Page 238 - Applied Process Design For Chemical And Petrochemical Plants Volume III

66131_Ludwig_CH10G 5/30/2001 4:37 PM Page 201

Heat Transfer 201

A satisfactory average of “f” fitting from the Crane Co. Total resistance to flow:
rd
Charts (“Fluid Flow” chapter, Vol. 1, 3 Ed. this series) is
0.331 0.289 0.67 0.087 1.45 2.8 psi
0.555
f 0.0077
2
3 DG
182154.52
Driving force 3.03 psi

3.24 lb>ft-hr 144
D 6 in.>12 0.5 ft
With the driving force being slightly greater than the total
resistance to flow, the recirculation ratio will be greater than
397,370 lb>hr the trial value of 73. For purposes of design, this is a satis-
2
G 1,928,000 lb>hr 1ft 2
0.2006 ft 2 factory basis to proceed.
Cross-sectional area of 6-in. pipe 0.2006 ft 2 Calculation of Tube Side Film Coefficient
0.555
f 0.0077 From calculated Reynold’s number 10,200
2 3.24 Read Figure 10-46, j H 45
3 0.511,928,0002
f 0.0077 0.00838 0.01608
d 6 in. h i j H 1k a 2 c
ba
b 0.14
a
54.5 lb/ft 3 D i k a
w
W 397,370 145210.0842 10.425212.422 1>3
h i c d 112
1.03 0.084
6
3.36 10 10.016082133.521397,3702 2 a b
p t 12
5
162 154.52
67 psi h i 94.2 Btu>hr 1ft 2 1°F2
2
70
Expansion losses in tubes due to vaporization (Kern rec- 1.03
ommendation): h io 94.2a 1.25 b 77.8
2
p t G >1144 g avg. 2 Assume: h o 1,500 for steam
Fouling: tube side 0.001
2
G 384,000 lb>hr 1ft 2
Shell side 0.001
2
8
g 32.3 ft>sec-sec 13,6002 4.17 1102 ft>hr-hr Neglect tube wall resistance
1384,0002 2
p t 0.0874 psi 1 1
8
1144214.17 10 2128.12 U
1 1 0.0154
0.001 0.001
77.8 1,500
Loss in outlet piping: 10 in. 2
Assume: 65 Btu>hr 1ft 21°F2
one 10-in.- 90° elbow 17 ft pipe
3 ft pipe 03 ft Required area for actual operation:
one 10-in. gate, open 06 ft
Total 26 ft pipe 1,528,600
A 392 ft 2
G 397,370/0.5457 ft 726,000 lb/hr (ft cross section) 651602
2
2
.555 Actual area in assumed unit:
f 0.0077
10
3
21 21 726,000 2
3.24
12
A 11782 10.32722 18 3>12 2 451 ft 2
f 0.0077 0.00972
f 0.0174 Factor of safety, or percent excess area:
This calculation is not accurate, because it does not 451 392
% 11002 15%
account for two-phase flow. 392
6
3.36 10 10.0174212621397,3702 2 This is a satisfactory selection.
p t 1.45 psi
5
1102 11>.6062 Overall coefficient information for operational guide: