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| Titel: |
An Experimental Test of the Concept of the Characteristic Drying Curve Using the Thin-Layer Method |
| Auteur: |
Keech, A. M. Keey, R. B. Zhang, Q. J. Langrish, T. A. G. Kemp, I. C. Pasley, H. S. |
| Verschenen in: |
Drying technology |
| Paginering: | Jaargang 13 (1995) nr. 5-7 pagina's 1133-1152 |
| Jaar: |
1995 |
| Inhoud: |
The drying behaviour of paticles ( purolit and silica gel) was studied using the thin-layer method described by Langrish et al ( 1). The experiments covered inlet air temperatures between 100 and 150°C, inlet air humidities from 0.02 to 0.052 kgkg1 superficial air velocities between 3.8 and 10.8 ms-1, with layer thicknem of 2 - 10mm. No constant mle period war observed. Characteristic drying curves were found to fall within a narrow band fur these ranges of process variables, for material of uniform size and shape and with relative moisture content defined in terms of the end of the induction period. Small changes in panicle shape, particle size distribution and uniformity of particle layers had negligible infuence on the drying kinetics. However, reduction in particle size from 5.2mm diameter to 0.86mm had a marked effect: the normalised drying rate at a given relative moisture content became larger as the particle size became smaller. This phenomenon is attributed to an increase in available contact area per unit volume with diminishing particle size. The thin-layer technique thus appears to be a useful and robust way of obtaining a general characteristic drying curve for a given particulate material. A review of various works ( Keey, 2) has shown that the concept ofa characteristic drying curve may be used to describe the drying kinetics of paniculate materials below 20mm in size for modest changes in process variables ( air temperature, humidity and velocity). This concept has found to be very useful to help model drying processes of a wide variety of particulates, cross-circulated slabs, heaped loaw fabric fibres, hygroscopic ceramic cylinders and discrete vermiculite particles. The drying of a single particle has been related lo the drying kinetics of a fluidized bed by the use of this ida. ( Tsotsas, 7). A grater understanding of the properties of the characteristic drying curve will provide a greater confidence in applying thir concept more generally to process design and the analysis of industrial drying equipment. The goal of this study was to examine further the experimental and theoretical foundations of the characteristic drying curve, using thin-layer methods. |
| Uitgever: |
Taylor & Francis |
| Bronbestand: |
Elektronische Wetenschappelijke Tijdschriften |
Details van artikel 8 van 37 gevonden artikelen
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