1. Introduction to Energy Management

2. Week/Lesson 9 part b Centrifugal Pumps and Hydronic Systems

3. After completing this chapter, you will be able to:
Centrifugal Pumps and Hydronic Systems
After completing this chapter, you will be able to:
Describe the operation and primary parts of a centrifugal pump
Describe how a centrifugal pump adds pressure to a fluid
Identify several types of centrifugal pumps
Explain pump performance characteristics such as head, flow rate, horsepower and efficiency

4. Use pump performance curves to evaluate a pump’s capability
Centrifugal Pumps and Hydronic Systems
Use pump performance curves to evaluate a pump’s capability
Evaluate the flow characteristics of a hydronic system
Calculate the flow requirement for a hydronic system

5. How a centrifugal pump works
Centrifugal Pumps and Hydronic Systems
How a centrifugal pump works
Uses centrifugal force
Force is created by an impeller
Force pushes outward
The faster the impeller, the greater the force
Volute – pump casing

6. Types of centrifugal pumps In-line pumps Low flow, low pressure
Centrifugal Pumps and Hydronic Systems
Types of centrifugal pumps
In-line pumps
Low flow, low pressure
Motors are less than one horsepower
Booster or circulator pump

7. Impeller connected to motor shaft Used in smaller applications
Centrifugal Pumps and Hydronic Systems
Close-coupled pumps
Impeller connected to motor shaft
Used in smaller applications
Flexible-coupled pumps
Impeller shaft and motor are isolated
Reduced vibration/noise transmission

8. Single suction Double suction End suction Casing types
Centrifugal Pumps and Hydronic Systems
Single suction
Double suction
End suction
Casing types
Horizontal split case
Vertical split case

9. Characteristics of centrifugal pumps Head Measure of pump pressure
Centrifugal Pumps and Hydronic Systems
Characteristics of centrifugal pumps
Head
Measure of pump pressure
Expressed in feet or psi
Flow rate (capacity)
Amount of water pumped
Expressed in gallons per minute (gpm)

10. More pumping requires more horsepower
Centrifugal Pumps and Hydronic Systems
Horsepower
Brake horsepower
More pumping requires more horsepower
Higher horsepower  higher energy usage
Speed
Speed of motor = speed of pump
Expressed in rotations per minute (rpm)

11. Ratio of output to input Input is always higher than output
Centrifugal Pumps and Hydronic Systems
Efficiency
Ratio of output to input
Input is always higher than output
Impeller diameter
Larger impellers require higher horsepower
Larger impellers move more water

12. Performance curves of centrifugal pumps Head-capacity curve
Centrifugal Pumps and Hydronic Systems
Performance curves of centrifugal pumps
Head-capacity curve
Plots head against flow rate
Largest head occurs at zero flow
Shutoff head = head at zero flow
Flat or steep curves

13. Horsepower-capacity curve Plots horsepower against flow rate
Centrifugal Pumps and Hydronic Systems
Horsepower-capacity curve
Plots horsepower against flow rate
Increases in flow rate require more horsepower

14. Efficiency-capacity curve Efficiency = water efficiency/horsepower
Centrifugal Pumps and Hydronic Systems
Efficiency-capacity curve
Efficiency = water efficiency/horsepower
Water efficiency – energy content of water
Efficiency plotted against flow rate
Efficiency = zero at zero flow
Efficiency reaches a peak and then declines

15. Using performance curves Intersection of 25 feet and 90 gpm
Centrifugal Pumps and Hydronic Systems
Example 12-1
Flow = 90 gpm, head = 25 feet
Using performance curves
Intersection of 25 feet and 90 gpm
Pulley size = 5 ½ inches
Efficiency = 65%
Motor size = 1 horsepower

16. Piping characteristics of hydronic systems Open piping systems
Centrifugal Pumps and Hydronic Systems
Piping characteristics of hydronic systems
Open piping systems
Closed piping systems
Required flow rate
System pressure loss

17. Calculating the flow rate GPM = Q/(500 x ΔT) Friction head losses
Centrifugal Pumps and Hydronic Systems
Calculating the flow rate
GPM = Q/(500 x ΔT)
Friction head losses
System characteristic curve
Elevation, static head loss
Only a factor in open systems

18. Operating characteristics of hydronic systems Flow rate and pressure
Centrifugal Pumps and Hydronic Systems
Operating characteristics of hydronic systems
Flow rate and pressure
Pump head-capacity curve
System characteristic curve
Output determined by head
System operating point

19. Using performance curves New flow rate = 60 gpm
Centrifugal Pumps and Hydronic Systems
Example 12-2
Impeller = 5½ inches
Head = 30 feet (from 25 feet)
Using performance curves
New flow rate = 60 gpm
Pump capacity has dropped

20. Controlling hydronic system pressure High pressure
Centrifugal Pumps and Hydronic Systems
Controlling hydronic system pressure
High pressure
Valve seating problems
Weakened pipe joints
Low pressure
Instant steam formation
Pump damage

21. Water expands when heated Used to control system pressure
Centrifugal Pumps and Hydronic Systems
Expansion tank
Water expands when heated
Used to control system pressure
Air venting valves
Located at highest system points
Open and close automatically
Help remove air from the system

22. Monitors pressure difference Outlet pump pressure Inlet pump pressure
Centrifugal Pumps and Hydronic Systems
Pressure bypass
Monitors pressure difference
Outlet pump pressure
Inlet pump pressure
Valve opens when differential is large
Allows supply water into the return

23. Pump Basics

24. A machine for moving fluid by accelerating the fluid RADIALLY outward.
Centrifugal Pumps
A machine for moving fluid by accelerating the fluid RADIALLY outward.
From the Center
of a Circle
RADIAL DIRECTION
To the Outside of a Circle

25. Centrifugal Pumps
This machine consists of an IMPELLER rotating within a case (diffuser)
Liquid directed into the center of the rotating impeller is picked up by the impeller’s vanes and accelerated to a higher velocity by the rotation of the impeller and discharged by centrifugal force into the case (diffuser).

26. Centrifugal Pumps
A collection chamber in the casing converts much of the Kinetic Energy (energy due to velocity) into Head or Pressure.

27. Pump Terminology

28. "Head" Reservoir of Fluid Pressure Gauge
Head is a term for expressing feet of water column
Head can also be converted to pressure
Pressure
Gauge
Reservoir of Fluid
100 feet
43.3 PSI

29. Conversion Factors Between Head and Pressure
Head (feet of liquid) =Pressure in PSI x 2.31 / Sp. Gr.
Pressure in PSI = Head (in feet) x Sp. Gr. / 2.31
PSI is Pounds per Square Inch
Sp. Gr. is Specific Gravity which for water is equal to 1
For a fluid more dense than water, Sp. Gr. is greater than 1
For a fluid less dense than water, Sp. Gr. is less than 1

30. Head
Head and pressure are interchangeable terms provided that they are expressed in their correct units.
The conversion of all pressure terms into units of equivalent head simplifies most pump calculations.

31. Centrifugal Impellers
Vanes
Thickness
of the impeller
“Eye of the Impeller”
Water Entrance
Diameter of
the Impeller
Thicker the Impeller- More Water
Larger the DIAMETER - More Pressure
Increase the Speed - More Water and Pressure

32. Two Impellers in Series
Direction of Flow
Twice the pressure
Same amount of water

33. Multiple Impellers in Series
Direction of Flow
Direction of Flow
Placing impellers in series increases the amount of head produced
The head produced = # of impellers x head of one impeller

34. Energy Loss in Valves Function of valve type and valve position
The complex flow path through valves can result in high head loss (of course, one of the purposes of a valve is to create head loss when it is not fully open)
Ev are the loss in terms of velocity heads