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Objectives

Objectives. Duct Design AND Diffuser Selection. DOAS System. www.doas.psu.edu. DOAS with multi-split systems. Fresh air?. DOAS fresh air configurations. DOAS fresh air configurations. Issues Related to DOAS. Split of sensible and latent load Selection of hydronic system

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Objectives

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  1. Objectives • Duct Design AND Diffuser Selection

  2. DOAS System • www.doas.psu.edu

  3. DOAS with multi-split systems Fresh air?

  4. DOAS fresh air configurations

  5. DOAS fresh air configurations

  6. Issues Related to DOAS • Split of sensible and latent load • Selection of hydronic system • Winter vs. summer operation • Winter operation with DX systems (heat pump)

  7. Pressures • Static pressure • Velocity pressure • Total pressure – sum of the two above

  8. Relationship Between Static and Total Pressure

  9. Total and static pressure drops are proportional to square of velocity Plot of pressure drop vs. volumetric flow rate (or velocity) is called system characteristic Duct Design

  10. System Characteristic

  11. Electrical Resistance Analogy

  12. Frictional Losses

  13. Non-circular Ducts • Parallel concept to wetted perimeter

  14. Dynamic losses • Losses associated with • Changes in velocity • Obstructions • Bends • Fittings and transitions • Two methods • Equivalent length and loss coefficients

  15. Loss Coefficients • ΔPt = CoPv,0

  16. Example 18.7 • Determine total pressure drop from 0 to 4

  17. Conversion Between Methods

  18. Air Distribution System Design • Describe room distribution basics • Select diffusers • Supply and return duct sizing

  19. Forced driven air flowDiffusers • Grill (side wall) • diffusers • Linear diffusers • Vertical • Horizontal one side

  20. Diffusers types • Valve diffuser • swirl diffusers • ceiling diffuser • wall or ceiling • floor

  21. Diffusers • Perforated ceiling diffuser • Jet nozzle diffuser • Round conical ceiling diffuser • Square conical ceiling diffuser • Wall diffuser unit • Swirl diffuser • Floor diffuser • Auditorium diffuser • Linear slot diffuser • DV diffuser • External louvre • Smoke damper • http://www.titus-hvac.com/techzone/ • http://www.halton.com/halton/cms.nsf/www/diffusers

  22. Low mixing Diffusers Displacement ventilation

  23. Reading asignement • Chapter 18 • 18.1-18.4 (including 18.4)

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