Print this page HVAC - Characteristics and Selection Parameters of Fans and Blower Systems
A. Bhatia, B.E.
Course Outline
Everybody is familiar
with the fans seen in everyday use, such as desk fans or the sophisticated types
seen in aircraft engines. Between these extremes is a whole range of fans and
fan types available to designers to meet their specific requirements. Fans are
widely used in processing to support production (material handling) or to maintain
safe working conditions (ventilation). In either case, right type of fan selection
operating at high efficiency is priority.
This 4- hour course outlines the considerations involved to properly select,
apply and control fans. Emphasis is placed upon matching the fan equipment to
the requirements of the system from several different perspectives.
The course includes a multiple-choice quiz at the end, which is designed to
enhance the understanding of the course materials.
Learning Objective
At the conclusion of this course, the student will:
- Describe the different type of fans commonly used in industrial & commercial applications;
- Understand the fan characteristics and laws governing airflow, power and static pressure;
- Describe the key terms, such as operating point, stall, airflow delivery, static pressure etc.;
- Understand the factors affecting the fan performance viz. air density and system effects;
- Learn the "Do and Don'ts" of fans installation;
- Understand the energy conservation achieved with different type of fan controls;
- Learn the ways to curb excessive noise;
- Describe multiple fan operation in series and parallel;
- Learn the importance of fan auxiliaries such as prime mover, belts and bearings;
- Learn the conditions of design and installation of fan drives;
- Understand the basic trouble shooting and maintenance tips; and
- Learn the useful
equations and their interpretation.
This course is aimed at students, mechanical and HVAC engineers, process engineers, architects, building designers, contractors, energy auditors, facility managers and general audience.
Course Introduction
The fan is an air
pump that causes airflow by creating a pressure difference. Fans produce pressure
and flow by rotating blades of the impeller, imparting kinetic energy to the
air by changing its velocity. By definition, the term "fan" is limited
to devices producing pressure differentials of less than 28in-wg at sea level.
Fans provide the necessary energy input to pump air from one location to another
while they overcome the various resistances created by the equipment and the
duct distribution system. The impeller does work on the air in giving it both
static and kinetic energy that varies in proportion, depending on the fan type.
This course provides a quick end-use briefing on the fan and blower systems.
Course Content
The course content is in a PDF file HVAC - Characteristics and Selection Parameters of Fans and Blower Systems . You need to open or download this document to study this course.
Course SummaryFans have been
classified in a general way as either centrifugal fans or axial-flow fans, according
to the direction of airflow through the impeller. There are a number of subdivisions
of each general type. Generally, the subdivisions consist of different styles
of impellers and the strength and arrangement of construction. Because of the
type of impeller dictates fan characteristics, it influences the amount of energy
(horsepower) the fan needs to move the required volume of air.
During this movement of air, it may also need to be heated, cooled, filtered
or de-humidified as part of the process. So, a fan is usually part of a 'system'
and the contents or structure of this system will have a direct effect on the
performance of the fan. Anything that contributes to the obstruction of the
free flow of air imposes a resistance to flow, which the fan has to overcome.
The fan selection procedure is to ensure that the chosen fan can overcome this
system resistance and still move the required volume of air. Of course, it would
be easy to fit an oversize fan but, cost, size and noise levels must form part
of the selection criteria. The most important factor for the designer to consider
is the square law relationship between pressure and flow within the system.
Fan manufacturers demonstrate their product's performance with a pressure/volume
characteristic. This gives an indication of the volume of air moved against
a resistance to flow - i.e. the fan develops pressure, which can be used to
overcome system resistance.
Key impacts that determine which fan type is the most appropriate include technical
and non technical attributes.
- Technical considerations include pressure, airflow rate, efficiency, space constraints, noise generation, drive configuration, temperature range, variations in operating conditions, and tolerance to corrosive or particulate-laden airstreams.
- Non-technical
reasons include cost, delivery time, availability, and designer/operator familiarity
with a fan model.
Quiz
Once you finish studying the above course content, you need to take a quiz to obtain the PDH credits.
DISCLAIMER: The materials contained in the online course are not intended as a representation or warranty on the part of PDH Center or any other person/organization named herein. The materials are for general information only. They are not a substitute for competent professional advice. Application of this information to a specific project should be reviewed by a registered architect and/or professional engineer/surveyor. Anyone making use of the information set forth herein does so at their own risk and assumes any and all resulting liability arising therefrom.
