Teaching the processing of particles is very affective with the use of visual aids. Currently the best interactive equipment available for students is of the undergraduate laboratory experiments, (Hopper discharge, Level 1&2 Undergraduate Laboratory modules, Chemical and Process Engineering department, University of Surrey). However, this only allows two parameters to be changed (particle size and orifice diameter). The University of Surrey would like to extend its particles teaching program, with the use of a commercially available software package, to be used interactively in the Level M module, Introduction to Processing Particulate Solids.
The use of the Discrete Element Modelling (DEM) program would allow the student to set up a simulation, and observe how different parameters (particle size/type/shape, hopper angle, inter-particle interactions, etc) affect the behaviour, and flow characteristics of particles. Observations can be made both visually (using the programs advanced animation package), and analytically/graphically (being able to export data to both a graph generator and/or Excel spreadsheets, for further data manipulation).
The use of this software will take occur in tutorials, along side taught lectures. Of the taught three hours a week, one of these will be a tutorial, using the EDEM software. A semester is 13 weeks (39 hours) long.
There are two desired case studies that are aimed at introducing the basics of particle handling, through to observing how the inter-particle behaviour on a micro scale can affect engineering functions on the macro scale.
The first case study exercise would include a simple hopper construction and discharge simulation. Variation in the hopper half angle would allow students to observe the Beverloo relationship and find a Rose & Tanaka modification value, while defining the difference between “mass” and “funnel” flow. Further sensitivity analysis could be employed, with relative ease compared with laboratory equipment, (allowing students to change orifice diameter, particle size/shape, or internal friction of the particles, etc), to reinforce the complexity of processing particles. EDEM can simulate such experiments to a good order of accuracy, in a suitably sort period of time, (quick enough to fit within a one or two hour tutorial). An advised simulation set up would be a two dimensional hopper, of dimensions; 0.05m x-direction, 0.3m y-direction, 1.5m z-direction, for an orifice of 0.05m in width, to discharge rock particles of 0.0065m in diameter (and a modified shear modulus of 5×106Pa), with the simulation running at a 50% Rayleigh time step.
The second case study would include a second group of particles (differing in size and/or material). Students would then see how this introduction affects flow in both the “funnel” and “mass” flow regimes, (and particularly for very small orifices for the former, where “bridging” is likely to occur). Students could then look at the Beverloo/Rose & Tanaka modification for binary mixtures, and observe how it compensates, with the Humby form of the Beverloo equation. Students would then be asked to observe the discharge pattern of each particle type, and the scale of percolation/segregation for both “mass” and “funnel” flow regimes. The literature predictions of Humby (1997) can only be applied for the “mass” flow discharges, which EDEM simulates to an acceptable order of accuracy.
Because the work under taken by the students in qualitative (eg changing one parameter throughout a range, and seeing how discharge, flow pattern, etc, is affected, to then develop or recognise some simple relationship or correlation), rather than quantitative (eg running the EDEM software to find a specific value to a high order of accuracy), the program set up can be modified to reduce the level of accuracy, to speed up the computational time. The program limits for such a purpose were found, and a recommended set of parameters were given for the first case study. The same parameters were not as applicable for the second case study (probably due to the present of a binary system), and this paper subsequently suggests using a smaller time step.
EDEM can easily be used as an interactive teaching aid for a taught lecture module. There are some areas which this paper was unable to research into sufficiently, in the allotted time. However recommendations for future work includes further “acid testing” of parameters for the second case study, which would better optimise the computational time, and the accuracy of the simulated results.
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|Commitee:||Tate, Andy, Tuzun, Ugur|
|School:||University of Surrey (United Kingdom)|
|Department:||Chemical and Process Engineering|
|Source:||MAI 51/03M(E), Masters Abstracts International|
|Subjects:||Chemical engineering, Educational technology|
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