active chilled beam system design & layout
TRANSCRIPT
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Active Chilled Beam
System Design & Layout
Salt Lake City, UT ASHRAE Chapter
December 2013
Nick Searle
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Contents
• Active Chilled Beam Basics
• Design Considerations
• Air System Design & Humidity Control
• Water System Design
• Heating with Active Beams
• Controls
• Beam Selection & Layout
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Fan Energy Use in Buildings
“Energy Consumption Characteristics of Commercial Building HVAC
Systems” � publication prepared for U.S. Department of Energy
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
Central VAV Central CAV Packaged CAV
Desig
n L
oad
KW
/SF
Chiller/Compressor
Supply & Return Fans
Chilled Water Pump
Condenser Water Pump
Cooling Tower Fan
Condenser Fan
0
1
2
3
4
5
6
7
Central VAV Central CAV Packaged CAV
En
erg
y U
se K
Wh
/SF
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Water = Efficient Transport
¾” diameterwater pipe
10”
1 Ton of Cooling
requires 550 CFM of air
or
4 GPM of water
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Active Chilled Beams1980 1990 2000 2010
Chilled Ceilings
Passive Chilled Beams
Active Chilled Beams
• Higher space loads
• Higher occupant densities
• Combined ventilation/cooling preferred
• Integration into fiber tile ceilings required
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Active Chilled Beam 0 Operation Principle
Suspended ceiling
Primary air plenum
Primary air nozzles
Heat exchanger
1 Part Primary Air
4 Parts Room Air
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Heat Removal Ratio
70% of sensible heat removed by chilled beam
water coil
Airflow requirement
reduced by 70%
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Active Chilled Beam 0 Airflow Pattern
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Active Chilled Beams 0 System Highlights
• Very high cooling capacity‒ Up to 100 BTUH/FT2 floor space‒ Up to 1500 BTUH per LF
• Integrated cooling, ventilation and heating‒ All services in the ceiling cavity
• Suitable for integration into all ceiling types‒ Reduces ceiling costs compared to Passive Beams
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Active Chilled Beams 0 System Highlights
• Significant space savings‒ Smaller ductwork saves space in shafts, plant rooms and ceiling
• Can be installed tight up against the slab‒ Reduced floor to floor heights‒ Reduced construction costs on new buildings
• Low noise levels
• Low maintenance‒ No moving or consumable parts
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Energy Savings 0 Compared to VAV
Source Technology Application % Saving*
US Dept. of Energy Report (4/2001) Beams/Radiant Ceilings General 25A30
ASHRAE 2010 Technology Awards Passive Chilled Beams Call Center 41
ACEE Emerging Technologies Report (2009) Active Chilled Beams General 20
ASHRAE Journal 2007 Active Chilled Beams Laboratory 57
SmithGroup Active Chilled Beams Offices 24
*Compared to VAV
“Energy Consumption Characteristics of Commercial Building HVAC
Systems” � publication prepared for U.S. Department of Energy
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Active Chilled Beams 0 Typical Installation
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Active Chilled Beams 0 Typical Installation
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9’A
10
”
12
’A0
”
Space Savings
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Space Savings
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Space Savings
8’A
0”
9’A
10
”
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Exp
osed C
hill
ed B
ea
ms
6 F
loo
rs
All
Air
HV
AC
Syste
m5
Flo
ors
Space Savings
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ACTIVE CHILLED BEAM DESIGN
CONSIDERATIONS
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Building Suitability
Building Characteristics that favor Active Chilled Beams
• Zones with moderateAhigh sensible load densities‒ Where primary airflows would be significantly higher than needed for
ventilation‒ Sensible Heat Ratio’s (SHR) of 0.8 and above
• Buildings most affected by space constraints‒ Hi – rises, existing buildings with induction systems
• Zones where the acoustical environment is a key design criterion
• Laboratories where sensible loads are driving airflows as opposed to air change rates
• Buildings seeking LEED or Green Globes certification
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Building Suitability
Characteristics that less favor Active Chilled Beams
• Buildings with operable windows or “leaky” construction
‒ Beams with drain pans could be considered‒ Building pressurization control should be used
• Zones with relatively low sensible load densities
• Zones with relatively low sensible heat ratios and low ventilation air requirements
• Zones with high filtration requirements for the reAcirculated room air
• Zone with high latent loads
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SHR’s for Typical Spaces
SHR Range
Auditoriums, Theaters 0.65 - 0.75
Apartments 0.8 - 0.95
Banks, Court Houses, Municipal Buildings 0.75 - 0.9
Churches 0.65 - 0.75
Dining Halls 0.65 - 0.8
Computer Rooms 0.8 - 0.95
Cocktail Lounges, Bars, Taverns, Clubhouses, Nightclubs 0.65 - 0.8
Jails 0.8 - 0.95
Hospital Patient Rooms, Nursing Home, Patient Rooms 0.75 - 0.85
Kitchens 0.6 - 0.7
Libraries, Museums 0.8 - 0.9
Malls, Shopping Centers 0.65 - 0.85
Medical/Dental Centers, Clinics and Offices 0.75 - 0.85
Motel and Hotel Public Areas 0.75 - 0.9
Motel and Hotel Guest Rooms 0.8 - 0.95
Police Stations, Fire Stations, Post Offices 0.75 - 0.9
Precision Manufacturing 0.8 - 0.95
Restaurants 0.65 - 0.8
Residences 0.8 - 0.95
Retail, Department Stores 0.65 - 0.9
Other Shops 0.65 - 0.9
School Classrooms 0.65 - 0.8
Supermarkets 0.65 - 0.85
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Role of the Primary Air
• Ventilate the occupants according to ASHRAE 62A2004
• Handle all of the latent load in the space‒ Primary air is only source of latent heat removal
• Create induction through chilled beam
• Pressurize the building
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Primary Air Design
• Central AHU sized to handle:‒ sensible and latent cooling/heating of the ventilation air ‒ portion of the sensible internal cooling/heating loads
AND‒ all of the internal and infiltration latent loads
• Primary air delivered continuously to the chilled beams
‒ VAV primary air can be considered for the perimeter if the sensible loads are high
• Chilled beam water coils provide additional sensible cooling/heating to control zones
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Primary Air Temperature 0 Cooling55°F or Lower 65°F or Higher
• Reduces or eliminates reheat
• Ideal for labs or hospitals with code required minimum air changes
• More or longer beams required in some applications
• Reduces lengths/quantities of beams
• Good for office buildings with high perimeter loads
• Often used with VAV in applications with high sensible loads
Air must be suitably dehumidified whatever
the dry bulb temp is!
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Room Neutral Air
• Sensible recovery device (downstream of coil)
• Desiccant dehumidification units
• Passive dehumidification wheels
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Reducing Primary Air Temperature
Active Chilled BeamsPrimary
Air
Pressure
Primary Air
Flow Rate
Supply
Air Flow
Rate
Supply Air
Temp Out
(Cooling)
Primary Air
Sensible
Cooling
Secondary
Air Sensible
Cooling
Nett Unit
Sensible
Cooling
Chilled
Water
Flow
Rate
Qty Unit TAG Zone Name Unit Model2 or 4 Pipe
Coil
Nominal
Length
(feet)
PPA (Inch
w.c.)QPA (CFM)
QSA
(CFM)tSAout (°F) qPAs (Btuh) qSCAs (Btuh) qs (Btuh)
QSCHW
(GPM)
2 ACBA1 1 DADANCO ACB50 2 8 0.7 105 529 59.3 2281 6770 9051 1.3
Room Design Primary Air Secondary Chilled Water Secondary Hot WaterElevation
Feet
% Propylene
Glycol
Cooling 75°F 50% RH 55°F 80% RH 58°F 110°F 0 0
Heating 70°F 50% RH 55°F 83% RH
Typically 25% + more chilled beams required when using 65°F primary air
Active Chilled BeamsPrimary Air
Pressure
Primary Air
Flow Rate
Supply
Air Flow
Rate
Supply Air
Temp Out
(Cooling)
Primary Air
Sensible
Cooling
Secondary Air
Sensible
Cooling
Nett Unit
Sensible
Cooling
Chilled
Water Flow
Rate
Water
Pressure
Drop
Qty Unit TAG Zone Name Unit Model 2 or 4 Pipe Coil
Nominal
Length
(feet)
PPA (Inch
w.c.)QPA (CFM) QSA (CFM) tSAout (°F) qPAs (Btuh) qSCAs (Btuh) qs (Btuh)
QSCHW
(GPM)
SCHW
pressure
drop (Feet
w.c.)
3 ACBA1 1 DADANCO ACB50 2 8 0.5 70 359 59.4 760 5325 6085 1.1 7.9
Room Design Primary Air Secondary Chilled Water Secondary Hot Water Elevation Feet % Propylene Glycol% Ethylene
Gylcol
Cooling 75°F 53% RH 65°F 70% RH 58°F 70°F 0 0 0
Heating 70°F 50% RH 107°F 83% RH
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Latent Load Calculation
• The amount of cooling required to remove themoisture from the air
QL = 0.68 x q x ∆wgr or QL = 4,840 x q x ∆ wlb
Where AQL= latent heat (Btuh)q = air volume flow (cfm)∆ wgr = humidity ratio difference (grains water/lb dry air)∆ wlb = humidity ratio difference (lb water/lb dry air)
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Dehumidification Air for 1 Person 0 200BTUH
0
5
10
15
20
25
30
35
40
45
44 45 46 47 48 49 50 51 52
Pri
ma
ry a
ir f
low
(C
FM
)
Primary air dew point (°F)
55% RH
52% RH
50% RH
30% less air
Room Design
Condition
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Supply Water Temperature Safety Margin
Climatic Ceilings by “Energie”
Passive Chilled Beams+ 1°F
Active Chilled BeamsA 2.9 °F
Do not design below room dew point!
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Condensation – Radiant Panel Test
Condensation after 8.5 hours on a chilled surface intentionally held 7.8°F colder than the space DPT. Not one droplet fell under these conditions
Chilled Ceilings in Parallel with Dedicated Outdoor Air
Systems: Addressing the Concerns of Condensation,
Capacity, and Cost Stanley A. Mumma, Ph.D., P.E.
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• Building was designed for 80 BTUH/ft2 perimeter load
• Actual load in building use was 40 BTUH/ft2
Parameter Proposed in design Actual observed load
Area (Sq.ft) 200 200
Sensible Load (Btuh) 16,000 8,000
Latent Load (Btuh) 400 400
Minimum Outside Air (CFM) 40 40
Quantity of ACB’s 2 2
Design Cooling Loads 0 Beware of Overrating!
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• Chilled beams selected for double actual required primary air to achieve overestimated load
• Primary air providing 65% of the total sensible cooling of the actual load
2 x beams at 115 CFM
Design Cooling Loads 0 Beware of Overrating!
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• Therefore if load drops to 65% no waterside cooling will occur
• If load drops below 65% space will overcool unless reheat is used
Design Cooling Loads 0 Beware of Overrating!
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• Assumptions on building materials performance
• Equipment loads that never eventuate
• Use of generic performance data
• Use of safety factors
• Lack of familiarity with load calculation software
Causes of Overrating Loads
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Exclude loads:A
�Outside air load
�Plenum gain
�Fan motor gain
�Duct losses
Location Sensible Zone Load
North 25A30 Btuh/Sq.ft
East 35A45 Btuh/Sq.ft
South 30A40 Btuh/Sq.ft
West 40A50 Btuh/Sq.ft
Interior 15A20 Btuh/Sq.ft
If loads exceed these values � review closely
Design Cooling Loads 0 Rules of Thumb
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WATER SYSTEM DESIGN
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CHW System Design Options
• Secondary loop‒ Tap into district CHW loop‒ Heat exchanger into return – no GPM demand‒ Can increase main plant efficiency
• Dedicated chiller & DX‒ Dehumidification by DX AHU‒ Significantly increased COP A 11+
• Twin chillers‒ One for AHU’s – 6 COP‒ One for chilled beam circuit – 11+ COP
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Mixing Valve
S T
Secondary chilled water
supply to beams
Secondary chilled
water return
Supply
temperature
monitor
Primary chilled
water supply
Primary chilled
water return
SCHW
Pump
45°F
58°F
64°F
T
Primary chilled
water return
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Secondary Loop
S
T
Secondary chilled water
supply to beams
Secondary chilled
water return
Supply
temperature
monitor
Primary chilled
water supply
Primary chilled
water return
Heat
Exchanger
SCHW
Pump
54°F
45°F
58°F
64°F
T
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Dedicated Chiller
T
To chilled beam zones
Bypass Valve
Chilled water
pump
Dedicated chiller
11+ COP
Cooling
Tower
Geothermal Loop
Geothermal Heat
Pump
64°F
58°F
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District Chilled Water Loops
• No demand in district loop GPM
• Increases main chiller plant COP
Tap into return pipe with heat
exchanger and secondary loop
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Reverse Return Pipe Design
S
T
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15 Minute Break
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HEATING WITH ACTIVE CHILLED BEAMS
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Advantages of 20Pipe Beams Versus 40Pipe
• Higher coil performance‒ 4 pipe performance is compromised‒ 75% Cooling (12 pipes)‒ 25% Heating (4 pipes)
• Fewer or shorter beams
• Lower hot water temperatures‒ 90°F for 2 pipe‒ 130°F for 4 pipe
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Boiler Efficiency 0 Lower Hot Water Temp
• Hot water typically 90A130°F
• Reduce boiler energy consumption by maximizing efficiency of a condensing boiler through very low return water temperatures
• Use of water to water heat pumps
(KN boiler efficiency chart courtesy of Hydrotherm)
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20Pipe Beams and Terminal Heating
S
S
T
Terminal Heating Coil
2APipe Active Chilled Beams
Chilled Water Supply
Chilled Water Return
Hot Water Supply
Hot Water Return
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Heating Using 60Way Valves
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60Way Valve
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CONTROL CONSIDERATIONS
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Airside Control
• Constant volume air‒ Reduces cost‒ Maintains constant control of humidity‒ Guarantees minimum fresh air delivery
• Monitor room dew point‒ Use small quantity of high quality sensors‒ Do not use RH sensors‒ Locate sensors in room not in ceiling
• Reduce primary moisture content to control room RH‒ Avoid turning off or rescheduling SCHW temp
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Waterside Control
• Variable water flow‒ Pressure independent control
• Two position valves or modulating valves
• 6Away valves can be used on 4 pipe into 2 pipe chilled beams
• Reschedule or shut off SCHW only if primary moisture content cannot reduced
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Waterside Control Sequence
71
72
73
74
75
76
Ro
om
Tem
pera
ture
(°F
)
Time
Dead Z
one
Dead Z
one
SCHW
ON
SCHW
OFF
SCHW
ON
SCHW
OFF
HW
ON
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Typical Start Up Control Sequence
• Dry out cycle before engaging SCHW pumps
• Setback primary air humidity ratio
• ONLY initiate pumps when room dew point is within design limits
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Condensation and Dew Point Sensors
Drip sensor
Condensation sensorDew point sensor
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ACTIVE BEAM SYSTEM DESIGN
COST CONTROL
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First Cost Control
• Many projects still designed with far to many beams‒ Caused by confusing selection software or low performance
beams
• 4Apipe system designs are costly‒ 2Apipe system with terminal heating or 6Away valves reduce cost
• Mechanical contractors unfamiliar with system‒ Install a mockup to show contractors
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PEX Piping Significantly Reduces Costs
• 70% reduced pipe material cost‒ $0.60 v’s $1.95 per linear foot
• Reduced labor, much faster installation‒ No torches or soldering, no glue
• Longevity – 50 year life expectancy‒ No corrosion
• Dampens water rushing noise and water hammer noise
• Does not require insulation
• Plenum rated systems available‒ With 25 year warranty
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Active Chilled Beam
Selection & Layout
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Room Load Data
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ACB Selection & Layout Tips
• Select beams for minimum possible primary air
• 0.4 – 0.7” w.c. typical airside beam ∆P
• Be aware of airside/waterside cooling ratio‒ Maximize waterside cooling
• Chilled beams throw more air than VAV diffusers‒ Be wary of air velocities‒ Use ASHRAE standard 55 guidelines for thermal comfort
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ACB Selection & Layout Tips
• Careful positioning near walls & columns‒ Can interfere with beam if too close
• Chilled beams positioned closer than 6’ centers may not cool correctly
‒ Minimum 2 x tile spacing rule of thumb
• Use manufacturers selection software‒ Best software allows selection of the entire building
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Tips to Minimize Primary Air Flow
• Be wary of overrating cooling loads
• Use low temperature primary air‒ 45 – 48°F is possible but beam must be internally insulated
• Locate beams along perimeter to increase output‒ Use a higher on coil temperature when beams are positioned
along perimeter‒ This additional capacity is often overlooked
• Use booster fans
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DOAS with Booster Fans
A+ A+Outdoor
Air
DEDICATED
OUTDOOR AIR UNIT
A A
FAN BOOSTERS
Return Air Return Air
ACTIVE CHILLED BEAM ZONESACTIVE CHILLED BEAM ZONES
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LAYOUT EXAMPLE
@ OFFICE BUILDING @
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Building With Exterior Cellular Offices
Office 135 BTUH/ft2
12’
12’
Office 235 BTUH/ft2
Office 350 BTUH/ft2
Office 530 BTUH/ft2
Office 630 BTUH/ft2
TOTAL AREA2,520 FT2
Office 730 BTUH/ft2
Office 430 BTUH/ft2
Occupants:Area:Ventilation:Cooling:Latent load:Heating Load:
1144 ft2
15 CFM7200 BTUH288 BTUH3000 BTUH
Occupants:Area:Ventilation:Cooling:Latent load:Heating Load:
1144 ft2
15 CFM5040 BTUH288 BTUH2500 BTUH
Occupants:Area:Ventilation:Cooling:Latent load:Heating Load:
1144 ft2
15 CFM5040 BTUH288 BTUH2500 BTUH
Occupants:Area:Ventilation:Cooling:Latent load:Heating Load:
1144 ft2
15 CFM4320 BTUH288 BTUH2100 BTUH
Occupants:Area:Ventilation:Cooling:Latent load:Heating Load:
1144 ft2
15 CFM4320 BTUH288 BTUH2100 BTUH
Occupants:Area:Ventilation:Cooling:Latent load:Heating Load:
1144 ft2
15 CFM4320 BTUH288 BTUH2100 BTUH
Occupants:Area:Ventilation:Cooling:Latent load:Heating Load:
1144 ft2
15 CFM4320 BTUH288 BTUH2100 BTUH
Occupants:Area:Ventilation:Cooling:Latent load:Heating Load:
151,512 ft2
170 CFM30,240 BTUH3024 BTUH0 BTUH
Office 820 BTUH/ft2
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ACB Design Parameters
• Room Conditions:‒ 75°F db/53% RH‒ 70°F db winter
• Primary Air Conditions:‒ 55°F db/51.6 wb (48.7 DP) – Summer & Winter
• Chilled Water‒ 57°F versus a 56.5°F room dewpoint (53% RH)
• Warm Water‒ 110°F
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Selection Software
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ACB Layout
12’
12’
Office 5 Office 6
TOTAL AREA2,520 FT2
Office 7Office 4
DOASMax.O/A
485 CFM
S/A
R/A
VAV
VA
V
AC
BA1
AC
BA2
ACBA3
AC
BA8
bA
CB
A8a
AC
BA8
fA
CB
A8e
ACBA4 ACBA5 ACBA6 ACBA7
PRIM. AIRMin. 15 CFMMax. 35 CFM
PRIM. AIR Min. 15 CFMMax. 35 CFM
PRIM. AIR Min. 15 CFMMax. 45 CFM
PRIM. AIRMin. 15 CFMMax. 25 CFM
PRIM. AIR Min. 15 CFMMax. 25 CFM
PRIM. AIR Min. 15 CFMMax. 25 CFM
PRIM. AIR Min. 15 CFMMax. 25 CFM
PRIM. AIR 270 CFMMin. 105 CFMMax. 215 CFM
Max. 270 CFM
Office 135 BTU’sAHR/FT2
Office 235 BTU’sAHR/FT2
Office 3
50 BTU’sAHR/FT2
30 BTU’sAHR/FT2
30 BTU’sAHR/FT2
30 BTU’sAHR/FT2
30 BTU’sAHR/FT2
InternalOffices
20 BTU’sAHR/FT2
AC
BA8
dA
CB
A8c
Min. 170 CFM
Min.O/A
275 CFM
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Beam Layout Notes
• 1Away beam in the perimeter offices‒ Captures solar load, increases beam output‒ Higher onAcoil temperature‒ Free’s up ceiling space for lighting‒ Works well for heating
• Interior office‒ 2Away throw beams‒ Check velocity between colliding airstreams‒ Minimum of 1 beam per 300 ft2
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10Way Perimeter Beam
• Increased on coil temp
• Increased cooling output
• Less primary air required
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10Way Beams at Perimeter – CFD Cooling
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10Way Beams at Perimeter – CFD Heating
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10Way Beams at Perimeter – CFD Heating
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VAV Reheat Design Parameters
• Room Conditions:‒ 75°F db/50% RH‒ 70°F db winter
• Primary Air Conditions:‒ 55°F db/55 wb – Summer & Winter
• Chilled Water‒ 45°F
• Hot Water‒ 150°F
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VAV Layout
Office 135 BTU’sAHR/FT2
12’
12’
Office 235 BTU’sAHR/FT2
Office 3
50 BTU’sAHR/FT2Office 5 Office 6
TOTAL AREA2,520 FT2
Office 7Office 4
AHU
O/A275 CFM
S/A
R/A
VAV 7
VA
V IO
MAX 232 CFM
MIN 63 CFM
MAX 232 CFM
MIN 63 CFM
MIN 63 CFM
MAX 332 CFM MAX 199 CFM
MIN 50 CFM
MAX 199 CFM
MAX 199 CFM
MAX 199 CFM
MIN 50 CFM
MIN 50 CFM
MIN 50 CFM
MIN 304 CFM
MAX 1,394 CFM
VAV 6VAV 5VAV 4
VA
V 2
VA
V 1
InternalOffices
20 BTU’sAHR/FT2
30 BTU’sAHR/FT2
30 BTU’sAHR/FT2
30 BTU’sAHR/FT2
30 BTU’sAHR/FT2
E/A275 CFM
Max. 2986 CFMMin. 693 CFM
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VAV ACB+DOAS
• Total Air System Size‒ 565 CFM
• Airflow @ Max Turndown‒ 275 CFM
• Max. Airflow‒ 0.22 CFM/FT2
• Min. Average Airflow‒ 0.11 CFM CFM/FT2
• Airflow @ 60% Load‒ 0.11 CFM FT2
• Total Air System Size‒ 2986 CFM
• Airflow @ Max Turndown‒ 693 CFM
• Max. Airflow‒ 1.18 CFM/FT2
• Min. Average Airflow‒ 0.27 CFM CFM/FT2
• Airflow @ 60% Load‒ 0.71 CFM FT2
Summary Comparison
84% airflow reduction at 60% load!
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CFD Modeling Critical Applications
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QUESTIONS?