Fans and Blowers

PEMP
RMD 2501

Fans and Blowers
Session delivered by:
Prof. Q H
Prof Q.H. Nagpurwala

06a

© M.S. Ramaiah School of Advanced Studies

1

Session Objectives

PEMP
RMD 2501

This session is intended to discuss the following:

• Types and working principle of fans and blowers
• Applications of various fans and blowers
• Pressure rise flow coefficient and efficiency
rise,
• Velocity triangles
• Performance characteristics
• Fan laws

06a

© M.S. Ramaiah School of Advanced Studies

2

What is a Fan?

PEMP
RMD 2501

 Any device that produces a current of air by the movement of
broad surfaces can be called a fan.
 Fans fall under the general classification of “turbomachinery”
turbomachinery
and have a rotating impeller at least partially encased in a
stationary housing.
 Fans are similar in many respects to pumps. Both are
turbomachines that transfer energy to a flowing fluid. It is easy to
distinguish between fans and pumps: pumps handle liquids; fans
handle gasses.
 Broadly speaking, the function of a fan is to propel, displace, or
move air or gas.
06a

© © M.S. Ramaiah School of Advanced Studies
M. S. Ramaiah School of Advanced Studies, Bangalore

3

Fans, Blowers and Compressors

PEMP
RMD 2501

Fans, bl
F
blowers and compressors are diff
d
differentiated b the method used to
i d by h
h d
d
move the air, and by the system pressure they must operate against.
Difference Between Fans, Blower and Compressors
Difference Between Fans Blower and Compressors
Equipment

Specific Ratio

Pressure Rise (mmWC)

Fans

Up to 1.11
Up to 1 11

1136

Blowers 

1.11 to 1.20

1136 to 2066

Compressors

More than 
More than
1.20

As per American Society of Mechanical Engineers
(ASME) the specific ratio – the ratio of the
discharge pressure to the suction pressure – is used
for defining the fans and blowers
06a

© © M.S. Ramaiah School of Advanced Studies
M. S. Ramaiah School of Advanced Studies, Bangalore

4

Components of Fan/Blower System

PEMP
RMD 2501

Turning Vanes
(typically used on
short radius elbows)
Outlet Diff
O tl t Diffusers

Provide air for
ventilation and
industrial
processes that
need air flow
Filter

Heat
Exchanger
Baffles

Inlet
Vanes
Motor
Controller

Centrifugal Fan/Blower
Belt Drive

06a

Variable Frequency Drive
Motor

© © M.S. Ramaiah School of Advanced Studies
M. S. Ramaiah School of Advanced Studies, Bangalore

5