page_title: Plenum chamber
section_title: Etymology
hierarchical_section_title: Plenum chamber / Etymology
caption_attribution_description: English: This file has been extracted from another file&#x3a;&#32; N&#38;AMOV - School.png
context_page_description: A plenum chamber is a pressurised housing containing a fluid at positive pressure. One function of the plenum is to equalise pressure for more even distribution, because of irregular supply or demand. Typically a plenum is relatively large in volume and thus has relatively low velocity. In a wind tunnels, rockets, and many flow applications - the plenum is a chamber upstream on the fluid flow where the fluid initially resides. A plenum chamber can also work as an acoustic silencer device.
  Examples of plenum chambers include those used with:
  Superchargers
  Hovercraft
  Corliss steam engines
  Raised floors and false ceilings in equipment rooms
  Some organs
  A number of aerophones, such as the bag of bagpipes and the slow air chamber of the Native American flute
  Plenum Chamber Anesthetic Vaporizers
  Rocket Motor Combustion Chambers. May have a section near the nozzle that is free of the propellant charge to improve mixing and combustion.
context_section_description: The term "plenum" derives originally from classical theories and the notion that "Nature abhors a vacuum". These gave rise to the notion of 17th century 'plenum' as the opposite of vacuum, and all things "being either Plenum or Vacuum".
  By the 19th century, the development of mechanical fans and industrial machinery had provided another, more technical use. This referred to "a system of artificial ventilation", which used a pressure raised slightly above atmospheric pressure, in contrast to the "vacuum system" which used a pressure below atmospheric. At a time when high pressure steam or hydraulic systems were well established, these were a distinct set of systems based on low pressure and high volume flows.
caption: Schoolroom ventilation on the plenum system
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