Page 151 - Applied Process Design For Chemical And Petrochemical Plants Volume III

66131_Ludwig_CH10D 5/30/2001 4:30 PM Page 115

Heat Transfer 115

Number of tubes per pass 11 Area available in assumed unit, second trial,
Water flow area (11)(0.00379) 0.0417 ft 2 A (0.2618)(44)(8 3 in./12) 89.2 ft 2
(For low-pressure design, 3 in. is sufficient allowance for two
tubesheets.)
100
Water velocity 5.34 ft>sec Percent excess area,
160217.48210.04172
89.2 80.2
Film coefficient, tube side, % 11002 10.2%
80.2
From Figure 10-50A and 10-50B, read:
h i 1,220
2
h io (1,220)(0.94)(0.834) 956 Btu/hr (ft )(°F) This is satisfactory.
Film coefficient, shell side, Pressure drop, shell side (see “Pressure Drop” section),
Select baffle spacing of 5.5 in., equal to 16 baffles.
2
f 1G2 1D s 21N c 12
P s (10-67A)
10
16,35021144211.252 5.22 1102 1D e 21s21 s 2
2
G s 69,300 lb>hr 1ft 2
112210.25215.52
where
10.062169,3002
R e 4,250 f 0.0025
0.978
G 69,300
D s 12/12 1 ft
Reading Figure 10-54, j H 35 N c 1 16 1 17
Reading Figure 10-140, D e 0.72/12 0.06
f 0.0025 (for plain tubes) s 0.78
s 1.0
135210.055211.812
h o 58.1
2
0.06 10.00252169,3002 1121172
P s 0.0835 psi
10
5.22 1102 10.06210.782
Use same fouling factors as for first trial.
Overall coefficient, Use P s 1.0 to 1.5 0.0835 psi for any critical pressure drop
considerations. This should be safe.
1 Pressure drop, tube side, from Figure 10-139.
U End return loss, P r (0.75) (4) 3.00 psi,
1 1
0.002 0.001 from Figure 10-138.
58.1 956
Lb water per tube/pass 50,000/11 4,550
2
47.2 Btu>hr 1ft 21°F2 P (7/100) (8 ft) (4 passes) 2.24 psi
Total pressure drop 2.24 3.0 5.24 psi
LMTD, Use P 6 psi
Nozzle sizes:
Shell Inlet water rate 100 gpm
176 105 Velocity in 3-in. connection 4.34 ft/sec
Tubes Head loss 0.0447 (6 in./12) 0.022 ft water
93 90 Outlet nozzle to be same.
83 15 Inlet shell side (bottom flow):
LMTD = 39.8°F 6,350
Liquid rate 16.2 gpm
Correction to LMTD read Figure 10-34, 160218.33210.782
93 90
P 0.0349 Kinematic viscosity 0.404/0.78 0.52 centistokes
176 90
From Cameron Miscellaneous Liquids Table (Fluid Flow Chapter,
176 105
R 23.6 Vol. I),
93 90 Velocity in 2-in. connection 1.53 ft/sec
1
F 0.99 Note that a 1 / 2 -in. connection is satisfactory; however many
Corrected LMTD (0.99)(39.8) 39.6°F plants prefer minimums of 2-in. connections on process vessels
Area required, for main stream flows.
Pressure loss is negligible 0.006 (6 in./12) 0.003 ft fluid
150,000 Outlet shell side:
A 80.2 ft 2
147.22139.62 Use same size as inlet, 2 in.