establishing primary airflow in wbcs systemstorontoashrae.com/resources/documents/ashrae chilled...

Establishing Primary Airflow in WBCS

Systems

Establishing Primary Airflow in WBCS

Systems

Chilled Beam Design Principles

How is capacity measured?

•Tested & reported as an assembly

•Is not simply a sum of component capacity

•ASHRAE Standard 200

How is capacity certified?

AHRI Standard 1240/1241 certification program

More information:

3

Chilled Beam Design Principles

Agenda

• WBCS Concept

• Occupant Comfort

• Establishing Primary Airflow Rate

• Energy Impact

• Demand Control Ventilation

• WBCS Concept

• Occupant Comfort

• Establishing Primary Airflow Rate

• Energy Impact

• Demand Control Ventilation

4 2015-12-15 Establishing Primary Airflow

Focusing on what our customers care about

5 2015-12-15 Establishing Primary Airflow

o Comfort vs. Capacity

o System Design vs. Product Features

VS.

Water Borne Climate System Concept

6 2015-12-15

Transportation Costs

7 2015-12-15 Company Presentation

Air

10” duct

Capacity 9900 Btuh

(20 ft/s Δt 14°F)

Water

3/4” pipe

Capacity 9900 Btuh

(110 ft/m Δt 7°F)

8

Treated fresh air

Cooling CoilNozzles

Inducedwarm room air

Supply air

Operates through induction

How a chilled beam works

WBCS Basics

9

Comfort Modules & Chilled Beams

1-Way 2-Way 4-Way

1-W

ay

1-W

ay

Chilled Beams and Occupant Comfort

11 2015-12-15

Heating/Cooling Capacity & Air Distribution

• A chilled beam is a combination energy source

and air distribution system so the selection is

doubly important.

• The space air distribution is equally important

to capacity in determining the comfort level.

Poor air distribution will result in poor comfort

no matter how much capacity is available.

• A chilled beam is a combination energy source

and air distribution system so the selection is

doubly important.

• The space air distribution is equally important

to capacity in determining the comfort level.

Poor air distribution will result in poor comfort

no matter how much capacity is available.

Chilled Beam – Energy source + air diffuser

14

Controllable by

chilled beam

Metabolic rate x

Clothing insulation x

Air temperature �

Radiant temperature x

Air speed �

Air direction / throw �

Humidity x

User adjustability �

ASHRAE Standard 55 Comfort Considerations

Air Distribution

Mixed SystemsMixed Systems

• All the air in the space is

mixed to same the same

temperature

• Overhead mixed air

systems use Coanda

effect

• Most beams are based

on mixed air approach

(overhead)

• All the air in the space is

mixed to same the same

temperature

• Overhead mixed air

systems use Coanda

effect

• Most beams are based

on mixed air approach

(overhead)

Displacement SystemsDisplacement Systems

• Air is introduced at floor

level at very low velocities

• Space is deliberately

stratified

• Only the occupant zone is

conditioned

• Air is introduced at floor

level at very low velocities

• Space is deliberately

stratified

• Only the occupant zone is

conditioned


16

Coanda effect

2015-12-15

Thanks to the negative pressure, the air follows the ceiling instead of falling straight down when it leaves the module

When the air reaches the occupied zone, it has attained a temperature and speed that reduces the risk of draft

17

Induction and Coanda Effect

Creating Coanda Effect

18

Diffuser nozzle design

• Beams have built in “Diffuser” technology

• Beam selection and placement to ensure comfort is

an important as when selecting diffusers

• “One big beam in a space may meet cooling load but

may not deliver the comfort that two smaller beams

would deliver”

Airflow Pattern


• Beams can offer wide range of airflow patterns to

suit space

202015-12-15 Indoor Climate Systems - Water based or Air?

2-way discharge strategy • Uses only small area of the ceiling• Air volume distributed into narrow region

4-way discharge strategy• Maximizes use of available ceiling area• Air volume distributed diffusely, more slowly• Flexible discharge patterns / field adjustable

Beam Selection For Comfort

WBCS Primary Airflow Analysis

21 12/15/2015Intro to ComVent - Establish

loads and Primary Airflow

Compare Office Vs. School

2015-12-15 Company Presentation 22

Cooling Load Summary


Sensible Load Latent Load Total Load SHR

Btu/h Btu/h-ft² Btu/h Btu/h-ft² Btu/h Btu/h-ft²

Classroom 24756 24.8 7795 7.8 32551 32.6 0.76

Office 23116 23.1 2573 2.6 25688 25.7 0.9

Cooling Load Calculations

• Loads same regardless of HVAC system

• Fancoil, WSHP, GSHP and VRF need zone latent and sensible loads separate from outdoor air load

• WBCS need zone sensible load separate from zone latent load and outdoor air latent and sensible load

• Loads same regardless of HVAC system

• Fancoil, WSHP, GSHP and VRF need zone latent and sensible loads separate from outdoor air load

• WBCS need zone sensible load separate from zone latent load and outdoor air latent and sensible load



WBCS Primary Airflow Design

• The primary airflow rate must be the larger of;

• The air flow rate to meet the ventilation rate required

to deliver acceptable indoor air quality.

• The airflow rate to provide latent cooling in the zone.

• The airflow rate required to assist in meeting the zone

sensible cooling rate.

• The primary airflow rate must be the larger of;

• The air flow rate to meet the ventilation rate required

to deliver acceptable indoor air quality.

• The airflow rate to provide latent cooling in the zone.

• The airflow rate required to assist in meeting the zone

sensible cooling rate.



Ventilation Rate

• Office

• Ventilation rate = 10 x 5 cfm

+ 0.06 x 1000 ft² = 110 cfm

• = 0.11 cfm/ft²

• Classroom


+ 0.12 x 1000 ft² = 423 cfm

• = 0.42 cfm/ft²

• Office


+ 0.06 x 1000 ft² = 110 cfm

• = 0.11 cfm/ft²

• Classroom


+ 0.12 x 1000 ft² = 423 cfm

• = 0.42 cfm/ft²


Latent Rate


75 °F DB

50% RH

64.6 gr/lb HR

Qp = Platent/(0.68 x (Wr - Wprimary air))

Sensible Rate


75 °F DB

50% RH

64.6 gr/lb HR

Qp = Psensible /(1.085 x ((Tr – Tp) + IR x (Tr – Ta))

Primary Airflow Summary

• Can’t go below ventilation rate

• Latent load usually dominates

• Offices 0.4 to 0.6 cfm/ft², 53 °F off coil

• Classroom 0.6 to 0.8 cfm/ft², 49 °F off coil (reheat required)

• Can’t go below ventilation rate

• Latent load usually dominates

• Offices 0.4 to 0.6 cfm/ft², 53 °F off coil

• Classroom 0.6 to 0.8 cfm/ft², 49 °F off coil (reheat required)

Ventilation Rate Latent Rate Sensible Rate

Btu/h cfm/ft² Btu/h cfm/ft² Btu/h cfm/ft²

Classroom 423 0.43 740 0.75 761 0.76

Office 110 0.11 461 0.46 333 0.33

2912/15/2015Intro to ComVent - Establish loads and

Primary Airflow


• The zone sensible cooling load should be between 20 to 40 Btu/h·ft².

• The primary airflow will be most likely set by the zone latent load. A good range is 0.4 to 0.6 cfm/ft².

• A good office system has 1/3 of the load met by the primary air and 2/3 of the load met by the chilled beam coil.

• Assume an induction ratio between 2.5 to 3.5. Start with 3.

• The zone sensible cooling load should be between 20 to 40 Btu/h·ft².

• The primary airflow will be most likely set by the zone latent load. A good range is 0.4 to 0.6 cfm/ft².

• A good office system has 1/3 of the load met by the primary air and 2/3 of the load met by the chilled beam coil.

• Assume an induction ratio between 2.5 to 3.5. Start with 3.



• The chilled water supply temperature should

be 2-3 °F above space dew point. 57 °F is a

common supply water temperature.

• The chilled water temperature range will be 4

to 6 °F. Consider putting the primary air

system in series with the chilled beams.

• The chilled water supply temperature should

be 2-3 °F above space dew point. 57 °F is a

common supply water temperature.

• The chilled water temperature range will be 4

to 6 °F. Consider putting the primary air

system in series with the chilled beams.


WBCS Energy Considerations



Design vs. Annual Energy Usage


Fans

25%

Chiller

56%

Pumps

14%

Tower

5%

Design Day

Fans

44%

Chiller

32%

Pumps

21%

Tower

3%

Annual

Annual Cooling Load Profile


0

50

100

150

200

250

300

350

400

450

500

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

Ho

urs

Percent Cooling Load

Standard DOAS Unit



Primary Airflow vs. Delta Humidity Ratio

12/15/2015 36

• All points of curve deliver same amount latent cooling to space

Platent = 0.68*Qp* (Wr – Wprimary air )

0

10

20

30

40

50

60

70

80

90

100

3.8 6.1 8.3 10.5 12.6 14.6 16.5

Pri

ma

ry A

irfl

ow

(cf

m)

Delta Humidity Ratio (gr/lb)

Cooling Capacity of Primary Airflow

37 12/15/2015

0

10

20

30

40

50

60

70

80

90

100

2062 1352 1043 864 753 678 625

Pri

ma

ry A

irfl

ow

(cf

m)

Primary Air Sensible Capacity (Btu/h)

• Primary cooling capacity drops off as airflow is reduced

• Shifts load to beam

Primary Airflow vs. Induction Ratio



0

10

20

30

40

50

60

70

80

90

100

1.1 2.8 4.4 5.9 7.4 8.9 10.2

Pri

am

ry A

irfl

ow

(cf

m)

Induction Ratio

• Higher beam load requires higher induction rate

• APD and noise become issue

DOAS Energy Model Design Parameters

Off Coil DB SA DB SA HR Delta HR SA Airflow

F F gr/lb gr/lb cfm

55 56 62.6 3.8 100

54 55 60.3 6.1 62

53 54 58.1 8.3 46

52 53 55.9 10.5 36

51 52 53.8 12.6 30

50 51 51.8 14.6 26

49 50 49.9 16.5 23



Annual Energy Usage Std DOAS Unit



0.0

100.0

200.0

300.0

400.0

500.0

600.0

700.0

100 62 46 36 30 26 23

An

nu

al E

ne

rgy

Usa

ge

(kW

h)

Primary Airflow (cfm)Rotor BIN Watts kWh SA Fan BIN Watts kWh

Chiller Plant BIN Watts kWh HW Plant BIN Watts kWh

RA Fan BIN Watts kWh

Energy Analysis Summary

• Fan work is dominant

• Generally shifting sensible load to beams from primary

is more efficient

• Practical limitation on induction ratio (5) and primary

air temperature (53 °)

• Reheat increases operating cost – only do it if you

have to (schools)

• Fan work is dominant

• Generally shifting sensible load to beams from primary

is more efficient

• Practical limitation on induction ratio (5) and primary

air temperature (53 °)

• Reheat increases operating cost – only do it if you

have to (schools)



Demand Control Ventilation


• Classrooms occupied 35%

• Offices occupied 22-38%

• ASHRAE Std 90.1

• 500 ft²

• 25 people per 1000 ft²

• greater than 3000 cfm

• ASHRAE Std 62

• Minimum airflow ≥ building load

component (Ra x Az)

• Classrooms occupied 35%

• Offices occupied 22-38%

• ASHRAE Std 90.1

• 500 ft²

• 25 people per 1000 ft²

• greater than 3000 cfm

• ASHRAE Std 62

• Minimum airflow ≥ building load

component (Ra x Az)



• Vary Primary airflow based on

• Occupancy

• Temperature

• CO2

• VOC

• Vary Primary airflow based on

• Occupancy

• Temperature

• CO2

• VOC


06:00 07:00 08:00 09:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00

Time

Air Volume l/s

150

200

250

Saving

CAV

DCV

100

Impact of Reduced Primary Airflow on Induction

0

50

100

150

200

250

300

350

400

0 10 20 30 40 50 60 70 80 90 100 110 120 130

Chilled Beam Discharge(CFM)

Primary Airflow Demand(CFM)

Induced

Primary

Chilled Beam with

Integral Damper

Discharge,

chilled beam

with upstream

VAV damper

12/15/2015Intro to ComVent - Establish

loads and Primary Airflow45

Demand Control VentilationDemand Control Ventilation

Dampers

ZONEDOAS

Demand Control Ventilation Summary

• DCV increases chilled beam turndown from 3 to 1 to

10 to 1

• Improves occupant comfort

• Spaces are rarely at design occupancy

• DCV allows significant fan power savings

• DCV control can be based on

• Occupancy sensor (single occupant office)

• CO2 or VOC (modulating for multi occupant

spaces)

• DCV increases chilled beam turndown from 3 to 1 to

10 to 1

• Improves occupant comfort

• Spaces are rarely at design occupancy

• DCV allows significant fan power savings

• DCV control can be based on

• Occupancy sensor (single occupant office)

• CO2 or VOC (modulating for multi occupant

spaces)



THANK YOU FOR YOUR TIME

establishing primary airflow in wbcs systemstorontoashrae.com/resources/documents/ashrae chilled...

Documents