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 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)

Ideal and Reasonable Throws

Diffuser testing

ADPI

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/

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

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

Balance Point

Fan Performance

Centrifugal fans

Axial Fans

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

Controlling Air Flow

Dampers

Effect on Fan Curve

VAV Operation

Dampers

Dampers

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

Pump curves NPSHR = Net Positive Suction Head Required