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 Winter vs. summer operation Winter operation with DX systems (heat pump)

Pressures Static pressure Velocity pressure Total pressure – sum of the two above

Relationship Between Static and Total Pressure

Duct Design 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

System Characteristic

Electrical Resistance Analogy

Frictional Losses

Non-circular Ducts Parallel concept to wetted perimeter

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

Loss Coefficients ΔPt = CoPv,0

Example 18.7 Determine total pressure drop from 0 to 4

Conversion Between Methods

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

Forced driven air flow Diffusers Grill (side wall) diffusers Linear diffusers Vertical Horizontal one side

Diffusers types Valve diffuser swirl diffusers ceiling diffuser wall or ceiling floor

Diffusers http://www.titus-hvac.com/techzone/ 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

Low mixing Diffusers Displacement ventilation

Reading asignement Chapter 18 18.1-18.4 (including 18.4)