1. Energy Efficient Fluid Flow

2. Pumping System Fundamentals
Welec = V DPtotal / [Effpumpx Effdrivex Effmotor ]
V = volume flow rate
DPtotal = pressure gain to overcome inlet/outlet affects and friction
DPstatic (pressure difference between inlet and outlet)
DPvelocity (velocity difference between inlet and outlet)
DPelevation (elevation difference between inlet and outlet)
DPfriction
Eff = efficiencies of pump, drive, motor

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

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

5. Reduce Pump/Fan DP

6. Minimize Elevation Gain Increase Initial Reservoir Level
Welev = V DPelevation difference between inlet and outlet
Reducing elevation difference reduces work to overcome elevation by 20%

7. Minimize Friction Use Large Diameter Pipes/Ducts
Wfriction = V DPfriction
DPfriction = k / D5
Wfriction = V k / D5
Work to overcome friction varies inversely with 5th power of pipe diameter
Doubling pipe diameter reduces work to overcome friction by 97%

8. Minimize Friction Use Smooth Pipes/Ducts
Wfriction = V DPfriction
DPfriction ~ friction factor f
fsteel = fplastic = 0.018
Smoother pipes reduce work to overcome friction by:
(0.021 – 0.018) / = 17%

9. Minimize Friction Use Gradual Elbows
Long radius elbows reduce work to overcome friction by 90%

10. Employ Energy Efficient Flow Control

11. Flow Control Systems designed for peak flow
Systems operate at less than peak flow
Use energy efficient method to control (reduce) flow

12. Inefficient Flow Control
By-pass loop
(No savings)
By-pass damper
(No savings)
Outlet valve/damper
(Small savings)
Inlet vanes
(Moderate savings) 12

13. Efficient Flow Control
Trim impellor for constant-volume pumps
Slow fan for constant-volume fans
VFD for
variable-volume pumps or fans 13

14. Energy Efficiency of Flow Control14

15. Pump/Fan and System Curves
Pump/Fan Curve DP
System Curve V
W = V DP = area of rectangle

16. Bypass Flow: Zero Energy Savings
Pump/Fan Curve DP
System Curve V
V2 = V1
When bypassing, V through pump is constant
Thus, pump work is constant and no savings

17. Throttle Flow: Small Energy Savings
Throttled System Curve DP
Design System Curve
V2 = V1 / 2 V1 V
With throttling and inlet vanes, V decreases but P increases
Thus, net decrease in W (area under curves) is small

18. Reduce Pump/Fan Flow: Big Energy Savings
Pump/Fan Curve DP
System Curve
V2 = V1 / 2 V1 V
W = V DP = V (k V2) = k V3
When flow reduced by pump/fan rather than system, W varies with cube of flow
Reducing flow by 50% reduces work to overcome friction by 88%

19. Three Ways to Reduce Pump/Fan Flow
Trim impellor for constant-flow pumping applications
Slow fan for constant-flow fan applications
Install VFD for
variable-flow pumps or fans 19

20. Constant Flow Pumping: Cooling Towers With Throttling Valves

21. Constant Flow Pumping: Process Pumps with Throttling Valves

22. Constant Flow Pumping: Open Throttling Valve and Trim Pump Impellor
A: Flow throttled by partially closed valve
B: Max flow with valve open
C: Valve open and impellor trimmed

23. Constant Flow Fans: Slow Fan by Changing Pulley Diameter

24. Constant Flow Fans: Slow Fan by Changing Pulley Diameter
A: Flow throttled by partially closed damper
B: Max flow with damper open
C: Damper open and fan speed (RPM) reduced

25. Variable Flow Pumping: Process Cooling Loop
W2 = W1 (V2/V1)3
Reducing flow by 50% reduces pumping costs by 87%

26. Variable Flow Pumping: HVAC Chilled Water Loops

27. Variable Flow Pumping: Open Throttling Valve and Install VFD

28. Full-Open Pumping: Install 2-Way Valves and VFDs

29. Big Cooling Towers

30. Big Cooling Loop Pumps

31. Worlds Largest Bypass Pipe

32. Savings From Installing VFDsB C
A: Flow throttled by partially closed valve
B: Max flow with valve open
C: Valve open and pump slowed by VFD
Wsav for throttle to VFD = A – C
Wsav for bypass to VFD = B – C
Wsav for bypass to VFD
W2 = W1(V2/V1)2.5
Wsav = W1 – W2

33. 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: Wfluid = V DP = k V3

34. Optimize Efficiency of Pumps/Fans

35. Correct Fan Inlet/Exit Conditions
No Yes

36. Resize Over-sized Pumps
Pump operating at off-design point M
Eff = 47%
Replace with properly sized pump
Eff = 80%
Savings: $14,000 /yr

37. Fluid Flow Summary Reduce Required Pump/Fan Head
Reduce excess elevation head
Use larger diameter pipes
Use smoother pipes/ducts
Use long-radius elbows and low-friction fittings
Employ Energy Efficient Flow Control
Constant flow pumping: trim impellor blade
Constant flow fans: Slow fan
Variable flow pumps and fans: Install VFDs
Pump slow, pump long
Improve Efficiency Pumps/Fans
Correct fan inlet/exit conditions
Resize miss-sized pumps/fans