Announcement Course Exam October 11 th (Tuesday) In class: 90 minutes long Examples are posted on the course website

Objectives Duct Design and Diffuser Selection Reading assignment: thextbook Chapter 18

Duct design (part of the HVAC Design successfully integrated into BIM)

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

Relationship Between Static and Total Pressure

Duct design method (defines the layout) Two design methods: -Equal friction -Static regain

System Characteristic

Static pressure drop (friction losses) in a duct is proportional to square of velocity or flow Duct Design It is a function of -Dynamic pressure -Length -Pipe diameter -Friction coefficient

Frictional Losses (in a staring round duct section)

Ductulator

Non-circular Ducts Parallel concept to wetted perimeter

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

Dynamics (Local) Loss Coefficients ΔP t = C o P dynamic

Conversion Between Methods

Example 18.7 Determine total pressure drop from 0 to 4

Diffuser selection Defines thermal comfort Air quality

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

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

Diffusers Perforated ceiling diffuserJet nozzle diffuser Square conical ceiling diffuser Round conical ceiling diffuser Wall diffuser unitSwirl diffuser Floor diffuser Auditorium diffuser DV diffuser External louvre Smoke damper Linear slot diffuser

Low mixing Diffusers Displacement ventilation