Page 268 - Mechanical Engineers' Handbook (Volume 4)

9 Fluid Flow 257

Figure 35 Pressure drop factors for flow of air or flue gas through tube banks. 1

Staggered Tubes Tubes in Line Factor F for x/D
x/D Factor F y/D 1.5 2 3 4
1.5 2.00 1.25 1.184 0.576 0.334 0.268
2 1.47 1.5 1.266 0.656 0.387 0.307
3 1.22 2 1.452 0.816 0.497 0.390
4 1.14 3 1.855 1.136 0.725 0.572
4 2.273 1.456 0.957 0.761

Stack draft, at ambient atmospheric temperature of 70 F, is shown in Fig. 38 as a func-
tion of flue gas temperature. Where greater drafts are desirable with a limited height of stack,
a jet-type stack can be used to convert the momentum of a cold air jet into stack draft.
Performance data are available from manufacturers.

9.2 Centrifugal Fan Characteristics
Performance characteristics for three types of centrifugal fans are shown in Fig. 39. More
exact data are available from fan manufacturers. Note that the backward curved blade has