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ASHRAE Rocky Mountain Chapter Evaporative Cooling 1 Rick Phillips, P.E., LEED AP Senior Mechanical Engineer The RMH Group, Inc. May 2, 2014.

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Presentation on theme: "ASHRAE Rocky Mountain Chapter Evaporative Cooling 1 Rick Phillips, P.E., LEED AP Senior Mechanical Engineer The RMH Group, Inc. May 2, 2014."— Presentation transcript:

1 ASHRAE Rocky Mountain Chapter Evaporative Cooling 1 Rick Phillips, P.E., LEED AP Senior Mechanical Engineer The RMH Group, Inc. May 2, 2014

2 Fundamentals 2 Dry Bulb Temperature Wet Bulb Temperature Evaporation Wet Bulb Depression = DB – WB Design Day in Denver 93° DB, 59° WB

3 Direct Evaporative Cooler 3

4 Media 4

5 Performance 5 Cooling Effectiveness = (%) EDB – LDB EDB – EWB

6 Indirect Evaporative Cooling 6

7 Hybrid Indirect Evaporative Cooler with Energy Recovery 7 (Used as IEC) (Could be DEC)

8 Psychrometrics 8 DIRECTINDIRECTINDIRECT / DIRECT

9 Direct Evaporative Cooling Pad Performance 9  Bin weather data, Denver, CO  Doesn’t include fan temperature rise OA DBHOURS/4" PAD8" PAD12" PADFINAL RM COND (74 DB) RANGEMCWBYEARLAT (DB) (WB)(%RH)

10 Indirect/Direct Evaporative Cooling System Performance 10 OA DBHOURS/INDIRECT 4" PAD8" PAD12" PADFINAL RM COND (74 DB) RANGEMCWBYEARLAT (DB)LAT (WB)LAT (DB) (WB)(%RH)  Bin weather data, Denver, CO  Doesn’t include fan temperature rise

11 Typical Meteorological Weather Data (TMY2) 11  Hourly weather data for a typical year (not averaged) – Includes typical extreme weather conditions  Database includes conditions like this: – 78°F DB, 66°F WB Under these conditions, direct evaporative cooling does not perform well. 12” PAD (LAT) Final Room Conditions 67°F DB74°F DB, 76% RH

12 Typical Meteorological Weather Data (TMY2) 12  Number of hours/year with high WB – > 60°F – 378 hours – > 63°F – 146 hours – > 65°F – 33 hours  Using a 63°F DAT requires 67% more airflow than using 55°F DAT.

13 Systems that Can Use Higher SAT 13 Displacement Ventilation UFAD Data Centers (hot aisle/cold aisle) 63  F - 68  F 60  F - 64  F 64  F - 80  F

14 For Conventional VAV Applications 14  Combine chilled water with direct evaporative cooling  Advantages – Can reduce chiller ton-hours/year by 2/3 ($$). – Can deliver 55°F DAT at any time. Don’t have to oversize fans and ducts. – Can limit humidity levels in the building. Note: still requires a full-sized chiller

15 CHW/DEC Component Arrangement for Optimal Performance 15 * Fan Upstream – 35% less CC energy (compared to CC upstream of DEC) (compared to DEC upstream of of CC) : :

16 For which types of buildings does evaporative cooling work? 16 Direct evaporative cooling alone  Warehouses  Vehicle repair facilities  Any type of building with low internal cooling loads  Makeup air for commercial kitchens  Gymnasiums  Spaces that are open to the outdoors

17 17 For which types of buildings does evaporative cooling work? Indirect evaporative cooling combined with direct evaporative cooling  Commercial office buildings  Retail spaces  Recreation center  Any type of building with moderate to low internal cooling loads Direct and/or indirect evaporative cooling combined with CHW or DX cooling  Any type of building

18 Pros 18  Saves energy  Works well in the Denver climate  Low tech and easy to maintain with unskilled labor  Lower cost than a chilled water cooling plant  Can also be used to cheaply humidify air  Direct evaporative cooling is inexpensive

19 Cons 19  If not maintained properly, can produce odors  If wrong materials are used, can have corrosion problems  Poor construction can result in leaks and water carryover, resulting in flooding of the space below the unit  People don’t understand how to maintain it or fix problems

20 Maintenance and Operation 20  Dry the pad out daily.  Drain the sump weekly.  Run the pad wild.  Don’t recirculate air.  Pads last approx years.  Pipe for maintenance (strainers, PRV, flowmeters, etc.).

21 Direct Evaporative Cooler Piping 21

22 Water Treatment 22  Scale buildup prevention  Continuous bleed or automatic control  Biocides

23 Control Sequence 23  Economizer (OA)  Direct evap first  Indirect/direct (if used)  Direct with chilled water  High humidity lockout  100% outside air whenever direct evap is active

24 Myths 24  Legionella disease  Over humidification  Smell  High maintenance  High water usage

25 Typical HVAC Systems Estimated Total Water Consumption 25 Assumptions Power plant overall efficiency of 35% Average O.A. temperature of 80 o F Cooling tower bleed rates of 20% to 33% Air Cooled Chiller 2.8COP=10Lb.H2OH2O Ton-Hr DX Air Conditioner 2.8COP=10Lb.H2OH2O Ton-Hr Water Cooled Chiller 5.55COP=25Lb.H2OH2O (150 ton – 300 ton) Ton-Hr Evaporative Cooler 80 o FO.A.=21Lb.H2OH2O (Direct/Indirect) Ton-Hr

26 Case Study − Golden Hill Office Center  212,000 sf office building constructed in 1983  Designed in conjunction with SERI (NREL)  Model project for energy- conscious design  National ASHRAE First Place Energy Award for New Construction,

27 Case Study − Golden Hill Office Center 27  Features – 100% indirect/direct evaporative cooling system – Solar hot water heating – Three 10 kW roof-mounted photovoltaic arrays – Passive solar design with east-west axis – Six high-efficiency, condensing boilers – Natural ventilation for parking garage – Heat and light reclaimed from atriums to offices – South side window overhangs – 38 kBtu/sk/year measured without atrium; DOE 1995 energy evaluation of comparative buildings is 90 kBtu/sf/year – 43 kBtu/sf/year measured with atrium – 28 kBtu/sf/year with light shelves (not installed)

28 Case Study − Golden Hill Office Center 28  Indirect/direct evaporative cooling process

29 Case Study − CU-Boulder ATLAS Center  66,000 sf of classroom, performance, and study space  Opened for classes in August 2006  Features direct evap + CHW cooling, carbon dioxide monitoring, and VAV systems  Certified LEED-NC Gold  4 points for optimizing energy performance – 30% reduction 29

30 Case Study − CU-Boulder Wolf Law Building  Five-story, 184,000 sf  Opened for classes in August 2006  Features direct/indirect evap + CHW cooling, carbon dioxide monitoring for demand ventilation, and VAV systems  Certified LEED-NC Gold 30

31 Case Study − CSM Student Recreation Center  110,000 sf facility  Direct/indirect evaporative cooling only – $500,000 deferred cost for chiller plant  Natatorium – IEC – Outside air for humidity control  Competition gymnasium – DEC/IEC 31

32 Case Study − Colorado Springs Utilities Laboratory  Project Description – 45,000 sf (2/3 laboratory space, 1/3 office space) – Direct evaporative cooling with chilled water, energy recovery – Designed with the Labs-21/LEED Guidelines – Certified LEED-NC Silver – 50% energy savings compared to base case – USGBC-CO Bldg. of the Year Award 32

33 Case Study − Colorado Springs Utilities Laboratory  2 AHUs – 62,000 cfm for labs, 25,000 cfm for offices  Annual chiller operating costs with chilled water cooling only - $17,900  Annual chiller operating costs with combined chilled water/ evaporative cooling - $5,900 33

34 34 Case Study − Colorado Springs Utilities Laboratory  Cost of adding direct evaporative cooling modules  Payback with addition of evaporative cooling = First Cost/ Yearly Savings = $20,000/ $12,000 = 1.67 years (20 months) Lab AHUOffice AHU Equip. Cost $9,500 $6,000 Hookup/Controls $2,500 $2,000 Total $12,000 $8,000


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