Page 219 - Design and Operation of Heat Exchangers and their Networks

208 Design and operation of heat exchangers and their networks

4 2
ρ ¼ 905:03 0:62602t +3:8112 10 t kg=m 3 (5.82)
oil
3 2
c p,oil ¼ 1835:4+ 3:5465t +4:4988 10 t J=kgK (5.83)
5
λ oil ¼ 0:14494 8:8455 10 t W=mK (5.84)
2 4 2 6 3
μ ¼ exp 0:1743 8:9038 10 t +6:1253 10 t 2:0359 10 t sPa
oil
(5.85)
Let the assumed oil outlet temperature and the wall temperature at the
tube outside be its specified value, t s,m ¼t s,w ¼63°C, which yields
3
ρ ¼ 867:1kg=m ,c p,s ¼ 2076:7J=kgK,λ s ¼ 0:13937 W=mK,
s
μ ¼ 0:029806 sPa, Pr s ¼ Pr s,w ¼ 444:14
s
(2) Calculation of geometric parameters
Eliminating the shell-to-tube bundle clearance δ st in Eq. (5.5) with
Eq. (5.6), we obtain the tube bundle outer tube limit diameter:

ð
ð
d otl ¼ d s 0:008ð Þ= 1+ 0:01Þ ¼ 0:336 0:008Þ=1:01 ¼ 0:3248 m
The diameter of the circle through the centers of the outermost tubes is
given by Eq. (5.12):
d ctl ¼ d otl d o ¼ 0:3248 0:019 ¼ 0:3058 m
For the tube bundle with 45degrees rotated square arrangement, the
longitudinal tube pitch
p ffiffiffi p ffiffiffi
s l ¼ s= 2 ¼ 0:025= 2 ¼ 0:01768 m
the transverse tube pitch
p ffiffiffi p ffiffiffi
s t ¼ 2s ¼ 2 0:025 ¼ 0:03536 m
the diagonal tube pitch
s d ¼ s ¼ 0:025 m
the minimum transverse tube pitch

2 1=2 2 1=2
s l,min ¼ 0:52s t d o + d ¼ 0:5 2 0:03536 0:019 + 0:019
o
¼ 0:02064 m
Because s l <s l,min , the effective transverse tube pitch is given by
∗
s t ¼ s d ¼ 0:025 m
The number of tubes N t is calculated by Eq. (5.11) with K¼0.156 and
n¼2.291 taken from Table 5.1:
n 2:291
ð
N t ¼ round Kd otl =d o Þ½ ð Š ¼ round 0:156 0:32475=0:019Þ ¼ 104
The number of tubes per pass is