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Design of 2, 4 Shell & Tube heat exchanger

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Computer Consulting
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AMIT K.
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  1. Introduction
  2. Overview of heat exchanger's
  3. Classification of heat exchanger's
  4. Shell & Tube Heat Exchanger
  5. Standards and codes
  6. Standards for Tubes and Shell
  7. Mechanical design considerations
  8. Design methods
  9. General Design procedure for Heat Exchanger
  10. Design Data
  11. Energy Conservation Techniques
  12. The Problem
  13. Solution to Design Problem
  14. Fluid allocation to shell and tube side
  15. Industrial heat exchangers
  16. Common failures in heat exchangers
  17. Temperature Profile Distortion
  18. Increasing heat Exchanger Performance
  19. Conclusion

This project report presents the application of Kern's Method for the optimal design of shell-and-tube heat exchangers. A primary objective in the heat exchanger design is the estimation of the minimum heat transfer area required for a given heat duty, as it governs the overall cost of the heat exchanger. Since many discrete combinations of the design variables are possible, the design engineer needs an efficient strategy in searching for the optimum design of heat exchanger with minimum cost and maximum operating efficiency.

In the present study, we have tested many design configurations obtained by varying the design variables viz. outer tube diameter, tube pitch, tube length, number of tubes, number of shell and tube passes and heat transfer area. Kern's method is used to find the optimum heat transfer area for a given set of constraints. For a case study taken up, it is observed that this method has a simple evolution strategy, significantly faster and accurate enough for preliminary design calculations. It is also used for designs where uncertainty in other design parameters and it is such that the use of more elaborate methods is not justified.

A heat exchanger is process equipment used for transferring heat from one fluid to another fluid through a separating wall. Usually heat exchangers are classified according to the functions for which they are employed. The most widely used heat exchanger is the Shell & Tube heat exchanger. It consists of parallel tubes enclosed in a shell. One of the fluid flows through the shell & the other flows through the tubes. The one, which flows through the shell side, is called as shell side fluid & the one flowing through the tubes is called as tube side fluid. "When none of the fluid condenses or evaporates, the unit is called as Heat Exchanger." In this only the sensible heat transfers from the one fluid to another.

This project report presents the application of Kern's Method for the optimal design of shell-and-tube heat exchangers. A primary objective in the heat exchanger design is the estimation of the minimum heat transfer area required for a given heat duty, as it governs the overall cost of the heat exchanger. Since many discrete combinations of the design variables are possible, the design engineer needs an efficient strategy in searching for the optimum design of heat exchanger with minimum cost and maximum operating efficiency.

[...] Deficiencies of the segmented baffle include the potential for dead spots in the exchanger and excessive tube vibration. Baffle enhancements have attempted to alleviate the problems associated with leakage and dead areas in the conventional segmental baffles. The most notable improvement has resulted in a helical baffle as shown in Figure 2. Van der Ploeg and Master17 describe how this baffle is most effective for high viscosity fluids and provide several refinery applications. The author further describes how the baffles promote nearly plug flow across the tube bundle. [...]


[...] Start with one shell pass and two tube passes. [pic]ºC [pic] [pic] Ft = 0.88, which is acceptable ?Tm = 0.88 x 80.7 = 71.0 ºC STEP 5: Heat Transfer Area [pic]m2 STEP 6: Layout and Tube Size Using a split-ring float head heat exchanger for efficiency and ease of cleaning. Neither of the fluid is corrosive and the operating pressure is not high, so plain carbon steel can be used for the shell and tubes. The crude is dirtier than the kerosene, so put the crude through the tubes and the kerosene in the shell. [...]


[...] NTU : It is a measure of effectiveness of heat exchanger. Fouling : The phenomenon of rust formation and deposition of fluid impurities is called as Fouling. The reciprocal of scale heat transfer coefficient, hs is called as fouling factor, Rf. Nomenclature Ao -Heat transfer area based on outer diameter, m2 Ai -Heat transfer area based on internal diameter, m2 Q -Heat duty, W K -Thermal conductivity, W/mºC Np -Number of passes on tube side Tm -Mean temperature difference Uo,ass -Assumed value of overall heat transfer coefficient based on outside area, W/m2ºC U0,cal -calculated value of overall heat transfer coefficient based on outside area, W/m2ºC Cpc -Heat capacity (constant pressure) of colder fluid, J/KgºC Cph -Heat capacity (constant pressure) of hot fluid, J/KgºC ?Tlm -Logarithmic mean temperature difference, ºC Db -Bundle diameter, m Ds -Shell diameter, m d0 -Tube outside diameter, m L -Tube length, m lb -Baffle spacing, m Re -Reynolds Number Pr -Prandtl Number Nu -Nusselt Number jh -Heat transfer factor F -LMTD correction factor P -Temperature ratio R -Capacity Ratio S -Effectiveness factor Appendix-A Table 1: Standard dimensions for steel tubes |Outside diameter, mm |Wall thickness, mm | |16 |1.2 |1.6 |2.0 |-- |-- | |20 |-- |1.6 |2.0 |2.6 |-- | |25 |-- |1.6 |2.0 |2.6 |3.2 | |30 |-- |1.6 |2.0 |2.6 |3.2 | |38 |-- |-- |2.0 |2.6 |3.2 | |50 |-- |-- |2.0 |2.6 |3.2 | Table 2: Minimum shell thickness, mm |Nominal shell |Carbon Steel |Alloy Steel | |diameter, mm | | | | |Pipe |Plate | | |152 |7.1 |-- |3.2 | |203-305 |9.3 |-- |3.2 | |330-737 |9.5 |9.5 |4.8 | |762-991 |-- |11.1 |6.4 | |1016-1524 |-- |12.7 |7.9 | Table 3: Shell and tube heat exchanger configuration |Nominal|Tube |No. [...]

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