ASHRAE Rocky Mountain Evaporative Cooling · ASHRAE Rocky Mountain Chapter Evaporative Cooling Rick Phillips, PEP.E., LEED AP Senior Mechanical Engineer The RMH Group, Inc. 1 April

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 Coolerp

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Media

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Performance

CoolingEffectiveness  =(%)

EDB – LDB

EDB – EWB

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Indirect Evaporative Coolingp g

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Hybrid Indirect Evaporative Cooler with Energy Recovery

(Could be DEC)

(Used as IEC)

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Psychrometricsy

DIRECT INDIRECT INDIRECT / DIRECT

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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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CHW/DEC Component Arrangement for Optimal Performance

* Fan Upstream – 35% less CC energy

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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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Direct Evaporative Cooler Pipingp p g

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Water Treatment

Scale buildup prevention

Continuous bleed or automatic control

Biocides

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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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Mythsy

i ll di Legionella disease Over humidification Smell High maintenance High water usage

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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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