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Centrifugal Pumps- Introduction

HYDRONICS SYSTEMDESIGN AND

APPLICATION SEMINARPump Curves

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Introduction and Definitions

Hydronics:

The science and art of providing thermal

comfort by using water as an intermediateheat transfer medium.

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Gravity Hot Water System

Open Expansion Tank

Overflow

to drain

Boiler  Manual fill valve

Large radiators

pitch

Large pipes

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0

20

40

60

80

100

120

140

160

160 170 180 190 200

Supply Temperature

(F)

Head(mils/ft)

Return Temperature 150 160 170

Gravity Head

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Forced Circulation Systems

Compression Tank

Circulator Small Radiators and Piping

Boiler 

PRV

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Centrifugal Pumps- Pump Basics

HYDRONICS SYSTEMDESIGN AND

APPLICATION SEMINARPump Curves

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Topics

Pump Definitions

Bernoulli's Theorem

Pump Components Impeller Types

Velocity Concept

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Pump Definition- Kinetic

Hydraulic Institute Standards

Pumps

Positive

Displacement

Kinetic

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Pump Definition - Kinetic

Kinetic

-- of or due to motion

-- (K. energy) -- body’s ability to do work by virtue

of its motion.

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Pump Definition- Centrifugal

Hydraulic Institute Standards

Kinetic

Special

Peripheral

Centrifugal

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Bernoulli’s Theorem

Daniel Bernoulli FRS; (8

February 1700 – 17 March

1782) was a Swiss

mathematician and physicistand was one of the many

prominent mathematicians

in the Bernoulli family

Conservation of Energy

Fluid Flow

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Bernoulli’s Theorema

b

P

W   Z 

V 

g

P

W   Z 

V 

g

a

a

a b

b

b

   

 

 

   

   

 

 

 

2 2

2 2

The total head of a fluid at “a” is equal to the total

head at “b”, provided that there’s no loss due tofriction or work, and no gain due to the application of

work.

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Centrifugal Acceleration

Low

 Velocity

 At rest Rotating

High Velocity

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Pump Definition - Centrifugal

A pump is a mechanism used to push a liquid with a specific force,

to overcome system friction loss and any existing difference in elevation

(static pressure).

A centrifugal pump is a mechanism that adds energy in the form of velocity

to a flowing liquid. The pump produces this velocity through the means of a

motor or driver which consumes energy in the process.

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Pump Definition - Centrifugal

Pressure is produced as a result of the

“centrifugal effect”

The velocity produced by the “centrifugal

effect” represents kinetic energy that has been

imparted to the fluid

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Pump Major Components

Casing Tongue

Volute Casing

Impeller Vanes Impeller 

Impeller Eye

Rotation

Pump Suction

 Area increases constantly

Discharge

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Pump Impeller

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Typical Single Suction Impeller

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Single Suction Impeller

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Open

Semi-open

Closed

Single suction

Double suction

Non-clogging

Axial flow

Mixed flow

Impeller Types

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Why so Many Impellers…?

Impeller “specific speed”, NS Correlates capacity, head, and rpm at optimum

efficiency.

NS = nQ.5/H.75, where NS, specific speed, dimensions not used

n, rpm

Q, gpm at best efficiency

H, head, feet

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Specific Speed

“… the revolutions per minute at which a

geometrically similar impeller would run if

it were of such a size as to discharge onegallon per minute against one foot of

head.”

Hydraulic Institute Standard 1.1-1.2 2000Section 1.1.4.1

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Impeller Profiles

Specific Speed

HI Standard

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Specific Speed

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Generally

Maximum efficiency lies in the range:

2000

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Typical Impellers

Single Suction Double Suction

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Typical Impellers- Application

End Suction- Single Suction Impeller Split Case- Double Suction Impeller

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Full Diameter Impeller

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Trimmed Impeller

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Impeller and Volute

 Arrows represent the

direction of water flow

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Velocity Through the Pump

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Impeller- Velocity Concept

The water is“Whipped”away from theeye by thevanes.

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