This presentation describes the considerations involved in selecting the shell and tube exchanger according to TEMA Designations. Also, it helps to identify whether fluid should be sent tube side or shell side

1. SELECTION OF SHELL AND
TUBE HEAT EXCHANGER
(STHE)
GAUTHAM S
PROCESS ENGINEER

2. Principal Components of STHE
 Shell
 Shell cover
 Tubes
 Channel
 Channel cover
 Tubesheet
 Baffles and
 nozzles

3. Other Components
 Tie-in rods and spacers
 Pass partition plates / Channel partitions
 Impingement plates/rods
 Longitudinal baffles
 Sealing strips and
 Supports

4. SCHEMATIC

5. TEMA DESIGNATIONS

6. TEMA DESIGNATIONS

7. SHELL SIDE OR TUBE SIDE?
 The General method of Selection is based on the necessity to reduce cost and
make maintenance easy
PARAMETER SHELL SIDE TUBE SIDE
Mechanical Cleaning Fouling fluids
Pressure High Pressure
Viscosity High Viscous Fluids
(Doubt)
Corrosion Very corrosive fluids
Metallurgy Expensive metallurgy

8. Straight Tube and Fixed Tubesheets
 Examples such as BEM, AEM, NEN, etc.,
 This TEMA type is the simplest design and is constructed without packed or
gasketed joints on the shell side.
 The tubesheet is welded to the shell and the heads are bolted to the tubesheet
 On the NEN heat exchanger, the shell and the head is welded to the tubesheet.
Typically, a cover plate design is provided to facilitate tube cleaning.
 NEN is the lowest cost TEMA design per square foot of heat transfer surface.

9. Straight Tube and Fixed Tubesheets
ADVANTAGES LIMITATIONS APPLICATIONS
Less costly than removable
bundle designs
Shell side can be cleaned
only by chemical methods
Oil Coolers, Liquid to Liquid,
Vapor condensers,
reboilers, gas coolers
Provides maximum amount
of surface
No provision to allow for
differential thermal
expansion, must use an
expansion joint
Provides for single and
multiple tube passes to
assure proper velocity

10. Removable Bundle, Externally Sealed
Floating Tubesheet
 Example such as, AEW, BEW
 This design allows for the removal, inspection and cleaning of the shell circuit and
shell interior.
 Special floating tubesheet prevents intermixing of fluids.
 Maximum surface for a given shell diameter for removable bundle design
 Tubes can be cleaned in AEW models without removing piping.
 Packing materials produce limits on design pressure and temperature

11. Removable Bundle, Externally Sealed
Floating Tubesheet
ADVANTAGES LIMITATIONS APPLICATIONS
Floating tubesheet allows for
differential thermal
expansion between the shell
and the tube bundle.
Fluids in both the shell and tube
circuits must be non-volatile, non-
toxic
Intercoolers and after
coolers, air inside the
tubes
Shell circuit can be steam or
mechanically cleaned
Tube side passes limited to single
or two pass design
Jacket water coolers
or other high
differential
temperature duty
The tube bundle can be
repaired or replaced without
disturbing shell pipe
All tubes are attached to two
tubesheets. Tubes cannot expand
independently so that large
thermal shock applications should
be
avoided

12. Removable Bundle, Outside Packed Head,
 Example such as, BEP, AEP, etc.,
 This design allows for the easy removal, inspection and cleaning of the shell circuit
and shell interior without removing the floating head cover.
 Special floating tubesheet prevents intermixing of fluids.
 In most cases, straight tube removable design is more costly than U-tube designs.
 On AEP design, tubes can be serviced without disturbing tubeside piping
 Less costly than TEMA type BES or BET designs

13. Removable Bundle, Outside Packed Head
ADVANTAGES LIMITATIONS
Floating tubesheet allows for differential thermal
expansion between the shell and the tube bundle.
Shell fluids limited to non volatile,
non toxic materials
Shell circuit can be inspected and steam cleaned.
If the tube bundle has a square tube pitch, tubes
can be mechanically cleaned by passing a brush
between rows
of tubes.
All tubes are attached to two
tubesheets. Tubes cannot expand
independently so that large thermal
shock applications should be
avoided
The tube bundle can be repaired or replaced
without disturbing shell piping
Packing limits shell side design
temperature and pressure

14. Removable Bundle, Internal Split Ring
Floating Head
 Example such as, AES, BES,
 Ideal for applications requiring frequent tube bundle removal for inspection and
cleaning
 Uses straight-tube design suitable for large differential temperatures between the
shell and tube fluids
 More forgiving to thermal shock than AEW or BEW designs.
 Suitable for cooling volatile or toxic fluids.
 Higher surface per given shell and tube diameter than “pull-through” designs such
as AET, BET, etc.

15. Removable Bundle, Internal Split Ring
Floating Head
ADVANTAGES LIMITATIONS
Floating head design allows for differential
thermal expansion between the shell and
the tube bundle.
Shell cover, split ring and floating head
cover must be removed to remove the
tube bundle, results in higher
maintenance cost than pull-through
Provides multi-pass tube circuit
arrangement
More costly per square foot of surface
than fixed tubesheet or U-tube designs
Shell circuit can be inspected and steam
cleaned. If it has a square tube layout,
tubes can be mechanically cleaned

16. Removable Bundle, Pull-Through Floating
Head,
 Example such as, AET, BET
 Ideal for applications requiring frequent tube bundle removal for inspection and
cleaning as the floating head is bolted directly to the floating tubesheet. This
prevents having to remove the floating head in order to pull the tube bundle

17. Removable Bundle, Pull-Through Floating
Head,
ADVANTAGES LIMITATIONS
Floating head design allows for differential
thermal expansion between the shell and
the tube bundle.
For a given set of conditions, this TEMA
style is the most expensive design
Shell circuit can be inspected and steam or
mechanically cleaned
Less surface per given shell and tube
diameter than other removable designs
Provides large bundle entrance area for
proper fluid distribution
Provides multi-pass tube circuit
arrangement.

18. Removable Bundle, U-Tube
 Example such as, BEU, AEU,
 Especially suitable for severe performance requirements with maximum thermal
expansion capability. Because each tube can expand and contract independently,
this design is suitable for larger thermal shock applications.
 While the AEM and AEW are the least expensive, U-tube bundles are an
economical TEMA design.

19. Removable Bundle, U-Tube
ADVANTAGES LIMITATIONS
U-tube design allows for differential
thermal expansion between the shell and
the tube bundle as well as for
individual tubes
Draining of tube circuit is difficult when
mounted with the vertical position with the
head side up.
Shell circuit can be inspected and steam
or mechanically cleaned
Because of u-bend, tubes can be cleaned
only by chemical means
Less costly than floating head or packed
floating head designs
Because of U-tube nesting, individual tubes
are difficult to replace
Provides multi-pass tube circuit
arrangement.
No single tube pass or true countercurrent
flow is possible
Bundle can be removed from one end for
cleaning or replacement
Tube wall thickness at the U-bend is thinner
than at straight portion of tubes

20. Discussion
 What type of exchanger do we select for a cost-wise economical design?
1. No Fouling/ Fouling condition
2. Non-Corrosive/ Corrosive condition
3. High differential thermal gradients
4. Combination of any 2
5. All the above expect 4

21. Front Head Selection

22. QUIZ
TYPE B TYPE C TYPE N

23. Fixed Tubesheet
 Shell side fluid is non-fouling or the fouling can be chemically cleaned.
 The Mean temperature differential between shell and tube wall must be less than
50 Deg C. Otherwise, expansion bellow is required.
 Stress caused by differential expansion between the shell and the tube should not
exceed the design stress limits considering winter and start up conditions

24. U-Tube Bundle
 The U-tube is limited to applications where the tube side fluid is non-fouling; any
fouling fluid must be routed through shell side only. In this respect, tube side
mechanical cleaning is considered possible, if the centre to centre distance
between the parallel legs of the U-tube is at least 150mm. However, this later
option may be used only if required by specific process requirements.
 Horizontal U-Tube should be used when condensing fluid in the tube side.

25. Floating head
 Split ring (S type), Pull through (T type), Externally sealed tubesheet (W Type) and
Outside packed (P Type)
 Type S and Type T are the common types of Floating head
 Floating head type or U-tube type heat exchanger should be selected if flexibility is
required to avoid overstressing. The maximum shell diameter is based upon tube-
bundle removal requirements and is limited by crane capacities. Thus, floating head
heat exchangers are often limited to a Shell ID of 1400 to 1500 mm.
 In S-type as there is an internal joint at the floating head, a careful design is necessary
to avoid leakage of one fluid to the other.

26. Shell Selection

27. QUIZ
TYPE E TYPE J TYPE G

28. E Shell
 Commonly used shell type
 Its limitations are shell side pressure
drop or problem due to flow-induced
vibrations
 Shell types such as Type J, Type X
,Type H can be used as alternatives.
 Special case of E type shell where
either entry or exit of the shell side
fluid can be split into two parts to
reduce pressure drop or flow induced
vibrations in the shell side.
J Shell

29. G Shell
 G shells have a longitudinal baffle
axially
 “G” shells are used for a maximum
tube length of twice the maximum
unsupported span as per TEMA as
there is one full support plate in the
tube bundle.
 It is used for horizontal
thermosyphon reboilers in order to
reduce the pressure drop as well as
to avoid flow mal-distribution
 H shells have a longitudinal baffle
axially
 “H” shells are used for a maximum
tube length of four times of the
maximum unsupported span due to
presence of 2 full support plates in
the tube bundle.
 It is used for horizontal
thermosyphon reboilers in order to
reduce the pressure drop as well as
to avoid flow mal-distribution
H Shell

30. F Shell
 This shell is used when there is a
temperature cross i.e., when the outlet
temperature of cold stream is higher
than the outlet temperature of the hot
stream.
 “F” shells are prone to leakage across
the longitudinal baffle in removable
bundle exchangers and hence their
use is generally not recommended.
 If “F” shell is employed in a removable
type exchanger, the shell side pressure
drop should be limited to 0.35 kg/cm2g.
 multiple shells in series are to be
employed when more number of tube
passes is required.
 This type of shell is called kettle
construction where there is an
enlarged shell above the tube bundle
for the disengagement of the vapor
from the boiling liquid.
 The kettle type is a special application
of the U-tube type and pull through
type of construction
K Shell

31. Rear End Selection

32. QUIZ
TYPE T TYPE S TYPE W

33. Rear End Selection
 Rear End selection depends on a number of factors such as cost, maintenance,
Fluid characteristics, application, etc.
 Normally, Rear End “Type M” is used for “Type A” (Bonnet Type) Front End but for
heat exchanger with “Type A” front end stationary head and an odd number of tube
passes, “Type L” shall be selected.
 Rear end head Type T shall be used for a kettle type exchanger with floating head.
TYPE M TYPE L TYPE T

34. Appendix – A (Baffle Design)
 Longitudinal baffles, cross baffles and support baffles are the 3 types of baffles.
 Commonly used baffle is single segmental but if it is necessary to reduce the shell
side pressure drop then double segmental baffle is used
 To reduce flow induced vibrations on the shell side, the no tube in windows design
with single segmental baffle can be used.
 Optimum baffle spacing is between 0.3 to 0.6 of Shell ID. The minimum baffle
spacing as per TEMA is one fifth of the shell inside diameter or 4” whichever is
lower

35. Appendix-B (Tube layout and Pitch)
 Triangular, rotated triangular, square and rotated square are different tube layouts
 Triangular or rotated triangular tube layouts is commonly used as it can
accommodate more number of tubes but it is limited to clean services
 Square and rotated square tube layouts is used for dirty shell side service and
when mechanical cleaning of shell side is necessary
 The minimum tube pitch should be 1.25 times tube OD.
 For square and rotated square layouts, a minimum cleaning lane of 6mm should
be provided.

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