Page 192 - Design and Operation of Heat Exchangers and their Networks

180 Design and operation of heat exchangers and their networks

Thonon and Bontemps (2002) used a crossflow plate heat exchanger of
0.3m by 0.3m with chevron angle of β¼45degrees for the condensation
heat transfer experiments. The fluid at the inlet and outlet was kept at sat-
uration condition of vapor and liquid, respectively. For three pure fluids
pentane, butane and propane, they obtained
Nu=Nu lo ¼ 1564Re 0:76 (4.199)
eq
in which the equivalent Reynolds number is defined by Eq. (4.190).
Han et al. (2003b) measured condensation heat transfer and pressure drop
using brazed plate heat exchangers with different chevron angles of 45, 55,
and 70degrees and obtained the following correlation equations:

αd h,ψ n 1=3
Nu ¼ ¼ CRe eq,ψ Pr (4.200)
λ l
0
f ¼ C Re n eq,ψ (4.201)
0
2LG 2 eq
Δp f ¼ f (4.202)
d h,ψ ρ m
Δp g ¼ ρ gL (4.203)
m
!
_ xG 2 eq
Δp a ¼ Δ (4.204)
ρ ρ v
l
where

2:83 4:5
C ¼ 11:22 l w =d h,ψ β (4.205)

0:23 1:48
n ¼ 0:35 l w =d h,ψ β (4.206)

β
0 4:17 7:75
C ¼ 3521:1 l w =d h,ψ (4.207)

β
0 0:0925 1:3
n ¼ 1:024 l w =d h,ψ (4.208)
0:5
G eq ¼ G 1 _x + _x ρ =ρð l v Þ (4.209)
Re eq ¼ G eq d h,ψ =μ (4.210)
l
β is the chevron angle in radian, and l w is the wavelength of herringbone-
type plates. The mean density is determined with the homogenous model by
Eq. (4.192). The hydraulic diameter d h,ψ is defined by Eq. (4.127).
(Note: In Eq. (12) of Han et al., 2003b,“N cp ”(N cp ¼2) should be an
error and might be replaced with “2.”)