This is an example of mechanical designing of a shell and tube heat exchanger

1. Design of a Heat Exchanger
Mini project – Heat exchanger design
Done by: Sarhan.FM
180571A

2. Background
• Distilled fatty acid (DFA) is used as a raw material in soap
manufacturing process.
• DFA is at solid state at room temperature. It should be melted in order
to ease the conveying process.
• The melting is done in two steps, first the solid DFA is melted by the
steam coils Installed at the bottom of the tank. After that the melted
liquid which is at the bottom of the tank is circulated through a heat
exchanger.
• This heat exchanger should be designed to heat the DFA at 55℃ to
85℃ .

3. Collected Data
• Cold liquid – Distilled Fatty acid (DFA)
• Hot fluid – Steam
• Cold liquid flow rate (kg/s) - 2.5962
• Cold Liquid Specific Heat Capacity (J/kg/K) -1988
• Cold Liquid Input Temperature (˚C) – 55
• Cold Liquid Output Temperature (˚C) – 85
• Hot fluid Flow Rate (kg/s) - 0.077777778
• Hot fluid Specific Heat Capacity (J/kg/K) - 2135.33
• Hot fluid Input Temperature (˚C) - 200
• Hot fluid Output Temperature (˚C) - 138.99

4. Collected Data
• Steam partially condenses in the heat exchanger
• Tube side maximum operating pressure (Gauge) – 2.5 bar
• Shell side maximum operating pressure (Gauge) – 2.5 bar
• Pressure drop – Negligible
• Construction material – Tubes and shell – S/S 304

5. Design calculations – Heat duty
• Heat duty = 𝑚𝑐𝑝∆𝑇
= 2.5962 × 1988 85 − 55
=154837.368 J/s
Steam enthalpy at inlet temperature 𝐻𝑖𝑛 = 2.86E+06
Enthalpy of evaporation 𝐻𝑓𝑔 = 2.15E+06
Steam enthalpy at outlet temperature 𝐻𝑜𝑢𝑡 = 2.73E+06
• Dry fraction of steam (x) =
154837.368
0.077777778
−2.86×106+2.73×106
2.15×106
= 0.865988059

6. Design calculations - LMTD
• LMTD =
200−85 −(138.99−55)
ln
(200−85)
(138.99−55)
= 98.68429923 ℃
Since the heat exchanger has one shell pass and one tube pass there is
no need for temperature correction.
• Selected overall heat coefficient for design
(U) = 37.91889772 𝑊𝑚−2
℃−1
Total heat transfer area (A) =
𝑄
𝑈(𝐿𝑀𝑇𝐷)
= 41.35842113 𝑚2

7. Design calculations – HX dimensions
• Pipe Outer Diameter (𝑑𝑜) 26.67 mm
• Thickness (𝑡𝑡) 2.11 mm
• Pipe Inner Diameter (𝑑𝑖) 22.45 mm
• Length (L+c) 1.8288 m
• Sum of tube Plate Allowance for both sides (c) 0.05 m
• Length for Heat transfer (L) 1.7788 m
• Outer tube surface area (𝜋 𝑑𝑜𝐿) 0.149039028 m²
• Number of tubes =
41.35842113
0.149039028
= 278

8. Design calculations – HX dimensions
• Triangular pitch is used for tube layout
• Tube bundle diameter 𝐷𝑏 = 𝑑𝑜(
𝑁𝑡
𝐾1
)
1
𝑛1
= 26.67(
278
0.319
)
1
2.142 = 629.0579695 𝑚𝑚
• Tube sheet is fixed
• BDC from graph = 14.29
• Shell inside diameter 𝐷𝑠 = 𝐷𝑏 + 𝐵𝐷𝐶 = 629.0579695 + 14.29
= 643.3479695 𝑚𝑚

9. Design calculations – Tube side coefficient
• Mass velocity of tube side fluid (𝐺𝑡) =
Mass flow rate of tube side liquid
Total cross sectional area of all tubes
=
2.5962
𝜋×278×
22.45 2
4 ×10−6
= 23.59232692 𝑘𝑔𝑚−2
𝑠−1
• Tube side liquid Viscosity (𝜇𝑡) = 0.01275 𝑁𝑠𝑚−2
• Reynolds number (Re) =
𝐺𝑡×𝑑𝑖
𝜇𝑡
= 41.54099916
• L/D ratio = 79.23385301
• Tube side heat transfer factor (𝑗ℎ) = 0.04

10. Design calculations – Tube side coefficient
• Thermal conductivity of tube side fluid 𝑘𝑓 = 0.168 𝑊𝑚−1
℃−1
• Specific heat capacity of tube side fluid 𝑐𝑝,𝑐= 1988 𝐽𝑘𝑔−1
℃−1
• Prandlt number 𝑃𝑟 =
𝑐𝑝,𝑐 .𝜇𝑡
𝑘𝑓
= 150.6060606
• Viscosity of water at 70℃ 𝜇𝑤 = 0.000404 𝑃𝑎. 𝑠
• Tube side coefficient ℎ𝑖 =
𝑘𝑓.𝑗ℎ.𝑅𝑒.𝑃𝑟0.33(
𝜇𝑡
𝜇𝑤
)0.14
𝑑𝑖
= 105.6746317

11. Design calculations – Shell side coefficient
• Number of baffles = 5
• Triangular pitch (𝑃𝑡) 1.25 do = 33.3375 mm
• Baffle spacing (B) = 128.6695939 mm
• Equivalent diameter 𝑑𝑒 =
1.1
𝑑𝑜
𝑃𝑡
2
− 0.917𝑑𝑜
2
= 18.9370335 mm
• Cross flow area 𝐴𝑠 = (𝑃𝑡−𝑑𝑜)𝐷𝑠 𝐵/𝑃𝑡 =16555.86439 𝑚𝑚2
• Mass velocity = 4.69789894 𝑚𝑠−1
• Shell side fluid viscosity = 1.48E-05 Pa.s

12. Design calculations – Shell side coefficient
• Reynolds number = 5991.747572
• Shell side heat transfer factor 𝑗ℎ,𝑠 = 0.0073
• Fluid thermal conductivity (W/m/C) = 0.031468
• Shell side fluid specific heat capacity (J/kg/C) = 2135.33
• Prandlt number = 1.00752996
• Shell side coefficient =
𝑘𝑓.𝑗ℎ.𝑅𝑒.𝑃𝑟0.33
𝑑𝑒
= 72.86509785

13. Overall heat transfer coefficient
• Fouling factor of DFA: ℎ𝑖𝑑 = 5000 𝑊𝑚−2℃−1
• Fouling factor of Steam: ℎ𝑜𝑑 = 5000 𝑊𝑚−2℃−1
• Overall heat transfer coefficient
1
U
=
1
72.86509785
+
1
5000
+
26.67 ln (
26.67
22.45
)
2×16.2 ×1000
+
26.67
22.45
×
1
5000
+
26.67
22.45
×
1
105.675
U = 39.14633665 𝑊𝑚−2℃−1

14. Shell thickness
• Design pressure = Maximum allowable operating pressure + 10%
= 2.5 + 0.25 = 2.75 bar
• Joint efficiency = 0.8
• Maximum allowable stress = 110 MPa
• Since the construction material is stainless steel, corrosion allowance
is not needed
• Shell thickness t =
𝑃𝐷
𝑓×𝑗−0.6𝑃
=
0.275×0.643
110×0.8−0.6×0.275
= 0.002014239 𝑚

15. Shell thickness
• Minimum shell thickness according to TEMA standards for the shell
diameter (610 -737 mm) is 4.8 mm
• Therefore shell thickness is 4.8mm

16. Shell cover design
• Heat exchanger type = AEL
• Shell cover type = Flat cover
• 𝑡 =
𝐷
10
𝐶𝑃
𝑓

17. • 𝑡 =
648.148
10
0.25 ×
0.275
110
• t = 1.62 mm
• Since shell thickness is greater than 1.62 mm, Shell cover thickness
also 4.8 mm
Shell cover design

18. Tube sheet thickness
• 𝑡 =
𝐹𝐺𝑝
3
𝑃
𝑘×𝑓
F = 1
Gp = Shell inner diameter
For triangular pitch 𝑘 = 1 −
0.907
(
𝑃𝑡
𝑑𝑜
)2
k = 1- 0.907/(33.34/26.67)² = 0.41952
t = 1 ×
643.3479695
3
0.275
0.41952×110
= 16.55 𝑚𝑚

19. Results & Discussion
Design Summary
Heat exchanger type AEL (TEMA standards)
Number of shell passes 1
Number of tube passes 1
Design pressure shell side 0.275 MPa
Shell inner diameter 643.35 mm
Shell thickness 4.8 mm
Tube outside diameter 26.67 mm
Tube thickness 2.11 mm
Number of tubes 278
Tube length 1.8288 m
Number of baffles 5
Baffles spacing 128.67 mm
Heat transfer area 41.36 m²

20. Results & Discussion
Heat transfer overall coefficient 39.15 W/m²/ ˚C
Shell cover type Flat cover
Shell cover thickness 4.8 mm
Tube sheet thickness 16.55 mm
Tube sheet layout Triangular

21. Results & Discussion

22. Results & Discussion

23. Results & Discussion
• The previous figures shows the existing heat exchanger dimensions in
the plant.
Parameters Design values Real values
Tube dimensions SCH 10, Dia 0.75” SCH 10, Dia 0.75”
Tube sheet layout Triangular Circular arrangement
Tube length 6 ft 6 ft
Number of baffles 5 5
Number of tubes 278 85
Shell thickness 4.8 mm 4 mm
Bundle diameter 630 mm 304.8 mm
Tube sheet thickness 16.55 mm 4 mm

24. Results & Discussion
• The design was done based on various assumption and
approximations. The properties of DFA used in this design calculations
are not accurate and the tube layout is also another factor for the
deviations from the real values.

25. References
• Chhabra, R. P., & Shankar, V. (2017, December 12). Coulson and Richardson’s Chemical Engineering: Volume 1B: Heat and Mass
Transfer: Fundamentals and Applications (7th ed.). Butterworth-Heinemann.
• Heat Exchanger Calculations. (n.d.). Google Docs. Retrieved October 1, 2022, from
https://docs.google.com/spreadsheets/d/1BCiPnfIOmQz91DqeFgGeFeOG0QXOCfh3xeIp6rGHRoQ/edit?usp=sharing
• LIPICO Technologies. (n.d.). Retrieved October 1, 2022, from https://www.lipico.com/technical_references_palm_oil_properties.html
• Steam Table Calculator | Superheated Steam Region | Spirax Sarco. (n.d.). Retrieved October 1, 2022, from
https://www.spiraxsarco.com/resources-and-design-tools/steam-tables/superheated-steam-region#article-top
• Tubular Exchanger Manufacturers Association. (2022, October 1). Standards of Tubular Exchanger Manufacturers Association (Fifth).
TEMA.