Active Chilled Beam System Design & Layout

Active Chilled Beam

System Design & Layout

Salt Lake City, UT ASHRAE Chapter

December 2013

Nick Searle

[email protected]

Contents

• Active Chilled Beam Basics

• Design Considerations

• Air System Design & Humidity Control

• Water System Design

• Heating with Active Beams

• Controls

• Beam Selection & Layout

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

Water = Efficient Transport

¾” diameterwater pipe

10”

1 Ton of Cooling

requires 550 CFM of air

or

4 GPM of water

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

Active Chilled Beam 0 Operation Principle

Suspended ceiling

Primary air plenum

Primary air nozzles

Heat exchanger

1 Part Primary Air

4 Parts Room Air

Heat Removal Ratio

70% of sensible heat removed by chilled beam

water coil

Airflow requirement

reduced by 70%

Active Chilled Beam 0 Airflow Pattern

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

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

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

Active Chilled Beams 0 Typical Installation

Active Chilled Beams 0 Typical Installation

9’A

10

”

12

’A0

”

Space Savings

Space Savings

Space Savings

8’A

0”

9’A

10

”

Exp

osed C

hill

ed B

ea

ms

6 F

loo

rs

All

Air

HV

AC

Syste

m5

Flo

ors

Space Savings

ACTIVE CHILLED BEAM DESIGN

CONSIDERATIONS

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

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

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

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

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

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!

Room Neutral Air

• Sensible recovery device (downstream of coil)

• Desiccant dehumidification units

• Passive dehumidification wheels

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

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)

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

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!

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.

• 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!

• 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


• Therefore if load drops to 65% no waterside cooling will occur

• If load drops below 65% space will overcool unless reheat is used


• 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

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

WATER SYSTEM DESIGN

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

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

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

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

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

Reverse Return Pipe Design

S

T

15 Minute Break

HEATING WITH ACTIVE CHILLED BEAMS

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

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)

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

Heating Using 60Way Valves

60Way Valve

CONTROL CONSIDERATIONS

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

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

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

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

Condensation and Dew Point Sensors

Drip sensor

Condensation sensorDew point sensor

ACTIVE BEAM SYSTEM DESIGN

COST CONTROL

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

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

Active Chilled Beam

Selection & Layout

Room Load Data

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

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

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

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

LAYOUT EXAMPLE

@ OFFICE BUILDING @

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


1144 ft2



1144 ft2



1144 ft2



1144 ft2



1144 ft2



1144 ft2



151,512 ft2

170 CFM30,240 BTUH3024 BTUH0 BTUH

Office 820 BTUH/ft2

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

Selection Software

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. AIRMin. 15 CFMMax. 25 CFM




PRIM. AIR 270 CFMMin. 105 CFMMax. 215 CFM

Max. 270 CFM

Office 135 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

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

10Way Perimeter Beam

• Increased on coil temp

• Increased cooling output

• Less primary air required

10Way Beams at Perimeter – CFD Cooling

10Way Beams at Perimeter – CFD Heating

10Way Beams at Perimeter – CFD Heating

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

VAV Layout


12’

12’


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

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!

CFD Modeling Critical Applications

QUESTIONS?

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Active Chilled Beam System Design & Layout

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