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Shell - Tube Heat Exchanger : Design procedure
How to design a shell tube heat exchanger (determination of exchange area, configuration, heat exchange coefficients)
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| Section summary |
|---|
| 1. Shell-Tube heat
exchangers |
| 2. Shell-Tube heat
exchanger calculation procedure |
1. Shell-Tube heat exchangers
Shell-Tube heat exchangers are among the most common type of heat exchanger equipment that can be found in the industry, especially in chemical, petrochemicals, oil and gas industries. The design of these heat exchangers is quite complex and required both computational tools and experience.
A design procedure is presented here and supported in detail by other specific pages of Process Engineer's Tools website. The calculation of the overall heat transfer coefficient of the heat exchanger is done thanks to the Bell-Delaware method which has been published in the 60s. Although this method is not very accurate compared to modern softwares (HTRI) it presents the advantage to be simpler to execute while allowing to get an idea of the size and performance of an heat exchanger. It is also interesting to help to understand the physical phenomena that happen in the heat exchanger and are taken into consideration, through most recent correlation, in simulation softwares.
Warning : the method presented in this page and other pages of
the website should be used for getting a rough idea of the
performance of a shell-tube heat exchanger, but should not be used
for detail design and construction.
2. Shell-Tube heat exchanger calculation procedure
How to calculate the heat transfer coefficient and exchange area of a shell tube heat exchanger ?
The following sequence is used to design a shell tube heat exchanger knowing the characteristics of the fluid on both sides and the duty to reach.
- Select the heat exchanger type (number of passes...)
- Chose which fluid is on tube side, which fluid on shell side
- Calculate the required duty (Q = m.Cp.ΔT)
- Calculate the LMTDcc
- Calculate the F correction factor
- Calculate required UA = Q / (F.LMTDcc)
- Estimate the overall heat transfer coefficient U
- Calculate in consequence the estimated heat exchange area A
- Calculate the heat exchange coefficient on tube side and calculate the heat exchanger(s) configuration actually to be installed : number of shells, tubes per shell, lenght of tubes... Aactual
- Calculate the required heat exchange coefficient Ureq = Q / (Aactual/(F.LMTDcc))
- Define the detailed characteristics of the exchanger (tubes, baffles...)
- Run the Bell-Delaware method to calculate the actual heat exchange coefficient UBD from the configuration and characteristics chosen
- Calculate the pressure drops
- Decision
- If UBD < Ureq, return to step 9
- If UBD >> Ureq, return to step 9
- If pressure drops are too high, return to step 9 OR step 1
- If UBD > Ureq (typically with an overdesign of 5-10%) AND pressure drops are reasonable, the design is concluded
After selecting the design, several precisions and verifications are required :
- Detailed material specification
- Cost optimization
- Vibration prevention