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Objectives

Objectives. Discuss Exam Finish with Diffuser Selection Learn about Fan and Pumps . Find Characteristic Length (L). Indicator of Air Distribution Quality . ADPI = air distribution performance index Fraction of locations that meet criteria: -3 °F < EDT < 2 °F or -1.5 °C < EDT < 1 °C

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Objectives

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  1. Objectives • Discuss Exam • Finish with Diffuser Selection • Learn about Fan and Pumps

  2. Find Characteristic Length (L)

  3. Indicator of Air DistributionQuality • ADPI = air distribution performance index • Fraction of locations that meet criteria: • -3 °F < EDT < 2 °F or -1.5 °C < EDT < 1 °C • Where, EDT = effective draft temperature • Function of V and Δt (Eqn 18.1) • EDT=(tlocal-taverage)-M(Vlocal-Vaverage) , M=7 °C/(m/s) ADPI considers ONLY thermal comfort (not IAQ)

  4. Ideal and Reasonable Throws

  5. Diffuser testing

  6. ADPI

  7. Select Register • Pick throw, volumetric flow from register catalog • Check noise, pressure drop http://www.titus-hvac.com/ecatalog/subcategory.aspx?refid=186 http://www.nailor.com/ http://www.price-hvac.com/

  8. Fans • Driving force to move air in buildings • Raise pressure and produce flow • Two main types: • Centrifugal • Axial

  9. Relevant Fan Parameters • Total pressure rise • Static pressure rise • Power requirement • Efficiency • Note ηtot does not account for motor efficiency

  10. Balance Point

  11. Fan Performance

  12. Centrifugal fans

  13. Axial Fans

  14. Fan Laws • “Approximate relationships” • Given two aerodynamically similar fans, can extrapolate performance data • Be very careful

  15. Controlling Air Flow

  16. Dampers

  17. Effect on Fan Curve

  18. VAV Operation

  19. Dampers

  20. Dampers

  21. Pumps • Driving force to move air water in buildings • Raise pressure and produce flow • One main type • Centrifugal

  22. Pump curves • NPSHR = Net Positive Suction Head Required

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