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

************************************