Moisture content and residence time distributions in mixed-flow grain dryers

• Published in: Biosystems engineering 2011-08, Vol.109 (4), p.297-307
• Main Authors: Mellmann, J., Iroba, K.L., Metzger, T., Tsotsas, E., Mészáros, C., Farkas, I.
• Format: Article
• Language: English
• Subjects: Agricultural machinery and engineering; Agronomy. Soil science and plant productions; air; Air ducts; Biological and medical sciences; Driers; Drying; energy; Fundamental and applied biological sciences. Psychology; Generalities. Biometrics, experimentation. Remote sensing; grain dryers; Grains; Moisture content; Pilots; Residence time distribution; Simulation; temperature; water content
• ISSN: 1537-5110; 1537-5129
• DOI: 10.1016/j.biosystemseng.2011.04.010

Unfavourable designs of mixed-flow grain dryers can cause inappropriate residence time distributions, locally different drying conditions and, hence, inhomogeneous drying. To study the effect of design elements and different air duct arrangements, residence time experiments, grain drying experiments and discrete element simulations were conducted both at pilot and industrial scale. These investigations revealed that present dryer designs give broad distributions of residence time, moisture content, and grain temperature. This is a consequence of different drying histories for individual grains. This variation is mainly influenced by the air duct arrangement applied but is affected by other structural and operating parameters as well. Uneven drying is one of the main reasons for elevated energy demands which are still comparatively high in mixed-flow dryers. A future goal will be to develop improved designs of mixed-flow dryers. Unfavourable designs of mixed-flow dryers can cause inappropriate moisture content and residence time distributions and, hence, inhomogeneous grain drying. To study the effect of different air duct arrangements, drying and residence time experiments as well as discrete element simulations on particle flow were conducted both at pilot and industrial scale dryers. As was demonstrated, especially the classical horizontal air duct arrangement caused high fluctuations of the grain moisture content over the cross-section. The future goal will be to develop new, better designs. [Display omitted] ► The effect air duct arrangements on the evenness of mixed-flow grain drying was investigated. ► Predicted and/or measured moisture content, temperature and residence time distributions were evaluated. ► The horizontal air duct arrangement caused high fluctuations in moisture content. ► The goal is to develop designs to improve product quality and to increase energyefficiency.