ASHRAE Journal - ACMA Supplement - Fall 2013 - 6

By AMCA InternAtIonAl’s
IndustrIAl ProCess/Power
GenerAtIon MArket GrouP

selection of Fans

T

for Industrial Process and
Power Generation Applications
Before discussing the aerodynamic principles associated with
fans, it is important to understand the definition of a fan. A fan
is a device that converts rotational mechanical energy to move
a continuous volume of gas while increasing the pressure of the
gas. A fan has at least one inlet and one outlet.

his is the first in a series of articles by AMCA’s
Industrial Process/Power Generation Group on

various aspects of fan performance and design

that are significant to fan applications in the Industrial
Process and Power Generation Markets.

When starting the selection process, one must determine if the
fan will have appurtenances that affect aerodynamic performance. This determination is normally established by defining
the inlet and outlet boundaries or planes for the fan.

The primary purpose of purchasing a fan for such applications
is to obtain a machine to provide the motive force for moving
air or gas within the system. The cost of the fan is often relatively small compared to the cost of annual operation, or the
value of the end product or service provided by the facility.
Making sure that the fan is properly selected to meet the needs
of the process using the least amount of energy and providing
the greatest reliability is of utmost importance. This article
reviews major concepts related to fan performance definitions
and selection criteria that are important to ensuring that the fan
chosen is appropriate for the application.

The next step is to consider aerodynamic parameters associated
with fans. The first of these is pressure, which is force per unit
area. Pressure can be described in several ways: Absolute Pressure
is the value of pressure when the datum is absolute zero; it is
always positive. Barometric Pressure is the Absolute Pressure
exerted by the atmosphere; it also is always positive. Gauge
Pressure is the value of pressure when the datum is barometric
pressure at the measurement point; it can be positive or negative.

Figure 1: Interpretation of fan pressures for rating purposes.
Image courtesy of AMCA International.

INLET DUCT

FAN
FAN MFR.

CUSTOMER

FAN INLET

FAN OUTLET

CUSTOMER

OUTLET DUCT

t2

Pv1

Pv

Pt

P

s2

Ps

0

+

P

Pv

+

1

Ps

1

Pv1

2

∆Ps

Pt1

AMBIENT
0 ATMOSPHERIC
PRESSURE

For fan applications, there are
some very specific definitions
concerning pressure. Fan

1. ENTRANCE LOSS
2. ACCELERATION ENERGY

6

Fa l l 2 0 1 3

There are three types of pressure we are concerned about
with fan applications: Static
Pressure, Velocity Pressure,
and Total Pressure. Static
Pressure is the pressure that
exists by virtue of compression and density only; it can
be positive or negative.
Velocity Pressure is the pressure that exists by virtue of
motion and density only; it
can only be positive. Total
Pressure is the sum of static
and velocity pressure at a
measurement point, and
therefore defines the total
energy at a given point; it can
be positive or negative.

a m c a I n t e r nat I o na l

inmotion

w w w. a m c a . o r g


http://WWW.AMCA.ORG

ASHRAE Journal - ACMA Supplement - Fall 2013

Table of Contents for the Digital Edition of ASHRAE Journal - ACMA Supplement - Fall 2013

Contents
ASHRAE Journal - ACMA Supplement - Fall 2013 - Cover1
ASHRAE Journal - ACMA Supplement - Fall 2013 - Cover2
ASHRAE Journal - ACMA Supplement - Fall 2013 - Contents
ASHRAE Journal - ACMA Supplement - Fall 2013 - 2
ASHRAE Journal - ACMA Supplement - Fall 2013 - 3
ASHRAE Journal - ACMA Supplement - Fall 2013 - 4
ASHRAE Journal - ACMA Supplement - Fall 2013 - 5
ASHRAE Journal - ACMA Supplement - Fall 2013 - 6
ASHRAE Journal - ACMA Supplement - Fall 2013 - 7
ASHRAE Journal - ACMA Supplement - Fall 2013 - 8
ASHRAE Journal - ACMA Supplement - Fall 2013 - 9
ASHRAE Journal - ACMA Supplement - Fall 2013 - 10
ASHRAE Journal - ACMA Supplement - Fall 2013 - 11
ASHRAE Journal - ACMA Supplement - Fall 2013 - 12
ASHRAE Journal - ACMA Supplement - Fall 2013 - 13
ASHRAE Journal - ACMA Supplement - Fall 2013 - 14
ASHRAE Journal - ACMA Supplement - Fall 2013 - 15
ASHRAE Journal - ACMA Supplement - Fall 2013 - 16
ASHRAE Journal - ACMA Supplement - Fall 2013 - 17
ASHRAE Journal - ACMA Supplement - Fall 2013 - 18
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ASHRAE Journal - ACMA Supplement - Fall 2013 - 25
ASHRAE Journal - ACMA Supplement - Fall 2013 - 26
ASHRAE Journal - ACMA Supplement - Fall 2013 - 27
ASHRAE Journal - ACMA Supplement - Fall 2013 - 28
ASHRAE Journal - ACMA Supplement - Fall 2013 - Cover3
ASHRAE Journal - ACMA Supplement - Fall 2013 - Cover4
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