Page 178 - Applied Process Design For Chemical And Petrochemical Plants Volume III

66131_Ludwig_CH10E 5/30/2001 4:33 PM Page 141

Heat Transfer 141

190210.009792 0.217 0.0358 1>3
h i a b 112.10210.7942 1>3
10.07292 0.00979
h i (12.10) (0.9262) 11.20
0.875
h io 11.20a b 7.84
1.25

Shell-Side (Water) Coefficient
Use 4-in. baffle spacing and 25% cut baffles in 6-in. O.D.
shell.
Use flow rate 30,000 lb/hr.
Shell-side equivalent diameter:

4c1p>221.8621p2 d o >4d
2
2
d e
d o
Figure 10-83. Heat duty variation with temperature difference as
vapor flows through unit. 2
1.625 11.252 2
4ca 1.862 1.625b d
2 2 4

L at 114°F 72.4 lb/ft 3 11.252
2
c pL at 114°F 0.615 Btu/lb (°F)
2
k aL at 114°F 0.280 Btu/hr (ft ) (°F/ft)
d e 1.06 in. 0.0886 ft
L at 114°F 1.30 centipoise (35 wt. % avg.) 3.15 lb/(hr) (ft)
D e 0.0886 ft
10.072921400,9152
DG e Shell-side bundle cross flow area:
R e 9.260
3.15
L 1D s 21c¿21B2 115.25210.3752142
a s
Reading Figure 10-75, p11442 1.62511442
h cm D c p 1>3 2

a b 100 0.0977 ft
k a k a
Allowing for the spread of data and tending to be conser- G s (30,000)/(0.0977) 307,000 lb/hr (ft )
2
vative, use 85% of value read from chart: (water at 74.3°F) 0.931 centipoise 2.25 lb/hr (ft)
use,
85 10.088621307,0002
Re s 12,070
185210.2802 0.615 3.15 1>3 12.252
h i a b 1326.5216.922 1>3
10.07292 0.280
j H 6.10, Figure 10-54
2
h i (326.5) (1.904) 622 Btu/hr (ft ) (°F)
c p 1.0
2
k a 0.348 Btu/hr (ft ) (°F/ft)
Referencing to outside of tube:
1622210.8752
2
h io 436 Btu>hr 1ft 21°F2 k c p 1>3 161.0210.3482 1.0 2.25 1>3
11.2502 h o j H a b a b
D e k 10.08862 0.348
Sensible Gas Cooling Coefficient h o (239) (6.46) 1/3 (239) (1.862) 445 Btu/hr (ft ) (°F)
2
v 0.0358 lb/hr (ft)
Fouling Factors and Tube Resistance
D 0.0729 ft
Assume inside fouling factor 0.00010
c p 0.217 Btu/lb (°F) (avg.)
2
k a 0.00979 Btu/hr (ft ) (°F/ft) Assume water side (shell) fouling factor 0.0015
3
R e 27,650 Tube resistance for / 8 -in. impervious graphite wall:
j H 90.0 (see Figure 10-54) 0.375
r t L w >k
2
k c p 1>3 1,020 Btu>hr 1ft 21°F>in.2
h i j H a b
D k r t 0.000368