duct design .ppt

Duct DesignSubmitted in partial fulfillment of requiredment for the award of the degree of BACHELOR OF TECHNOLOGY IN MECHANICAL ENGINNEERING Submitted by MD ZEESHAN 13X01A0366 SANDEEP SINGH 13X01A0392 ZAFARYAB HAIDER 13X01A03C2 MD RIZWAN 13X01A0367

Ductwork Considerations• Shape• Size• Aspect ratio• Velocity• Static Pressure of the system• Space conflicts

Terms• Aspect ratio• Flexible ductwork• Overhead system• Underfloor air

distribution (UFAD) system

• Displacement system

• Dumping

• Diffuser• Grille• Register• Slot diffuser• Shift Zone• Plenum

Materials• Sheet metal (by

gauge)• Galvanized • Iron• Aluminum• Stainless steel

• Flexible• Insulated• Tube (socks)

• Other• PVC• Fiberglass

Congested Corridors

Shape and Size

Round

Oval

Rectangular

Rectangular• Lower aspect ratios

• More energy efficient• Use less ductwork

• Velocity and Area have an inverse relationship to the CFM (CFM = V x A)

• Velocity and Pressure Drop have a direct relationship

W

D

Aspect ratio = W / D

1 to 1

Air Distribution Systems• Three Types

• Above Ceiling• Displacement• Underfloor

• Services• Supply air• Return air• Ventilation air• Relief air• Exhaust air

Above Ceiling Distribution System

horizontalheat pump

supplyduct

returnduct

diffuser

return airgrille

American Standard © 1999

Dilute the Air

+ pressure

1600 CFM

200 CFM

1400 CFM

OA

SA

RA MA1600 CFM

Outside Air (OA) v. “Fresh Air”• Source of outside

air must be carefully considered.

• May have to pre-filter or condition

Other Design Considerations• Thermal mass• Prevailing winds• Natural light• Solar shading• Control strategies• Life safety issues• Infiltration• Bioterrorism

• Mixed Air (MA) conditions

• Energy in the air• Comfort level of

the air• The amount of

water in the air

Diffusers/Grilles/Registers

Short Circuiting

DISPLACEMENT PRINCIPLES

•Conditioned air moves upward past the persons breathing zone.

•This invisible plume continues an upward movement toward the ceiling.

•A person will breathe lower contaminant levels vs. a mixing design.

DISPLACEMENT DIFFUSERS RECESSED IN WALL

UNOCCUPED ZONE

SHIFT ZONE

OCCUPIED ZONE:

TEMPERATURE GRADIANT

HE IGHT

Thermal Displacement VentilationTemperature Stratification

By only cooling the occupied zone, tonnage requirements may be reduced

DISPLACEMENT: Delivering fresh air where it is needed

•Better IAQ, lower particulate concentrations than mixing systems.

•Increase use of outdoor air without energy penalty.

•Quiet diffusers, draftless conditions for the occupants.

Displacement Advantages/Disadvantages

• Advantages• Moderate supply air

temperature• Low velocity• Air delivered to the

comfort zone without mixing

• Aesthetics• Better IAQ• Can accommodate

more outside air for same energy cost

• Very quiet

• Disadvantages• Higher initial cost• Less well understood• Aesthetics• Too quiet

Underfloor System

• Reduces floor to floor height

Underfloor Systems

▪Passive swirl diffusers; pressurized plenum; displacement theory

▪Occupant may control airflow volume; 3’ clear zone around diffuser

Air Delivery: UF-HVAC Diffuser Types

Tate Building Technology Platform®

Rooftop Chiller HVAC SolutionEquipment room(chiller, pumps, controls)

Chilled water supply& return

Cooling tower

Supply air outlet

Stub duct

Indoor air handler

VAV MIT terminals

Supply air loop

Tate Building Technology Platform®

Take-Aways (The Ah Hahs)• Eliminate the contaminant is

always the first step• Capture it if you can’t eliminate it

• Healthy buildings are well ventilated• Watch your outside air sources!

• Operating cost and usually first cost go up as your ventilation goes up

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