the coking properties of coal at elevated pressures. - Argonne ...

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Chaung (15) showed that the deviation of the particle fluxes predicted by the two
models was less than the uncertainty in the results of the more accurate version.
Detailed description of the essential features of the model.
Initial velocity distribution.
A log-normal fit was made to the distribution of ejected particle velocities
given by George and Grace (4). which were normalized to the absolute bubble velo-
cities, Ub. The geometric mean particle velocity and standard deviation were 2.44
Ub and 1.43, respectively.
Initial Entrainment
George and Grace (4), defined a parameter, 5, equal to the ratio of the
volumes of entrained particles and bursting bubble. Using this parameter, the en-
trainment from the bed surface, Eo, can be expressed by
Glicksman et al. (17) give an expression for the visible bubble flow rate, Qb. valid
over the entire range of bubble volume fraction, 6:
The total energy of a bubble before bursting can be equated to the energy of
the entrained particles and the energy of the bubble through-flow gas. The total
energy of the bubble is given by the following equation from Davidson and
Harrison (18) :
1 2
(KE)b = -
2 %,eff "b
where the effective mass of a bubble, %,eff, is
1
%,eff = 7 (mass of fluid displaced by the bubble)
Defining the root-mean-square velocity of the entrained particles as v the total
kinetic energy of the particles ejected by the bubble is:
P'
where
The kinetic energy of bubble through-flow gas is approximately
which is usually negligible compared with
(KE)b S (KE)p, then yields:
2
U.
5 =- b
2
or (KE)
P'
The energy balance, i.e.,
2 7
P
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