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ASHRAE Rocky Mountain Chapter Evaporative Cooling

ASHRAE Rocky Mountain Chapter Evaporative Cooling. Rick Phillips, P.E., LEED AP Senior Mechanical Engineer The RMH Group, Inc. May 2, 2014. Fundamentals. Evaporation. Dry Bulb Temperature. Wet Bulb Temperature. Wet Bulb Depression = DB – WB Design Day in Denver 93 ° DB, 59° WB.

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ASHRAE Rocky Mountain Chapter Evaporative Cooling

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

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

  3. Direct Evaporative Cooler

  4. Media

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

  6. Indirect Evaporative Cooling

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

  8. Psychrometrics DIRECT INDIRECT INDIRECT / DIRECT

  9. 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 57.3 90-94 59 118 74.5 65.8 62.6 62.65 55.9 85-89 58 235 71.6 63.9 61.2 62.13 54.1 80-84 57 348 68.8 62.1 59.8 61.59 52.3 75-79 55 390 65.3 59.5 57.4 60.64 49.2 70-74 54 472 62.5 57.7 56.0 60.09 47.4 65-69 52 697 59.1 55.1 53.7 59.1 44.2 60-64 50 699 55.6 52.5 51.3 58.23 41.5 55-59 47 762 51.7 49.1 48.1 56.75 36.9 Direct Evaporative Cooling Pad Performance • Bin weather data, Denver, CO • Doesn’t include fan temperature rise

  10. 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 43.7 90-94 59 118 71.9 51.86 61.3 56.0 54.1 58.96 43.7 85-89 58 235 69.3 51.71 60.0 55.3 53.6 58.96 43.7 80-84 57 348 66.8 51.43 58.6 54.6 53.1 58.81 43.3 75-79 55 390 63.6 50.01 56.4 52.8 51.5 58.23 41.5 70-74 54 472 61.0 49.85 55.1 52.1 51.1 58.23 41.5 65-69 52 697 57.9 48.43 52.9 50.4 49.5 57.50 39.2 60-64 50 699 54.7 47.11 50.7 48.7 47.9 56.90 37.4 55-59 47 762 50.9 44.35 47.4 45.7 45.1 55.68 33.7 Indirect/Direct Evaporative Cooling System Performance • Bin weather data, Denver, CO • Doesn’t include fan temperature rise

  11. Typical Meteorological Weather Data (TMY2) • 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 DB 74°F DB, 76% RH

  12. Typical Meteorological Weather Data (TMY2) • 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 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 • 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 : : (compared to DEC upstream of of CC) (compared to CC upstream of DEC) * Fan Upstream – 35% less CC energy

  16. 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

  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 • 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 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 • Dry the pad out daily. • Drain the sump weekly. • Run the pad wild. • Don’t recirculate air. • Pads last approx. 8-12 years. • Pipe for maintenance (strainers, PRV, flowmeters, etc.).

  21. Direct Evaporative Cooler Piping

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

  23. Control Sequence • 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 • Legionella disease • Over humidification • Smell • High maintenance • High water usage

  25. Typical HVAC SystemsEstimated Total Water Consumption • Assumptions • Power plant overall efficiency of 35% • Average O.A. temperature of 80oF • Cooling tower bleed rates of 20% to 33%

  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, 1988

  27. 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 • 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 • 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

  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

  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

  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

  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

  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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