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: –W elec = W fluid / [Eff pump x Eff drive x Eff motor ] –W elec = 1 kWh / [.70 x.92 x.90 ] = 1.7 kWh

Fluid Flow System Fundamentals W fluid = V  P total

Fluid Flow System Fundamentals W fluid = V  P total = V (k V 2) = k V 3 W friction = V  P friction = k / D 5

Pumping System Savings Opportunities Reduce volume flow rate Reduce required pump head  P static  P velocity  P elevation  P headloss Increase pump, drive, motor efficiency W elec = V  P total / [Eff pump x Eff drive x Eff motor ]

Fluid Flow System Saving Opportunities Reduce Required Pump/Fan  P Employ Energy Efficient Flow Control Improve Efficiency of Pumps/Fans

Reduce Pump/Fan  P

Increase Reservoir Level to Reduce Elevation Head

Minimize Pipe Friction: Use Bigger Pipes/Ducts  Use large diameter pipes:   P headloss ~ k / D 5  Doubling pipe diameter reduces friction by 97%

Minimize Pipe Friction Use Smooth Pipes/Ducts  Use smooth plastic pipes:  f steel = f plastic =  Pumping savings from plastic pipe (0.021 – 0.018) / = 17%

Use Gradual Elbows

Employ Energy Efficient Flow Control

Inefficient Flow Control By-pass loop (No savings) By-pass damper (No savings) Outlet valve/damper (Small savings) Inlet vanes (Moderate savings)

Efficient Flow Control Trim impellor for constant-volume pumps Slow fan for constant-volume fans VFD for variable-volume pumps or fans

Inefficient and Efficient Flow Control

Cooling Towers

Cooling Loop Pumps

Worlds Largest Bypass Pipe

For Constant Speed Pump Applications: Trim Pump Impellor Look 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 Diameter Look for discharge damper at < 100% open More energy-efficient to slow fan than throttle flow

For Variable Flow Applications: Install VFD W 2 = W 1 (V 2 /V 1 ) 3 Reducing flow by 50% reduces pumping costs by 87%

Variable Speed Pumping on HVAC Chilled Water Loops Replace 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 Slow Identify intermittent pumping applications More energy to pump at high flow rate for short period than low flow rate longer Example: –Current: Two pumps in parallel for four hours –Recommended: One pump for six hours –Estimated Savings: $500 /yr Reason: W fluid = V DP = k V 3

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 Pumps Pump operating at off- design point M Eff = 47% Replace with properly sized pump Estimated savings: $14,000 /yr

Fluid Flow Summary Reduce Required Pump/Fan Head –Reduce excess elevation head –Smoother pipes/ducts –Larger diameters –Gradual elbows Employ Energy Efficient Flow Control –Constant speed pumping: trim impellor blade –Constant speed fans: Slow fan –Variable flow: Install VFDs –Pump slow, pump long Improve Efficiency Pumps/Fans –Correct fan inlet/exit conditions –Refurbish inefficient pumps –Resize miss-sized pumps/fans