Chemical Engineering March 2016 - 61

Feature Report
Shell-and-tube heat
exchangers: the design cycle
Following this step-by-step approach will ensure that the heat exchanger will perform
as required when finally fabricated
S
hell-andtube
heat
exchangers
are among
Front-end
stationary head types
E
A
the most commonly
used equipment in
the chemical process
industries (cpi), especially
in petroleum
refineries and chemical
manufacturing
facilities. the design
cycle of a heat exchanger
starts with
the process engineer.
however, to ensure a
smooth fabrication,
startup and operation,
the cycle further
goes through a mechanical
design stage
followed by detailed
design by the fabrication
vendor. the final
geometry of the heat
exchanger released for fabrication should
meet both the process as well as the mechanical
requirements.
the design of a shell-and-tube heat exB
Bonnet
(integral cover)
Removable
tube
C
bundle
only
Channel integral with tube-sheet
and removable cover
N
Channel integral with tube-sheet
and removable cover
D
X
W
Special high pressure closure
Cross flow
Externally sealed floating tubesheet
Figure 1. TEMA construction types for shell-and-tube heat exchangers (source: TEMA)
changer involves a close interaction among
three parties: the process engineer, the mechanical
engineer and the fabrication vendor.
the process engineer and the mechanical
engineer belong to the engineering company
that carries out the detailed engineering
design. the third-party is the fabrication
vendor. the success of the design depends
on how effectively all three parties have coordinated
in the course of the design cycle
of this equipment.
Shell-and-tube heat exchanger types
there are three most common types of
shell-and-tube heat exchangers - fixed
tubesheet design, u-tube design, and the
floating head type [1].
Fixed tubesheet. the main feature of the
fixed-tubesheet heat exchanger is that it
has straight tubes that are secured at both
ends to tubesheets, which are welded to the
shell. Figure 1 shows the different types of
front heads, rear heads and shell types as
specified by the tubular exchanger manufacturers
assn. (tema; tarrytown, n.y.;
www.tema.org).
the fixed tubesheet design is low in cost
because of its simple construction. in addition,
mechanical cleaning of the inside
of the tubes is possible after removal of
the channel cover or bonnet. however, the
bundle is fixed to the shell. as a result, the
bundle cannot be removed and therefore,
the outside of the tubes cannot be cleaned
ChemiCal engineering www.Chemengonline.Com marCh 2016
61
K
Kettle type reboiler
U
U-tube bundle
J
Divided flow
T
Pull through floating head
StepS in the deSign
cycle
a caSe Study
Final RemaRkS
H
Double split flow
S
Floating head with backing device
geometRical
paRameteRS
Channel and removable cover
F
Two pass shell with longitudinal baffle
G
Split flow
P
Outside packed floating head
N
Fixed tubesheet like " N "
stationary head
One pass shell
M
Shell types
L
Fixed tubesheet like " A "
stationary head
Fixed tubesheet like " B "
stationary head
rear-end head types
Saheli
Bhattacharyya
and Siddhartha
Mukherjee
air liquide global
e&c Solutions india
In BrIef
Shell-and-tube heat
exchangeR typeS
ShellSide and
tubeSide FluidS
http://www.tema.org http://www.Chemengonline.Com
Chemical Engineering March 2016

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