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Energy Efficient Fluid Flow. Fluid Flow System Fundamentals. W motor = W fluid / (Eff motor x Eff drive x Eff pump ). Look For “Inside” Opportunities to Max Savings. Efficiency losses in distribution and primary energy conversion systems multiply “inside” savings Example: - PowerPoint PPT Presentation
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Energy Efficient Fluid Flow
Fluid Flow System FundamentalsWmotor = Wfluid / (Effmotor x Effdrive x Effpump)
Look For Inside Opportunities to Max SavingsEfficiency losses in distribution and primary energy conversion systems multiply inside savings
Example:Welec= Wfluid / [Effpumpx Effdrivex Effmotor ]Welec= 1 kWh / [.70 x .92 x .90 ] = 1.7 kWh
Fluid Flow System FundamentalsWfluid = V DPtotal
P
V
Pump Curve
System Curve
Wfluid = V P
Fluid Flow System FundamentalsWfluid = V DPtotal = V (k V2) = k V3Wfriction = V DPfriction = k / D5
P
V
Pump Curve
System Curve
Wfluid = V P
Pumping System Savings OpportunitiesReduce volume flow rateReduce required pump headDPstatic DPvelocity DPelevation DPheadlossIncrease pump, drive, motor efficiencyWelec = V DPtotal / [Effpumpx Effdrivex Effmotor ]
Fluid Flow System Saving Opportunities Reduce Required Pump/Fan DPEmploy Energy Efficient Flow Control Improve Efficiency of Pumps/Fans
Reduce Pump/Fan DP
Increase Reservoir Level toReduce Elevation Head
Minimize Pipe Friction:Use Bigger Pipes/Ducts Use large diameter pipes: DP headloss ~ k / D5 Doubling pipe diameter reduces friction by 97%
Minimize Pipe FrictionUse Smooth Pipes/DuctsUse smooth plastic pipes: fsteel = 0.021 fplastic = 0.018 Pumping savings from plastic pipe (0.021 0.018) / 0.018 = 17%
Use Gradual Elbows
Use Gradual Elbows
Employ Energy Efficient Flow Control
Inefficient Flow ControlBy-pass loop(No savings)By-pass damper (No savings)Outlet valve/damper(Small savings)Inlet vanes(Moderate savings)
Efficient Flow ControlTrim impellor for constant-volume pumpsSlow fan for constant-volume fansVFD for variable-volume pumps or fans
Inefficient and Efficient Flow Control
Chart2
1.0018640.9951131
0.9739132240.7106170.64
0.8807452320.6506570.36
0.7378879280.6291850.16
0.5608692160.20.04
Outlet Damper
Variable Inlet Vane
Variable Frequency Drive
Volume Flow Rate (%)
Power (%)
Sheet1
FanPower.XLS
For Inlet Vanes
VWVnormWnormWnormVnormVnorm2Vnorm3
4.6001.7001.0001.0001.0001.0001.0001.000
4.3001.4500.9350.8530.8530.9350.8740.817
3.9001.3000.8480.7650.7650.8480.7190.609
3.4501.1500.7500.6760.6760.7500.5630.422
2.3001.1000.5000.6470.6470.5000.2500.125
Wnorm = -0.042487 + 3.6573 * V -6.4957 * V2 + 3.8760 * V3
R2 = 0.997
For Outlet Dampers
VnormWWnormWnormVnormVnorm2Vnorm3
11.6111.0001.0001.0001.000
0.81.580.98136645960.9810.8000.6400.512
0.61.40.86956521740.8700.6000.3600.216
0.41.20.74534161490.7450.4000.1600.064
0.20.90.55900621120.5590.2000.0400.008
for Vnorm >= 0.5: Wnorm = 0.365217 + 0.998965 * V -0.03882 * V^2 +-0.323498 * V^3
r2 = 0.998
for 0>=Vnorm > 0.5: Wnorm = 0.589 + 0.116 * V
For VFD assuming P = k V^2Graph
WnormVnormVnormOutlet DamperVariable Inlet VaneVariable Frequency Drive
1.0001.000100%1.001.001.00
0.6400.80080%0.970.710.64
0.3600.60060%0.880.650.36
0.1600.40040%0.740.630.16
0.0400.20020%0.560.04
Wnorm = Vnorm^2
R2 = 1.0
Sheet1
Outlet Damper
Variable Inlet Vane
Variable Frequency Drive
Volume Flow Rate (%)
Power (%)
800hpfans
W/VIV in blast
%TimeCFMCFM/CFMmaxW/WmaxW
5%20,0000.80.71147323.6635461
75%18,0000.720.670446334.718630316
10%16,0000.640.65443543.5308538384
10%14,0000.560.64943243.2391905936
Average445
w/VFD in blast
%TimeCFMCFM/CFMmaxW/WmaxW
5%20,0000.80.64042621.312
75%18,0000.720.518345258.9408
10%16,0000.640.41027327.27936
10%14,0000.560.31420920.88576
Average328
Sheet3
Cooling Towers
Cooling Loop Pumps
Worlds Largest Bypass Pipe
For Constant Speed Pump Applications: Trim Pump ImpellorLook for discharge valve at < 100% open More energy-efficient to downsize the pump by trimming impellor blades than throttle flow
Trim Impellor and Open Throttling Valve
For Constant Speed Fan Applications: Slow Fan Speed by Changing Pulley DiameterLook for discharge damper at < 100% open More energy-efficient to slow fan than throttle flow
For Variable Flow Applications:Install VFD W2 = W1 (V2/V1)3
Reducing flow by 50% reduces pumping costs by 87%
warm water
cool water
cooling tower
city water make-up
7.5 hp pump
25 hp pump
reservoir
process water return
bypass / pressure relief valve
cooling water to process loads
dP
VSD
Variable Speed Pumping on HVAC Chilled Water LoopsReplace 3-way Valve with 2-way valve on AHU
VFDs on Vent Hoods
Need Controls for VFDs on Dust Collection
Use VFDs on Cooling Tower Fans
Pump Long, Pump SlowIdentify intermittent pumping applicationsMore energy to pump at high flow rate for short period than low flow rate longerExample: Current: Two pumps in parallel for four hoursRecommended: One pump for six hoursEstimated Savings: $500 /yrReason: Wfluid = V DP = k V3
Optimize Efficiency of Pumps/Fans
Correct Fan Inlet/Exit Conditions No Yes
Refurbish Inefficient Pumps Pump not operated at peak efficiency in middle of operating range
Resize Miss-sized PumpsPump operating at off-design point MEff = 47%Replace with properly sized pumpEstimated savings: $14,000 /yr
Fluid Flow SummaryReduce Required Pump/Fan HeadReduce excess elevation headSmoother pipes/ductsLarger diametersGradual elbowsEmploy Energy Efficient Flow Control Constant speed pumping: trim impellor bladeConstant speed fans: Slow fanVariable flow: Install VFDsPump slow, pump longImprove Efficiency Pumps/FansCorrect fan inlet/exit conditionsRefurbish inefficient pumpsResize miss-sized pumps/fans
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