A generalized method for predicting the minimum fluidization velocity

Abstract

Lu and Wang ( 3 ) . This has the advantage that in the absence of quaternary data, the corresponding &jkl may be set to zero to obtain a better approximation than by setting (Eijkl -C i j k l ) to zero.excess Gibbs free energy i, i, k, 1, m, n, p = index representing components n = moles P =pressure R = gas constant = binary two-and three-suffix coefficient T = absolute temperature x = mole fraction y = activity coefficient In a recent article Narsimhan (18) presented a generalized expression for the minimum fluidization velocity by extending the correlation proposed by Leva, Shirai, and Wen (14) into intermediate and turbulent flow reions. Based on a similar approach by employing the &ed-bed pressure drop equation of Ergun (7), an expression for the minimum fluidization velocity quite different from that of Narsimhan has been obtained ( 2 3 ) . It is the purpose of this communication to compare these two correlations and to examine the validity and applicability of each. The generalized expression given by Narsimhan consists of three equations [Equations ( 6 ) , (9), and ( 11) in his communication (18) 1. The correlation obtained by Wen and Yu ( 2 3 ) can be represented by ( N R~)~~ = d ( 3 3 . 7 ) ' + 0.0408 N G~ -33.7 (1)For nonspherical particles, the particle diameter dp is defined as the equivalent diameter of a spherical particle with the same volume. As an approximation, the particle diameter may be calculated from the geometric mean of the two consecutive sieve openings without introducing serious errors ( 2 6 ) .The major differences between the two correlations are the minimum fluidization voidage emf and the shape factor 4%.1. Narsimhan considered that for spherical emf has the value of 0.35 and is independent of e particle diameter, provided that the wall effect can be neglected. From the literature data (16, 20, 2 4 ) , as well as trrticles from the experimental data of the present investigation ( 2 3 ) , emf for spherical particles can be shown to vary from 0.36 to 0.46. Different average values of emf have V Van Heerden, et a l . ( Z Z ) 0 Fancher and Lewis (9) o.ol -Narsimhan's correlation I 0.001 aooz 0.004 aoi aoz 03 dp (in.) 986 emf Fig. 1. Correlation of voidage shape factor function -.(1 -emf)2

Predicting Sedimentation in Urban Sewer Conduits

“…ρ f and µ are the density and viscosity of a moving fluid, U m f is sedimentation velocity, g is gravitational acceleration, and ρ s is the density of a moving particle [38].…”

“…The minimum Reynolds' number for suspension was obtained using Equation (10) [38], which was used for vertical flows at first. However, given that the diameter of the conduit was 120 times that of the maximum diameter of a particle in this study, it was used for horizontal flows as well.…”

Modeling of the chemical-looping combustion of methane using a Cu-based oxygen-carrier

“…Several equations can be found in the literature to calculate the Reynolds number at minimum fluidization conditions. In this work, a widely used correlation proposed by Wen and Yu was used [17]:…”

A Study of Vertical Gas Jets in a Bubbling Fluidized Bed

“…Ergun (1952) D sv Wen & Yu (1966) Chitester et. al (1984) [ ] D v Haider & Levenspiel (1989) [ Additionally the Khan and Richardson (1989) equation is used for finding the hindered settling velocity for all drag correlations, given the settling velocity of a single particle.…”