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Heat Transfer and Pressure Drop Performance of Spiral Baffle Heat Exchangers

Zaker Hosseini, Farhad | 2016

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 48871 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Farhadi, Fathollah
  7. Abstract:
  8. In this work, a numerical investigation on shell side performance of a continuous helical baffle helixchanger along with smooth and helically ribbed tubes using CFD commercial code, Fluent, has been performed. The results of simulation for this type of exchanger were compared to a similar heat exchanger with segmental baffles. The geometries are created and meshed using Solidworks and Ansys Meshing softwares, respectively. Mesh generation is carried out using unstructured tetrahedral type elements. Element size (or number of elements) are chosen in such a manner that maintain accuracy and reliability of results in a reasonable run time. Simulation validation were carried out by comparison of results with Aspen B-jac outcomes. The Realizable- κ-ε turbulence model was used to describe the effects of turbulence on the flow and heat transfer. The governing equations are iteratively solved by the finite-volume-method with SIMPLE pressure velocity coupled algorithm. For the solution algorithm, the pressure based (segregated) approach is selected. The QUICK scheme is used to discretize the convective terms and standard scheme for pressure interpolation. Simulation results shows that on average, pressure drop in helixchangers are 61% lower, while transferred heat and overall heat transfer coefficient are just 14% and 18% lower than heat exchangers with segmental baffles, respectively. Therefore, compared to exchangers with segmental baffles, heat transfer coefficient to pressure drop ratio is 52% higher for helixchangers, on average. Moreover, it was discovered that while the main resistance against heat transfer is in shell side, using helically ribbed tube would not offer any enhancement in thermohydraulic performance of heat exchanger. About tube vibration topic, using helical baffle could reduce the magnitude of velocity component perpendicular to tubes, while increasing unsupported tube spans. Accordingly, it seems that more accurate trade-off is inevitable to decide whether using this type of baffles could decrease/increase tube vibration possibility. However, reducing baffle helix angle along with using double helix arrangements have been named as two solution methods for such a problem if any vibration possibility exists. About exchanger fouling subject, simulation results and analysis of industrial application reports indicate that by using helical baffles, approximately 3 times longer operation run-length could be achieved
  9. Keywords:
  10. Computational Fluid Dynamics (CFD) ; Fouling ; Heat Transfer ; Pressure Drop ; Helical Baffle ; Shell and Tube Heat Exchenger

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