Abstract
Non-uniform moisture content distribution of grains at the discharge of Mixed-Flow Grain Dryers is one of the sources of product quality loss during subsequent storage. Unfavorable design of this kind of dryers may cause uneven residence times of single grain portions resulting in non-uniform drying. It is then of paramount importance to understand the physical phenomena that control the flow of grains in a mixed-flow dryer to guarantee their quality and minimize the risk of quality loss and waste of energy, thereby optimizing the process drying condition. With this objective, a two dimensional simulation model for the grain mass flow in a mixed-flow dryer based on Discrete Element Method (DEM) has been developed. The influences of the side walls and air ducts on solids mass flow were studied by evaluating the residence time distribution (RTD), particle velocity profiles and particle trajectories. The simulation results were validated with experiments using a semi-technical dryer test station with transparent Plexiglas front wall. The obtained results revealed the complexity of the drying process, the influences of the wall friction and half air ducts positioned directly on the wall on the bulk particle movement. Grains in mixed-flow dryers have different vertical velocities resulting in different residence times of every single portion of grains. The experimental validation confirms and verifies the DEM calculation ability for predicting particle flow.
Article PDF
Similar content being viewed by others
Explore related subjects
Discover the latest articles, news and stories from top researchers in related subjects.Avoid common mistakes on your manuscript.
Abbreviations
- A :
-
Cross-sectional area (m2)
- d :
-
Diameter (m)
- E :
-
Modulus of elasticity (Nm−2)
- k :
-
Stiffness (Nm−1)
- n :
-
Total number of time intervals, see (2)
- N :
-
Number
- \({\dot{N}}\) :
-
Dimensionless particle discharge rate
- P n :
-
Probability of tracer particles being discharged
- t :
-
Time (s)
- Δt :
-
Time interval (s)
- T m :
-
Mean residence time (s)
- x,y :
-
Cartesian coordinates (m, m)
- τ :
-
Dimensionless time
- B :
-
break-through
- cont :
-
continuous
- i :
-
current number of time interval
- m :
-
mean
- n :
-
normal
- P :
-
particle
- s :
-
shear
- st :
-
step
- t :
-
total
- TP :
-
tracer particle
References
Bruce D.M.: Simulation of multiple-bed concurrent-, counter-, and mixed-flow grain driers. J. Agric. Eng. Res. 30, 361–372 (1984)
Courtois F., Abud Archila M., Bonazzi C., Meot J.M., Trystram G.: Modeling and control of a mixed-flow rice dryer with emphasis on breakage quality. J. Food Eng. 49, 303–309 (2001)
Liu H., Zhang J., Tang X., Lu Y.: Fuzzy control of mixed-flow grain dryer. Dry. Technol. 21, 807–819 (2003)
Liu X., Chen X., Wu W., Zhang Y.: Process control based on principal component analysis for maize drying. Food Control 17, 894–899 (2006)
Cenkowski S., Miketinac M., Kelm A.: Airflow patterns in a mixed-flow dryer. J. Can. Agric. Eng. 32, 85–90 (1990)
Cao C.W., Yang D.Y., Liu Q.: Research on modeling and simulation of mixed-flow grain dryer. Dry. Technol. 25, 681–687 (2007)
Mellmann J., Richter I.-G., Maltry W.: Experiments on hot-air drying of wheat in a semi-technical mixed-flow dryer. Dry. Technol. 25, 1287–1295 (2007)
Kocsis, L., Teodorov, T., Mellmann, J., Gottschalk, K., Mészáros, C., Farkas, I.: Analysis of grain flow experiments in a mixed-flow grain dryer. In: Proceedings of the 17th World Congress of International Federation of Automatic Control (IFAC), pp. 1608–1612. Seoul, Korea, 6–11 July (2008)
Itasca Consulting Group, Inc.: PFC 2D, Version 3.1, Theory and Background Manual. Minneapolis, USA (2004)
Cundall, P.A.: A computer model for simulating progressive large scale movements in blocky rock systems. In: Proceedings of the Symposium of the International Society of Rock Mechanics, vol. 1, Paper No. II-8. Nancy, France (1971)
Cundall P.A., Strack O.D.: A discrete numerical model for granular assemblies. Geotechnique 29, 47–65 (1979)
Mankoc C., Janda A., Arévalo R., Pastor J.M., Zuriguel I., Garcimartín A., Maza D.: The flow rate of granular materials through an orifice. Granular Matter 9, 407–414 (2007)
Teufelsbauer H., Wang Y., Chiou M.-C., Wu W.: Flow-obstacle interaction in rapid granular avalanches: DEM simulation and comparison with experiment. Granular Matter 11, 209–220 (2009)
Bertrand F., Leclaire L., Levecque G.: DEM-based models for the mixing of granular materials. Chem. Eng. Sci. 60, 2517–2531 (2005)
Stewart R., Bridgwater J., Zhou Y., Yu A.: Simulated and measured flow of granules in bladed mixer—a detailed comparison. Chem. Eng. Sci. 56, 5457–5471 (2001)
Sykut J., Molenda M., Horabik J.: DEM simulation of the packing structure and wall load in a 2-dimensional silo. Granular Matter 10, 273–278 (2008)
Langston P.A., Matchett A.J., Fraige F.Y., Dodds J.: Vibration induced flow in hoppers: continuum and DEM model approaches. Granular Matter 11, 99–113 (2009)
Kruggel-Emden H., Wirtz S., Simsek E., Scherer V.: Modeling of granular flow and combined heat transfer in hoppers by discrete element method. J. Press. Vessel Technol. 128, 439–444 (2006)
Kwapinska M., Saage G., Tsostas E.: Mixing of particles in rotary drums: a comparison of discrete element simulations with experimental results and penetration models for thermal processes. Powder Technol. 161, 69–78 (2006)
Tsostas E., Kwapinska M., Saage G.: Modeling of contact dryers. Dry. Technol. 25, 1377–1391 (2007)
Iroba, K.L., Weigler, F., Mellmann, J., Metzger, T., Tsotsas, E.: Residence time distribution in mixed-flow grain dryers. Dry. Technol. 28 (2010), in press
Markauskas D., Kačianauskas R., Džiugys A., Navakas R.: Investigation of adequacy of multi-sphere approximation of elliptical particles for DEM simulations. Granular Matter 12, 107–123 (2010)
Luding S.: Cohesive, frictional powders: contact models for tension. Granular Matter 10, 235–246 (2008)
Itasca Consulting Group, Inc.: PFC 2D, Version 3.1, Augmented Fishtank, Minneapolis, USA (2004)
Sokhansanj S., Lang W.: Prediction of kernel and bulk volume of wheat and canola during adsorption and desorption. J. Agric. Eng. Res. 63, 129–136 (1996)
Mohsenin N.N.: Physical Properties of Plants and Animal Materials, Vol. 1. Gordon and Breach Science Publishers Inc, New-York (1970)
Kunibert M.: Transport, Umschlag, Lagerung in der Landwirtschaft. VEB Verlag Technik, Berlin (1983)
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Iroba, K.L., Mellmann, J., Weigler, F. et al. Particle velocity profiles and residence time distribution in mixed-flow grain dryers. Granular Matter 13, 159–168 (2011). https://doi.org/10.1007/s10035-010-0222-7
Received:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s10035-010-0222-7