pdf_tech_presentations_february 2007 ashrae meeting - displacement ventilation presentation - alf...
TRANSCRIPT
Displacement Ventilation
Displacement Ventilation
• Displacement Ventilation vs. Dilution Ventilation
• Characteristics• Design Considerations• Layout and Selection• Product Overview• Casino Case Study
Dilution Air Distribution• Induce as much as possible
• Ensure maximum 50 fpm within Occupied Zone
• High velocity jets at diffusers
• Diffuser Performance aerodynamic dependant
• Supply air used to dilute pollution in space
• Diffuser located Outside OZ
• Complete Mixing in Entire Space
• Minimal Temperature Stratification
• Uniformity is Sought
• Supply of 55°F - < 0 > +Temperature
9 FT
Dilution Air Distribution
Displacement Air Pattern
• Low Velocity Supply
• Low Induction
• Uniform Distribution
• Often Located in the Occupied Zone
• Supply between 65°F and 75°F
Body’s Thermal Plume
Air Distribution Characteristics
• 5-10 deg F Cooling Differential
• Supply Air Flows Along Floor
• Rises When Heat Source is Contacted
• Displaces Room Air Upward
Air Pattern Cooling
2-10 oF Cooling Differential 0-5 oF Heating Differential 5 oF+ Heating DifferentialMorning Warm-up
Heating Options• Perimeter Radiation
• Radiant Ceiling Panels
• Fan Coil Units
Air Distribution Characteristics
• Stratified Room Temperature
• Maximum 5 deg F in Occupied Zone*
• 80-85 deg F Return Air
*Based on ASHRAE 55. Current research is showing that occupants may becomfortable with a larger temperature gradient
Air Distribution Characteristics
• Warm Air at Top
• Pollutants at Top
• High Level Return
Ventilation Effectiveness
• How effectively airborne contaminants are removed from a room.
Mix air Systems DV SystemsEc= 0.8 – 1.0 Ec=1.2 - 1.4
Occupant
Exhaustc C
CE =
Limitations
• Pollutants Need to be Buoyant in Air – Warmer/lighter
• Ceiling Height of at least 9 ft Recommended• Large Drafts Cause Unwanted Mixing• Limit in Cooling of 38 BTU/Hr/ft^2
– Radiant cooling systems• Chilled Beams/Sails• Radiant Panels/Floors
– Limit Loads into Space• Higher R walls• Low E windows
Humidity Control
Side-Stream Bypass
RETURNAIR
SUPPLYAIR 65 F
PRIMARYAIR 55 F
EXHAUST AIR
OUTSIDE AIR
COOLING COIL
Layout and Selection
Performance Data
• Sound - NC Level
• Pressure Drop -Inches W.G.
• ASHRAE Test Standard
• Throw Not Applicable
Performance Data
• Supply air is injected directly into occupied zone
• Designers must be cautious to limit the velocities near occupants
• The aspect ratio or the diffusers is important– Taller diffusers have higher velocities in the
near zone
Displacement Ventilation and Comfort
Effect of Air Motion on Comfort
Ankle Region Neck Region
Percentage of Occupants Objecting to Drafts in Air-Conditioned Spaces
Feeling ofCoolness
Feeling of Warmth
Feeling of Warmth
Feeling Of
Cool-ness
TEMPERATURE DIFFERENCE, °F TEMPERATURE DIFFERENCE, °F
AIR
VEL
OC
ITY,
FPM
AIR
VEL
OC
ITY,
FPM
Comfort Criteria
• Maximum 40 FPM Face Velocity* per ASHRAE Research Project RP-949
• Based on Commercial Applications
• Velocity can be increased for Transient Spaces
• Higher airflow rates are acceptable for Industrial Applications.
Selection
• Outlet Type Determined by Room Layout and Architecture
• Outlet Quantity Determined by Air Volume and Room Layout
• Outlet Size Based on Performance
• Maximum 40 FPM Face Velocity• Sound and Pressure Drop not Significant
Layout Considerations
• Heat sources pull supply air to region
• Easily moves along walls to source entire room
Layout Considerations
Layout Considerations
• For large open spaces, diffuser can be located in the space
• Areas of high load should have more diffusers
Layout Considerations
• Diffusers should be located at least 2 ft from occupants
• Diffusers should not be located behind large objects that might restrict air flow to the zone
Ceiling Diffusers• Ceiling mounted diffusers
– Supply air will gain someheat during fall
• Reduced if along a surface
• Reduced Ventilation Effectiveness
– Recommend to mount near walls to limit heat gain
– Ensure that space below diffuser is a transient space
Air Volume Calculations
• ASHRAE Design Guide
• Calculation Method
• Supply Air Volume
• Supply Air Temperature
• Exhaust Air Temperature
• Only suitable for zones with ~9ft ceiling height
• Need another calculation method for large volumes
Loads
• Two Components to loads– Convection
– Radiation
• ASHRAE handbook lists portions attributable to each
Room Load Calculations
• Room Load Coefficients– Occupants, Lamps,
Equipment (aoe) = 0.295*
– Overhead Lighting (al) = 0.132*
– Conduction and Radiation (aex) = 0.185*
• Remember: Building Loads are same as OH
*From ASHRAE Design Guide based on RP-949This methodology should only be used for typical office spaces
Energy / Airflow Modeling
• CFD Analysis Useful for Validation of Design
• Can Predict Airflow in Building
Why Use DV?
• IAQ– Efficient removal of smoke,
odors• Pollutants lighter than supply
air
– VE of 1.2 – 1.4 (typically)• Can be > 3
– Thermally comfortable environment
• Meet ASHRAE 55• Higher SAT• No Drafts
Why Use DV?
• Energy Efficiency– Reduced Room Cooling Load
– Extended Economizer Cycle
– Efficient System
• Load Flexibility– Cool supply air will find the heat load.
– As loads are reconfigured or move, the system will automatically compensate.
• Architectural Flexibility– DV is a robust system
– Diffusers can be mounted in various locations
• Ceiling
• In walls
• In furniture
• In the floor
• In architectural elements
Why Use DV?
Displacement Outlet Types• Flat 1 Way Diffuser• Flat 3 Way Diffuser• Flat Wall Diffuser• Flat Corner Diffuser• Flat Riser Diffuser• Linear Enclosures• Round Full Circular Diffuser • Round Half Circular Diffuser• Round Corner Diffuser• Floor Diffusers• Flat multi-way Industrial
Diffusers• Special Applications
Displacement Diffuser
• Low Velocity Supply
• Low Induction
• Uniform Distribution
• Dual Perforated face
Flat 1-way
• 1 way discharge• Side wall application where one
way discharge required• Square or rectangular• Mounted against wall inside of
occupied space• 3.6 to 14.2 ft2 face area• 100-700 CFM• Top, left, right, and rear ducted
options• Accessories
– Duct Cover– Base
1-Way Pattern
Flat 3- Way
• Square or Rectangular• Side wall application where
three way pattern is required• 3-way Air Pattern• 7.7 to 27.2 ft2 face area• 150-1300 CFM• Top and rear ducted
available• Accessories
– Duct cover– Bases
3-Way Pattern
Flat Corner Unit
• Square or Rectangular
• Mounted in Corner
• 90 Degree Air Pattern
• 3.8 to 17.6 ft2 face area
• 80-800 CFM
• Accessories– Duct cover
– Base
Corner Pattern
Wall Unit
• Square or Rectangular• Mounted in Wall• Provided with plenum• Square inlet• 1-way Air Pattern• 3.6 to 7.4 ft2 face area• 80-300 CFM
Recessed Unit
• Rectangular• Mounted in Wall / Stair Riser /
Integrated into baseboards• 1-way Air Pattern• 20-875 CFM• .19 to 17.5 ft2 face area• Snaps into mounting flange
flush with wall• Can be used in any wall
mounted application where a pressurized plenum can be provided
• Ideal for concealed look
Linear Enclosure
• Displacement Linear Enclosure
• Attractive Linear Grille
• Rigid Steel Construction – Heavy Duty
• Ducted from below, behind or from the side
• Ideal for:– Offices
– Boardrooms
– Classrooms
Available 2nd QTR 2006
Circular Unit• Round Face• Mounted Free Standing in
Interior Space• Can be ducted from above
or below• 360 Degree Air Pattern• 1.5 to 62.5 ft2 face area• 115-3100 CFM• Designed for large
capacities• Accessories
– Bases– Expansion Collars
Circular Pattern
Elevated Circular Unit
• Round Face
• Fastened directly to elevated ductwork
• 360 Degree Air Pattern
• 1.5 to 62.5 ft2 face area
• 115-3100 CFM
• Designed for large capacities
Elevated Circular Unit
Used where supply cannot be within the occupied zone
Large open space
Far from walls
Raised floor not an option
Valuable floor space
Half Round Unit
• Round Face• Side wall application• 180 Degree Air Pattern• 4 to 31 ft2 free area• 85 - 1550 CFM• Top or rear ducted option,
round or rectangular inlets available
• Accessories– Duct cover– Base
Half Round Pattern
Corner Round Unit
• Round Face
• Mounted In Corner
• 90 Degree Air Pattern
• 2 to 15.5 ft2 face area
• 40-775 CFM
• Accessories– Duct Cover
– Base
Floor Displacement Outlet
• 8” Round Aluminum Face
• Mounted In The Floor • Horizontal Air Pattern• 50-80 CFM• Compatible with
underfloor products• Used with raised floors
or can be installed directly in floor slab
Specials• Sizes• Shapes• Face Types• Colors• Material
Displacement Diffuser Accessories
• Duct Covers– Conceal Duct work
• Bases– Match room features
– Protect diffuser while cleaning
• Expansion Collar
Application of Displacement Ventilation in a Casino
Edgewater Casino, Vancouver, BC
Major Project Challenges
• Retrofit of Existing Building
• Must Maintain Transparency –Heritage Requirement
• Owner Demanded High Level of Comfort & IAQ
• Central Atrium
• 24 Hour Occupancy
• Fast Track Project
CFD ModelingTemperature Contour
Design Solutions
• Double Skin System
• New Air Handlers on Main Floor
• Utilized Existing Air Handlers on Second Floor
• Raised Floor Added to Main Level
• Under Floor Air Delivery on Main Floor
• Displacement Delivery on Main Floor
• Generates Twist Effect Using Linear Slots in Combination With Inclined Discharge
• Produces Angular Vertical Pattern
• High Induction Turbulent Flow for Rapid Temperature Equalization
• Mixing Within Occupied Zone (6 ft from floor)
• Projects Air Upwards 3-6 Feet
Turbulent Floor Outlet
• Radial Slots With Inclined Discharge
• Produces Horizontal Pattern Close to Floor
• Low Turbulence
• Low Velocity
• Minimal Mixing
• Air Buoyancy Carries Heat and Pollutants to Ceiling for Exhausting.
Displacement Floor Outlet
Lab Mockup
• Attended by Design Team and Owner
• 6 Slot Machines Simulated
• Floor Outlets Located Below Each Chair
• Measured Velocity and Temperature at Several Flows
• Opportunity to “Feel” the System
Lab Mockup
Various Wall Mounted Displacement Outlets Were Also Demonstrated
Displacement Benefits
• Low Velocity/High Comfort
• Heat Sources Pull Supply Air to Region
• Ideal for Variable Occupancy
• Minimal Impact by Furnishings
• Easily Moves Along Walls to Fill Entire Room
HVAC System Details
• 36,000 CFM Supply Air Capacity
• Constant Volume with Reheat
• 67 Deg F Supply Air Temperature
• 3 CFM per Sq Ft in General Areas
• Demand Control Ventilation
• Return Through Top of Atrium
Main Floor HVAC
Main Floor HVAC
• Displacement Floor Air Outlets in Gaming Area – 1300 Units
• Displacement Wall Outlets in Lobby and Eating Area
Second Floor HVAC
Second Floor HVAC
• Displacement Wall Outlets Throughout
Displacement Wall Outlets
• Diffuser Face Recessed into Millwork
• Coordination with Architect Critical
• Air Delivered Through Pressurized Plenums
• Self Balancing System
• Diffuser Face Sized for Maximum 40 FPM Face Velocity
• Sizes up to 36” x 72”
• 220 Units
Results
• Open Since February 05
• Minimal Balancing Required
• Passed Opening Day Test
• No Draft Complaints
• Excellent Temperature Control-Within 1 Deg F
Results
• Supply Air Drawn to Occupants for High IAQ and Comfort
• Flexible System
• Extended Hours of Free Cooling
• Lower Fan HP
• Two New BC Casino’s Under Design with Displacement
Conclusions
• Casino’s are a Good Application for Displacement Delivery
• Comfort ,IAQ and Energy Efficiency are Benefits
• CFD is a Valuable Design Tool
• Lab Mock Ups are Extremely Beneficial
• Coordinated Effort by Entire Design Team and Owner Ensures Success
Questions?