1. Design and Construction
BY- Prerona Das 10010744
Pritom Sharma 10010745
Rijumoni Boro 10010746
Rohitash Meena 10010747

2. Introduction
 A heat exchanger is a device in which two fluid streams, one
hot and another cold, are brought into ‘thermal contact’ in order
to effect transfer of heat from the hot fluid stream to the cold.
 It provides relatively large area of heat transfer for a given
volume of the equipment.
 They are in frequent use in the chemical process industries as
well as in the refrigeration,cryogenic,waste-heat
recovery, metallurgical and manufacturing applications.
 The driving force for the operation of a heat exchanger is the
temperature difference between the fluids.
 The Indian code for heat exchanger design is IS 4503 and the
British code is BS 3274.
 The heat exchanger ‘design code’ for mechanical design
calculations is TEMA (US code).

3. Classification of heat exchangers
Contacting
technique
Flow Basis of
arrangement classification Construction
Surface
compactness

4. Contacting technique Indirect contact
Direct contact
Tubular [double-pipe, shell and tube, spiral tube]
Plate [plate and frame (gasketed and welded plate),
spiral plate]
Heat Construction
H
exchangers Extended surface [plate-fin, tube-fin]
Regenerative
Single pass [parallel flow, counter-flow, cross –flow]
Flow arrangement
Multi-pass [parallel flow, counter-flow, split-flow,
divided flow]
Non-compact [surface area density < 700 m2/m3]
Surface compactness
Compact [surface area density > 700 m2/m3]
Fig: Classification of heat exchangers

5. TEMA
Heat
Exchanger
Tubular Exchanger Manufacture’s
Association(TEMA) is the most
widely used ‘standard’ or
‘stipulated’ heat exchanger ‘design
code’.This is a US code and is
used together with ASME Section
VIII(for the design of unfired
pressure vessels).The TEMA code
specifies the mechanical design
procedure, tolerances allowed and
the dimensions of the various parts
of an exchanger.

6. Front Head Type
A-Type B-Type C-Type

7. Shell type
E-Type F-Type
J-Type K-Type

8. Rear End Head Types
M-Type S-Type T-Type
Fixed Tubesheet Floating Head Pull-Through
Floating Head

9. Double pipe heat
exchanger
A typical double pipe heat
exchanger basically consists of a
tube or pipe fixed concentrically
inside a larger pipe or tube.
They are used when the flow rates
of the fluids and the heat duty are
small (less than 500 kW).
These are simple to construct, but
may require a lot of physical space
to achieve the desired heat transfer
area.

10. Construction of double pipe
Straight construction
It has single sections of inner and outer pipes.
It requires more space.

11. Hairpin construction
It has two sections each of the inner and outer pipes.
It is more convenient because it requires less space.

12. Several hairpins may be connected in series to obtain large
heat transfer area.
All the return bends of the inner pipe are kept outside the
jacket and do not contribute to the heat transfer area.

13. Hairpin heat exchanger

14. Components
Packing & gland
The packing and gland provides sealing to the annulus and support
the inner pipe.
Return bend
The opposite ends are joined by a U-bend through welded joints.
Support lugs
Support lugs may be fitted at these ends to hold the inner pipe
position.
Flange
The outer pipes are joined by flanges at the return ends in order that
the assembly may be opened or dismantled for cleaning and
maintenance.
Union joint
For joining the inner tube with U-bend.

15. Flow arrangements
Co-current flow Counter-current flow
(Fluids flow in same direction) (Fluids flow in opposite direction)

16. The Dirt factor or Fouling factor
 Deposition of any undesired material on heat transfer surfaces
is called fouling, and the heat transfer resistance offered by the
deposit is called the fouling factor or dirt factor, commonly
denoted by Rd.
 Fouling increases the overall thermal resistance and lowers the
overall heat transfer coefficient of heat exchangers.
 The fouling factor is zero for a new heat exchanger.
 It can be only be determined from experimental data on heat
transfer coefficient of a fouled exchanger and a clean
exchanger of similar design operated at identical conditions.

17. Types of fouling
Chemical fouling Corrosion fouling

18. Crystallization fouling Biological fouling

19. Log MeanTemperature
evaluation
T2 T1
TLn
T2
ln
T1
Co-current flow
1 2 T 10
T1 T2
T4 T5
T3 T6
∆ T1 T8 T9
T7
∆ T2 P ara ll el Fl ow
in in
T1 T h T c T3 T7
∆A
A T2 Thout Tcout T6 T10

20. Counter-current flow
T 10
1 2 T2
T1 T4 T5
T3 T4 T6 T3 T6
T6
T1
Wall
T7 T2 T8 T9
T7
T8
Co un t e r - C u r re n t F l ow
T9
T10
in out
A T1 T h T c T3 T7
out in
T2 T h T c T6 T10

21. Log Mean Temperature
Difference Correction Factor
The Logarithmic Mean Temperature Difference(LMTD) is
valid only for heat exchanger with one shell pass and one
tube pass. For multiple number of shell and tube passes
the flow pattern in a heat exchanger is neither purely co-
current nor purely counter-current. Hence to account for
geometric irregularity, Logarithmic Mean Temperature
Difference (LMTD) has to be multiplied by a Mean
Temperature Difference (MTD) correction factor(F) to
obtain the Corrected Mean Temperature Difference
(Corrected MTD) or the effective driving force.

22. Where,
LMTD = Log mean temperature
difference
CLMTD = Corrected Log mean
temperature difference
F = Correction factor
Th1 = hot fluid inlet temperature
Th2 = hot fluid outlet temperature
Tc1 = cold fluid inlet temperature
Tc2 = cold fluid outlet
temperature
N = number of shell passes = shell
passes per shell x number of shell
units in series
P = temperature efficiency
R=capacity ratio
X=temperature ratio

23. Overall Heat Transfer
coefficients
 Calculate convective heat transfer coefficient for tube side (hi).
 Calculate convective heat transfer coefficient for shell side (ho).
 Outside surface area of tube (Ao)
 Inside surface area of tube (Ai )
 Mean surface area (Am)
 Based on the outside tube area, clean overall heat transfer coefficient
becomes
1/Uo = 1/ho + (Ao/Am) x (ro - ri / kw) + Ao/Ai(1/hi)
 Based on the outside tube area,the relation for the overall heat
transfer coefficient becomes
1/Ud = 1/ho +Rdo + (Ao/Am) x (ro - ri / kw) + (Ao /Ai) x Rdi +
Ao /Ai(1/hi)

24. Energy Balance and Heat duty
The Heat transfer rate taking into account the fouling or the dirt
factor and LMTD correction factor is as follows:
Q = UdAFT∆Tm
Where,
Ud = the overall heat transfer coefficient that takes into
account the fouling or the dirt factor Rd.
FT ∆Tm = the true temperature difference.
If U is the clean overall coefficient, then by addition of heat
resistances, we have
1/Ud = (1/U) + Rd
Overall resistance of the fouled exchanger = overall resistance of
the clean exchanger + heat transfer resistance due to dirt or
scaling on both sides of the tube.

25. An overall heat balance for the counter current double-pipe exchanger
may be written as follows:
Q=WcCpc(Tc1-Tc2) = Wh Cph(Th1-Th2)
Where, c=cold fluid T=Temperature
h=hot fluid Q=Heat duty or load duty of exchanger
Cp=Specific heat W=Flow rate of a stream
In this calculation, the heat exchange (gain or loss) with the ambient
medium, if any, is neglected.

26. Pressure drop calculations
Tube-side pressure drop
where,
f = friction factor
Gt = mass velocity of the fluid
L = length of the tube, m
g =9.8m/s2
pt = density of tube fluid
di= inside diameter of tube
n =the number of tube passes
Φt = dimensionless viscosity ratio
∆Pt =pressure drop
Φt=(viscosity at bulk temperature/viscosity at wall temperature)^m
where m=0.14 for Re > 2100 and m= 0.25 for Re < 2100

27. In a multi-pass exchanger, in addition to frictional loss the head
loss known as return loss has to be taken into account.
The pressure drop owing to the return loss is given by-
Where,
n=the number of tube passes
V=linear velocity of the tube fluid
The total tube-side pressure drop is
∆PT = ∆Pt + ∆Pr

28. Shell-side pressure drop
For an unbaffled shell the following equation may be used
Where,
L=shell length, m
N=number of the shell passes
ps=shell fluid velocity, m/s
Gs=shell-side mass velocity, kg/m2 s
DH=hydraulic diameter of the shell, m
Φs=viscosity correction factor for the shell-side fluid

29. Where,
do=the outer diameter of the tube, m
Ds=the inside diameter of the shell, m
Nt=the number of tubes in the shell
and

30. For a shell with segmented baffles,
Where,
Nb=the number of baffles
DH=the hydraulic diameter of the shell, m
The Reynolds number of the shell-side flow is given by

31. The Design Procedure
 Calculate the log mean driving force, LMTD.
 Select the diameters of the inner and outer pipes.If the
allowable pressure drops for the individual streams are
given,they may provide a basis for selection of the pipe
diameters.
 Calculate the inner fluid Reynolds number; estimate the
heat transfer coefficient hi from the Dittus-Boelter
equation or from jH factor chart.
Nu = hidi/k = 0.023(Re)0.8(Pr)0.3

32.  Calculate the Reynolds number of the outer fluid flowing
through the annulus.Use the equivalent diameter of the
annulus.Estimate the outside heat transfer coefficient ho
using the equation or the chart mentioned above.
 Calculate the clean overall heat transfer coefficient;
calculate the design overall coefficient Ud using a suitable
value of the dirt factor.
 Calculate the heat transfer area A(for a counter flow
double-pipe exchanger LMTD correction factor, F=1
Determine the length of the pipe that will provide the
required heat transfer area.If the length is large use a
number of hairpins in series.
 Calculate the pressure drop of the fluids.Use the Reynolds
number calculated above to determine the friction factor.

33. Shell and tube heat
exchanger
Shell and tube heat
exhangers are one of the
most common heat exchange
equipment found in all plants.
They are the most versatile
type of heat exchangers.
This type provides a large heat transfer surface in a small space.
They can operate at high pressures, are easy to clean and can be made
of a wide variety of materials.

34. Components
Tube Shell fluid
fluid in out
Shell-fluid
nozzle
Shell
Tube fluid in
15 16
fluid out
1-Channel cover 9-Baffles
2-Stationary head channel 10-Floating head backing device
3-Channel flange 11-Floating tube sheet
4-Pass partition plate 12-Floating head
5- Tube sheet 13-Floating head flange
6-Shell flange 14-Stationary head bonnet
7-Tube 15-Heat exchanger support
8-Shell 16-Shell expansion joint

35. The shell [item 8]
The shell is the enclosure and passage of the shell-side fluid.
It has a circular cross-section.
The selection of the material depends upon the corrosiveness of
the fluid and the working temperature and pressure.
Carbon steel is a common material for the shell under moderate
working conditions.
The tubes [item 7]
The tubes provide the heat transfer area in a shell and tube heat
exchanger.
Tubes of 19mm and 25mm diameter are more commonly used.
The tube wall thickness is designated in terms of BWG
(Birmingham wire gauge).
Tubes are generally arranged in a triangular or square pitch.

36. The tube sheets [item 5]
The tube sheets are circular, thick metal plates which hold the
tubes at the ends.
The arrangement of tubes on a tube sheet in a suitable pitch is
called tube-sheet layout.
Two common techniques of fixing the ends of a tube to the tube
sheet are: (i)expanded joints and (ii) welded joints.
A few common joints between the tube and the tube sheet:
(a)Grooved joint (b)Plain joint (c)Belled or beaded joint (d)Welded
joint

37. The bonnet and the channel [item 14 and 2]
The closure of heat exchanger is called bonnet or channel
depending upon its shape and construction.
A bonnet has an integral cover and a channel closure has a
removable cover.
The bonnet closure consists of a short cylindrical section with a
bonnet welded at one end and a flange welded at the other end.
The bonnet-type closure is replaced by a channel-type closure if a
nozzle is required to be fitted.
The pass partition plate [item 4]
The channel is divided into compartments by a pass partition
plate.
The number of tube and shell-side passes can be increased by
using more pass partition plates for both the sides.
The number of passes in either the shell or the tube side indicates
the number of times the shell or the tube side fluid traverses the

38. length of the exchanger.
For a given number of tubes, the area available for flow of the
tube-side fluid is inversely proportional to the number of passes.
An even number of passes on any side is generally used (For
example,1-2,1-4,2-4,2-6 etc; 1-3,2-5 etc are not used).
2-4 pass heat exchanger
1-2 pass heat exchanger

39. Nozzles
Nozzles are small sections of pipes welded to the shell or the
channel which act as the inlet or outlet of the fluids.
The shell-side inlet nozzle is often provided with an
‘impingement plate’.
The impingement plate prevents impact of the high velocity inlet
fluid stream on the tube bundle.
Fig: Two types of impingement
plates.
A-The plates
B-Expanded nozzle
C-Nozzle flange

40. Baffles [item 9]
A baffle is a metal plate usually in the form of the segment of a
circle having holes to accommodate tubes.
Segmental baffle is the most popular type of baffle.
Functions of shell-side baffles-(i)to cause changes in the flow
pattern of the shell fluid creating parallel or cross flow to the tube
bundle and (ii)to support the tubes.
A few types of baffles:
Rod baffle
Disc and doughnut baffle

41. Segmented baffles
Baffle cut
Baffle cut orientation

42. Tie rods and baffle spacers
Tie rods having threaded ends are used to hold the baffles in
position.
The baffle spacers maintain the distance or spacing between
successive baffles.
Flanges and gaskets [item 13]
The flanges fixes the bonnet and the channel closures to the tube
sheets.
Gaskets are placed between two flanges to make the joint leak-
free.
Expansion joint [item 16]
The expansion joint prevents the problem of thermal stress which
may occur when there is a substantial difference of expansion
between the shell and the tubes because of the temperature
difference between the two fluid streams.

43. Tube Layout

44. Design Procedure
 Perform the energy balance and calculate the exchanger
heat duty.
 Obtain the necessary thermo physical property at mean
temperature (If the variation of viscosity is large then we
would do the same at the caloric temperature of hot and
cold fluid).
 Select the tentative number of shell and tube passes;
calculate the LMTD and the correction factor FT.
 Assume a reasonable value of Ud on outside tube area
basis. This is available in the literature.

45.  Select tube diameter, its wall thickness(in terms of BWG or
SWG) and the tube length. Calculate the number of tubes
required to provide the area A calculated above.
 Select the type, size, number and spacing of baffles.
 Estimate the tube side and shell side heat transfer coefficient.
 Calculate the clean overall coefficient U, select the dirt
factor, and then calculate Ud and the area on the basis of Ud.
 Now compare the Ud and the area to that assumed earlier. If the
configuration gives 10% excess area than its fine. Otherwise
the configuration has to be changed.
 Calculate the tube side and shell side pressure drop. If pressure
drop value is more than corresponding allowable value then
further adjustment in configuration will be necessary.