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ASHRAE Rocky Mountain ChapterEvaporative CoolingEvaporative Cooling
Rick Phillips P E LEED APRick Phillips, P.E., LEED AP Senior Mechanical Engineer
The RMH Group, Inc.
1April 19, 2013
Fundamentals
Dry Bulb Temperature
Wet Bulb Temperature
Evaporation
Wet Bulb Depression = DB – WB
Design Day in Denver 93° DB 59° WB
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Design Day in Denver 93 DB, 59 WB
Direct Evaporative Cooling Pad Performance
OA DB HOURS/ 4" PAD 8" PAD 12" PAD FINAL RM COND (74 DB)RANGE MCWB YEAR LAT (DB) LAT (DB) LAT (DB) (WB) (%RH)
95‐99 60 3 77.4 67.6 64.1 63.05 57.390‐94 59 118 74.5 65.8 62.6 62.65 55.985‐89 58 235 71.6 63.9 61.2 62.13 54.180‐84 57 348 68.8 62.1 59.8 61.59 52.375‐79 55 390 65.3 59.5 57.4 60.64 49.270‐74 54 472 62.5 57.7 56.0 60.09 47.465‐69 52 697 59.1 55.1 53.7 59.1 44.2
Bin weather data Denver CO
60‐64 50 699 55.6 52.5 51.3 58.23 41.555‐59 47 762 51.7 49.1 48.1 56.75 36.9
Bin weather data, Denver, CO Doesn’t include fan temperature rise
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Indirect/Direct Evaporative Cooling System Performance
OA DB HOURS/ INDIRECT INDIRECT 4" PAD 8" PAD 12" PAD FINAL RM COND (74 DB)RANGE MCWB YEAR LAT (DB) LAT (WB) LAT (DB) LAT (DB) LAT (DB) (WB) (%RH)
95-99 60 3 74.4 52.13 62.6 56.7 54.6 58.96 43.790-94 59 118 71 9 51 86 61 3 56 0 54 1 58 96 43 790 94 59 118 71.9 51.86 61.3 56.0 54.1 58.96 43.785-89 58 235 69.3 51.71 60.0 55.3 53.6 58.96 43.780-84 57 348 66.8 51.43 58.6 54.6 53.1 58.81 43.375-79 55 390 63.6 50.01 56.4 52.8 51.5 58.23 41.570-74 54 472 61.0 49.85 55.1 52.1 51.1 58.23 41.565-69 52 697 57.9 48.43 52.9 50.4 49.5 57.50 39.265 69 52 697 57.9 48.43 52.9 50.4 49.5 57.50 39.260-64 50 699 54.7 47.11 50.7 48.7 47.9 56.90 37.455-59 47 762 50.9 44.35 47.4 45.7 45.1 55.68 33.7
Bin weather data Denver CO Bin weather data, Denver, CO Doesn’t include fan temperature rise
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Typical Meteorological Weather Data (TMY2)
Hourly weather data for a typical year (not averaged)year (not averaged)– Includes typical extreme weather
conditions
b i l d di i lik 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
° °11
67°F DB 74°F DB, 76% RH
Typical Meteorological Weather Data (TMY2)
Number of hours/year with high WB– > 60°F – 378 hours– > 63°F – 146 hours
65°F 33 h– > 65°F – 33 hours Using a 63°F DAT requires 67%
more airflow than using 55°F DAT.more airflow than using 55 F DAT.
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Systems that Can Use Higher SATy g
Displacement Ventilation 63F 68FDisplacement Ventilation
UFAD
63 F ‐ 68 F
60F ‐ 64F
Data Centers (hot aisle/cold aisle)
64F ‐ 80F
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For Conventional VAV Applicationspp 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
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For which types of buildings does evaporative cooling work?
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
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For which types of buildings does evaporative cooling work?
I di i li bi d i h diIndirect evaporative cooling combined with directevaporative cooling
C i l ffi b ildi Commercial office buildings Retail spaces Recreation centerRecreation center Any type of building with moderate to low internal cooling
loads
Direct and/or indirect evaporative cooling combined with CHW or DX cooling
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Any type of building
Pros
Saves energy Works well in the Denver climate Low tech and easy to maintain with unskilled labor Lower cost than a chilled water cooling plantg p Can also be used to cheaply humidify air Direct evaporative cooling is inexpensiveDirect evaporative cooling is inexpensive
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Cons
If not maintained properly can produce odors If not maintained properly, can produce odors If wrong materials are used, can have corrosion problemsproblems
Poor construction can result in leaks and water carryover, resulting in flooding of the space below y , g g pthe unit
People don’t understand how to maintain it or fix pproblems
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Maintenance and Operationp
Dry the pad out daily.
Drain the sump weekly.
Run the pad wild.
Don’t recirculate air Don t recirculate air.
Pads last approx. 8‐12 years.
Pipe for maintenance (strainers, PRV, flowmeters, etc.).
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Control Sequenceq
( ) Economizer (OA) Direct evap first Indirect/direct (if used) Direct with chilled water High humidity lockout 100% outside air whenever direct evap is active
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Typical HVAC SystemsEstimated Total Water Consumption
Air Cooled Chiller 2 8 COP = 10 Lb H OAir Cooled Chiller 2.8 COP = 10 Lb. H2O
Ton‐Hr
DX Air Conditioner 2.8 COP = 10 Lb. H2O
Ton‐Hr
Water Cooled Chiller 5.55 COP = 25 Lb. H2O
(150 ton – 300 ton) Ton‐Hr
Evaporative Cooler 80oF O.A. = 21 Lb. H2O
(Direct/Indirect) Ton‐Hr
Assumptions
•Power plant overall efficiency of 35%
•Average O.A. temperature of 80oF
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g p
•Cooling tower bleed rates of 20% to 33%
Case Study − Golden Hill Office Centery
212 000 sf office building 212,000 sf office building constructed in 1983
Designed in conjunction withDesigned in conjunction with SERI (NREL)
Model project for energy‐p j gyconscious design
National ASHRAE First Place Energy Award for New Construction, 1988
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Case Study − Golden Hill Office Center
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– 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 kBt / f/90 kBtu/sf/year
– 43 kBtu/sf/year measured with atrium– 28 kBtu/sf/year with light shelves (not installed)
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Case Study − Golden Hill Office Center
Indirect/direct evaporative cooling processIndirect/direct evaporative cooling process
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Case Study − CU‐Boulder ATLAS Center y
66 000 sf of classroom66,000 sf of classroom, performance, and study space
Opened for classes in August 2006
Features direct evap + CHW l bcooling, carbon dioxide
monitoring, and VAV systems Certified LEED NC Gold Certified LEED‐NC Gold 4 points for optimizing energy
performance – 30% reductionperformance 30% reduction
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Case Study − CU‐Boulder Wolf Law Building
Five‐story 184 000 sf Five story, 184,000 sf Opened for classes in August 2006August 2006
Features direct/indirect evap + CHW cooling, carbon p g,dioxide monitoring for demand ventilation, and VAV systems
Certified LEED‐NC Gold
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Case Study − CSM Student Recrea on Center
110 000 sf facility 110,000 sf facility Direct/indirect evaporative cooling onlycooling only– $500,000 deferred cost for chiller plant
Natatorium– IEC– Outside air for humidity control
Competition gymnasium Competition gymnasium– DEC/IEC 31
Case Study − Colorado Springs U li es Laboratory
Project DescriptionProject Description– 45,000 sf (2/3 laboratory space, 1/3 office space)Di i li i h– Direct evaporative cooling with chilled water, energy recovery
– Designed with the Labs‐21/LEED Guidelines
– Certified LEED‐NC Silver50% energy savings compared to– 50% energy savings compared to base case
– USGBC‐CO Bldg. of the Year Award
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Case Study − Colorado Springs U li es Laboratory
2 AHUs – 62,000 cfm for labs,2 AHUs 62,000 cfm for labs, 25,000 cfm for offices
Annual chiller operating costsAnnual chiller operating costs with chilled water cooling only ‐$17,900
Annual chiller operating costs with combined chilled water/ evaporative cooling $5 900evaporative cooling ‐ $5,900
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Case Study − Colorado Springs U li es Laboratory
Cost of adding direct evaporativeCost of adding direct evaporative cooling modules
Lab AHU Office AHUEquip. Cost $9,500 $6,000
P b k ith dditi f
q p $ , $ ,Hookup/Controls $2,500 $2,000
Total $12,000 $8,000
Payback with addition of evaporative cooling
= First Cost/Yearly Savings
= $20,000/$12,000
= 1.67 years (20 months)
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