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Objectives

Objectives. Finish duct design Discuss HW4 Learn about pumps. Frictional Losses. Non-circular Ducts. Dynamic (local) losses. Losses associated with Changes in velocity Obstructions Bends Fittings and transitions. Loss Coefficients. Δ P t = C o Δ P v,o. Duct Design Example.

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Objectives

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  1. Objectives • Finish duct design • Discuss HW4 • Learn about pumps

  2. Frictional Losses

  3. Non-circular Ducts

  4. Dynamic (local) losses • Losses associated with • Changes in velocity • Obstructions • Bends • Fittings and transitions

  5. Loss Coefficients ΔPt = Co ΔPv,o

  6. Duct Design Example • Determine total pressure drop from in this duct system F l1=150ft l3=100ft l2=50ft B A VA = 2000 CFM pdiffuserB = 15Pa VA = 1000 CFM pdiffuserA = 10Pa VA = 1000 CFM

  7. Solution Equal friction method:

  8. Two design methods Equal friction method (Example 18.9): Static regain method (Example 18.10):

  9. Fan Performance

  10. Controlling Air Flow

  11. VAV Operation

  12. How to use multiple pumps

  13. Dampers

  14. Summary of Air Distribution Systems • Select diffuser based on ADPI • Given a layout of duct system • Calculate total pressure drop • Deal with non-circular ducts and fitting losses • Select the fan based on fan and duct curve

  15. HW4 • Design: • Air handling unit (AHU) with components (cooling coil and fan) • Duct system • Diffusers • Chiller • Pump • Power requirement

  16. Pumps and Plumbing • Very similar to fans and ducts • Same principles based on fluid dynamics • With some specifics

  17. Hydronic Terms • Head loss • Open-loop vs. closed loop

  18. Head Loss

  19. Fittings

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

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

  22. Use Multiple Pumps

  23. Plumbing Arrangements

  24. Example 19.7 • Similar to equal friction method • Calculate head loss for common pieces of system • Size pipes to have equal head loss between points 2 and 3

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