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66131_Ludwig_CH10G 5/30/2001 4:38 PM Page 231

Heat Transfer 231

Table 10-41
Estimating Overall Heat Transfer Rates, U o ,
for Longitudinal Finned Heat Exchangers

With water for cooling or steam for heating, these are estimated
values for preliminary study only.

Process Estimated Overall
Rates “U o ”
Heating viscous materials
Double pipe—cut & twist fins 12
Multitube bare tubes 15
Medium HC viscosity 3—15 cp avg.
Heating—double pipe w/fins 15
Multitube bare tube 25
Cooling—double pipe w/fins 12
Multitube bare tube 20 Figure 10-153A. For determination of h o , shell-side (finned side) film
Light HC viscosity 1 cp coefficient h o K 0.667 C 0.333 for longitudinal fins, flow laminar. h o must be
Double pipe w/fins 25 corrected for fin efficiency using Figure 10-154 and mechanical data
as Table 10-42. (Used by permission: Bul. “How to Design Double
Multitube w/fins 40
Pipe Finned Tube Heat Exchangers.” © Brown Fintube Company, A
Multitube bare tube 75
Koch Engineering Company, Houston, Texas.)
®
Condensing & vaporizing—bare tube 150
Very light HC—bare tubes 150
Gases
1
0 psig w/ / 2 psi P bare tube 25
}
100 psig w/1 psi P fin tube 15
Water to water—bare tubes 200
Glycol to glycol
Double pipe w/fins 10
Multitube bare tube w/turbulators 30
Many factors affect heat transfer rates for example velocity, tube wall
temperature and pressure drop. These rates listed do not represent the
limit, but are suggested values for study and estimating.
Used by permission: Bul. “Application and Design Estimating of Double
®
Pipe and Hairpin Exchangers.” © Brown Fintube Co., A Koch Engineering
Co., Houston, Texas.

Figure 10-153B. Shell-side film coefficient for longitudinal fins, tran-
sition flow. See Figure 10-153A for applicable details. (Used by per-
mission: Brown Fintube Company, A Koch Engineering Company,
®
Houston, Texas.)
Table 10-42
Brown Fintube’s Typical Mechanical Design Data for Fintube Sections As Needed for Design Calculations

2
BFT Tube O.D. Shell Fin Nominal Surface, Ft A o
Section No. No. & Wall Size Sch. Height Net Free D e Equiv. Nominal Length of Section
Type Tubes Fins Thick (in.) 40 IPS in. Area, in. 2 Dia., in. A f ,A o A o ,A i 5 ft 10 ft 15 ft 20 ft 25 ft
X51 1 24 1.900 3 in. 1 / 2 4.11 .415 .801 5.93 25 50 76 101 126
36 .145 3.89 301 .858 8.3 35 71 106 141 177
X53 1 24 1.900 4 in. 1 9.03 .542 .889 10.67 45 91 136 182 227
36 .145 8.60 .379 .923 15.42 66 131 197 262 328
Notes:
1. Fin thickness equals 0.035 in. (narrow web).
2. A f /A o ratio of fin surface to total external heated surface.
3. A o /A i ratio of total external heated surface to inside tube surface.
®
Used by permission: “How to Design Double-Pipe Finned Tube Heat Exchangers.” ©Brown Fintube Co., A Koch Engineering Co., Houston, Texas.