optimizing chilled water plant performance - big ten and friends
TRANSCRIPT
2013 BIG TEN AND FRIENDSMECHANICAL & ENERGY CONFERENCE
Optimizing Chilled WaterPlant Performance
David Herman, PE, LEED APPrincipal
EnerG Associates, LLC
Optimizing Chilled Water PlantPerformance
Learning Objectives• Review the design and operating characteristics of each
equipment component of a chilled water plant• Understand how the design characteristics and
operation of each equipment component effects overallchiller plant efficiency
• Learn how to evaluate strategies to optimize chilledwater plant performance based on existing chilled waterplant design and operation
• Review actual operating data from central chilled waterplants before and after implementation of optimizationstrategies
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Optimizing Chilled Water PlantPerformance
• Benchmark the existing equipment• Ensure proper preventive maintenance• Optimize operation of existingequipment
• Evaluate possible capital retrofits
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A Typical Chiller Plant
What is the average total kW/ton for anexisting chiller plant including chillers,
cooling towers and pumps?Approx. 1.0 kW/ton
What is an optimized total kW/ton for achiller plant?
Approx. 0.8 1.0 kW/ton(lower with capital investment)
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A Typical Chiller Plant
What is one of the most useful diagnostictools for benchmarking pumps?
The Pump Curve
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Benchmarking Pumps
Example:TACO Model #TA1538HP 75GPM 1400HD 140�’IMP 12.5RPM 1750
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Benchmarking Pumps
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Benchmarking Pumps
How can pump impeller size beconfirmed?
By deadheading the pump
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Benchmarking Pumps
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Benchmarking Pumps
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Benchmarking Pumps
Why is it important to use the same gaugeto measure suction and discharge
pressures?
To avoid gauge error since the differentialpressure is needed
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Benchmarking Pumps
Example:Measured Suction P: 9 psigMeasured Discharge P: 58 psigMeasured P: 58 psigMeasured P: 134�’ head
To convert psi to head, multiply by 2.31
Deadhead: 163�’
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Benchmarking Pumps
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Benchmarking Pumps
Basic Formulas
• 1 ton = 12,000 Btuh
• GPM = Q / (500 x T)
• Tons = GPM x T / 24
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Benchmarking Chillers
What T is the basis of the rule of thumbof 2.4 GPM/ton for evaporator flow?
T = 10 degrees
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Benchmarking Chillers
Tag # Manuf Model # NomTons
#1 Trane CVHE090R00 925#2 Trane CVHE090R00 925#3 Trane CVHE 050 F BC 515
Evaporator
GPM Ent Temp Lvg Temp Temp Diff
1,350 58.4 42.0 16.41,350 58.4 42.0 16.4750 58.5 42.0 16.5
Condenser
GPM Lvg Temp Ent Temp Temp Diff
1,800 99.9 85.0 14.91,800 99.9 85.0 14.91,000 100.0 85.0 15.0
FLA kW kW/ton Refrig Charge Starts Hours927 666 0.72R 123 1,111 34,236927 666 0.72R 123 1,131 25,575526 382 0.74R 11 1170 2,276 > 21935
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Benchmarking Chillers
Barrel Nom Tons Rated Flow Rated PD FT Rated TempDiff
Evap 515 750 8.1 16.5
Cond 1,000 9.7 15.0
Meas Ent P Meas Lvg P Meas Diff P Meas PD FT Meas Flow
84 80 4 9 801
78 68 10 23 1,543
Meas Ent T Meas Lvg T Meas TempDiff Tons Amps kW kW/ton
54.0 40.0 14.0 467 440 315 0.67
80.0 89.0 9.0
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Benchmarking Chillers
Measured Flow =Rated Flow * (Rated PD/Measured PD)^0.5
kW =(3)^0.5 *V * A * PF / 1000
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Benchmarking Chillers
• Pumps• Chillers• Cooling Towers
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Ensure Proper Maintenance
• Over pumping results in:Flow problemsEnergy penalty
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Optimize Pump Operation
• Lower condenser water temperature setpoint
• For every one degree drop in condenserwater temperature, chiller efficiency willincrease 2%
• Consider the trade off between lowercompressor energy and increasedcooling tower fan energy
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Optimize Chiller Operation
What is the typical location of thedifferential pressure sensor controlling the
pump variable speed drive?
Somewhere along the chilled water supplyand return piping
What is the optimum location?
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Optimize Chiller Operation
• Relocate differential pressure sensorcontrolling pump variable speed drive
• Optimum location is across the chilledwater supply and return piping at thefarthest chilled water coil
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Optimize Chiller Operation
• Install variable speed drive on existingchiller(s)
• Significant energy savings in chillerenergy use is possible (up to 30% insome applications)
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Evaluate Capital Retrofits
Optimizing Chilled Water PlantPerformance
• Benchmark the existing equipment• Ensure proper preventive maintenance• Optimize operation of existingequipment
• Evaluate possible capital retrofits
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To download a copy of thispresentation, go to
www.energengineers.com
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