Energy Efficient Fluid Flow Fluid Flow System Fundamentals

Energy Efficient Fluid Flow

Fluid Flow System Fundamentals Wmotor = Wfluid / (Effmotor x Effdrive x Effpump)

Look For “Inside” Opportunities to Max Savings • Efficiency losses in distribution and primary energy conversion systems multiply “inside” savings • Example: – Welec= Wfluid / [Effpumpx Effdrivex Effmotor ] – Welec= 1 k. Wh / [. 70 x. 92 x. 90 ] = 1. 7 k. Wh

Fluid Flow System Fundamentals Wfluid = V DPtotal

Fluid Flow System Fundamentals Wfluid = V DPtotal = V (k V 2) = k V 3 Wfriction = V DPfriction = k / D 5

Pumping System Savings Opportunities Welec = V DPtotal / [Effpumpx Effdrivex Effmotor ] • Reduce volume flow rate • Reduce required pump head DPstatic DPvelocity DPelevation DPheadloss • Increase pump, drive, motor efficiency

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

Reduce Pump/Fan DP

Increase Reservoir Level to Reduce Elevation Head

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

Minimize Pipe Friction Use Smooth Pipes/Ducts §Use 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 Control By-pass loop By-pass damper Outlet valve/damper Inlet vanes (No savings) (Small savings) (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 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 Reason: Wfluid = V DP = k V 3 • Example: – Current: Two pumps in parallel for four hours – Recommended: One pump for six hours – Estimated Savings: $500 /yr

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