Active Chilled Beam System Design & Layout

Transcription

1 Active Chilled Beam System Design & Layout Salt Lake City, UT ASHRAE Chapter December 2013 Nick Searle

2 Contents Active Chilled Beam Basics Design Considerations Air System Design & Humidity Control Water System Design Heating with Active Beams Controls Beam Selection & Layout

3 Fan Energy Use in Buildings 4.5 Chiller/Compressor 7 Design Load KW/SF Supply & Return Fans Chilled Water Pump Condenser Water Pump Cooling Tower Fan Condenser Fan Energy Use KWh/SF Central VAV Central CAV Packaged CAV 0 Central VAV Central CAV Packaged CAV Energy Consumption Characteristics of Commercial Building HVAC Systems publication prepared for U.S. Department of Energy

4 Water = Efficient Transport 10 1 Ton of Cooling requires 550 CFM of air or ¾ diameter water pipe 4 GPM of water

5 Active Chilled Beams Chilled Ceilings Passive Chilled Beams Active Chilled Beams Higher space loads Higher occupant densities Combined ventilation/cooling preferred Integration into fiber tile ceilings required

6 Active Chilled Beam 0 Operation Principle Primary air nozzles Primary air plenum 1 Part Primary Air Suspended ceiling Heat exchanger 4 Parts Room Air

7 Heat Removal Ratio Airflow requirement reduced by 70% 70% of sensible heat removed by chilled beam water coil

8 Active Chilled Beam 0 Airflow Pattern

9 Active Chilled Beams 0 System Highlights Very high cooling capacity Up to 100 BTUH/FT 2 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

10 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

11 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

12 Active Chilled Beams 0 Typical Installation

13 Active Chilled Beams 0 Typical Installation

14 Space Savings 12 A0 9 A10

15 Space Savings

16 Space Savings 9 A10 8 A0

17 Space Savings All Air HVAC System 5 Floors Exposed Chilled Beams 6 Floors

18 ACTIVE CHILLED BEAM DESIGN CONSIDERATIONS

19 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

20 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 rea circulated room air Zone with high latent loads

21 SHR s for Typical Spaces SHR Range Auditoriums, Theaters Apartments Banks, Court Houses, Municipal Buildings Churches Dining Halls Computer Rooms Cocktail Lounges, Bars, Taverns, Clubhouses, Nightclubs Jails Hospital Patient Rooms, Nursing Home, Patient Rooms Kitchens Libraries, Museums Malls, Shopping Centers Medical/Dental Centers, Clinics and Offices Motel and Hotel Public Areas Motel and Hotel Guest Rooms Police Stations, Fire Stations, Post Offices Precision Manufacturing Restaurants Residences Retail, Department Stores Other Shops School Classrooms Supermarkets

22 Role of the Primary Air Ventilate the occupants according to ASHRAE 62A 2004 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

23 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

24 Primary Air Temperature 0 Cooling 55 F or Lower 65 F or Higher Reduces lengths/quantities of beams Good for office buildings with high perimeter loads Reduces or eliminates reheat Ideal for labs or hospitals with code required minimum air changes Often used with VAV in applications with high sensible loads More or longer beams required in some applications Air must be suitably dehumidified whatever the dry bulb temp is!

25 Room Neutral Air Sensible recovery device (downstream of coil) Desiccant dehumidification units Passive dehumidification wheels

26 Reducing Primary Air Temperature Active Chilled Beams Primary 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 Model 2 or 4 Pipe Coil Nominal Length (feet) P PA (Inch w.c.) Q PA (CFM) Q SA (CFM) t SAout ( F) q PAs (Btuh) q SCAs (Btuh) q s (Btuh) Q SCHW (GPM) 2 ACBA1 1 DADANCO ACB Room Design Primary Air Secondary Chilled Water Secondary Hot Water Elevation % Propylene Feet 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 Active Chilled Beams Primary 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) P PA(Inch w.c.) Q PA(CFM) Q SA(CFM) t SAout( F) q PAs(Btuh) q SCAs(Btuh) q s(btuh) Q SCHW (GPM) SCHW pressure drop (Feet w.c.) 3 ACBA1 1 DADANCO ACB Room Design Primary Air Secondary Chilled Water Secondary Hot Water Elevation Feet% Propylene Glycol Cooling 75 F 53% RH 65 F 70% RH 58 F 70 F Heating 70 F 50% RH 107 F 83% RH Typically 25% + more chilled beams required when using 65 F primary air % Ethylene Gylcol

27 Latent Load Calculation The amount of cooling required to remove the moisture from the air Q L = 0.68 x q x w gr or QL = 4,840 x q x w lb Where A Q L = latent heat (Btuh) q = air volume flow (cfm) w gr = humidity ratio difference (grains water/lb dry air) w lb = humidity ratio difference (lbwater/lb dry air)

28 Dehumidification Air for 1 Person 0 200BTUH Primary air flow (CFM) % less air Primary air dew point ( F) Room Design Condition 55% RH 52% RH 50% RH

29 Supply Water Temperature Safety Margin Passive Chilled Beams + 1 F Do not design below room dew point! Active Chilled Beams A 2.9 F Climatic Ceilings by Energie

30 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.

31 Design Cooling Loads 0 Beware of Overrating! Building was designed for 80 BTUH/ft 2 perimeter load Actual load in building use was 40 BTUH/ft 2 Parameter Proposed in design Actual observed load Area(Sq.ft) Sensible Load(Btuh) 16,000 8,000 Latent Load(Btuh) Minimum Outside Air(CFM) Quantity of ACB s 2 2

32 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

33 Design Cooling Loads 0 Beware of Overrating! Therefore if load drops to 65% no waterside cooling will occur If load drops below 65% space will overcool unless reheat is used

34 Causes of Overrating Loads 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

35 Design Cooling Loads 0 Rules of Thumb Location Sensible Zone Load North East South West Interior 25A30 Btuh/Sq.ft 35A45 Btuh/Sq.ft 30A40 Btuh/Sq.ft 40A50 Btuh/Sq.ft 15A20 Btuh/Sq.ft Exclude loads:a Outside air load Plenum gain Fan motor gain Duct losses If loads exceed these values review closely

36 WATER SYSTEM DESIGN

37 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

38 Mixing Valve Supply temperature monitor Secondary chilled water supply to beams Primary chilled water supply S 58 F T 45 F SCHW Pump T Primary chilled water return Primary chilled water return 64 F Secondary chilled water return

39 Secondary Loop Supply temperature monitor Secondary chilled water supply to beams Primary chilled water supply 45 F S 58 F SCHW Pump T T 54 F Primary chilled water return Heat Exchanger 64 F Secondary chilled water return

40 Dedicated Chiller To chilled beam zones Bypass Valve T Chilled water pump 64 F Cooling Tower Dedicated Geothermal chiller Heat 11+ Pump COP 58 F Geothermal Loop

41 District Chilled Water Loops Tap into return pipe with heat exchanger and secondary loop No demand in district loop GPM Increases main chiller plant COP

42 Reverse Return Pipe Design S T

43 15 Minute Break

44 HEATING WITH ACTIVE CHILLED BEAMS

45 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

46 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)

47 20Pipe Beams and Terminal Heating Chilled Water Supply Terminal Heating Coil Hot Water Supply 2APipe Active Chilled Beams Hot Water Return S T Chilled Water Return S

48 Heating Using 60Way Valves

49 60Way Valve

50 CONTROL CONSIDERATIONS

51 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

52 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

53 Waterside Control Sequence 76 Room Temperature ( F) SCHW ON Dead Zone SCHW OFF SCHW ON SCHW OFF Dead Zone 71 Time HW ON

54 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

55 Condensation and Dew Point Sensors Dew point sensor Condensation sensor Drip sensor

56 ACTIVE BEAM SYSTEM DESIGN COST CONTROL

57 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

58 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

59 Active Chilled Beam Selection & Layout

60 Room Load Data

61 ACB Selection & Layout Tips Select beams for minimum possible primary air 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

62 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

63 Tips to Minimize Primary Air Flow Be wary of overrating cooling loads Use low temperature primary air 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

64 DOAS with Booster Fans DEDICATED OUTDOOR AIR UNIT Outdoor Air + A A A FAN BOOSTERS Return Air Return Air ACTIVE CHILLED BEAM ZONES ACTIVE CHILLED BEAM ZONES

65 LAYOUT OFFICE

66 Building With Exterior Cellular Offices Office 3 Office 4 Office 5 Office 6 50 BTUH/ft 2 30 BTUH/ft 2 30 BTUH/ft 2 Occupants: 1 Area: 144 ft 2 Ventilation: 15 CFM Cooling: 7200 BTUH Latent load: 288 BTUH Heating Load: 3000 BTUH Occupants: 1 Area: 144 ft 2 Ventilation: 15 CFM Cooling: 4320 BTUH Latent load: 288 BTUH Heating Load: 2100 BTUH Occupants: 1 Area: 144 ft 2 Ventilation: 15 CFM Cooling: 4320 BTUH Latent load: 288 BTUH Heating Load: 2100 BTUH 30 BTUH/ft 2 Occupants: 1 Area: 144 ft 2 Ventilation: 15 CFM Cooling: 4320 BTUH Latent load: 288 BTUH Heating Load: 2100 BTUH Office 7 30 BTUH/ft 2 Occupants: 1 Area: 144 ft 2 Ventilation: 15 CFM Cooling: 4320 BTUH Latent load: 288 BTUH Heating Load: 2100 BTUH Office 2 35 BTUH/ft 2 Occupants: 1 Area: 144 ft 2 Ventilation: 15 CFM Cooling: 5040 BTUH Latent load: 288 BTUH Heating Load: 2500 BTUH Office 1 35 BTUH/ft 2 Occupants: 1 Area: 144 ft 2 Ventilation: 15 CFM Cooling: 5040 BTUH Latent load: 288 BTUH Heating Load: 2500 BTUH 12 Office 8 20 BTUH/ft 2 Occupants: 15 Area: 1,512 ft 2 Ventilation: 170 CFM Cooling: 30,240 BTUH Latent load: 3024 BTUH Heating Load: 0 BTUH TOTAL AREA 2,520 FT 2 12

67 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

68 Selection Software

69 ACB Layout ACBA3 PRIM. AIR Min. 15 CFM Max. 45 CFM Office 3 50 BTU sahr/ft 2 PRIM. AIR Min. 15 CFM Max. 25 CFM Office 4 ACBA4 ACBA5 ACBA6 ACBA7 30 BTU sa HR/FT 2 PRIM. AIR Min. 15 CFM Max. 25 CFM 30 BTU sa PRIM. AIR Min. 15 CFM Max. 25 CFM Office 5 HR/FT 2 Office 6 30 BTU sa HR/FT 2 Office 7 PRIM. AIR Min. 15 CFM Max. 25 CFM 30 BTU sa HR/FT 2 Min. O/A 275 CFM Max. O/A 485 CFM DOAS ACBA1 ACBA2 PRIM. AIR Min. 15 CFM Max. 35 CFM Office 2 35 BTU sahr/ft 2 PRIM. AIR Min. 15 CFM Max. 35 CFM Office 1 35 BTU sahr/ft 2 12 ACBA8b ACBA8a PRIM. AIR 270 CFM ACBA8d ACBA8c ACBA8f ACBA8e VAV Min. 105 CFM Max. 215 CFM Min. 170 CFM Max. 270 CFM Internal Offices 20 BTU sahr/ft 2 VAV S/A 12 TOTAL AREA 2,520 FT 2 R/A

70 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 ft 2

71 10Way Perimeter Beam Increased on coil temp Increased cooling output Less primary air required

72 10Way Beams at Perimeter CFD Cooling

73 10Way Beams at Perimeter CFD Heating

74 10Way Beams at Perimeter CFD Heating

75 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

76 VAV Layout MAX 332 CFM MIN 63 CFM MAX 199 CFM MIN 50 CFM MAX 199 CFM MIN 50 CFM MAX 199 CFM Office 3 30 BTU sa 30 BTU sa Office 4 HR/FT Office 5 Office 6 50 BTU sahr/ft 2 2 HR/FT 2 MIN 50 CFM 30 BTU sa HR/FT 2 MAX 199 CFM Office 7 MIN 50 CFM 30 BTU sa HR/FT 2 O/A 275 CFM E/A 275 CFM VAV 4 VAV 5 VAV 6 VAV 7 S/A AHU MAX 232 CFM MIN 63 CFM VAV 2 Min. 693 CFM Max CFM Office 2 35 BTU sahr/ft 2 VAV IO MAX 1,394 CFM MAX 232 CFM MIN 63 CFM Office 1 35 BTU sahr/ft 2 VAV 1 12 MIN 304 CFM Internal Offices 20 BTU sahr/ft 2 R/A 12 TOTAL AREA 2,520 FT 2

77 Summary Comparison VAV Total Air System Size 2986 CFM Max Turndown 693 CFM Max. Airflow 1.18 CFM/FT 2 Min. Average Airflow 0.27 CFM CFM/FT 2 60% Load 0.71 CFM FT 2 ACB+DOAS Total Air System Size 565 CFM Max Turndown 275 CFM Max. Airflow 0.22 CFM/FT 2 Min. Average Airflow 0.11 CFM CFM/FT 2 60% Load 0.11 CFM FT 2 84% airflow reduction at 60% load!

78 CFD Modeling Critical Applications

79 QUESTIONS?