results of kern method basic kinematic details group no. tube side velocity (m/s) number of tubes...
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Results of Kern Method
Basic Kinematic Details
Group No.
Tube Side
Velocity (m/s)
Number of Tubes
Shell Diameter
length STHX
(m)
Ds/L
1
2
3
4
5
Performance Details
Group No.
Number of Tubes
Tube side Re
Shell side Re
Tube side h
(W/m2.K)
Shell side h
(W/m2.K)
1
2
3
4
5
Performance Details
Group No.
Tube side p, Pa
Shell side p, kPa
Uclean Ufouled
1
2
3
4
5
Actual Shell Side Heat Transfer Coefficient :Bell-Delaware Method
P M V SubbaraoProfessor
Mechanical Engineering Department
I I T Delhi
Five corrections to Cross Flow Heat Transfer…..
Shell-side heat transfer coefficient
Where hi is heat transfer coefficient for ideal cross flow past a tube bank.
Jc : Segmental baffle window correction factor Jl : Correction factors for baffle leakage effects for heat transferJb : Correction factors for bundle bypass effects for heat transfer Js : Heat transfer correction for unequal baffle spacing at inlet and/or outlet.Jr : correction factor for adverse temperature gradient in laminar flow
rsblcis JJJJJhh
Heat transfer coefficient for Ideal Cross Flow
14.0
,
32
ws
s
sps
s
m
spsii C
k
S
mCjh
Area for Ideal Cross Flow
Selection of Shell Diameter
A simple but reasonably accurate correlation was developed by Bell’s Group for single pass.
2
278.0
T
ctltubes PCL
DN
CL is tube layout constant , CL =0.87 for 30º and 60º layouts or CL=1.0 for 45º and 90º layouts.
For multipass arrangement, a correction factor ψn must be used to account for the decrease of tube count due to tube pass
2Re33.1
1a
s
a
o
Ti
dP
aj
Where 43
Re14.01 as
aa
2Re33.1
1b
s
b
o
Ti
dP
bf
Where 43
Re14.01 bs
bb
s
outertube
s
ss
d
A
m
Re
Shell-Side Reynolds Number
14.0
,
32
ws
s
sps
s
m
spsii C
k
S
mCjh
Coefficients of Correlations
Baffle Geometry
Segmental baffle window correction factor, Jc
cc FJ 72.055.0
2
sin
3602121 ctlctl
twC FF
Segmental Baffle Cut Geometry
Segmental baffle cut height :Lbch
Recommended segmental baffle cut values
Jl : Correction factors for baffle leakage effects for heat transfer
Ssb is the shell-to-baffle leakage area.
Stb is the tube-to-baffle hole leakage area.
Sm is the cross flow area at the bundle centerline
Shell-to-baffle leakage area
• The shell-to-baffle leakage area within the circle segment occupied by the baffle is calculated as:
Lsb is the diametral leakage clearance between the shell diameter and the baffle diameter, Db .
Tube-to-baffle hole leakage area for one baffle
The total tube-to-baffle leakage area within one baffle is Stb.
Correction factors for bundle bypass effects for heat transfer Jb, and pressure drop Rb
ptlotlsb LDDBS m
bsbp S
SF
Lptl =0 for single pass
Unequal Baffle Spacing
Heat transfer correction for unequal baffle spacing at inlet and/or outlet, Js
n is approximately a constant, found to be 0.6 for laminar flow and 0.333 for turbulent flow.
If L* is larger than 2, it would be considered poor design, especially if combined with low Nb .
In such cases an annular distributor or other measures should be used.
Heat transfer correction factor for adverse temperature gradient in laminar flow
where Nc is the total number of tube rows crossed in the entire heat exchanger:
Shell side Fluid Flow in STHE