Establishing Primary Airflow in WBCS Establishing Primary Airflow in WBCS Systems Systems
Chilled Beam Design Principles More information: 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
Chilled Beam Design Principles 3
Agenda • • WBCS Concept WBCS Concept • • Occupant Comfort Occupant Comfort • • Establishing Primary Airflow Rate Establishing Primary Airflow Rate • • Energy Impact Energy Impact • • Demand Control Ventilation Demand Control Ventilation 4 2015-12-15 Establishing Primary Airflow
Focusing on what our customers care about Comfort vs. Capacity o System Design vs. Product Features o VS. 2015-12-15 Establishing Primary Airflow 5
Water Borne Climate System Concept 2015-12-15 6
Transportation Costs Water 3/4” pipe Capacity 9900 Btuh (110 ft/m Δt 7 � F) Air 10” duct Capacity 9900 Btuh (20 ft/s Δt 14 � F) 7 2015-12-15 Company Presentation
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WBCS Basics 9
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Chilled Beams and Occupant Comfort 2015-12-15 11
Heating/Cooling Capacity & Air Distribution • A chilled beam is a combination energy source • A chilled beam is a combination energy source and air distribution system so the selection is and air distribution system so the selection is doubly important. doubly important. • The space air distribution is equally important • The space air distribution is equally important to capacity in determining the comfort level. to capacity in determining the comfort level. Poor air distribution will result in poor comfort Poor air distribution will result in poor comfort no matter how much capacity is available. no matter how much capacity is available.
Chilled Beam – Energy source + air diffuser
ASHRAE Standard 55 Comfort Considerations Controllable by chilled beam Metabolic rate x Clothing insulation x � Air temperature Radiant temperature x � Air speed � Air direction / throw Humidity x � User adjustability 14
Air Distribution Mixed Systems Mixed Systems Displacement Systems Displacement Systems • All the air in the space is • All the air in the space is • Air is introduced at floor • Air is introduced at floor mixed to same the same mixed to same the same level at very low velocities level at very low velocities temperature temperature • Space is deliberately • Space is deliberately • Overhead mixed air • Overhead mixed air stratified stratified systems use Coanda systems use Coanda • Only the occupant zone is • Only the occupant zone is effect effect conditioned conditioned • Most beams are based • Most beams are based on mixed air approach on mixed air approach (overhead) (overhead) 15 2015-12-15 Company Presentation
Coanda effect 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 ! "# $% "% $
Induction and Coanda Effect 17
Creating Coanda Effect 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” 18
Airflow Pattern • Beams can offer wide range of airflow patterns to suit space 19 2015-12-15 Company Presentation
Beam Selection For Comfort 2-way discharge strategy 4-way discharge strategy • Uses only small area of the ceiling • Maximizes use of available ceiling area • Air volume distributed into narrow region • Air volume distributed diffusely, more slowly • Flexible discharge patterns / field adjustable 2015-12-15 Indoor Climate Systems - Water based or Air? 20
WBCS Primary Airflow Analysis Intro to ComVent - Establish 12/15/2015 21 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 23 2015-12-15 Company Presentation
Cooling Load Calculations • Loads same regardless of • Loads same regardless of HVAC system HVAC system • Fancoil, WSHP, GSHP and • Fancoil, WSHP, GSHP and VRF need zone latent and VRF need zone latent and sensible loads separate sensible loads separate from outdoor air load from outdoor air load • WBCS need zone sensible • WBCS need zone sensible load separate from zone load separate from zone latent load and outdoor air latent load and outdoor air latent and sensible load latent and sensible load Intro to ComVent - Establish 24 12/15/2015 loads and Primary Airflow
WBCS Primary Airflow Design • The primary airflow rate must be the larger of; • The primary airflow rate must be the larger of; • The air flow rate to meet the ventilation rate required • The air flow rate to meet the ventilation rate required to deliver acceptable indoor air quality. to deliver acceptable indoor air quality. • The airflow rate to provide latent cooling in the zone. • The airflow rate to provide latent cooling in the zone. • The airflow rate required to assist in meeting the zone • The airflow rate required to assist in meeting the zone sensible cooling rate. sensible cooling rate. Intro to ComVent - Establish 25 12/15/2015 loads and Primary Airflow
Ventilation Rate • Office • Office • Ventilation rate = 10 x 5 cfm • Ventilation rate = 10 x 5 cfm + 0.06 x 1000 ft² = 110 cfm + 0.06 x 1000 ft² = 110 cfm • • = 0.11 cfm/ft² = 0.11 cfm/ft² • Classroom • Classroom • Ventilation rate = 30 x 10 cfm • Ventilation rate = 30 x 10 cfm + 0.12 x 1000 ft² = 423 cfm + 0.12 x 1000 ft² = 423 cfm • • = 0.42 cfm/ft² = 0.42 cfm/ft² 26 2015-12-15 Company Presentation
Latent Rate Q p = P latent /(0.68 x (W r - W primary air )) 75 °F DB 50% RH 64.6 gr/lb HR 27 2015-12-15 Company Presentation
Sensible Rate Q p = P sensible /(1.085 x ((T r – T p ) + IR x (T r – T a )) 75 °F DB 50% RH 64.6 gr/lb HR 28 2015-12-15 Company Presentation
Primary Airflow Summary 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 • Can’t go below ventilation rate • Can’t go below ventilation rate • Latent load usually dominates • Latent load usually dominates • Offices 0.4 to 0.6 cfm/ft², 53 ° F off coil • 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 • Classroom 0.6 to 0.8 cfm/ft², 49 ° F off coil (reheat required) required) Intro to ComVent - Establish loads and 12/15/2015 29 Primary Airflow
Primary Airflow Summary • The zone sensible cooling load should be • The zone sensible cooling load should be between 20 to 40 Btu/h·ft². between 20 to 40 Btu/h·ft². • The primary airflow will be most likely set by • The primary airflow will be most likely set by the zone latent load. A good range is 0.4 to the zone latent load. A good range is 0.4 to 0.6 cfm/ft². 0.6 cfm/ft². • A good office system has 1/3 of the load met • A good office system has 1/3 of the load met by the primary air and 2/3 of the load met by by the primary air and 2/3 of the load met by the chilled beam coil. the chilled beam coil. • Assume an induction ratio between 2.5 to 3.5. • Assume an induction ratio between 2.5 to 3.5. Start with 3. Start with 3. 30 2015-12-15 Company Presentation
Primary Airflow Summary • The chilled water supply temperature should • The chilled water supply temperature should be 2-3 ° F above space dew point. 57 ° F is a be 2-3 ° F above space dew point. 57 ° F is a common supply water temperature. common supply water temperature. • The chilled water temperature range will be 4 • The chilled water temperature range will be 4 to 6 ° F. Consider putting the primary air to 6 ° F. Consider putting the primary air system in series with the chilled beams. system in series with the chilled beams. 31 2015-12-15 Company Presentation
WBCS Energy Considerations Intro to ComVent - Establish 12/15/2015 32 loads and Primary Airflow
Design vs. Annual Energy Usage Design Day Annual Tower 3% Tower Pumps Fans 5% Pumps 14% 25% Fans 21% 44% Chiller 56% Chiller 32% 33 2015-12-15 Company Presentation
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