Compact Heat Exchangers

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Basic concepst in heat exchangers, uses, types and fouling

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Compact Heat Exchangers

  1. 1. Adlin Miranda Morales INTD 3355 Prof. Liz Pagan
  2. 2. Agenda  What is a compact heat exchanger?  Types  Advantages and limitations  Cost of heat exchangers  Fouling  Security and Environmental aspect  Design  Conclusion
  3. 3. Basic Definitions  Heat exchanger: apparatus that has two streams of fluid that exchange temperatures in order to heat or cool the system.  Fouling: type of contamination in the heat exchanger that can damage its purpose.
  4. 4. Description  Basically this presentation focuses on what are compact heat exchangers, the various types, costs, advantages and disadvantages and how fouling may affect.  The main option for research was internet and the library ( books, journals, thesis, etc.)
  5. 5. What is a Compact Heat Exchanger?  Area density greater than 700 m2/m3 for gas or greater than 300 m2/m3 when operating in liquid or two-phase streams.  Highly efficient  Reduce volume, weight and cost
  6. 6. Types of CHEs  Plate and frame heat exchangers: (PHE)
  7. 7. Plate and Frame Heat Exchanger  Most common type of PHE  Consists of plates and gaskets  Materials: stainless steel, titanium and non-metallic  Operation limits: - temperatures from -35°C to 220°C - pressures up to 25 bar - flow rate up to 5000 m3/h
  8. 8. Brazed Plate Heat Exchanger (PHE)
  9. 9. Brazed Plate Heat Exchanger  Operates at higher pressures than gasketed units  Materials: stainless steel, copper contained braze  Operating limits: - From -195°C to 200°C - Pressures up to 30 bar  It is impossible to clean. The only way is by applying chemicals.
  10. 10. Welded Plate Heat Exchanger (PHE)
  11. 11. Welded Plate Heat Exchanger  Plates welded together to increase pressure and temperature limits  Materials: stainless steal and nickel based alloys. Can be made with copper , titanium or graphite  Operation Limits: - temperature limits depend on the material - can tolerate pressures in excess of 60 bar
  12. 12. Spiral Heat Exchanger (SHE)
  13. 13. Spiral Heat Exchanger (SHE)  Two long strips of plate wrapped to form concentric spirals  Materials: carbon steel, stainless steel and titanium  Operation limits: - Temperatures up to 400°C (depends on gasketed materials) - Pressures up to 25 bar
  14. 14. Plate Fin Heat Exchanger (PFHE)
  15. 15. Plate Fin Heat Exchanger (PFHE)  High area density and handles several streams  Materials: aluminum, corrosion and heat resistant alloys, and stainless steel (available in titanium)  Operation limits: - Temperature limits depend on the material - cryogenic temperature up to 100°C (aluminum) - stainless steel up to 650°C - Pressures up to 100 bar for aluminum and 90 bar for stainless steel
  16. 16. Printed-circuit heat exchangers (PCHE)
  17. 17. Printed-circuit heat exchangers (PCHE)  Flexibility of design and high strength offered by techniques of construction  Materials: Stainless steel 316L, alloys, nickel and titanium.  Operating limits: - temperature ranges from -200°C to 900°C - pressures up to 400 bar
  18. 18. Compact Shell-and-Tube Heat Exchanger To increase surface area, this equipment has a large number of small diameter tubes
  19. 19. Other Types of CHE  Compact types retaining a shell  APV Paratube Heat Exchanger  Fluidized Bed Heat Exchanger  Twisted Tube Heat Exchanger
  20. 20. Advantages and Limitations  Improved energy efficiency - Closer approach temperatures allows greater energy transfer.  Smaller volume and weight  Higher efficiency  Lower cost  Multi-stream and multi-pass configurations  Tighter temperature control  Power savings  Improved safety
  21. 21. Limitations  Lack of industrial awareness Companies remain aware of technology of CHE  Limited choice Particularly for high-pressure  Conservatism in the user industries Process industries are reluctant to adopt what they may seen either as new technologies.  Susceptibility to fouling Perception that small passages are likely to foul.
  22. 22. Cost of compact heat exchangers  Compact heat exchanger tend to be cheaper especially when their total installed cost is considered.  In some cases the materials used to manufacture is expensive, but when we consider the cost of unit plus the installation, the cost is less than equivalent shell and tube.
  23. 23. Cost of compact heat exchangers
  24. 24. Fouling  Crystallization or precipitation Solutes in the fluid is precipitated and crystals are formed  Particulate fouling or silting Solid particles are deposited on the heat transfer surface  Biological fouling Deposition and growth of organism on surfaces  Corrosion fouling Carrying of corrosion products from other part of the system being left on the heat transfer area surface  Chemical reaction fouling Arises from reactions between constituents in the process fluids  Freezing or solidification fouling Occurs when the temperature of a fluid passing through a heat exchanger becomes too low
  25. 25. Security Aspects  Fouling: - Use of non-fouling fluids wherever possible is of course recommended, for example clean air or gases, light carbons and refrigerants. - In open systems, check the possible application of self-cleaning strainers, and the installation of systems to dose with biocides, scale inhibitors, etc., to control fouling. - Use self-cleaning filter if possible - Consider chemical cleaning. If this is undertaken, the system must be designed to allow the introduction and complete removal of cleaning fluids.
  26. 26. Corrosion:  In some CHEs, the wall thicknesses are less than in a shell-and-tube heat exchanger, so corrosion rates and allowances need to be accessed carefully  Although CHEs are often made from more corrosion- resistant materials than the shell-and-tube units, other corrosion mechanisms such as cracking may occur, and the compatibility of the material with the fluids in the CHE should be checked.
  27. 27. Design  Analysis based on ε and Ntu method  Convection and friction coefficients have been determined by Kays and London.  Some data of design can be supplied by manufacturers.  Results for heat transfer and friction factors for circular tube- circular fin and for circular tubes – continuous fin.
  28. 28.   VA fr m m G V max A ff A ff A fr A ff área mínima flujo libre A fr área frontal 2 /3 jH St Pr St h /Gc p G V max Re GD h /
  29. 29. 2 /3 jH St Pr   VA fr m m G V max A ff A ff A fr St h /Gc p A ff área mínima flujo libre G V max A fr área frontal Re GD h /
  30. 30. Environmental Aspects  Energy conservation and environmental considerations are the driving forces behind changes aimed at reducing both chemical and thermal waste.  More efficient use of energy and raw materials  Recovery of heats of reaction  High intensity mixing, enhancing process selectivity  Minimum risk of runaway reactions  Smaller and cheaper plant  Ability to handle high-pressure reactions
  31. 31. Conclusion  Compact heat exchangers are available in a wide variety of configurations to suit most processes heat transfer requirements.  The advantages of CHEs, and associated heat transfer enhancement techniques, extend far beyond energy efficiency.  Lower capital cost, reduced plant size, and increased safety are typical of the benefits arising from the use of CHEs.  Compact heat exchangers can replace some normal size heat exchangers bringing advantages and performance.
  32. 32. Conclusion  This research took a lot of time, since the specific details of a theme like this take time to search.  Even though it took time, I really enjoyed making this presentation.
  33. 33. References  ADVANCES IN COMPACT HEAT EXCHANGERS. (n.d.). Retrieved March 5, 2009, from http://www.rtedwards.com/books/164/index.html  Al-Qahtani, Abdullah Mushabbab Zuhair, M.S., 2008, Design and operate a fouling monitoring device to study fouling at twisted tube. King Fahd University of Petroleum and Minerals (Saudi Arabia), 171 pages; AAT 1456206.  An Assessment of the Performance and Requirements for quot;Adiabaticquot; Engines. (1988, May 27). Science Magazine, 240, 1157-1162. Retrieved March 5, 2009, from http://library.uprm.edu:2132/cgi/content/abstract/sci;240/4856/1157?maxtoshow=&HITS =10&hits=10&RESULTFORMAT=&fulltext=heat+exchangers&searchid=1&FIRSTINDEX=1 0&resourcetype=HWCIT  Bell, L. E. (2008, September 12). Cooling, Heating, Generating Power, and Recovering Waste Heat with Thermoelectric Systems . Science Magazine, 321, 1457-1461. Retrieved March 5, 2009, from http://library.uprm.edu:2132/cgi/content/abstract/sci;321/5895/1457?maxtoshow=&HITS =10&hits=10&RESULTFORMAT=&fulltext=heat+exchangers&searchid=1&FIRSTINDEX=0 &resourcetype=HWCIT
  34. 34. References  Compact Heat Exchangers. (n.d.). Retrieved March 5, 2009, from http://www.eca.gov.uk/etl/find/_85.htm  Designing Shell and Tube Heat Exchangers. (n.d.). Retrieved March 5, 2009, from http://www.cheresources.com/designexzz.shtml  Energy Savers: Heat Exchangers for Solar Water Heating Systems. (n.d.). Retrieved March 5, 2009, from http://www.energysavers.gov/your_home/water_heating/index.cfm/m ytopic=12930  Enhanced, Compact and Ultra-Compact Heat Exchangers: Science, Engineering and Technology. (n.d.). Retrieved March 5, 2009, from http://services.bepress.com/eci/heatexchangerfall2005/
  35. 35. References  Hawkins, G. A. (1954, December 10). Heat Transmission. Science Magazine, 532.  Heat Exchangers - Shell & Tube, Plate, Air-Cooled : API Heat Transfer. (n.d.). Retrieved March 5, 2009, from http://www.apiheattransfer.com/  Heat Exchangers for the HVAC Industry. (n.d.). Retrieved March 5, 2009, from http://www.heatexchangersonline.com/  Heat Exchangers. (n.d.). Retrieved March 5, 2009, from http://www.flatplate.com/?gclid=CNbbnaC1pZoCFRKIxwodJDnU8w  Heat Transfer Engineering. (1979, January 8). Heat Transfer Engineering, 1, pp. 2.  JM Heat Exchangers - Heat Transfer Specialists. Shell & Tube Exchangers, Fin Coils, Calorifiers, Plate Heat Exchangers, Charge Air Coolers, Fin Fan Exchangers. (n.d.). Retrieved March 5, 2009, from http://www.jmheatexchangers.com/
  36. 36. References  Macro Power from Micro Machinery. (1997, May 23). Science Magazine, 276, 1211. Retrieved March 5, 2009, from http://library.uprm.edu:2132/cgi/content/summary/sci;276/5316/1211?maxtoshow=&HITS =10&hits=10&RESULTFORMAT=&fulltext=heat+exchangers&searchid=1&FIRSTINDEX=0 &resourcetype=HWCIT  Veronica, Daniel Alexander, Ph.D., 2008, Detecting heat exchanger fouling automatically with an embedded data-driven agent using expert signature maps. University of Colorado at Boulder, 245 pages; AAT 3303899  (2004). Compact Multifunctional Heat Exchangers: A Pathway to Process Intensification. Grenoble, France: CEA-Grenoble.  (2001). Handbook of Heating, Ventilation, and Air Conditioning. Boca Raton: CRC Press LLC.  (2003). Heat Transfer in Single and Multiphase Systems. Boca Raton: CRC Press LLC.  (2000). The CRC Handbook of Thermal Engineering. Boca Raton: CRC Press LLC.

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