Page 216 - Design and Operation of Heat Exchangers and their Networks

Optimal design of heat exchangers 205

where
0:18
J r,l ¼ 10= N rc + N rw Þ½ ð Š (5.71)

5.2.3 Shell-side pressure drop calculation correlations
The shell-side pressure drop consists of three components: (1) pressure drop
in the crossflow section, Δp c ; (2) pressure drop in the window area, Δp w ; and
(3) pressure drop in the shell-side inlet and outlet sections, Δp io :

Δp s ¼ Δp c + Δp w + Δp io
(5.72)
¼ N b 1ÞΔp b,id ζ ζ + N b Δp w,id ζ +2Δp b,id 1+ N rw =N rc Þζ ζ
ð
ð
b l
b s
l
where the correct factors are given by Eqs. (5.60), (5.66), (5.69).
The pressure drop in an ideal tube bundle, Δp b,id , is given by
μ 2
Δp b,id ¼ N ∗ Hg (5.73)
rc 2
ρd
o
where Hg is the Hagen number for tube bundle given by Eq. (5.45) for
inline tube bundles and Eq. (5.46) for staggered tube bundles, respectively.
∗
N rc is the number of tube rows in the flow direction along which the max-
imum velocity occurs:

N rc , s l s
∗ l,min
N ¼ N rc 1, s l < s l,min (5.74)
rc
The valid ranges of Eqs. (5.45), (5.46) for the pressure drop, Eq. (5.73),
5
are: 1<Re tb <3 10 , N rc 5, 7.9mm d o 73mm, 1.25 s t /d o 3.0,
and 1.2 s l /d o 3.0 for inline tube bundles and 1.25 s t /d o 3.0,
0.6 s l /d o 3.0, and s d /d o 1.25 for staggered tube bundles.
The pressure drop in an ideal window section, Δp w,id , is given by
8 2
G
> w
> ð 1+0:3N rw Þ , Re s,d > 100
<
ρ
Δp w,id ¼ 26G w μ 2 (5.75)
> N rw l bc G w
> + + ,Re s,d 100
: 2
ρ d ρ
s t d o
hw
in which
4A sw
d hw ¼ (5.76)
N tw πd o + d s θ ds =2
_ m
p (5.77)
G w ¼ ffiffiffiffiffiffiffiffiffiffiffiffiffiffi
A sc A sw