Download - 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
Access Floors…
Advancements in Building Systems
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Advancements in Building Systems