area of dehydration has been widely extended to search products with few alterations in their sensorial and nutritional characteristics. Drying is one of the oldest and usual unit operations employed in industrial processes. The drying rate is so small for biological materials compared with other materials that they require a longer drying time. This long drying time induces to high drying cost. Therefore, the understanding of the drying system, process and equipment, is essential for food engineers to design an optimized drying system. Among the contributions that technological advances did to the understanding of drying systems, one is the improvement of computational methods. The progress in computer science and conveniences created by the personal computer, as well as the applications of drying process simulation with drying mathematical models are essential.