collision process details control the hydrodynamics and heat transfer in fluidized bed reactors
TRANSCRIPT
CHINA PARTICUOLOGY Vol. 3, Nos. 1-2, 2005
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Conclusions Adhesion force distributions have to be measured and
interpreted when meaningful results are expected for rough surfaces. We propose three different types of adhesion force distributions: a monomodal Weibull distribution, a bimodal Weibull distribution, when the contact geometry is well defined by distinct asperities, and a broad lognormal distributions for very rough surfaces with a wide variety of contact geometries. Experimental results on model sur-faces support these theoretical findings. These results are complemented by experimental studies on the influence of various parameters including humidity and contact time. These measurements show that the detachment of parti-cles from a substrate is not a static but a dynamic process originating from material transfer between the adhesion partners. MD-simulations for the alumina system indicate that this mass transfer occurs due to nano-fiber formation either between adsorbed water layers or surprisingly be-tween alumina partners in the absence of water.
Acknowledgement Financial support of German Research Association (DFG) is
gratefully acknowledged.
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Manuscript received January 20, 2005 and accepted February 1, 2005.
COLLISION PROCESS DETAILS CONTROL THE HYDRODYNAMICS AND HEAT TRANSFER
IN FLUIDIZED BED REACTORS Masayuki Horio
Department of Chemical Engineering, Tokyo University of Agriculture and Technology, Koganei, Tokyo, 184-8588 Japan E-mail: [email protected]
Abstract In the '90s DEM simulation research was successful in exploring its potential in the simulation of fluidization phenomena
and in its application to the design of fluidized-bed processes. Nevertheless, not much progress has been made regarding the realistic treatment of collision processes that are critical in determining macroscopic mode of fluidization. All through the second half of the '90s, the author investigated/demonstrated the issue by introducing different surface interactions caused by formation of liquid and/or solid bridges, van der Waals force and the existence of surface roughness. In the first part of the presentation these are to be summarized and the tasks remaining are discussed. In the second part, are pre-sented the results from a newly developed force-deformation meter to demonstrate the significance of the surface roughness and its elasto-plastic characteristics.