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232 Applied Process Design for Chemical and Petrochemical Plants

Figure 10-153C. Shell-side film coefficient, h o , for longitudinal fins,
flow turbulent. See Figure 10-153A and mechanical data from Table
10-42 for applicable details. The value of h o must be corrected using
Figure 10-154 and data of Table 10-42. (Used by permission: Brown
Fintube Co., A Koch Engineering Company, Houston, Texas.)
®

The needed equivalent diameter, D e , is determined: 211
4NFA
D e (10-249) Figure 10-154. Finned transfer efficiency is never as great per unit
1D s D t 2 2N112
area as the bare pipe; therefore, fin efficiency must be calculated to
arrive at correct h o , shell-side heat transfer coefficient. (Used by per-
where NFA net free area, in. from typical manufacturer’s mission: Technical paper. © Brown Fintube Co., A Koch Engineering
2
®
data as Table 10-42. The denominator is the Company, Houston, Texas.)
wetted perimeter.
D s shell I.D., in.
Mat’l K
D t tube O.D., in.
N number of fins per tube Al 100
l fin height, in. CU 200
*Average K values for temperatures 100–600°F. For temperatures beyond
After determining the h o from the preceding figures, the this range, see literature.
film coefficient must be corrected for fin efficiency using
**Use E chart 0.70 for design efficiency for this material.
Figure 10-154.
The total surface area, A o , in the annulus is the sum of the
where E 100 (TanH X)/X
extended surface area and the bare pipe surfaces not covered
X L(H F /6KT) 0.50
by fins. See Table 10-40. The fin efficiency, h w , e f or E, from
L fin height, in.
H F fin film coefficient Figure 10-154 is corrected for the percent surface that is
2
K conductivity of fin material, Btu/(hr) (ft )(°F/ft) finned. The corrected value, h w , is the effective surface effi-
E % fin efficiency ciency.
T fin thickness, in.
Conductivity values* w 1E>10021A f >A o 2 11 A f >A o 2 (10-250)
Mat’l K
where A f /A o fraction finned area
Monel 15.0 (1 A f /A o ) fraction bare or unfinned tube area
18-8 st.stl 9.5**
The net effective surface true film heat transfer rate is
C.steel 25.0
Low chrom stl 17.0 obtained by correcting the coefficient for the bare surface;
Nickel 35.0 thus, 211 fouling is excluded:
Adm.% brass 65.0
h bare 1h o K 0.667 c p 0.333 21K 0.667 c p 0.333 2 ,