Optimization of mixed flow dryers to increase energy efficiency

ABSTRACT

Agricultural driers are used for grain or maize drying with a limited annual operating time of about 100–1,000?h. To compensate the increasing costs of energy, permanent optimization of the drying process and the drying apparatus is necessary to increase energy efficiency. To attain higher energy efficiency, the drying potential of air should be fully utilized. The objective of this study is to investigate the medium flow in mixed flow dryers to identify adverse drying conditions. The investigation is based on experimental and numerical modeling and takes into account the bed motion (discrete element method) and the drying air flow (computational fluid dynamics). The results show superposition of a homogeneous air flow distribution with a particle flow profile, resulting in locally inhomogeneous residence time, different drying conditions, and ultimately uneven grain drying. Uneven drying is one of the main reasons for high energy consumption. Considering the results, a new mixed flow dryer geometry was developed which should equalize the drying process and thus be more energy efficient.