Heat exchangers transfer thermal energy between two or more fluids at different temperatures. They are classified based on their transfer process, geometry, heat transfer mechanism, and flow arrangement. Shell-and-tube heat exchangers consist of a set of tubes in a shell container and are the most important type, used across many industries. Their design involves calculating the heat transfer rate, selecting appropriate materials and geometry, and ensuring optimal fluid velocities and pressure drops within design limits.

1. 1
Engr. Dr. Farhan Javed

2. Heat Exchangers:
Heat exchangers are devices that provide the flow of thermal
energy between 2 or more fluids at different temperatures.
They are used in a wide variety of applications. These include
power production, process, chemical, food and manufacturing
industries, electronics, environmental engg. , waste heat
recovery, air conditioning applications.
Heat Exchangers may be classified according to the following criteria.
•Recuperators/ regenerators
•Transfer process: direct and indirect contact
•Geometry of construction; tubes, plates, and extended
surfaces.
•Heat transfer mechanism: single phase and two phase
•Flow arrangement: Parallel, counter, cross flow.

3. Heat Exchanger Classification
 Recuperative:
Cold and hot fluid flow through the unit
without mixing with each other. The transfer
of heat occurs through the metal wall.
 Regenerative
Same heating surface is alternately exposed
to hot and cold fluid. Heat from hot fluid is
stored by packings or solids; this heat is
passed over to the cold fluid.
 Direct Contact
Hot and cold fluids are in direct contact and
mixing occurs among them; mass transfer
and heat transfer occur simultaneously.

4. CLASSIFICATION OF HEAT
EXCHANGER

7. Based on process function:
• COOLER – Cools using water or air, without phase change.
• CHILLER – Refrigerates below that obtainable with water.
• CONDENSER – Condenses vapour/ vapour mixture.
• STEAM HEATER – Uses steam for heating.
• STEAM GENERATOR – Produces steam from water.
• REBOILER – Uses steam/hot fluid to heat, for distillation
column.

8. Types of Heat Exchangers

9. Double-Pipe Exchanger

10. Shell-and-Tube Heat Exchanger

11.  Shell-and-Tube Heat Exchangers are the most
important type of HE.
 It is used in almost every type of industry.
 This type of heat exchanger consists of a set of
tubes in a container called a shell.
 The fluid flowing inside the tubes is called the
tube side fluid and the fluid flowing on the outside
of the tubes is the shell side fluid.

12. Main Components of Shell-and-Tube
Heat Exchangers

13. Shell-Side Flow

14. Some common heat-exchanger
terms
 Tube side: Inside the tubes.
 Shell side: Outside the tubes, between the
tubes and the shell.
 Tube sheet A thick plate provided with holes
(one per tube) in which the tubes are fixed.
 Tube bundle Consists of tubes, tube sheet and
baffle plates
 Shell A cylinder of plate in which the tube bundle
is placed

15. The standard nomenclature for shell and tube heat exchanger
1. Stationary Head-Channel
2. Stationary Head-Bonnet
3. Stationary Head Flange-Channel or
Bonnet
4. Channel Cover
5. Stationary Head Nozzle
6. Stationary Tube sheet
7. Tubes
8. Shell
9. Shell Cover
10. Shell Flange-Stationary Head End
11. Shell Flange-Rear Head End
12. Shell Node
13. Shell Cover Flange
14. Expansion Joint
15. Floating Tube sheet
16. Floating Head Cover
17. Floating Head Cover Flange
18. Floating Head Backing Device
19. Split Shear Ring
20. Slip-on Backing Flange
21. Floating Head Cover-External
22. Floating Tube sheet Skirt
23. Packing Box
24. Packing
25. Packing Gland
26. Lantern Ring
27. Tie-rods and Spacers
28. Support Plates
29. Impingement Plate
30. Longitudinal Baffle
31. Pass Partition
32. Vent Connection
33. Drain Connection
34. Instrument Connection
35. Support Saddle
36. Lifting Lug
37. Support Bracket
38. Weir
39. Liquid Level Connection
40. Floating Head Support
15

16. Types of Shell and Tube HEAT EXCHANGERS
Types of shell and tube type heat exchanger most commonly used in
refinery and petrochemicals :
1. U-TUBE Exchanger –
• Tube Expansion independent of other tubes.
• Tubes difficult to clean.

17. 2. FIXED TUBE SHEET EXCHANGER –
• Cheapest and most economical.

18. 3. FLOATING HEAT EXCHANGER –
• Permits free expansion/contraction.
• Easy to clean.

19. 4. REBOILER/ KETTLE TYPE EXCHANGER
• Can handle large fluctuation of loads.

20.  R C B Fundamental classes -
• Class R – Used for severe requirement of
petroleum related processing applications.
• Class C – Used for moderate requirements of
commercial and process applications.
• Class B – Used for chemical process service.
 TEMA designations for shell and tube heat
exchanger -
• STATIONARY HEAD TYPES – A,B,C,D
• SHELL TYPES – E,F,G,H,J,K
• REAR HEAD TYPES – L,M,N,P,S,T,U
TEMA Standards:

21. TEMA
Standards

22. Plate Heat Exchanger

23. General view of
plate exchanger

24. Air-Cooled or Fin-Fan
Exchanger

25. Air-cooled exchanger
 Air blown across finned tubes (forced
draught type)
 Can suck air across (induced draught)
Finned tubes

26. Spiral Heat Exchanger

27. Spiral Heat Exchangers
 Spiral heat exchangers can be used in most applications in the
chemical process industry
 In many difficult applications where fouling and plugging are
problems, a standard shell and tube design may not be
effective
 While a spiral heat exchanger often has a higher initial cost, it
may provide a lower life cycle cost due to lower fouling rates
and ease of maintenance

28.  A spiral heat exchanger is composed
of two long, flat plates wrapped
around a mandrel or center tube,
creating two concentric spiral
channels
 In a spiral heat exchanger, the hot
fluid flows into the center of the unit
and spirals outward toward the outer
plates while at the same time, the cold
fluid enters the periphery and spiral
inward, exiting at the center

30. Selection of Heat Exchangers
• The selection depends on several factors:
– heat transfer rate
– cost
• procurement, maintenance, and power.
– pumping power,
– size and weight,
– Type,
– Materials,
– miscellaneous (leak-tight, safety and reliability, Quietness).

31. Design of Shell and Tube Heat
Exchangers
 Kern method:
 Does not take into account bypass and leakage streams.
 Simple to apply and accurate enough for preliminary design
calculations.
 Restricted to a fixed baffle cut (25%).
 Bell-Delaware method
 Most widely used.
 Takes into account:
 Leakage through the gaps between tubes and baffles and the
baffles and shell.
 Bypassing of flow around the gap between tube bundle and
shell.

32. Basic Design Procedure (Kern
Method)
 General equation for heat transfer is:
where Q is the rate of heat transfer (duty),
U is the overall heat transfer coefficient,
A is the area for heat transfer
ΔTm is the mean temperature difference
m
T
UA
Q 


33. Overall Heat Transfer Coefficient
 Overall coefficient given by:
h0 (hi) is outside (inside) film coefficient
hod (hid) is outside (inside) dirt
coefficient
kw is the tube wall conductivity
do (di) is outside (inside) tube diameters
i
i
id
i
w
i
od h
d
d
h
d
d
k
d
d
d
h
h
U
1
1
2
ln
1
1
1 0
0
0
0
0
0














34. Typical Overall Coefficients

37. Mean Temperature Difference
(Temperature Driving Force)
 To determine A, ΔTm must be estimated
 True counter-current flow – “logarithmic
temperature difference” (LMTD)
m
T
UA
Q 


38. LMTD
 LMTD is given by:
where T1 is the hot fluid temperature, inlet
T2 is the hot fluid temperature, outlet
t1 is the cold fluid temperature, inlet
t2 is the cold fluid temperature, outlet















1
2
2
1
1
2
2
1
ln
)
(
)
(
t
T
t
T
t
T
t
T
Tlm

39. Counter-current Flow –
Temperature Proflies

40. 1:2 Heat Exchanger –
Temperature Profiles

41. True Temperature Difference
 Obtained from LMTD using a correction
factor:
ΔTm is the true temperature difference
Ft is the correction factor
 Ft is related to two dimensionless ratios:
lm
t
m T
F
T 


)
(
)
(
1
2
2
1
t
t
T
T
R



)
(
)
(
1
1
1
2
t
T
t
t
S




44. Fluid Allocation

45. Shell and Tube Fluid Velocities
 High velocities give high heat-transfer coefficients but
also high pressure drop.
 Velocity must be high enough to prevent settling of
solids, but not so high as to cause erosion.
 High velocities will reduce fouling
 For liquids, the velocities should be as follows:
 Tube side: Process liquid 1-2m/s
Maximum 4m/s if required to reduce
fouling
Water 1.5 – 2.5 m/s
 Shell side: 0.3 – 1 m/s

46. Pressure Drop
 As the process fluids move through the
heat exchanger there is associated
pressure drop.
 For liquids: viscosity < 1mNs/m2
35kN/m2
Viscosity 1 – 10 mNs/m2 50-70kN/m2

47. Tube Pitch

48. Construction Details - Baffles
 Optimal baffle cut ~ 20-25%

49. Figure 12.28. Equivalent diameter, cross-sectional
areas and wetted perimeters.
An estimate of the bundle diameter Db can be obtained from equation 12.3b,
which is an empirical equation based on standard tube layouts. The constants for
use in this equation, for triangular and square patterns, are given in Table 12.4.

50. Figure 12.28. Equivalent diameter, cross-sectional
areas and wetted perimeters.

53. Tube-side Heat Transfer
Coefficient
 For turbulent flow inside conduits of uniform cross-section,
Sieder-Tate equation is applicable:
C=0.021 for gases
=0.023 for low viscosity liquids
=0.027 for viscous liquids
μ= fluid viscosity at bulk fluid temperature
μw=fluid viscosity at the wall
14
.
0
33
.
0
8
.
0
Pr
Re 








w
C
Nu


f
e
i
k
d
h
Nu 

 e
td
u

Re
f
p
k
C 

Pr

54. Tube-side Heat Transfer
Coefficient
 Butterworth equation:
 For laminar flow (Re<2000):
 If Nu given by above equation is less than 3.5, it
should be taken as 3.5
505
.
0
205
.
0
Pr
Re 

 E
St
p
t
i
C
u
h
Nu
St



Pr
Re
 
2
Pr)
(ln
0225
.
0
exp
0225
.
0 

E
14
.
0
33
.
0
33
.
0
Pr)
(Re
86
.
1 














w
e
L
d
Nu



55. Heat Transfer Factor, jh
 “j” factor similar to friction factor used for
pressure drop:
 This equation is valid for both laminar and
turbulent flows.
14
.
0
33
.
0
Pr
Re 








w
h
f
i
i
j
k
d
h



56. Tube Side Heat Transfer
Factor

57. Heat Transfer Coefficients for
Water
 Many equations for hi have developed
specifically for water. One such equation is:
where hi is the inside coefficient (W/m2 0C)
t is the water temperature (0C)
ut is water velocity (m/s)
dt is tube inside diameter (mm)
2
.
0
8
.
0
)
02
.
0
35
.
1
(
4200
i
t
i
d
u
t
h



58. Tube-side Pressure Drop
where ΔP is tube-side pressure drop (N/m2)
Np is number of tube-side passes
ut is tube-side velocity (m/s)
L is the length of one tube
m is 0.25 for laminar and 0.14 for
turbulent
jf is dimensionless friction factor for heat
exchanger tubes
2
5
.
2
8
2
t
m
w
i
f
p
t
u
d
L
j
N
P
































59. Tube Side Friction Factor

60. Procedure for Kern’s Method
 Calculate area for cross-flow As for the hypothetical
row of tubes in the shell equator.
pt is the tube pitch
d0 is the tube outside diameter
Ds is the shell inside diameter
lB is the baffle spacing, m.
 Calculate shell-side mass velocity Gs and linear
velocity, us.
where Ws is the fluid mass flow rate in the shell in
kg/s
t
b
s
t
s
p
D
d
p
A

)
( 0


s
s
s
A
W
G  
s
s
G
u 

61. Procedure for Kern’s Method
 Calculate the shell side equivalent
diameter (hydraulic diameter).
 For a square pitch arrangement:
 For a triangular pitch arrangement
0
2
0
2
4
4
d
d
p
d
t
e









 

2
4
2
1
87
.
0
2
4
0
2
0
d
d
p
p
d
t
t
e

 











62. Shell-side Reynolds Number
 The shell-side Reynolds number is given by:
 The coefficient hs is given by:
where jh is given by the following chart



e
s
e
s d
u
d
G


Re
14
.
0
3
/
1
Pr
Re 









w
h
f
e
s
j
k
d
h
Nu



63. Shell Side Heat Transfer
Factor

64. Shell-side Pressure Drop
 The shell-side pressure drop is given
by:
where jf is the friction factor given by
following chart.
14
.
0
2
2
8



























w
s
B
e
s
f
s
u
L
d
D
j
P





65. Shell Side Friction Factor

66. Problem:
 Design an exchanger to sub-cool condensate from a methanol condenser
from 95 °C to 40 °C. Flow rate of methanol 100,000 kg/h. Brackish water
will be used as the coolant, with a temperature rise from 25° to 40 °C.

67. Bell’s Method
 In Bell’s method, the heat transfer
coefficient and pressure drop are
estimated from correlations for flow
over ideal tube banks.
 The effects of leakage, by-passing, and
flow in the window zone are allowed for
by applying correction factors.

71. Bell’s Method – Shell-side Heat
Transfer Coefficient
where hoc is heat transfer coeff for cross
flow over ideal tube banks
Fn is correction factor to allow for
No. of vertical tube rows
Fw is window effect correction factor
Fb is bypass stream correction factor
FL is leakage correction factor
L
b
w
n
oc
s F
F
F
F
h
h 

73. Bell’s Method – Ideal Cross Flow
Coefficient hoc
 The Re for cross-flow through the tube
bank is given by:
Gs is the mass flow rate per unit area
d0 is tube OD
 Heat transfer coefficient is given by:



0
0
Re
d
u
d
G s
s


14
.
0
3
/
1
0
Pr
Re 








w
h
f
oc
j
k
d
h



76. Bell’s Method – Tube Row
Correction Factor Fn
 For Re>2100, turbulent flow, Fn is obtained
as a function of Ncv (no. of tubes between
baffle tips) from the chart below:
 Ncv is number of constrictions crossed =
number of tube rows between baffle tips

77. Bell’s Method – Tube Row
Correction Factor Fn
 For Re 100<Re<2100, transition region,
Fn=1.0
 For Re<100, laminar region,
18
.
0
'
)
( 
 c
n N
F

79. Bell’s Method – Window
Correction Factor Fw

80. Bell’s Method – Window
Correction Factor Fw

81. Bell’s Method – Window
Correction Factor Fw

82. Bell’s Method – Bypass Correction
Factor Fb
 Clearance area between the bundle and
the shell
 For the case of no sealing strips, Fb as a
function of Ab/As can be obtained from
the following chart
)
( b
s
B
b D
D
A 
 

83. Bell’s Method – Bypass Correction
Factor Fb

84. Bell’s Method – Bypass Correction
Factor Fb

85. Bell’s Method – Leakage
Correction Factor FL
 Tube-baffle clearance area Atb is given by:
 Shell-baffle clearance area Asb is given by:
where Cs is baffle to shell clearance and θb is the angle subtended by
baffle chord
 Total leakage area AL=Atb+Asb
where βL is a factor obtained from following chart
)
(
2
8
.
0 0
w
t
tb N
N
d
A 


)
2
(
2
b
s
s
sb
D
C
A 
 






 


L
sb
tb
L
L
A
A
A
F
)
2
(
1 

86. Bell’s Method – Leakage
Correction Factor FL

87. Shell-side Pressure Drop
 Involves three components:
 Pressure drop in cross-flow zone
 Pressure drop in window zone
 Pressure drop in end zone

88. Pressure Drop in Cross Flow Zone
where ΔPi pressure drop calculated for an equivalent ideal tube
bank
Fb’ is bypass correction factor
FL’ is leakage correction factor
where jf is given by the following chart
Ncv is number of tube rows crossed
us is shell-side velocity
'
'
L
b
i
c F
F
P
P 


14
.
0
2
2
8











w
s
cv
f
i
u
N
j
P




90. Bell’s Method – Bypass Correction
Factor for Pressure Drop
α is 5.0 for laminar flow, Re<100
4.0 for transitional and turbulent flow, Re>100
Ab is the clearance area between the bundle and shell
Ns is the number of sealing strips encountered by
bypass stream
Ncv is the number of tube rows encountered in the
cross- flow section



























3
/
1
' 2
1
exp
cv
s
s
b
b
N
N
A
A
F 

92. Bell’s Method – Leakage Factor
for Pressure Drop
where Atb is the tube to baffle clearance area
Asb is the shell to baffle clearance area
AL is total leakage area = Atb+Asb
βL’ is factor obtained from following
chart





 


L
sb
tb
L
L
A
A
A
F
)
2
(
1 '
'


93. Coefficient for FL’

96. Pressure Drop in End Zones
 Ncv is the number of tube rows
encountered in the cross-flow section
 Nwv is number of restrictions for cross-
flow in window zone, approximately
equal to the number of tube rows.
'
)
(
b
cv
cv
wv
i
e F
N
N
N
P
P 




 




97. Bell’s Method – Total Shell-side
Pressure Drop
zones
window
N
zones
crossflow
N
zones
end
P
b
b
s




 )
1
(
2
w
b
c
b
e
s P
N
P
N
P
P 






 )
1
(
2