INDUSTRIAL AND ENGINEERING CHEMISTRY
1840
Vol. 43, No. 8
used the ratio A p / A p a !There Apa was calculated a t the saiiic superficial air velocity as that obtaining in the measurement of Ap. Figure 4 was drawn using Apa a t the same velocity as that of the mixture. However, the shape of the curve is not changed by using Apa a t the same superficial air velocity. Belden a i d Kassel ( 2 ) report that the ratio of particle diameter to tuhe diameter has no appreciable effect on the relative pressure drop. From this investigation no conclusion can be drawn as to the effect of particle diameter, but the tube diameter has been found to have a definite effect. In the correlations attempted, the data deviate from the straight line a t high flow rates-that i-, a t low values of y. I possible reason for this trend is a change in the flow mechanism in this region. None of the methods of correlation so far proposed is entirely adaptable to the data of this investigation, although a modihcation of that of Vogt and White appears to be most useful. I t is apparent that the problem needs further study, and by the use of the feeder described in this article the range of solid-gas ratios can be considerably extended and any desired gas-solid ratio readily obtained. h OME\CLATURE
G. MASS Figure 3.
V E L O C I T Y , L E . / SEC.-SO FT.
Effect of hIass Velocity on Fanning Friction Factor for Various Sizes of Tubes
D De
h
= =
Fanning friction factor for coal-air mixture, no units
= mass velocity of coal-air mixture, pounds per (second) =
=
on which this correlation was based, however, were all obtained with the same pipe size (0.5-inch standard), but the particle diameter was varied by using different batches of closely sized particles. In this investigation, on the other hand, different tube sizes were used, but the average particle size n-as constant, though not uniform, being the product of grinding coal in a ball mill. In Figure 4 ( R e , / y ) ( p c / p a ) ( 1/D) is plotted against A p / A p a . Except for the deviation a t high rates of flow, the curve has the same slope as that of Vogt and White. However, the use of the first poner of the diameter fits the data much more closely than the second porer, as used by Vogt and White. T’ogt and White
tube diameter, feet
= particle diapleter, feet
Ap = Apa =
Reo =
si
= =
y
p
=
pa
=
pa+
