We found a match
Your institution may have access to this item. Find your institution then sign in to continue.
- Title
An examination of Wen and Yu’s formula for predicting the onset of fluidisation.
- Authors
Gibson, I.A.; Slim, C.J.; Zheng, Yaoyao; Scott, S.A.; Davidson, J.F.; Hayhurst, A.N.
- Abstract
Graphical abstract Highlights • Wen and Yu’s equation does not reliably predict the gas velocity for minimum fluidisation. • Now the onset of fluidisation can be predicted knowing only the particles’ size and sphericity. • A relation is suggested between the voidage at incipient fluidisation and the particles’ sphericity. Abstract Classical methods (measuring the pressure drop across a bed for different flowrates of air through the bed) were used to determine the superficial velocity for minimum fluidisation, <italic>U mf </italic>, of sieved particles of alumina. The particles were characterised optically using an instrument (Morphologi G3, Malvern Instruments), which, from pixelated, enlarged photographs, measured the particles’ mean diameter, <italic>d p </italic>, to be 0.48 ± 0.04 mm and their sphericity, <italic>ϕ</italic>, to be 0.77 ± 0.09. Values of <italic>U mf </italic> were measured for the temperature in the electrically heated bed varying from 14 to 920 °C. The results were analysed using Ergun’s equation; one outcome was that the voidage, <italic>ε mf </italic>, in an incipiently fluidised bed was found to be related to the particles’ sphericity by: ( 1 − ε m f ) / ϕ 2 ε m f 3 = 12.2 ± 0.4. The measured <italic>U mf </italic> were significantly larger than the values predicted by Wen and Yu’s equation, if the mean diameter of the particles was taken, as recommended, to be the geometric mean of the upper and lower sieve sizes, used when preparing the particles. Alternatively, the measured values of <italic>U mf </italic> were over-predicted by Wen and Yu’s equation, when using the optically measured mean size of the particles. The best predictions of <italic>U mf </italic> were made by using the optically measured mean values of both <italic>d p </italic> and <italic>ϕ</italic>, together with Ergun’s equation and the above equation coupling <italic>ε mf </italic> and <italic>ϕ</italic>. Such a procedure is proposed for estimating <italic>U mf </italic> in general. No evidence was found for <italic>ε mf </italic> varying with temperature.
- Subjects
FLUIDIZATION; ALUMINUM oxide; PACKED beds (Chemical industry); SPHERICITY (Statistics); REYNOLDS number
- Publication
Chemical Engineering Research & Design: Transactions of the Institution of Chemical Engineers Part A, 2018, Vol 135, p103
- ISSN
0263-8762
- Publication type
Article
- DOI
10.1016/j.cherd.2018.05.009